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This study explored the influence of different take-off thresholds on the reliability and magnitude of countermovement jump (CMJ) performance variables. Twenty-three men were tested on two separate sessions. CMJ performance variables were obtained against three external loads (0.5-30-60 kg) using three take-off thresholds: 10 N (arbitrary value of 10 N), 5SD (mean value plus 5 standard deviations of the vertical force recorded during the flight phase), and PRF (peak difference between the vertical force trace and 0 N during the flight phase). No significant differences in reliability were observed between the three thresholds (CV and ICC values of one threshold were within 95% CI of the other thresholds). The magnitude of the variables generally differed between the 10 N threshold and the 5SD and PRF thresholds (P < 0.05), but not between the 5SD and PRF thresholds (P > 0.05). These results demonstrate that the take-off threshold influences the magnitude of CMJ performance variables but not their reliability.

An a-posteriori multicentre reliability study was conducted to compare the reliability and magnitude of the maximum power (P[subscript max]) and optimal velocity (V[subscript opt]) between the force-power-velocity relationships during the leg cycle-ergometer and bench press throw exercises. The force-power-velocity relationships were determined in two separate sessions considering the values of force, velocity, and power collected under multiple loads. The force-velocity relationship was also determined from the force and velocity values collected under only the two most distant loads. Reliability of all regression models was high for P[subscript max] and V[subscript opt] during the leg cycle-ergometer (CV[subscript range]: 1.73-2.98%) and for P[subscript max] during the bench press throw (CV[subscript range]: 4.47-4.73%), while the reliability was acceptable for V[subscript opt] during the bench press throw (CV[subscript range]: 6.52-7.34%). Significant differences between the force-power-velocity relationships were observed for both P[subscript max] and V[subscript opt] (P < 0.001). All regression models can be confidently used to determine P[subscript max] and V[subscript opt], but these should not be used interchangeably.

This study aimed to explore the relationship between the inter-limb differences in unilateral countermovement (CMJ) height and the inter-limb differences in bilateral CMJ force production, and to elucidate whether the self-reported preferred leg contributes more to force production than the non-preferred leg. Twenty-three senior basketball players performed in a single session eight unilateral CMJs (four with each leg) and four bilateral CMJs. Impulse, peak force, mean force were recorded during the bilateral CMJ, and jump height during the unilateral CMJ. Small correlations were observed between the inter-limb differences in unilateral CMJ height and the inter-limb asymmetries in bilateral CMJ impulse, peak force, and mean force (p ≥ 0.171; r≤-0.142). The self-reported preferred leg revealed a higher performance in 7 out of 23 participants (Kappa = −0.20) for the unilateral CMJ height, 7 out of 23 participants (Kappa = −0.11) for the bilateral CMJ impulse, 6 out of 23 participants (Kappa = −0.36) for the bilateral CMJ peak force, and 8 out of 23 participants (Kappa = −0.34) for the bilateral CMJ mean force. These results highlight that the asymmetries detected during bilateral CMJs cannot be extrapolated to unilateral CMJs, and that the preferred leg generally contributes less to force production than the non-preferred leg during both bilateral and unilateral CMJs. [ABSTRACT FROM AUTHOR]

This study investigated how equipment and sex affect the prediction accuracy of the maximum number of repetitions performed to failure (RTF) using the fastest mean velocity of the set (MVfastest). Sixteen men and twelve women completed four sessions (two using free-weight equipment and two sessions using the Smith machine). Each session involved three sets of repetitions to failure against the 65%, 75%, and 85% of the one-repetition maximum, interspersed by 10-min of rest. The goodness-of-fit of the individualized RTF-MVfastest relationships was comparable between both equipment types and sexes (P ≥0.510). Moreover, there were not significant differences in the MVfastest associated with RTF between equipment types (P ≥0.258). However, the MVfastest associated with RTF was higher for men than for women in repetitions 6 to 15 (P ≤0.043; ES≥0.69). In addition, the absolute errors when predicting RTF showed no significant differences between equipment types and loads (P <0.444). Specifically, these RTF estimates were within an acceptable range for men (<2 repetitions), but not for women (≥2 repetitions) (main effect of sex: P ≤0.018; ES≥0.58). These findings suggest that individualized RTF-MVfastest equations estimate the RTF with an acceptable precision in men during bench press exercises in both equipment types but exhibit lower precision for women. [ABSTRACT FROM AUTHOR]

Background: Physical testing is crucial for athlete monitoring, talent identification, optimizing training, and tailoring programs to enhance game-performance in elite competitions. Hypothesis: Load-velocity (L-V) relationship variables discriminate between elite and junior volleyball players, correlate with volleyball-specific performance, and are generalizable across lower- and upper-body exercises. Study Design: Cross-sectional study. Level of Evidence: Level 3. Methods: A total of 9 elite and 11 junior volleyball players were assessed for the L-V relationship (load-axis intercept [ L 0], velocity-axis intercept [ v 0], and area under the L-V relationship line [ A line]) during the countermovement jump (CMJ) and bench press throw (BPT) exercises. Block and spike jump height, as well as standing and jumping spike speed were assessed 24 hours later. Results: Elite players presented greater magnitude in the L-V variables (P ≤ 0.03; effect size [ES] ≥ 1.06) and higher volleyball-specific performance (P ≤ 0.03; ES ≥ 1.09) than juniors (except for CMJ v 0 and A line). The L-V relationship variables were significantly associated with the block and spike jump height and jumping spike speed only in elite players (r ≥ 0.703 and P ≤ 0.04 in 11 out of 18 correlations). No significant associations were observed between CMJ and BPT for any L-V relationship variable (r ≤ 581; P ≥ 0.08, except for A line in junior players). Conclusion: The L-V relationship is a practical procedure to assess volleyball players' maximal mechanical capacities, which are associated with volleyball-specific performance in elite players. However, these data should not be used interchangeably between playing standards or exercises. Clinical Relevance: This information might help strength and conditioning coaches to prescribe more effective training programs that focus on developing the specific physical capacities necessary for players to potentially advance to elite status. [ABSTRACT FROM AUTHOR]

A military-specific reaction time (RT) test was developed to explore its reliability and sensitivity to discriminate between military personnel and sport science students. Fifteen male professional Spanish soldiers and 16 male sport science students completed two RT test modalities: military-specific and nonspecific RT tests. For each RT test modality, both the Simple (i.e., one stimulus, one response) and the Go, No-Go RT (i.e., true, and false stimuli, one response) were tested. The military-specific RT test consisted of a video presented through virtual reality glasses of a forest environment in which soldiers would appear from behind different bushes (stimuli) and the response consisted of pressing the button of a gun-shaped mouse (when they saw a soldier pointing a rifle at them). Both Simple and Go, No-Go RT reached acceptable reliability in both populations (coefficient of variation ≤ 9.64%). Military personnel presented a lower RT than sport science students during the military-specific RT test (p ≤ .001), while no differences were obtained during the nonspecific RT test. RT values were not significantly correlated between the military-specific and nonspecific RT tests (r ≤ .02). These findings collectively suggest that the novel military-specific RT test is an ecologically valid alternative to evaluate the information processing abilities of military personnel. [ABSTRACT FROM AUTHOR]

This document discusses the use of wearable and portable devices in sport biomechanics and training science. It highlights the limitations of traditional laboratory testing and the benefits of using wearable devices for more ecologically valid assessments. The document features twelve original articles and a systematic review that cover various topics such as biomechanical changes in running shoes, metabolic power and energy cost in sprinting, assessment of torque-velocity profile in cycling, motor development and training, reliability of wearable systems, effects of pressurization modes on muscle activation, real-time monitoring in fencing, thermoregulation in athletes, and the discriminatory power of physical tests. The document concludes that wearable devices offer valuable insights into sports biomechanics and training science, particularly for real-time monitoring and biofeedback. [Extracted from the article]

This study aims to determine the variability of the components of fitness along the menstrual cycle (MC) of physically active eumenorrheic women. Fifteen subjects were monitored along two consecutive MCs through the calendar-based counting method in combination with a urine luteinizing hormone surge kit. Subjects were tested at the early follicular phase (EFP), pre-ovulatory or late follicular phase (LFP), and post-ovulatory or mid-luteal phase (MLP). In each session, the back squat one-repetition maximum (1-RM), maximum fat oxidation (MFO), maximum oxygen uptake (VO2max) and acute recovery capacity were determined. The results revealed a wide variability among components of fitness and a low to high variability among subjects (acute recovery: 3.6% [range 1.5 to 9.5%]; back squat 1-RM: 6.1% [range 2.2 to 11%]; VO2max : 6.6% [range 1.1 to 15%]; MFO: 23% [range 4.6 to 35%]). Despite the individual nature, considering the number and magnitude of the responses in each MC phase, VO2max and acute recovery capacity tended to be enhanced at the LFP, the MFO at the MLP, and the back squat 1-RM remained stable along the MC. Thus, practitioners are aware of which components are susceptible to change along the MC phase, but an individual monitoring is recommended. [ABSTRACT FROM AUTHOR]

Objective: To explore (1) the goodness of fit of generalized and individualized relationships between the maximum number of repetitions performed to failure (RTF) and the fastest mean velocity and peak velocity of the sets (RTF–velocity relationships), (2) the between-sessions reliability of mean velocity and peak velocity values associated with different RTFs, and (3) whether the errors in the prediction of the RTF under fatigued and nonfatigued conditions differ between generalized and individualized RTF–velocity relationships. Methods: Twenty-three sport-science students performed 4 testing sessions with the prone bench pull exercise in a Smith machine: a 1-repetition-maximum [1RM] session, 2 identical sessions consisting of singles sets of RTF against 4 randomized loads (60%–70%–80%–90%1RM), and 1 session consisting of 4 sets of RTF against the 75%1RM. Results: Individualized RTF–velocity relationships presented a higher goodness of fit (r2 =.96–.97 vs.67–.70) and accuracy (absolute errors = 2.1–2.9 repetitions vs 2.8–4.3 repetitions) in the prediction of the RTF than generalized RTF–velocity relationships. The reliability of the velocity values associated with different RTFs was generally high (average within-subject coefficient of variation = 4.01% for mean velocity and 3.98% for peak velocity). The error in the prediction of the RTF increased by ~1 repetition under fatigue (ie, set 1 vs sets 2–4). Conclusions: Individualized RTF–velocity relationships can be used with acceptable precision and reliability to prescribe the loads associated with a given RTF during the match a specific XRM during the prone bench pull exercise, but a lower accuracy is expected in a fatigued state. [ABSTRACT FROM AUTHOR]

This study aimed to determine the influence of the testing environment (track vs. treadmill), time trial order (long-short vs. short-long), and timing (within-session vs. between-sessions) on the critical power (CP) and work over CP (W´), using the power metric in runners. Fifteen highly trained athletes performed three test sessions composed of two time trials of 9- and 3-min, separated by a 30-min rest period. One session was performed on a track, and two sessions on a treadmill, alternating the order of the time trials. The CP and W´ values determined on the track were significantly greater and lower than on the treadmill, respectively (p<0.001; CP≥89 W; W´≥3.7 kJ). Their degree of agreement was low (SEE CP>5%; W´>10%) and therefore was not interchangeable. There were no performance differences in the timing of the time trials (p=0.320). Lastly, performing the 9-min trial first resulted in a greater power output compared to when executed last (p<0.001; 4.9 W), although this resulted in similar CP and W´ values (Bias<5 and 10%, respectively). In conclusion, it is feasible to test CP and W´ in a single testing session, irrespective of the time trial order, although not interchangeably between track and treadmill. [ABSTRACT FROM AUTHOR]

This study aimed to compare the acute effect of four back squat velocity-based training (VBT) protocols in terms of intensity (60% vs. 80% of the one repetition maximum [1RM]) and volume (10% vs. 30% threshold for velocity loss in the set) on the maximal aerobic speed (MAS) estimated from a running track test (RTT) in recreationally trained young adult men and women. Twenty participants (eleven men and nine women) undertook five randomized protocols in separate occasions: (i) RTT alone (control condition); (ii) VBT with 60% 1RM and a 10% velocity loss followed by RTT (VBT60–10 + RTT); (iii) VBT with 60% 1RM and a 30% velocity loss followed by RTT (VBT60–30 + RTT); (iv) VBT with 80% 1RM and 10% velocity loss followed by RTT (VBT80–10 + RTT); (v) VBT with 80% 1RM and 30% velocity loss followed by RTT (VBT80–30 + RTT). All VBT protocols involved three sets with three minutes of rest. The MAS was higher for RTT (control) than VBT60–30 + RTT (p < 0.001; Δ = 3.8%), VBT60–10 + RTT (p = 0.006; Δ = 2.8%), VBT80–10 + RTT (p = 0.008; Δ = 2.7%), and VBT80–30 + RTT (p = 0.019; Δ = 1.9%). No protocol × sex interaction was noted (p = 0.422). Therefore, regardless of sex, MAS is acutely impaired after VBT, especially if the training sets are performed with a low relative load and a high velocity loss threshold. [ABSTRACT FROM AUTHOR]

This study examined the impact of different inter-repetition rest (IRR) configurations (zero seconds [IRR0], three seconds [IRR3], and self-selected less than five seconds [SSIRR]) on estimating the number of repetitions (Nrep) and the percentage of completed repetitions relative to the maximum number of repetitions possible to failure (%rep) after reaching 10%, 20%, and 30% velocity loss thresholds (VLT). Eighteen men completed three sessions, each with a different IRR configuration, separated by 48–72 hours. Single sets of repetitions to momentary muscular failure were performed against 65%, 75%, and 85% of the one-repetition maximum during free-weight back squat and bench press exercises. No significant differences were reported between IRR configurations for the Nrep (P ≥0.089) and %rep (P ≥0.061), except for %rep after reaching the 20–30%VLT against 65%1RM and the 10–20%VLT against 75%1RM in the bench press exercise (P ≤0.048). Additionally, both Nrep and %rep exhibited high interindividual variability (between-subject CV=14–79%) across the different IRR configurations. The individual %rep-%VLT relationships were slightly stronger than the general %rep-%VLT relationships (median R2 =0.914–0.971 vs. 0.698–0.900). Overall, regardless of the IRR configuration, this novel velocity-based approach does not guarantee the same effort levels across subjects in the free-weight back squat and bench press sets. [ABSTRACT FROM AUTHOR]

The aims of this study were (i) to estimate the functional threshold power (FTP) and critical power (CP) from single shorter time trials (TTs) (i. e. 10, 20 and 30 minutes) and (ii) to assess their location in the power-duration curve. Fifteen highly trained athletes randomly performed ten TTs (i. e. 1, 2, 3, 4, 5, 10, 20, 30, 50 and 60 minutes). FTP was determined as the mean power output developed in the 60-min TT, while CP was estimated in the running power meter platform according to the manufacturer's recommendations. The linear regression analysis revealed an acceptable FTP estimate for the 10, 20 and 30-min TTs (SEE≤12.27 W) corresponding to a correction factor of 85, 90 and 95%, respectively. An acceptable CP estimate was only observed for the 20-min TT (SEE=6.67 W) corresponding to a correction factor of 95%. The CP was located at the 30-min power output (1.0 [–5.1 to 7.1] W), which was over FTP (14 [7.0 to 21] W). Therefore, athletes and practitioners concerned with determining FTP and CP through a feasible testing protocol are encouraged to perform a 20-min TT and apply a correction factor of 90 and 95%, respectively. [ABSTRACT FROM AUTHOR]

Ruiz-Alias, SA, Nncupil-Andrade, AA, Pe' rez-Castilla, A, and Garc'ıa-Pinillos, F. Can we predict long-duration running power output? Validity of the critical power, power law, and logarithmic models. J Strength Cond Res 38(2): 306-310, 2024--Predicting long-distance running performance has always been a challenge for athletes and practitioners. To ease this task, different empirical models have been proposed to model the drop of the running work rate with the increase of time. Therefore, this study aims to determine the validity of different models (i.e., CP, power law, and Peronnet) to predict long-duration running power output (i.e., 30 and 60 minutes). In a 4-week training period, 15 highly trained athletes performed 7-time trials (i.e., 3, 4, 5, 10, 20, 30, and 60 minutes) in a randomized order. Then, their power-duration curves (PDCs) were defined through the work-time critical power model (CPwork), power-1/time (CP1/time), 2-parameter hyperbolic (CP2hyp), 3-parameter hyperbolic (CP3hyp), the undisclosed Stryd (CPstryd), and Golden Cheetah (CPcheetah) proprietary models, and the power law and Peronnet models using the 3 to 20 minutes time trials. These ones were extrapolated to the 30- and 60-minute power output and compared with the actual performance. The CP2hyp, CP3hyp, CPstryd, and CPcheetah provided valid 30- and 60-minute power output estimations (#2.6%). The CPwork and CP1/time presented a large predicting error for 30 minutes ($4.4%), which increased for 60 minutes ($8.1%). The power law and Peronnet models progressively increased their predicting error at the longest duration (30 minutes: #21.6%; 60 minutes: #2 6.6%), which was conditioned by the endurance capability of the athletes. Therefore, athletes and practitioners are encouraged to applicate the aforementioned valid models to their PDC to estimate the 30-minute and 60-minute power output. [ABSTRACT FROM AUTHOR]

The field of sports biomechanics has experienced significant growth due to advancements in technology. These advancements have allowed for precise motion measurement and practical evaluations of inertial forces in human movements. This Special Issue of Applied Sciences focuses on optimizing athletic performance and preventing injuries through the use of data analysis and processing techniques. The issue includes eleven original articles, a scope review, and a systematic review and meta-analysis. The articles cover a range of topics, including the relationship between mechanical parameters and change-of-direction performance in soccer players, the effects of different types of footwear on running performance, and the impact of golf club types on posture and swing power. Overall, this Special Issue provides valuable insights for researchers, athletes, and coaches in the field of sports biomechanics. [Extracted from the article]

This study aimed to explore the acute effect of 4 velocity-based resistance training (VBT) protocols on 2000-m rowing ergometer (RE2000) time trial, as well as the behavior of the maximal neuromuscular capacities when RE2000 is performed alone or preceded by VBT protocols in the same session. Fifteen male competitive rowers (15-22 years) undertook 5 randomized protocols in separate occasions: (a) RE2000 alone (control condition); (b) VBT against 60% of 1 repetitionmaximum (1RM) with a velocity loss in the set of 10% followed by RE2000 (VBT60-10 + RE2000); (c) VBT against 60% 1RM with a velocity loss in the set of 30% followed by RE2000 (VBT60-30 + RE2000); (d) VBT against 80% 1RM with a velocity loss in the set of 10% followed by RE2000 (VBT80-10 + RE2000); (e) VBT against 80% 1RM with a velocity loss in the set of 30% followed by RE2000 (VBT80-30+ RE2000). The load-velocity relationship (load-axis intercept [L0], velocity-axis intercept [v0], and area under the load-velocity relationship line [Aline]) was used to evaluate the maximal neuromuscular capacities during the prone bench pull exercise before and after each protocol. The time trial was significantly longer for VBT60-30 + RE2000 and VBT80-30 + RE2000 than for RE2000, VBT60-10 + RE2000 and VBT80-10 + RE2000 (all p, 0.001; ES 5 0.10-0.15). L0 and Aline were significantly reduced after all protocols (p, 0.001; ES 5 0.10-0.13), with Aline reduction more accentuated for VBT60-10 + RE2000, VBT60-30 + RE2000, VBT80-30 + RE2000, and RE2000 (all p 5 0.001; ES 5 0.11-0.18) than for VBT80-10 + RE2000 (p 5 0.065; ES 5 0.05). Therefore, VBT protocols with greater velocity loss in the set (30% vs. 10%) negatively affected subsequent rowing ergometer performance, in line with impairment in Aline pulling performance. [ABSTRACT FROM AUTHOR]

This study aims to compare the effect of the Nike ZoomX Dragonfly track spikes and the Nike ZoomX VaporflyNext% 2 marathon shoes on the fatigue manifestations present over and after a long-distance track training session. Thirteen highly trained athletes completed two training sessions (i. e., 9- and 3-minute time trials with complete recovery) with the aforementioned footwear models. The pace, ground contact time, and stride length were measured over the time trials, and maximal countermovement jumps were performed previously and after the training session. The results revealed that, although there was no significant interaction in the pace distribution (p≥0.072), athletes tend to be only able to increase the pace at the last lap with the marathon shoes (5.4 meters [−3.7 to 14.5 meters]) meanwhile with the track spikes it further decreased (−3.1 meters [−9.8 to 3.6 meters]). A reduced ground contact time over the session (p=0.025) and a tendency toward increasing stride length (p=0.09) in the last time trial were observed. The significant interaction on the countermovement jump height (p=0.023; Track spikes: −5.60%; Marathon shoes: 0.61%) also indicates that footwear influences the resulted allostatic load. [ABSTRACT FROM AUTHOR]

Ruiz-Alias, SA, Pe' rez-Castilla, A, Soto-Hermoso, VM, and Garc'ıa-Pinillos, F. Influence of the world athletics stack height regulation on track running performance. J Strength Cond Res 37(11): 2260-2266, 2023--A new footwear regulation based on limiting the stack height (i.e., amount of material between the feet and the ground) has been established byWorld Athletics to ensure that performance is achieved through the primacy of human effort over technology in running shoes. Analyzing the effect of legal and illegal shoes on running performance is therefore needed to determine its effectiveness. Thus, this study aimed (a) to compare the effect of 2 footwear models categorized as legal and illegal by the World Athletics regulation on track running performance and (b) to analyze the derived metrics of the athletes' biomechanics when using each footwear model at racing paces. Within 1 week, 14 highly trained athletes performed 2 testing sessions composed of 2 time trials of 9- and 3-minute duration with 30 minutes of recovery between them. The athletes wore the "Nike ZoomX Dragonfly" track spikes model and the "Nike ZoomX Vaporfly Next % 2" marathon shoe model in a counterbalanced randomized order. The results revealed that (a) there was only a small worthwhile improvement in the 3-minute time trial when using themarathon shoes of 0.97%(20.04 to 1.98%) and (b) there was amain effect of footwear in 7 of the 9 biomechanical variables analyzed (p # 0.050). The ground contact time was the unique performance predictor (p 5 0.005, adjusted R2 5 0.476). Altogether, the use of legal and illegal running shoes altered the runners form, which only influenced the mid-distance performance. [ABSTRACT FROM AUTHOR]