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Purpose: Continuous glucose monitors (CGMs) are becoming increasingly popular among endurance athletes despite unconfirmed accuracy. We assessed the concurrent validity of the FreeStyle Libre 2 worn on 2 different sites at rest, during steady-state running, and postprandial. Methods: Thirteen nondiabetic, well-trained recreational runners (age = 40 [8] y, maximal aerobic oxygen consumption = 46.1 [6.4] mL·kg–1·min–1) wore a CGM on the upper arm and chest while treadmill running for 30, 60, and 90 minutes at intensities corresponding to 50%, 60%, and 70% of maximal aerobic oxygen consumption, respectively. Glucose was measured by manually scanning CGMs and obtaining a finger-prick capillary blood glucose sample. Mean absolute relative difference, time in range, and continuous glucose Clarke error grid analysis were used to compare paired CGM and blood glucose readings. Results: Across all intensities of steady-state running, we found a mean absolute relative difference of 13.8 (10.9) for the arm and 11.4 (9.0) for the chest. The coefficient of variation exceeded 70%. Approximately 47% of arm and 50% of chest paired glucose measurements had an absolute difference ≤10%. Continuous glucose Clarke error grid analysis indicated 99.8% (arm) and 99.6% (chest) CGM data fell in clinically acceptable zones A and B. Time-in-range analysis showed reduced accuracy at lower glucose levels. However, CGMs accurately detected trends in mean glucose readings over time. Conclusions: CGMs are not valid for point glucose monitoring but appear to be valid for monitoring glucose trends during steady-state exercise. Accuracy is similar for arm and chest. Further research is needed to determine whether CGMs can detect important events such as hypoglycemia during exercise. [ABSTRACT FROM AUTHOR]

Purpose: To quantify the change in session rating of perceived exertion training impulse (RPE-TRIMP) that may occur in response to increased running distance at 3 running velocity ranges in elite sprinters. Methods: We monitored training load in elite sprinters (women: n = 7; men: n = 11) using wearable Global Positioning System technology and RPE-TRIMP for a total of 681 individual training sessions during a 22-week competition-preparation period. Internal training load was operationalized by RPE-TRIMP, and external training load was operationalized by distance covered in 3 velocity ranges. A linear mixed-effects model with athlete as a random effect was fit to RPE-TRIMP with total distance covered at ≤69.99% (low-velocity running [LVR]), 70% to 84.99% (high-velocity running [HVR]), and 85% to 100% (very-high-velocity running [VHVR]) of individual maximum velocity. Results: Increased running distance in all 3 velocity ranges (LVR, HVR, and VHVR) resulted in a significant (P <.001) increase in RPE-TRIMP. Coefficients (95% CIs) were.10 (.08–.11) for LVR,.23 (.18–.28) for HVR, and.44 (.35–.53) for VHVR. A 50-m increase in running distance covered in the LVR, HVR, and VHVR velocity ranges was associated with increases in RPE-TRIMP of 5, 11.5, and 22 arbitrary units, respectively. Conclusions: Internal training load, calculated as RPE-TRIMP, increased with increases in total distance covered in the LVR, HVR, and VHVR velocity ranges (P <.001). RPE-TRIMP can be a practical solution for monitoring global training-session load in elite sprinters. [ABSTRACT FROM AUTHOR]

Purpose: This cohort study aimed to investigate the relationship between subjective (wellness and internal training load [ITL]) and objective (neuromuscular fatigue) monitoring markers and performance aspects (reception quality [RQ] and attack efficiency [AE]) in professional female volleyball players. Methods: The study was conducted over an 8-week period during the final mesocycle of the competitive phase. A total of 24 training sessions and 10 matches were included in the analysis. Subjective measures of wellness and ITL were assessed, and neuromuscular fatigue was evaluated using countermovement-jump (CMJ) height. RQ and AE were determined based on game statistics. Results: The study found a positive relationship between wellness and RQ, particularly affecting outside hitters and liberos. ITL showed a positive association with AE, primarily impacting outside hitters, opposite hitters, and middle blockers. Additionally, ITL demonstrated a negative correlation with RQ, mainly affecting outside hitters and liberos. CMJ performance was associated with AE, where a decrease in CMJ height was linked to reduced AE. Conclusions: The findings highlight the importance of considering players' wellness scores in training and match strategies for different positions. Careful management of training loads, considering both physical and technical demands, is crucial for optimizing performance outcomes. Monitoring neuromuscular fatigue, as indicated by CMJ performance, is particularly relevant for outside hitters, opposite hitters, and middle blockers involved in attack actions. Coaches, trainers, and sports practitioners can use these insights to develop position-specific training protocols and implement effective strategies for maintaining or improving performance metrics under various stressors. [ABSTRACT FROM AUTHOR]

Purpose: The monitoring of training loads and quantification of physical performance are common practices in youth soccer academies to support coaches in prescribing and programming training for individuals. The interaction between training load and physical performance is unknown during a preseason period in youth soccer players. The current study assessed changes in training load and physical assessments across a 4-week preseason period. The relationship between physical performance and match playing time in youth male soccer players was also investigated. Methods: The training loads of 25 professional youth academy male soccer players were monitored throughout a 4-week preseason period. Assessments of power, agility, speed, and aerobic capacity were undertaken in the first training session. Session ratings of perceived exertion (sRPE) and well-being questionnaires were collected during all training sessions and preseason matches. Playing time during subsequent competitive matches was recorded. Results: T test and 30-m-sprint assessments, conducted on the first day of preseason, were predictors of sRPE throughout preseason (t test χ2/df = 2.895, poor adjustment; 30-m sprint χ2/df = 1.608, good adjustment). YoYo Test performance was related with changes in perceived fatigue (χ2/df = 0.534, very good adjustment). Faster players reported higher values of sRPE, and players with higher aerobic capacity reported higher levels of fatigue across preseason. Well-being, perceived fatigue and soreness, and sRPE decreased across preseason. Greater match durations were related to higher levels of fatigue during preseason (P <.05). Conclusion: The current study highlights the relationship between training load, physical assessments, and playing time. Coaches and practitioners can use physical test data at the start of preseason as an indication of players that report higher sRPE, perceived fatigue, and reduced well-being across preseason, supporting decisions around individualized training prescriptions. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the relationship between items of the Short Recovery and Stress Scale (SRSS) related to physical stress and recovery and the biomarker creatine kinase (CK) in professional handball. Methods: CK and SRSS items (physical performance capability, overall recovery, muscular stress, and overall stress) were assessed in an observational study of 16 adult male professional handball players from a team in the highest German league during the 2019–20 preseason. Their preseason training schedule included several microcycles, each consisting of 3 consecutive days of intense training followed by a rest day. On 5 of these rest days, when players were classified as nonrested, and the 5 immediately following days, when players were classified as rested, players completed the SRSS between 8:00 and 9:00 AM, followed by blood sampling. Correlations between SRSS items were performed using Kendall τ. The relationship between each SRSS item and CK levels over time was examined using a mixed-effects model with a random intercept. Results: CK levels and SRSS stress items were significantly higher and SRSS recovery items were significantly lower in nonrested players. SRSS items were significantly positively or negatively correlated (all items: P <.001) and showed a significant effect indicating lower CK levels in rested players (all items: P ≤.001; η p 2 =.1 −.32). Conclusions: The investigated SRSS items may be a viable option for assessing muscle recovery in adult male professional handball players in a cost-effective and noninvasive manner. They can be used as a single monitoring tool or as part of a multimodal approach. [ABSTRACT FROM AUTHOR]

Recent literature has shown that the provision of feedback can enhance vertical jump performance acutely, as well as chronically when implemented during phases of training. The aim of our study was to investigate the influence of two types of visual feedback on performance and variability of countermovement jump-derived force-time characteristics in a cohort of male and female National Collegiate Athletic Association Division 1 basketball players. Specifically, individual visual feedback (IVF) was compared to a form of social comparison feedback (SCF), and authors hypothesized there to be performance increases and more stable measures in the SCF condition. In line with this hypothesis, findings suggested significantly enhanced performance in the SCF condition for seven out of eight force-time metrics (e.g. jump height and reactive strength index modified). However, given the small between-condition effect sizes, differences between conditions may lack practical significance. Furthermore, findings suggested less between-jump variability in the SCF condition, compared to the IVF condition, making for a more stable assessment. This in particular makes for more reliable measures, for which when studied over time, more subtle changes in performance may be observed. In summary, our findings highlight acutely enhanced vertical jump performance, and more stable measures, when athletes are exposed to an SCF condition, compared to a normal IVF condition. Practitioners are encouraged to consider these findings when planning vertical jump assessments and are discouraged from implementing different types of feedback at random, especially when measuring performance over time. [ABSTRACT FROM AUTHOR]

Swim coaches routinely monitor the performance and performance determining variables of their athletes to optimize training programs in an individual-specific manner with the ultimate aim to swim faster and win races. To interpret the collected data, they require a suitable, and practically useful, conceptual framework, which can be found in the power balance of swimming. For coaches a heuristic model for training and performance optimization based on the power balance has been proposed. We build on this model and illustrate how it can be employed in the training practice using data of an exemplary sub-elite swimmer (700 FINA points), which was collected continuously during two training sessions. Variables that are used in daily swim training practice, such as heart rate (HR), stroke count (SC), stroke rate (SR), and lap time (LT), were measured. By combining external load variables (e.g. LT) and internal load variables (e.g. HR) with technical variables (e.g. SR), the degree to which the swimmer complies with the training program can be determined. The measured values of these variables are presented using a traffic light feedback system indicating the degree of compliance. The traffic light system enables coaches to adjust the program if deemed necessary. It is thus shown how the model and commonly measured variables can assist swim coaches in the design and evaluation of training sessions in their pursuit of personal performance improvement leading to greater athletic success. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to differentiate external and internal training loads during on-snow biathlon training by adding an accelerometer-derived metric. Methods: Eleven adolescent athletes were fitted with a combined heart rate (HR) and accelerometer to be worn during all training sessions. Duration, HR, training impulse (TRIMP), and average net force (A v F N e t ) were used as training variables. All training was divided into either low-intensity training (LIT), or high-intensity training (HIT) based on reported intensity. The training was further categorized as training without any shooting practice (NS) or as a combination of skiing and shooting (COMB). Duration, HR, TRIMP, and A v F N e t were analyzed in a linear mixed model for the different training modalities. Results: All training was similar in duration for LIT and HIT sessions (p =.0521) and NS and COMB sessions (p =.988). TRIMP did not differentiate between LIT or HIT training (p =.350) or for NS compared to COMB (p =.298). While A v F N e t decreased during COMB compared to NS during LIT sessions (p <.001) it remained similar during HIT training (p = 1.00). Conclusion: The study's findings indicated that there were no notable differences in internal training load (TRIMP) when comparing various training intensities and modes. However, the type of training had a significant impact on A v F N e t , especially leading to a decrease during COMB sessions under LIT conditions. Incorporating an external load metric could offer a fresh approach when prescribing and evaluating training, providing deeper insights into the training load. [ABSTRACT FROM AUTHOR]

Context: Physical changes following activity are well documented, but there is limited information about self-reported outcomes around competitive matches. High training volumes and poor recovery could predispose athletes to overuse injury. The purpose of this study was to identify the changes in daily athlete health measures before, during, and after the day of each match in high- and low-volume groups. Design: Prospective cohort. Methods: Fifty-five soccer athletes (age: 19.8 [1.2] y, 26 males, 29 females) provided daily measures of readiness, physical fatigue, mental stress, sleep quality, and soreness intensity match days, days 1 (D01) and 2 (D02) following matches, and standard practice days. Participants were grouped into high volume and low volume, based off the minutes played during the season. Results: Soreness increased, readiness decreased, and fatigue increased on D01 compared with match days (P <.008) in the high-volume group. Between groups, the high-volume group demonstrated higher soreness on D01 and D02, lower readiness on D01 and D02, and lower fatigue on D01, compared with the low-volume group (P <.008). Conclusions: Soccer athletes demonstrate significant changes in self-reported athlete health variables around competitive matches. These changes are similar to physical outcomes, potentially indicating that the athlete health variables may be used to track athlete recovery from competition, potentially limiting the impact of overuse injuries. [ABSTRACT FROM AUTHOR]

Abstract Background This study used metabolic phenotyping to explore the responses of highly-trained cross-country skiers to a standardized exercise test, which was part of the athletes’ routine testing, and determine whether metabolic phenotyping could discriminate specific physiological, performance, and illness characteristics. Methods Twenty-three highly-trained cross-country skiers (10 women and 13 men) participated in this study. Capillary whole-blood samples were collected before (at rest) and 2.5 min after (post-exercise) a roller-ski treadmill test consisting of 5–6 × 4-min submaximal stages followed by a self-paced time trial (~ 3 min) and analyzed using mass spectrometry. Performance level was defined by International Ski Federation distance and sprint rankings. Illness data were collected prospectively for 33 weeks using the Oslo Sports Trauma Research Center Questionnaire on Health Problems. Orthogonal partial least squares-discriminant analyses (OPLS-DA) followed by enrichment analyses were used to identify metabolic phenotypes of athlete groups with specific physiological, performance, and illness characteristics. Results Blood metabolite phenotypes were significantly different after the standardized exercise test compared to rest for metabolites involved in energy, purine, and nucleotide metabolism (all OPLS-DA p

Abstract Background Limited research has investigated the association between training load and performance of basketball players during games. Little is known about how different indicators of player performance are affected by internal and external loads. The purpose of this study was to determine whether external and internal loads influence basketball players’ performance during games. Method This longitudinal study involved 20 professional male basketball players from a single team, classified as first-level athletes by the Chinese Basketball Association. During 34 games, external load was measured as PlayerLoad using micro-sensors, while internal load was assessed using session rating of perceived exertion (sRPE). Player performance was quantified using three metrics: Efficiency, Player Index Rating (PIR), and Plus-Minus (PM). Pearson correlation coefficients were calculated to assess the strength of the relationships between training loads and performance metrics. Linear mixed-effects models were applied to further analyze the influence of internal and external loads on basketball performance. Results Pearson correlation analysis revealed moderate positive correlations between both sRPE and PlayerLoad with Efficiency and PIR. Specifically, sRPE (r = 0.52) and PlayerLoad (r = 0.54) were both significantly correlated with Efficiency. For PIR, sRPE (r = 0.50) and PlayerLoad (r = 0.56) also demonstrated moderate correlations. These correlations were further substantiated by linear mixed-effects models, which showed that sRPE (β = 2.21, p

Purpose: This study aimed to differentiate external and internal training loads during on-snow biathlon training by adding an accelerometer-derived metric. Methods: Eleven adolescent athletes were fitted with a combined heart rate (HR) and accelerometer to be worn during all training sessions. Duration, HR, training impulse (TRIMP), and average net force (AvFNet) were used as training variables. All training was divided into either low-intensity training (LIT), or high-intensity training (HIT) based on reported intensity. The training was further categorized as training without any shooting practice (NS) or as a combination of skiing and shooting (COMB). Duration, HR, TRIMP, and AvFNet were analyzed in a linear mixed model for the different training modalities. Results: All training was similar in duration for LIT and HIT sessions (p = .0521) and NS and COMB sessions (p = .988). TRIMP did not differentiate between LIT or HIT training (p = .350) or for NS compared to COMB (p = .298). While AvFNet decreased during COMB compared to NS during LIT sessions (p < .001) it remained similar during HIT training (p = 1.00). Conclusion: The study's findings indicated that there were no notable differences in internal training load (TRIMP) when comparing various training intensities and modes. However, the type of training had a significant impact on AvFNet, especially leading to a decrease during COMB sessions under LIT conditions. Incorporating an external load metric could offer a fresh approach when prescribing and evaluating training, providing deeper insights into the training load. [ABSTRACT FROM AUTHOR]

Active life monitoring via chemosensitive sensors could hold promise for enhancing athlete monitoring, training optimization, and performance in athletes. The present work investigates a resistive flex sensor (RFS) in the guise of a chemical sensor. Its carbon 'texture' has shown to be sensitive to CO2, O2, and RH changes; moreover, different bending conditions can modulate its sensitivity and selectivity for these gases and vapors. A three-step feasibility study is presented including: design and fabrication of the electronic read-out and control; calibration of the sensors to CO2, O2 and RH; and a morphological study of the material when interacting with the gas and vapor molecules. The 0.1 mm−1 curvature performs best among the tested configurations. It shows a linear response curve for each gas, the ranges of concentrations are adequate, and the sensitivity is good for all gases. The curvature can be modulated during data acquisition to tailor the sensitivity and selectivity for a specific gas. In particular, good results have been obtained with a curvature of 0.1 mm−1. For O2 in the range of 20–70%, the sensor has a sensitivity of 0.7 mV/%. For CO2 in the range of 4–80%, the sensitivity is 3.7 mV/%, and for RH the sensitivity is 33 mV/%. Additionally, a working principle, based on observation via scanning electron microscopy, has been proposed to explain the chemical sensing potential of this sensor. Bending seems to enlarge the cracks present in the RFS coverage; this change accounts for the altered selectivity depending on the sensor's curvature. Further studies are needed to confirm result's reliability and the correctness of the interpretation. [ABSTRACT FROM AUTHOR]

This study aimed to compare the predictive accuracy of absolute and relative external load indices (ELI) across three machine learning models, and predict the rating of perceived exertion (RPE) of elite Gaelic football players using ELI, personal characteristics, wellness scores, and training workloads. ELI and related variables were collected from 49 elite Gaelic football players over three competitive seasons resulting in 1617 observations. ELI included total distance, high speed running distance (≥ 4.72 m · s-1number of accelerations and decelerations (n ± 3 m · s-2), expressed in both absolute and relative terms. Variables related to personal characteristics, wellness scores, and training workloads were also included. Data were analysed using decision tree, random forest (RF), and bootstrap aggregation (BS) models. The RF model had the highest predictive accuracy using absolute and relative ELI only, at 54.3% and 48.3%, respectively. Total and relative distance were the strongest predictors of RPE in the RF model, accounting for 38.8% and 27.9% of the normalised importance. The BS model had the highest accuracy at 67.0% and 65.2% for absolute and relative ELI when performed in conjunction with the related variables, respectively. The current models demonstrate potential to predict RPE and subsequently optimise training load in Gaelic football. [ABSTRACT FROM AUTHOR]

Physical performance in cycling is commonly evaluated with laboratory-based performance markers. However, these markers are not monitored on a regular basis, mainly due to the high costs of testing equipment, invasive sampling and time-intensive protocols. The use of mathematical modeling offers a promising alternative allowing for consistent performance monitoring, identification of influential variables affecting performance, and facilitation of planning, monitoring, and predictive analysis. Wearable technology, such as physiological and biomechanical sensors, can be integrated with mathematical models to enhance the practicality of performance monitoring and enable real-time feedback and personalized training recommendations. In this systematic review, we attempted to provide an overview of the developments in predicting and modeling of performance in cycling and their respective practical applications. The PRISMA framework yielded 52 studies that met the inclusion criteria. The models were discussed according to their modeling goal: characterizing kinetics, alternatives to the gold-standard, training control, observing training effects, predicting competitive performance and optimizing performance. Field-based models and technological advancements were highlighted as solutions to the limitations of gold-standard testing. Due to the lower accuracies of modeling techniques, the gold-standard laboratory-based methods of testing will not be replaced by mathematical models. However, models do form a more practical alternative for regular monitoring and a powerful tool for training and competition optimization. A modeling technique needs to be individualized to the goal and the person and be as simple as possible to allow regular monitoring. Ideally, the technique would work in the field, uses submaximal exercise intensities and integrates technological advancements such as wearable technology and machine learning to increase the practicality even more. [ABSTRACT FROM AUTHOR]

The purpose of this study was to characterize critical speed (CS) models for summarizing high-resolution speed-duration profiles from GPS tracking data obtained from soccer players. GPS data from 15 male NCAA Division I soccer players were collected during practices and games over a 6-week period. Moving averages of the speed data were computed for each file for duration windows spanning 0.1 to 600 seconds at 0.1-second resolution. Speed-duration profiles for each session and for the entire sampling period ("global") were generated for each player by selecting the maximal mean speeds for each duration. Four models were fit to the profiles: the two-parameter CS (CS2) model, the three-parameter CS (CS3) model, the omni-domain speed-duration (OmSD) model, and the five-parameter logistic (5PL) model. The 5PL, CS3, and OmSD models exhibited similar goodness of fits, and all outperformed the CS2 model. Similar CS estimates were obtained for each model, whereas maximum speed (S max) estimates were lower for OmSD compared to the 5PL. Players exhibited a range of parameter values for CS, D ′, and S max. S max and CS estimated from session-specific speed-duration profiles were on average higher for games compared to practices. We conclude that CS models are useful for empirically describing speed-duration profiles and for assessing peak running demands for soccer practices and games. The proposed approach could help coaches design practice activities to better mimic game demands. [ABSTRACT FROM AUTHOR]

This study evaluated internal load (IL) and wellness between consecutive field hockey matches played over a 2-day period across a 7-week season consisting of 12 total matches. Twelve NCAA Division I hockey players' IL was assessed by heart rate (HR) zones (zone 1 = 50–60% HRmax, zone 2 = 60–70% HRmax, zone 3 = 70–80% HRmax, zone 4 = 80–90% HRmax, and zone 5 > 90% HRmax) and HR-derived training impulse. Wellness items (sleep, stress, fatigue, soreness, and total wellness) were obtained to measure the players' subjective responses. Linear mixed models were used to examine the main effects of time (matched pairs of games) and the interaction between match (match 1 vs 2) and week (week 1–6) for IL. For wellness, main effects for time (mid-week, post-match 1, and post-match 2) and the interaction between day (mid-week, post-match 1, and post-match 2) and week (week 1–5) were examined. More time was spent in HR zone 1 in match 2 versus 1 (mean difference (MD) = 4.2 ± 3.0 minutes). Total wellness, fatigue, and soreness were all worse post-match 2 compared to mid-week (MD = 1.8 ± 1.4 AU, MD = 0.4 ± 0.6 AU, and MD = 0.8 ± 0.4 AU, respectively). Our results indicate that evaluation of specific wellness items may help practitioners determine the source of decreased wellness and adjust the weekly training load or recovery strategies based off the results of the changes in IL. [ABSTRACT FROM AUTHOR]

Despite advances in strength and conditioning science, a gap exists in the optimal utilization of training logs for athlete monitoring. Accurate logs serve as a critical interface for player development, offering real-time evaluation and enabling long-term data analysis. This article addresses the reluctance among professionals to transition from traditional paper-based methods to digital platforms, citing this as a hindrance to correlating workout data with performance metrics. It emphasizes the individualized nature of training adaptation and the necessity of advanced technologies and software skills for effective program evaluation. The article also details critical variables to be captured in workout logs, both quantitative and qualitative, and underscores their role in decision-making, workout efficacy, and athlete safety. By embracing digital advancements, professionals can elevate the quality of strength and conditioning programs, ensuring they are executed as designed and achieve desired outcomes. [ABSTRACT FROM AUTHOR]

With innovative portable force plate systems being widely implemented for lower-body neuromuscular performance assessment in an applied sports setting and the existing gap in the scientific literature regarding player performance during in-game competitive scenarios, the purpose of the present study was to compare changes in countermovement vertical jump (CVJ) performance pre-post a simulated 3×3 basketball tournament. Seven current or former members of a 3×3 national basketball team volunteered to participate in the present investigation. Upon completing standardized warm-up procedures, athletes stepped on a uni-axial force plate system sampling at 1,000 Hz and performed three maximal-effort CVJs with no arm swing. Then, the athletes proceeded to play a simulated 3×3 basketball tournament composed of two consecutive games, separated by a 15-min rest interval. Immediately following the completion of the second game, the identical CVJ testing procedures were repeated. Paired sample t-tests were used to examine prepost-tournament differences in nineteen CVJ performance metrics (p < 0.05). The results reveal that force-time metrics during both eccentric and concentric phases of the CVJ remain relatively unchanged pre-post simulated 3×3 basketball tournament. However, multiple force-time metrics within the eccentric phase of the CVJ changed by 12.1%-19.1% (e.g., eccentric peak power and peak velocity, eccentric duration), suggesting that the eccentric phase of CVJ might be responsive to performance stimulus to a greater extent than the concentric phase. Overall, these findings further support the importance of comprehensive CVJ analysis when intending to measure changes in neuromuscular performance. [ABSTRACT FROM AUTHOR]

Background: This study used metabolic phenotyping to explore the responses of highly-trained cross-country skiers to a standardized exercise test, which was part of the athletes' routine testing, and determine whether metabolic phenotyping could discriminate specific physiological, performance, and illness characteristics. Methods: Twenty-three highly-trained cross-country skiers (10 women and 13 men) participated in this study. Capillary whole-blood samples were collected before (at rest) and 2.5 min after (post-exercise) a roller-ski treadmill test consisting of 5–6 × 4-min submaximal stages followed by a self-paced time trial (~ 3 min) and analyzed using mass spectrometry. Performance level was defined by International Ski Federation distance and sprint rankings. Illness data were collected prospectively for 33 weeks using the Oslo Sports Trauma Research Center Questionnaire on Health Problems. Orthogonal partial least squares-discriminant analyses (OPLS-DA) followed by enrichment analyses were used to identify metabolic phenotypes of athlete groups with specific physiological, performance, and illness characteristics. Results: Blood metabolite phenotypes were significantly different after the standardized exercise test compared to rest for metabolites involved in energy, purine, and nucleotide metabolism (all OPLS-DA p < 0.001). Acute changes in the metabolic phenotype from rest to post-exercise could discriminate athletes with: (1) higher vs. lower peak blood lactate concentrations; (2) superior vs. inferior performance levels in sprint skiing, and (3) ≥ 2 vs. ≤ 1 self-reported illness episodes in the 33-week study period (all p < 0.05). The most important metabolites contributing to the distinction of groups according to (1) post-exercise blood lactate concentrations, (2) sprint performance, and (3) illness frequency were: (1) inosine, hypoxanthine, and deoxycholic acid, (2) sorbitol, adenosine monophosphate, and 2-hydroxyleuroylcarnitine, and (3) glucose-6-phosphate, squalene, and deoxycholic acid, respectively. Conclusion: Metabolic phenotyping discriminated between athlete groups with higher vs. lower post-exercise blood lactate concentrations, superior vs. inferior sprint skiing performance, and more vs. less self-reported illnesses. While the biological relevance of the identified biomarkers requires validation in future research, metabolic phenotyping shows promise as a tool for routine monitoring of highly-trained endurance athletes. Key Points: • The standardized exercise test led to alterations in metabolites primarily involved in carbohydrate metabolism and the tricarboxylic acid cycle, purine/pyrimidines, and nucleoside/nucleotides. • Acute changes in metabolic phenotypes could differentiate athletes with higher vs. lower [La-]peak and superior vs. inferior sprint skiers, and between athletes who were susceptible vs. non-susceptible to illness. • Metabolic phenotyping shows promise as a tool for routine monitoring of endurance athletes if cost and turnaround time is improved. [ABSTRACT FROM AUTHOR]

Background: Limited research has investigated the association between training load and performance of basketball players during games. Little is known about how different indicators of player performance are affected by internal and external loads. The purpose of this study was to determine whether external and internal loads influence basketball players' performance during games. Method: This longitudinal study involved 20 professional male basketball players from a single team, classified as first-level athletes by the Chinese Basketball Association. During 34 games, external load was measured as PlayerLoad using micro-sensors, while internal load was assessed using session rating of perceived exertion (sRPE). Player performance was quantified using three metrics: Efficiency, Player Index Rating (PIR), and Plus-Minus (PM). Pearson correlation coefficients were calculated to assess the strength of the relationships between training loads and performance metrics. Linear mixed-effects models were applied to further analyze the influence of internal and external loads on basketball performance. Results: Pearson correlation analysis revealed moderate positive correlations between both sRPE and PlayerLoad with Efficiency and PIR. Specifically, sRPE (r = 0.52) and PlayerLoad (r = 0.54) were both significantly correlated with Efficiency. For PIR, sRPE (r = 0.50) and PlayerLoad (r = 0.56) also demonstrated moderate correlations. These correlations were further substantiated by linear mixed-effects models, which showed that sRPE (β = 2.21, p < 0.001) and PlayerLoad (β = 1.87, p = 0.004) had significant independent effects on Efficiency. Similarly, sRPE (β = 2.15, p < 0.001) and PlayerLoad (β = 2.36, p < 0.001) significantly predicted PIR. Additionally, a significant interaction effect between PlayerLoad and sRPE was found on Plus-Minus (β = -2.49, p < 0.001), indicating that the combination of high physical and psychological loads negatively impacted overall team performance. However, the correlation strengths for Plus-Minus were relatively low (sRPE: r = 0.16; PlayerLoad: r = 0.10). Conclusion: Both external and internal loads positively contribute to performance, the integration of objective (accelerometry) and subjective (sRPE) measures of load provides a comprehensive understanding of the physiological and psychological demands on athletes, contributing to more effective training regimens and performance optimization. [ABSTRACT FROM AUTHOR]

A comprehensive examination of the external and internal workloads in collegiate women's lacrosse athletes has yet to be reported. Thus, the primary purpose of this study was to determine the absolute and relative external and internal training and game workloads of National Collegiate Athletic Association (NCAA) Division II women's lacrosse athletes throughout an entire season. Data from 19 Division II women's lacrosse athletes were analyzed, encompassing each training session and game across an entire competitive season (February-May). External workloads were assessed using a wearable global positioning system, whereas internal workloads were determined through heart rate (HR) variables and session rating of perceived exertion. Game days were associated with significantly (p < 0.05) greater absolute external and internal workloads. However, when comparing workloads relative to session duration, relative workloads between training and games were no longer significant (p > 0.05) for total distance, high-speed running (≥15 km⋅h-1), HR-derived training impulse, or caloric expenditure. Nonetheless, relative sprint distance (>19 km⋅h-1) was significantly lower during games, whereas high-intensity accelerations (>2 m⋅s-2) and decelerations (<-2 m⋅s-2) were significantly greater during training compared with games (p < 0.05). Practical applications of these findings suggest that coaches can better prepare athletes for game day conditions by adjusting training plans to replicate the duration and intensity of games. Overall, this comprehensive examination of internal and external workloads provides valuable data for coaches and practitioners to support performance comparisons, rehabilitation protocols, and workload analyses in collegiate women's lacrosse athletes. [ABSTRACT FROM AUTHOR]

Several youth volleyball tournaments are played across multiple consecutive days with athletes averaging 3–4 matches/day. This study evaluated the differences in workload of female youth volleyball athletes across days and by position during multi-day tournaments. Athletes (n = 22, 16.4 ± 0.4 years) wore an accelerometer during 12 two- and three-day tournaments. Workload was measured via kinetic energy (KE, J/lb), total jumps (TJ), high jumps (HJ, >51 cm), average jump height (cm), and percentage of high stress movements (%) via VERT accelerometers. Data were analyzed across days and by position as an average per day and analyzed via repeated measures analyses of variance. Across days, workload averages ranged 484.8–558.0 J/lb for KE, 27.3–31.2 TJ/match, 37.5–37.9 cm/jump, 5.2–6.5 HJ/match, and 20.1–20.7% high stress movements/match, with no difference (p = 0.300). Setters (49.2 ± 24.3 jumps) jumped more than liberos (13.0 ± 6.8 TJ, p = 0.005), and middles (45.8 ± 4.1 cm) jumped higher than all other positions (setters: 28.8 ± 3.6 cm, outside hitters: 41.3 ± 4.2 cm, and liberos: 27.0 ± 4.1 cm, p = 0.000–0.044). Athletes appeared to perform and recover sufficiently between days of play such that their external load was not affected. The level of competition tends to become more evenly matched as the tournament progresses, thus there may have been less physical demand early in the tournaments due to unequal competition levels compared to the final day of the tournament. [ABSTRACT FROM AUTHOR]

The aim of this study was to quantify the session rating of perceived exertion (sRPE), duration, and training load accrued across typical training weeks undertaken by youth soccer players. Differences between starters, nonstarters, and variations in training load variables were also investigated. Data were collected from 230 elite youth players in 4 age groups (U15, U16, U17, and U19) during 5 competitive seasons. Mixed models were used to describe variation between age groups and compare starters with nonstarters, with season as a fixed covariate effect. Week-to-week variation in training load was expressed as the percentage coefficient of variation. The main findings may be used to highlight a significant effect of age and playing status on training intensity, duration, and internal training load. Weekly training load increased progressively from the U15 to U17, with significant differences between each age group (p < 0.03). Lower mean weekly perceived intensity (sRPE) was noted in U15 when compared with the older age groups (4.2 vs. 4.6-4.9 arbitrary unit for U16 to U19, p < 0.001). Low weekly training load variation was observed across the different phases of the season in each age group, with the preseason exhibiting the greatest variance (3.6-6.2%). Differences in the training load are likely more attributable to changes in training duration rather than sRPE. Control of session duration seems to play an important role when aiming to control load in the academy environment, and practitioners should closely monitor the differences in duration and load being recorded between starters and nonstarters. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine seasonal changes in match demands in a collegiate women's soccer team. Forty-eight NCAA Division III women soccer athletes (age: 19.5 ± 1.2 years; height: 1.67 ± 0.05 m; body mass: 64.8 ± 7.4 kg; fat-free mass: 50.0 ± 4.5 kg; body fat %: 22.6 ± 6.0) were equipped with wearable global positioning systems with inertial sensors and heart rate (HR) monitors during matches throughout the 2019 (n = 22) and 2021 seasons (n = 26). Players were classified by position: flank player (FP; n = 28), center midfielder (CM; n = 11), and center back fielder (CB; n = 9) and as starters (S, n = 17) or reserves (R, n = 31). Variables included HR, training load, total distance, high-speed distance, distance per minute, and weighted distance. Differences in match and practice session demands were analyzed using linear mixed-effects models with season (2 levels; 2019 and 2021) as a fixed factor, with alpha set to p = 0.05. Data across all matches and training sessions were collapsed and presented as mean ± SD for descriptive purposes and then grouped by session type (i.e., match or training) and position. Athletes traveled more distance at high speeds during match play in the 2021 season compared with 2019 (mean difference, 95% confidence intervals [CI]) (200,95% CI: 104,304 km; p < 0.05) but had a lower training load in 2021 compared with 2019 (-50,95% CI: -63, -36; p < 0.05) during match play. For training sessions, mean HR (4, 95% CI: 2, 5 bpm), total distance (0.5, 95% CI: 0.4, 0.7), distance per minute (5.6, 95% CI: 4.5, 6.7 m⋅min-1), high-speed distance (43,95% CI: 43,18,67 m), high accelerations (8.6,95% CI: 5.4,11.8 n), and high accelerations per minute (0.1, 95% CI: 0.1, 0.1 n⋅min-1) were all higher in 2021 compared with 2019 (p < 0.05). As a team, several differences in measures of external workload were found between seasons in both session types (training and matches). Variations in positional demands of match play appear to fluctuate by year. [ABSTRACT FROM AUTHOR]

This investigation examined the effect of cardiovascular function and exercise stress on sleep quality in female soccer players. Twenty-four (n = 24) female soccer players volunteered to be participants over a six-month longitudinal study consisting of six-data collection periods recorded once a month and separated by 30-day intervals. A sub-group analysis examined the association between accumulated exercise stress and sleep quality over a two-month period. Exercise stress was recorded using a heart rate (HR) and GPS monitor (Polar Team Pro. Resting cardiovascular function included; cardiac output, stroke volume, systemic vascular resistance, heart rate variability and blood pressure. Sleep quality and disturbance was examined using the Pittsburgh Sleep Quality Index (PSQI). Mean (± SD) global PSQI scores over six-months was 5.8 ± 2.0 and ranged between 2.0–13.0, classifying participants as poor sleepers. Hypotensive individuals had significantly lower PSQI scores compared to normotensive individuals (Hypo 7.4 ± 2.4 'vs' Normo 5.2 ± 2.1, p < 0.001, ES = 0.95). Significant inverse associations were observed between global PSQI scores and mean arterial blood pressure (r = −0.30, p < 0.01) and both systolic (r = −0.31 ± 0.20, p < 0.01) and diastolic blood pressure (r = −0.23, p < 0.05). PSQI scores were not significantly associated with training load (r = −0.02, p = 0.92) or total distance covered (r = − 0.05, p = 0.79). Low blood pressure was significantly associated with reduced sleep quality in female collegiate soccer players. Furthermore, associations between exercise stress and sleep quality were non-existent. [ABSTRACT FROM AUTHOR]

The editorial discusses the importance of understanding the dose-response relationship to exercise in athletes, emphasizing the need for personalized training programs based on individual physiological responses. The Research Topic in the journal contains four manuscripts that analyze this relationship to enhance athletic development. The studies focus on soccer-specific activities in female collegiate players, off-ice predictors of on-ice performance in youth ice hockey, complex resistance training methods, and the effects of endurance training on muscle oxygen saturation. The findings aim to provide coaches and practitioners with valuable insights to optimize training protocols and foster long-term athlete development. [Extracted from the article]

The physical demands of a single long-distance triathlon (LDT) are sufficient to cause robust physiological perturbations. In this unique case study, an ultraendurance athlete completed 100 LDTs in 100 days (100LDT). Purpose: This study aims to describe and analyze this single athlete's performance, physiological biomarkers, and sleep parameters throughout the 100LDT. Methods: An ultraendurance athlete completed an LDT (2.4-mile swim, 112-mile bike ride, and 26.2-mile marathon) each day for 100 consecutive days. Physical work, physiological biomarkers, and sleep parameters were recorded each night using a wrist-worn photoplethysmographic sensor. Clinical exercise tests were performed before and after the 100LDT. Time-series analysis assessed changes in biomarkers and sleep parameters across the 100LDT, and cross-correlations considered the associations between exercise performance and physiological metrics at varying time lags. Results: The swim and cycling performances varied across the 100LDT, while the run was relatively stable. Resting heart rate, heart-rate variability, oxygen saturation, sleep score, light sleep, sleep efficiency, and sleep duration were all best characterized by cubic models. Additional post hoc subanalyses suggest that the first half of the 100LDT most influenced these dynamics. Conclusions: The 100LDT resulted in nonlinear alterations to physiological metrics. This world record was a unique event but allows valuable insights into the limits of human endurance performance. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate whether sleep quantity and quality of professional hockey players is affected by external training load (TL), their perception of well-being, and contextual factors associated with match participation. Methods: Fifty male athletes were monitored daily during the 28 weeks of the regular season using well-being and sleep surveys. On-ice external TL was monitored using portable inertial measurement units during practices and matches. Linear mixed-effects models were applied to evaluate whether well-being perception (ie, pain, nutrition, stress, and rest) and external TL may affect sleep quality and quantity. Results: High levels of well-being positively affected sleep duration and quality (P <.001), whereas high-intensity TL had a detrimental impact on sleep duration (P =.007). Moreover, away and evening matches had a detrimental effect on sleep quantity and quality (P <.001). Finally, a high match on-ice load per minute had a negative association with sleep quality (P =.04). Conclusions: Findings indicate that well-being and high-intensity trainings can impair sleep duration and quality. In addition, high-intensity match load, away matches, and evening matches can impair postmatch sleep. Therefore, monitoring well-being in conjunction with TL is essential to understand sleep disturbances in athletes. Practitioners should also implement sleep hygiene strategies that facilitate longer time in bed after high-intensity, away, and evening matches to help athletes recover. [ABSTRACT FROM AUTHOR]

Several youth volleyball tournaments are played across multiple consecutive days with athletes averaging 3–4 matches/day. This study evaluated the differences in workload of female youth volleyball athletes across days and by position during multi-day tournaments. Athletes (n = 22, 16.4 ± 0.4 years) wore an accelerometer during 12 two- and three-day tournaments. Workload was measured via kinetic energy (KE, J/lb), total jumps (TJ), high jumps (HJ, >51 cm), average jump height (cm), and percentage of high stress movements (%) via VERT accelerometers. Data were analyzed across days and by position as an average per day and analyzed via repeated measures analyses of variance. Across days, workload averages ranged 484.8–558.0 J/lb for KE, 27.3–31.2 TJ/match, 37.5–37.9 cm/jump, 5.2–6.5 HJ/match, and 20.1–20.7% high stress movements/match, with no difference (p = 0.300). Setters (49.2 ± 24.3 jumps) jumped more than liberos (13.0 ± 6.8 TJ, p = 0.005), and middles (45.8 ± 4.1 cm) jumped higher than all other positions (setters: 28.8 ± 3.6 cm, outside hitters: 41.3 ± 4.2 cm, and liberos: 27.0 ± 4.1 cm, p = 0.000–0.044). Athletes appeared to perform and recover sufficiently between days of play such that their external load was not affected. The level of competition tends to become more evenly matched as the tournament progresses, thus there may have been less physical demand early in the tournaments due to unequal competition levels compared to the final day of the tournament.

Purpose: To investigate the relationship between physical performance tests and on-ice external load from simulated games (scrimmages) in ice hockey. Methods: A total of 14 players completed a physical performance test battery consisting of 30-m sprint test—run and 30-m sprint test—skate (including 10-m split times and maximum speed), countermovement jump, standing long jump, bench press, pull-ups, and trap bar deadlift and participated in 4 scrimmages. External load variables from scrimmages included total distance; peak speed; slow (< 11.0 km/h), moderate (11.0–16.9 km/h), high (17.0–23.9 km/h), and sprint (> 24.0 km/h) speed skating distance; number of sprints; PlayerLoad™; number of high-intensity events (> 2.5 m/s); accelerations; decelerations; and changes of direction. Bayesian pairwise correlation analyses were performed to assess the relationship between physical performance tests and external load performance variables. Results: The results showed strong evidence (Bayes factor > 10) for associations between pull-ups and high-intensity events (τ =.61) and between maximum speed skate and peak speed (τ =.55). There was moderate evidence (Bayes factor >3 to <10) for 6 associations: both maximum speed skate (τ =.44) and countermovement jump (τ =.44) with sprint speed skating distance, countermovement jump with number of sprints (τ =.46), pull-ups with changes of direction (τ =.50), trap bar with peak speed (τ =.45), and body mass with total distance (τ =.49). Conclusion: This study found physical performance tests to be associated with some of the external load variables from scrimmages. Nevertheless, the majority of correlations did not display meaningful associations, possibly being influenced by the selection of physical performance tests. [ABSTRACT FROM AUTHOR]

Monitoring training load is essential for optimizing the performance of athletes, allowing practitioners to assess training programs, monitor athlete progress, and minimize the risk of injury and overtraining. However, there is no universal method for training load monitoring, and the adoption of wearable global positioning system (GPS) and accelerometer technology in team sports has increased the volume of data and, therefore, the number of possible approaches. This survey investigated the usage, applications, and understanding of this technology by team sports practitioners. Seventy-two practitioners involved in team and athlete performance monitoring using GPS and accelerometer technology completed the survey. All respondents reported supporting the use of GPS technology in their sport, with 70.8% feeling that GPS technology is important for success. Results showed that 87.5% of respondents use data from wearable technology to inform training prescription, although only 50% use the data to influence decisions in competition. In addition, results showed that GPS metrics are used more than accelerometer-derived metrics; however, both are used regularly. Discrepancies in accelerometer usage highlighted concerns about practitioners' understanding of accelerometer-derived metrics. This survey gained insight into usage, application, understanding, practitioner needs, and concerns and criticisms surrounding the use of GPS and accelerometer metrics for athlete load monitoring. Such information can be used to improve the implementation of this technology in team sport monitoring and highlight gaps in the literature that will help to design future studies to support practitioner needs. [ABSTRACT FROM AUTHOR]

Background: Velocity-based training (VBT) is commonly used for programming and autoregulation of resistance training. Velocity may also be measured during resistance training to estimate one repetition maximum and monitor fatigue. This study quantifies the validity of Metric VBT, a mobile application that uses camera-vision for measuring barbell range of motion (RoM) and mean velocity during resistance exercises. Methods: Twenty-four participants completed back squat and bench press repetitions across various loads. Five mobile devices were placed at varying angles (0, ±10, and ±20°) perpendicular to the participant. The validity of Metric VBT was assessed in comparison to Vicon motion analysis using precision and recall, Lin's concordance correlation coefficient, and Bland-Altman plots. Proportional bias was assessed using linear regression. Results: Metric VBT accurately detected over 95% of repetitions. It showed moderate to substantial agreement with the Vicon system for measuring RoM in both exercises. The average Limits of Agreement (LoA) for RoM across all camera positions were −5.45 to 4.94 cm for squats and −5.80 to 3.55 cm for bench presses. Metric VBT exhibited poor to moderate agreement with the Vicon system for measuring mean velocity. The average LoA for mean velocity were 0.03 to 0.25 m/s for squats and −5.80 to 3.55 m/s for bench presses. A proportional bias was observed, with bias increasing as repetition velocity increased. Conclusions: Metric VBT's wide LoA for measuring RoM and mean velocity highlights significant accuracy concerns, exceeding acceptable levels for practical use. However, for users prioritizing repetition counts over precise RoM or mean velocity data, the application can still provide useful information for monitoring workout volume. [ABSTRACT FROM AUTHOR]

Balancing of strength programming intensity with sport demands is necessary to avoid excessive workloads that could inhibit performance. To expand previous jump height focused literature, this study evaluated whether countermovement jump (CMJ) movement strategies, including eccentric characteristics, might reveal CMJ execution strategy shifts to achieve similar afternoon CMJ height following a morning resistance training session (RTS). Fifteen collegiate women’s soccer and volleyball athletes (18–24 years, 73.6 ± 8.4 kg, 1.74 ± 0.19 m) participating in an offseason RTS completed five CMJs during two afternoon sessions (48 h apart), one 4–6 h post morning RTS, and one on a rest day. The RTS consisted of 2 sets of 10 repetitions at 70–80% 1RM for the back squat, the front squat, and the forward lunge. Vertical ground reaction forces were recorded from which 13 outcome measures describing elements of the eccentric and concentric CMJ phases were computed. No significant differences in jump height (p = 0.427, d = 0.17) or outcome measures (p = 0.091–0.777, d = −0.07–0.21) between sessions with exception of a significant concentric phase time decrease (p = 0.026, d = 0.23) following the RTS were identified. Given the magnitude of the mean concentric phase time change (0.01 s), the result likely has limited practical meaning. As these results confirm previous CMJ height literature, practitioners have further evidence that a morning RTS does not interfere or enhance afternoon CMJ performance in athletic women. [ABSTRACT FROM AUTHOR]

Beach variants of popular sports like soccer and handball have grown in participation over the last decade. However, the characterization of the workload demands in beach sports remains limited compared to their indoor equivalents. This systematic review aimed to: (1) characterize internal and external loads during beach invasion sports match-play; (2) identify technologies and metrics used for monitoring; (3) compare the demands of indoor sports; and (4) explore differences by competition level, age, sex, and beach sport. Fifteen studies ultimately met the inclusion criteria. The locomotive volumes averaged 929 ± 269 m (average) and 16.5 ± 3.3 km/h (peak) alongside 368 ± 103 accelerations and 8 ± 4 jumps per session. The impacts approached 700 per session. The heart rates reached 166–192 beats per minute (maximal) eliciting 60–95% intensity. The player load was 12.5 ± 2.9 to 125 ± 30 units. Males showed 10–15% higher external but equivalent internal loads versus females. Earlier studies relied solely on a time–motion analysis, while recent works integrate electronic performance and tracking systems, enabling a more holistic quantification. However, substantial metric intensity zone variability persists. Beach sports entail intermittent high-intensity activity with a lower-intensity recovery. Unstable surface likely explains the heightened internal strain despite moderately lower running volumes than indoor sports. The continued integration of technology together with the standardization of workload intensity zones is needed to inform a beach-specific training prescription. [ABSTRACT FROM AUTHOR]

Introduction: Ironman triathletes undergo high workloads during competition preparation which can result in nonfunctional overreaching or overtraining syndrome if not matched with adequate recovery. Purpose: The purpose of this case study was to observe changes in physiological and psychological status over the course of a competitive season in a free-living triathlete. Methods: The subject was a 41-year-old triathlete competing in three 113.1-km events. Over the course of a 40-week period, the participant arrived at the laboratory every 4 weeks and underwent body composition testing via air displacement plethysmography, a blood draw for analysis of various biomarkers, and a treadmill-based lactate threshold test. Workload during training and competitions was monitored via a wearable heart rate-monitoring device. Results: Throughout the season, training volume remained high (12.5 ± 3.4 h/week) and body mass and fat-free mass (FFM) continuously decreased, while biomarkers including cortisol, testosterone, and markers of immunological status exhibited minor changes. Laboratory performance remained relatively consistent, while competition performance continually improved. Following the completion of the competitive period, training volume decreased, FFM remained below baseline levels, free cortisol increased, and both free and total testosterone decreased. Conclusions: Workload and recovery seem to have been properly managed throughout the season, evidenced by minimal fluctuations in endocrine and immunological markers. The reason for changes observed in testosterone, cortisol, and body composition following the last competition is unclear, though it may be attributed to changes in stressors and recovery practices outside of training. It is recommended that athletes follow a structured plan during the transition period into the offseason to ensure recovery of physiological state and to set up a productive offseason. [ABSTRACT FROM AUTHOR]

The strength of the shoulder musculature involved with internal rotation and arm extension plays an important role in the overhead throwing motion for baseball athletes, both for throwing-related performance and injury risk. The maintenance of shoulder strength is a high priority for baseball athletes throughout a season; however, little is known in regards to the expected changes in strength throughout a season. To examine pre-post changes in shoulder strength, lower body power, and body composition among collegiate baseball players after the completion of a summer baseball league season. Amateur baseball players (n = 12; age: 20.9 ± 1.0 years.; height: 181.6 ± 5.6 cm; body mass: 86.4 ± 11.1 kg; BMI: 26.0 ± 2.6 kg/m2) participated in the current study. Pre- and post-competitive season, the participants completed shoulder strength assessments and body composition and countermovement vertical jump (CMJ) tests. An upper-body isometric test (athletic shoulder [ASH] test) was used to evaluate shoulder strength for each arm. Each subject completed maximal isometric contractions for both the throwing and non-throwing arms at four separate angles of abduction (180°, 'I'; 135°, 'Y'; 90°, 'T'; and −180°, 'A') while lying in a prone position. For shoulder strength, the primary dependent variable of interest was a composite measure that represented the average of the forces produced across all four positions of the ASH test (I, Y, T, A). For the ASH test composite measure, there was a trend toward a significant arm-by-time interaction effect (p = 0.08), as shoulder strength decreased by 9.03% for the throwing arm (ES = 0.72; 95% CI = [−0.27, −0.01]), compared to only 2.03% for the non-throwing arm (ES = 0.15; 95% CI = [−0.16, 0.09]), over the course of the season. The main effects of time (p = 0.16) and arm (p = 0.58) were not significant for the ASH test composite measure. There was no relationship between lower body power and throwing arm strength at baseline (r = 0.20, p = 0.56), and only a non-significant weak relationship at post-test (r = 0.28, p = 0.41). Throughout a season, baseball players may experience reductions in shoulder strength of the throwing arm with minimal changes in shoulder strength in the non-throwing arm. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the relationship between external workload exposure and changes in countermovement jump force-time characteristics over the course of an entire basketball season, in a sample of National Collegiate Athletic Association Division I, female, basketball players. Data for 12 players were retrospectively analyzed, with external workload being quantified by means of an exponentially weighted, acute, and chronic workload, as well as an acute:chronic workload ratio derived from an inertial measurement unit--based system worn by athletes for all practices and games during the regular season. Countermovement jumps were performed on a total of 26 test days over the span of the in-season competitive period. To statistically analyze these relationships, and to account for multiple observations of the same athletes in a data set, linear mixed-effects models with athlete identity (ID) intercept as the random effect were used. Study findings suggested that associations between external workload exposure and respective force-time characteristics after controlling for the random effect of athlete ID were dependent on the specific metric or metric subgroup used, as well as the type of workload exposure (e.g., acute vs. chronic). Force-time signatures from the braking phase (e.g., average braking force) seemed to be particularly associated with higher degrees of acute workload exposure, whereas strategy-based metrics such as countermovement depth showed significant associations with chronic workload exposure. Furthermore, model results suggested the importance of analyzing neuromuscular responses to external workload on an individual basis, rather than across an entire team. Findings might help practitioners in their selection process related to metrics of interest in monitoring neuromuscular fatigue and readiness. [ABSTRACT FROM AUTHOR]

In this study, we examined and compared internal and external loads during an official Ultimate Frisbee (UF) competition, focusing on match performance outcomes and playing positions. The research involved 56 UF players from 8 teams competing in mixed-gender championship Thailand. Each team comprised 4 male and 3 female players, and all participants were observed across 4 competitive matches, including the first round, quarterfinals, semifinals, and finals. The heart rate and distance covered in each speed zone were collected using Polar Team Pro™ throughout 4 official matches, After each match, athletes were separated for statistical analysis based on performance (winners vs. losers) and position (handler, cutter, and deeper positions). Data were analyzed using mean, standard deviation, independent t-test, and one-way ANOVA. All tests used the 0.05 level of significance. The results showed that for the winners, the HR (heart rate), % HRmax, distance covered, and number of sprints were higher (P<0.05) than for the losers; in addition, the winners spent more (P<0.05) time at high intensity and very high-intensity levels than the losers, as well as more (P<0.05) time doing highspeed running and sprinting than the losers. Comparing the playing positions in the match, the deeper was higher (P<0.05) than the handler and cutter positions, as well as spending more (P<0.05) time at high intensity, very high intensity, high-speed running and sprinting levels than the handler and cutter positions. The data from this study should be helpful for coaches and athletes for the development of a specific training program to improve the performance of UF players, which is an essential instrument in the modern planning and application of training loads. [ABSTRACT FROM AUTHOR]

Background: High-intensity sprint exercises (HIS) are central to sprinter training and require careful monitoring of athlete muscle fatigue to improve performance and prevent injury. While the countermovement jump (CMJ) may be used to monitor neuromuscular fatigue (NMF), little is known about the specific effects from HIS. The purpose of this study is to investigate the effects of HIS on the CMJ to assess its utility for assessing NMF following HIS. Methods: Ten male collegiate 400 m sprinters completed a 400 m sprint fatigue protocol and underwent five CMJ-testing sessions (baseline, 3 minutes, 10 minutes, 1 hour and 24 hours) over two days. Three CMJ trials, performed on a force plate, were completed each trial, with rating of perceived exertion (RPE) recorded as a subjective fatigue measure. Changes in RPE, CMJ variables, force-time and power-time curves at baseline and post fatigue were assessed. Results: Significant changes were observed in most variables following the fatigue protocol. In particular, concentric mean power remained significantly lower after 24 hours compared to baseline. In addition, the force-time curves exhibited a significant reduction in all conditions following the fatigue protocol. This decline was most pronounced within 50–75%of the concentric phase relative to baseline measurements. Conclusion. Results indicate that the CMJ may be a useful tool for monitoring fatigue in at least 400 m sprinters. These data also indicate that HIS may disproportionately reduce force output in during concentric movement. These insights may improve training prescriptions and injury prevention strategies for sprint athletes. [ABSTRACT FROM AUTHOR]

PurposeThis study aimed to differentiate external and internal training loads during on-snow biathlon training by adding an accelerometer-derived metric.MethodsEleven adolescent athletes were fitted with a combined heart rate (HR) and accelerometer to be worn during all training sessions. Duration, HR, training impulse (TRIMP), and average net force (AvFNet) were used as training variables. All training was divided into either low-intensity training (LIT), or high-intensity training (HIT) based on reported intensity. The training was further categorized as training without any shooting practice (NS) or as a combination of skiing and shooting (COMB). Duration, HR, TRIMP, and AvFNet were analyzed in a linear mixed model for the different training modalities.ResultsAll training was similar in duration for LIT and HIT sessions (p = .0521) and NS and COMB sessions (p = .988). TRIMP did not differentiate between LIT or HIT training (p = .350) or for NS compared to COMB (p = .298). While AvFNet decreased during COMB compared to NS during LIT sessions (p

With innovative portable force plate systems being widely implemented for lower-body neuromuscular performance assessment in an applied sports setting and the existing gap in the scientific literature regarding player performance during in-game competitive scenarios, the purpose of the present study was to compare changes in countermovement vertical jump (CVJ) performance pre-post a simulated 3×3 basketball tournament. Seven current or former members of a 3×3 national basketball team volunteered to participate in the present investigation. Upon completing standardized warm-up procedures, athletes stepped on a uni-axial force plate system sampling at 1,000 Hz and performed three maximal-effort CVJs with no arm swing. Then, the athletes proceeded to play a simulated 3×3 basketball tournament composed of two consecutive games, separated by a 15-min rest interval. Immediately following the completion of the second game, the identical CVJ testing procedures were repeated. Paired sample t-tests were used to examine pre-post-tournament differences in nineteen CVJ performance metrics (p < 0.05). The results reveal that force-time metrics during both eccentric and concentric phases of the CVJ remain relatively unchanged pre-post simulated 3×3 basketball tournament. However, multiple force-time metrics within the eccentric phase of the CVJ changed by 12.1%–19.1% (e.g., eccentric peak power and peak velocity, eccentric duration), suggesting that the eccentric phase of CVJ might be responsive to performance stimulus to a greater extent than the concentric phase. Overall, these findings further support the importance of comprehensive CVJ analysis when intending to measure changes in neuromuscular performance.

Purpose: The aim of this study was to identify the relationships between continuously measured internal and external load variables during volleyball competition. Methods: A total of 8 male elite volleyball athletes (Belgian Liga A and Liga B) were monitored during official competition matches. In total, 63 individual measurements are included in this study. The authors used heart-rate (HR) data as internal load and accelerometer-based activity as external load. Data were recorded at a sampling frequency of 1 Hz using wearable technology during official competition. Workload during continuous game play and individual jumps performed while serving and spiking (selected by means of video analysis) were studied using correlation analysis and dynamic time-series modeling. Results: Significant linear correlations were observed between peak acceleration and maximal HR of individual serves (ρ =.62; P = 1.6e−5) and spikes (ρ =.49; P = 1.2e−3) that were performed during the warm-up. These same actions performed during the match did not show significant correlations. The correlation between the mean HR and mean activity throughout the entire match was also found to be significant (ρ =.67; P = 2.0e−9). With respect to the time-series models, the mean value for the goodness of fit ( R T 2 ) between HR and activity was equal to.83 and.67 for the individual actions and the entire matches, respectively. Conclusions: The results show that there are strong relationships between internal and external load during volleyball competition. Second-order transfer function models are capable of explaining the main dynamics of HR (internal load) in response to accelerometer-based activity (external load). Time-series analysis of continuously measured workload is proposed for use in practice. [ABSTRACT FROM AUTHOR]

Introduction: The parasympathetically derived marker of heart rate variability, root mean square of successive R-R differences (RMSSD), and the daily fluctuations as measured by the coefficient of variation (RMSSDCV) may be useful for tracking training adaptations in athletic populations. These vagally derived markers of heart rate variability may be especially pertinent when simultaneously considering a female athlete's menstrual cycle. Purpose: The purpose of this study was to observe the perturbations in RMSSDCV, while considering RMSSD, across a season in the presence and absence of menses with training load in female collegiate rowers. Methods: Thirty-six (20 [1] y, 25.6 [3.4] kg·m−2) National Collegiate Athletic Association Division I female rowers were monitored for 18 consecutive weeks across a full season. Seated, ultrashortened RMSSD measurements were obtained by the rowers on at least 3 mornings per week using a smartphone photoplethysmography device. Following the RMSSD measurement, athletes indicated the presence or absence of menstruation within the application. Individual meters rowed that week and sessions rate of perceived exertion were obtained to quantify training load. Results: Longitudinal mixed-effects modeling demonstrated a significant effect of menses and time, while also considering RMSSD, such that those who were on their period had a significantly greater RMSSDCV than those who were not (11.2% vs 7.5%, respectively; P <.001). These changes were independent of meters rowed, sessions rate of perceived exertion, body mass index, birth-control use, and years of rowing experience, which were all nonsignificant predictors of RMSSDCgV (P >.05). Conclusion: The presence of menses appears to significantly impact RMSSDCV when also considering RMSSD, which may allow coaches to consider individualized training plans accordingly. [ABSTRACT FROM AUTHOR]

Beach sports, such as handball, volleyball, and soccer, involve dynamic actions, primarily jumps. Nonetheless, there is a need for more established measurement devices that are both valid and feasible in accurately evaluating jumping performance on sand surfaces. This study aims to assess the reliability and concurrent validity of MyJump2 and an inertial measurement unit (VERT) for quantifying countermovement jump performance on the sand. Twenty-one subjects performed 5 countermovement jumps on the sand. Jumping height was measured simultaneously byaforce plate, VERT, and MyJump2. The VERT and MyJump2 reliability measures were evaluated using the intraclass correlation coefficients (ICC) for both absolute agreement (ICC2,1) and consistency (ICC3.1). The day-to-day reliability of both devices and the interrater and intrarater reliability of the MyJump2 were assessed. The concurrent validity of the VERT and MyJump2 was assessed using ICCs2.1, 3.1 and Bland-Altman plots. A near-perfect agreement was seen for intrarater (ICC = 0.98) and interrater (ICC = 0.98) reliability of the MyJump2. Moreover, a near-perfect agreement was also observed when comparing the MyJump2 with the force plate (ICC 5 0.92), with a mean bias of -2.31 cm. The VERT device only demonstrated a moderate agreement (ICC = 0.55) with a mean bias of 6.31 cm compared with the force plate, despite showing good day-to-day reliability (ICC = 0.79). The study's results indicate that MyJump2 is valid and reliable for assessing jump heights on sand surfaces, whereas VERT cannot be recommended. [ABSTRACT FROM AUTHOR]

The purpose was to evaluate reliability of measurements during drop jump (DJ) and magnitude of differences in vertical jump height (VJH) when calculated using two variables: time-in-the-air and center-of-mass velocity. Thirty-seven handball players performed three single-leg and double-leg DJs on a portable force plate during two sessions. Sixteen outcome measures and four sets of reliability metrics, including intraclass correlation coefficients (ICCs), were estimated. All outcome measures, except vertical time-to-stabilization, yielded high (0.70–0.89) to very high (0.90–0.96) interday and intraday ICCs for the single-leg and double-leg DJ tests. These results indicated that the single-leg and double-leg DJ tests can be considered reliable for short-term and long-term monitoring of collegiate handball players of both sexes. In addition, the single-leg DJ VJH calculated using these two variables differed in magnitude (mean difference in test measurements: 0.64 cm, p <.001, effect size: 0.165). Therefore, we recommend using the same method to calculate single-leg VJH for long-term monitoring. [ABSTRACT FROM AUTHOR]

This study evaluated the differences in training and match volume per set by season phase in female high school volleyball. Twelve athletes wore a device to measure total jumps (TJ) and high jumps (HJ), movements per minute (MPM), kinetic energy expended, and stress percent throughout the season phases: preseason, tournament, and district. In matches, athletes jumped less and had lower MPM in preseason (4.4 ± 2.3 TJ/set, 1.9 ± 0.5 MPM/set) compared with tournament (13.2 ± 8.1 TJ/set, 6.4 ± 1.7 MPM/set) and district (16.5 ± 9.9 TJ/set, 6.7 ± 1.8 MPM/set; p ≤.001 for all) phases. District registered more HJ/set (2.6 ± 2.2 HJ/set) than preseason (0.7 ± 0.7 HJ/set, p =.007) and tournament phases (292 ± 172 J/lb/set, p <.001), and more kinetic energy expended/set (488 ± 174 J/lb/set) than preseason (201 ± 94 J/lb/set, p =.001). The highest training volume occurred during preseason with more TJ (preseason: 70.9 ± 26.0; tournament: 44.3 ± 19.3, p <.001; district: 34.7 ± 3.4, p =.004) and kinetic energy expended (preseason: 1,645 ± 547 J/lb; tournament: 980 ± 506 J/lb, p =.018; district: 1,108 ± 362, p =.016). Preseason training had higher stress percent (16.6 ± 3.0%) than tournament (19.4 ± 3.7%, p =.004) and more HJ (7.7 ± 6.3%) than district (3.1 ± 2.9%, p =.012). Match volume was unbalanced across the season phases, with preseason showing the lowest volume and district having the highest volume. This was counterbalanced with a higher training volume during the preseason compared with the other phases. [ABSTRACT FROM AUTHOR]

Cormier, P, Meylan, C, Agar-Newman, D, Geneau, D, Epp-Stobbe, A, Lenetsky, S, and Klimstra, M. A systematic review and metaanalysis of wearable satellite system technology for linear sprint profiling: technological innovations and practical applications. J Strength Cond Res 38(2): 405-418, 2024--An emerging and promising practice is the use of global navigation satellite system (GNSS) technology to profile team-sports athletes in training and competition. Therefore, the purpose of this narrative systematic review with meta-analysis was to evaluate the literature regarding satellite system sensor usage for sprint modeling and to consolidate the findings to evaluate its validity and reliability. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, an electronic search of the databases, PubMed and SPORTDiscus (EBSCO), was conducted. Concurrent validity and reliability studies were considered, and 16 studies were retained for the review from the initial 1,485 studies identified. The effects on outcomes were expressed as standardized mean differences (SMDs, Cohen's d) for each outcome (i.e., maximal sprint speed [MSS], the acceleration constant [t], maximal theoretical velocity [V0], relative force [F0], and relative power [Pmax]). Effect magnitudes represented the SMD between GNSS-derived and criterion-derived (i.e., radar and laser) and resulted in the following estimates: small for MSS (d 5 0.22, 95% CI 0.01 to 0.42), t (d520.18, 95% CI 20.60 to 0.23), V0 (d 5 0.14, 95% CI 20.08 to 0.36), relative F0 (d 5 0.15, 95% CI 20.25 to 0.55), and relative Pmax (d 5 0.21, 95% CI 20.16 to 0.58). No publication bias was identified in meta-analyzed studies and moderator analysis revealed that several factors (sampling rate and sensor manufacturer) influenced the results. Heterogeneity between studies was considered moderate to high. This highlighted the differences between studies in sensor technology differences (i.e., sampling rate, sensor fusion, and satellite network acquisition), processing techniques, criterion technology used, sprint protocols, outcome reporting, and athlete characteristics. These findings may be useful in guiding improvements in sprint modeling using GNSS technology and enable more direct comparisons in future research. Implementation of all-out linear sprint efforts with GNSS technology can be integrated into sport-specific sessions for sprint modeling when robust and consistent data processing protocols are performed, which has important implications for fatigue monitoring, program design, systematic testing, and rehabilitation in individual and team sports. [ABSTRACT FROM AUTHOR]