Search

As technology within elite basketball advances and is more available to sporting organizations, novel approaches for assessing and addressing athletic performance during practice or competition are being continuously explored. The aim of this investigation was to examine changes in neuromuscular performance during live basketball play. Eight professional male basketball players volunteered to participate in this study. The testing procedures were conducted during a pre-tournament camp over a span of 2 days. During the first day, the athletes were familiarized with the testing procedures, and baseline measurements were obtained. Using a uniaxial force plate system sampling at 1,000 Hz, each athlete performed 3 countermovement vertical jumps (CVJ) without an arm swing before proceeding with their regular training activities. During the second day of the pre-tournament camp, the athletes repeated identical CVJ testing procedures before the start of the first quarter and post-first, second, third, and fourth quarter of a simulated 5- on-5 basketball game. Repeated-measures testing design was used to examine statistically significant differences in various forcetime metrics of interest in comparison to the baseline levels (p, 0.05). Besides a trivial decrease in eccentric mean force, the findings of this study revealed no statistically significant changes in any force-time metrics of interest within both eccentric and concentric phases of the CVJ (i.e., mean and peak force and power, jump height, impulse, velocity, and contraction time). Thus, we can conclude that these variables were not sensitive to acute fatigue, suggesting that the neuromuscular performances of professional male basketball players tend to remain unchanged throughout a 5-on-5 simulated game. [ABSTRACT FROM AUTHOR]

Short sprints are predominantly assessed using timing gates and analyzed through parameters of the mono-exponential equation, including estimated maximal sprinting speed ( M S S ) and relative acceleration ( T A U ), derived maximum acceleration (MAC), and relative propulsive maximal power ( P M A X ), further referred to as the No Correction model. However, the frequently recommended flying start technique introduces a bias during parameter estimation. To correct this, two additional models (Estimated TC and Estimated FD) were proposed. To estimate model precision and sensitivity to detect the change, 31 basketball players executed multiple 30 m sprints. Athlete performance was simultaneously measured by a laser gun and timing gates positioned at 5, 10, 20, and 30 m. Short sprint parameters were estimated using a laser gun, representing the criterion measure, and five different timing gate models, representing the practical measures. Only the MSS parameter demonstrated a high agreement between the laser gun and timing gate models, using the percent mean absolute difference ( % M A D ) estimator ( % M A D < 10%). The MSS parameter also showed the highest sensitivity, using the minimum detectable change estimator ( % M D C 95 ), with an estimated % M D C 95 < 17%. Interestingly, sensitivity was the highest for the No Correction model ( % M D C 95 < 7%). All other parameters and models demonstrated an unsatisfying level of sensitivity. Thus, sports practitioners should be cautious when using timing gates to estimate maximum acceleration indices and changes in their respective levels. [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]

Cabarkapa, DV, Cabarkapa, D, Philipp, NM, and Fry, AC. Competitive season-long changes in countermovement vertical jump force-time metrics in female volleyball players. J Strength Cond Res 38(2): e72-e77, 2024--Although force plates remain one of the most widely used tools for neuromuscular performance assessment in applied sports-specific settings, there is still a lack of scientific literature focused on studying changes in countermovement vertical jump (CVJ) performance in team sports such as volleyball, especially within the female athlete population. Thus, the purpose of the present study was to examine season-long neuromuscular performance changes in volleyball players. Eighteen National Association of Intercollegiate Athletics Division-I collegiate female athletes performed 3 maximal-effort CVJs while standing on a uniaxial force plate system sampling at 1,000 Hz at 5 different testing timepoints throughout a competitive season span (;11 weeks). The testing sessions were separated 2-3 weeks apart and performed at the approximately same time of the day (12:00 hours). Repeated-measures analysis of variance revealed that both concentric and eccentric force-time metrics remain relatively unchanged throughout a regular season span (e.g., concentric peak force and power, eccentric impulse and duration). However, the eccentric metrics such as peak and mean power and peak velocity displayed a slight improvement after a brief tapering period purposely implemented before the post-season competition to optimize the athlete's recovery (;15, 18, and 14% increase, respectively). In addition, the outcome metrics such as vertical jump height and reactive strength index-modified did not display notable fluctuations across the competitive season span. These findings can help coaches, sports scientists, and strength and conditioning practitioners to obtain a deeper insight into collegiate female athletes' force-time characteristics that may aid with developing adequate training regimens targeted toward optimizing on-court performance. [ABSTRACT FROM AUTHOR]

Cabarkapa, D, Cabarkapa, DV, Philipp, NM, Knezevic, OM, Mirkov, DM, and Fry, AC. Pre-post practice changes in countermovement vertical jump force-time metrics in professional male basketball players. J Strength Cond Res 37(11): e609-e612, 2023--Despite the countermovement vertical jump (CVJ) being one of the most popular noninvasive and time-efficient methods for monitoring neuromuscular status, there is a lack of scientific literature focused on examining fatigue-induced alterations in performance in elite athletes. Thus, the purpose of this study was to examine changes in force-time metrics pre-post practice in professional male basketball players. Seventeen athletes competing in first-tier and second-tier national basketball leagues in Europe participated in this study. While standing on a uniaxial force plate sampling at 1,000 Hz, each athlete completed 3 CVJs pre-practice and post-practice. The practice consisted of individual and team shooting drills, position-specific player development drills, 5-on-0 offensive actions, and 5-on-5 play, including full-court transition (;2 hours). The findings reveal that pre-post practice changes in force-time metrics seemto be phase specific. Despite a trivial increase in eccentric mean force (920.4 6 100.2, 929.4 6 100.0 N), most changes were observed within the concentric phase of the CVJ. The concentric phase duration increased pre-post practice (0.233 6 0.027, 0.242 6 0.033 seconds), whereas concentric impulse (262.9618.8, 258.6621.6 N·s), peak velocity (2.9360.22, 2.8660.22m·s21), mean force (2052.46179.2, 2002.76188.2 N), mean power (3,165.56269.5, 3,030.96326.8W), and peak power (5,523.46607.3, 5,246.6 6663.7W) experienced a significant decrease. Moreover, alongside longer contraction time(0.66360.065, 0.68660.074 seconds), lower vertical jump height (41.0 6 6.8, 38.9 6 6.6 cm) and reactive strength index-modified (0.634 6 0.113, 0.579 6 0.111 m·s21) values were observed post-practice. Overall, these findings may allow practitioners to detect fatigue-induced changes in CVJ forcetime metrics in professional male basketball players that can ultimately improve the acute and longitudinal training-adaptation monitoring process. [ABSTRACT FROM AUTHOR]

Basketball is a sport that is characterized by various physical performance parameters and motor abilities such as speed, strength, and endurance, which are all underpinned by an athlete's efficient use of the stretch-shortening cycle (SSC). A common assessment to measure SSC efficiency is the countermovement jump (CMJ). When performed on a force plate, a plethora of different force-time metrics may be gleaned from the jump task, reflecting neuromuscular performance characteristics. The aim of this study was to investigate how different CMJ force-time characteristics change across different parts of the athletic year, within a sample of elite collegiate male basketball players. Twelve basketball players performed CMJ's on near-weekly basis, combining for a total of 219 screenings. The span of testing was broken down into four periods: pre-season, non-conference competitive period, conference competitive period, and post-season competitive period. Results suggest that basketball players were able to experience improvements and maintenance of performance with regards to various force-time metrics, transitioning from the pre-season period into respective later phases of the in-season period. A common theme was a significant improvement between the pre-season period and the non-conference period. Various force-time metrics were subject to change, while outcome metrics such as jump height remained unchanged, suggesting that practitioners are encouraged to more closely monitor how different force-time characteristics change over extended periods of time. [ABSTRACT FROM AUTHOR]

Given the multidirectional nature of the sport, handball athletes must frequently perform high-intensity decelerations to avoid defenders, generate space, or perform directional changes. The aim of the present study was twofold: (i) to investigate different kinematic measures of horizontal deceleration performance by comparing the acceleration-deceleration assessment (ADA) with the 5-0-5 test and (ii) to investigate relationships between force-time characteristics derived from the countermovement vertical jump (CVJ) and measures of horizontal deceleration performance. Eleven female handball players competing in the first-tier professional league in Europe performed three CVJs while standing on a uni-axial force plate system sampling at 1000 Hz, followed by two ADAs (i.e., maximal-effort acceleration over a 10 m distance, followed by rapid deceleration) and 5-0-5 test trials. Tripod-mounted radar sampling at 47 Hz, placed 5 m behind the start line, was used to record horizontal velocity data. Each test was separated by a 5–7 min rest interval to minimize the influence of fatigue. No statistically significant differences were found in horizontal deceleration performance parameters between ADA and the 5-0-5 test. However, athletes with a higher CVJ height and reactive strength index-modified showed better performance in terms of horizontal deceleration measures such as maximal approach velocity and average and maximal deceleration. Overall, these results may be of interest to practitioners working with multidirectional sport athletes such as handball players as they provide critical insight for the selection of assessments and training strategies targeted toward optimizing on-court athlete performance. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine acute changes in salivary testosterone (T), cortisol (C), and testosterone-to-cortisol ratio (T/C) during a simulated 5-on-5 basketball game. Seven professional male basketball players volunteered to participate in this study. Repeated-measures analysis design was used to examine changes in hormonal concentrations across 8 testing time points: immediately upon arrival to the gymnasium- baseline (BS); post-warm-up (PW); post-first (P1Q), second (P2Q), third (P3Q), and fourth quarter (P4Q); and 30 (P30) and 60 minutes (P60) postgame. The findings of this study indicate that a simulated 5-on-5 basketball game provoked significant changes in salivary T, C, and T/C. When compared to the BS levels (... ± SD [nmol⋅L-1]; 6.72 ± 2.53), salivary C concentration experienced a notable increase P3Q (16.20 ± 7.70) and remained elevated throughout the rest of the sampling periods, with values failing to return to BS levels P60 (11.88 ± 5.58). Conversely, a significant increase in salivary T occurred P1Q (0.76 ± 0.21) when compared to the BS levels (0.58 ± 0.12) and remained elevated up to P30 (0.75 ± 0.20), with values returning to BS levels P60 (0.63 ± 0.14). In addition, despite no significant intragame alterations, T/C exhibited a notable decrease P30 (0.06 ± 0.02) and P60 (0.07 ± 0.04), when compared to BS values (0.10 ± 0.04). Overall, these findings provide additional insight into the physiological stress that basketball players are exposed to during 5-on-5 competitive play and can be used to appropriately adjust and monitor training loads to optimize recovery and on-court basketball performance. [ABSTRACT FROM AUTHOR]

The primary aim of the present study was to investigate how the fatigue induced through a repeat sprint protocol acutely affected different measures of neuromuscular performance. Recreationally trained basketball players (n = 25) volunteered to participate in the study, and performed three countermovement jumps (CMJ), as well as three drop jumps (DJ) prior to a fatiguing repeat sprint protocol. These procedures were repeated two minutes, and 15 minutes, following the protocol. Various force-time metrics were extracted from the jump tasks, and linear mixed models with subject ID as the random factor, and time as the fixed factor were used to investigate changes across the three time points. To account for the performance during the repeat sprint protocol, a second, two factor model was performed with time and repeat sprint ability (RSA) as the fixed factors. Study results indicated that the sample as a whole merely experienced fatigue-induced decreases in jump height from pre-repeat sprint ability protocol (pre-RSA) within the CMJ compared to two minutes post-repeat sprint ability protocol (post-RSA1) and 15 minutes post-repeat sprint ability protocol (post-RSA2), while jump height within the DJ was only significantly different from pre-RSA at post-RSA1. Further, despite the implementation of the fatiguing RSA protocol, over the course of the three time-points, participants seemed to perform the two jump tasks more efficiently, seen through significantly lower contraction times, greater eccentric (ECC) peak power, and greater ECC mean deceleration force within the CMJ following the RSA task. The two-factor model revealed that several significant time*RSA interactions were found for metrics such as ECC peak velocity and peak power in the CMJ, as well as reactive strength index in the DJ. This suggests that the level of RSA influenced changes across CMJ and DJ characteristics and should be accounted for when interpreting fatigue-induced changes in neuromuscular performance. [ABSTRACT FROM AUTHOR]

Three-dimensional force plates are important tools for biomechanics discovery and sports performance practice. However, currently, available 3D force plates lack portability and are often cost-prohibitive. To address this, a recently discovered 3D force sensor technology was used in the fabrication of a prototype force plate. Thirteen participants performed bodyweight and weighted lunges and squats on the prototype force plate and a standard 3D force plate positioned in series to compare forces measured by both force plates and validate the technology. For the lunges, there was excellent agreement between the experimental force plate and the standard force plate in the X-, Y-, and Z-axes (r = 0.950–0.999, p < 0.001). For the squats, there was excellent agreement between the force plates in the Z-axis (r = 0.996, p < 0.001). Across axes and movements, root mean square error (RMSE) ranged from 1.17% to 5.36% between force plates. Although the current prototype force plate is limited in sampling rate, the low RMSEs and extremely high agreement in peak forces provide confidence the novel force sensors have utility in constructing cost-effective and versatile use-case 3D force plates. [ABSTRACT FROM AUTHOR]

Sontag, SA, Cabarkapa, D, and Fry, AC. Testosterone and cortisol salivary samples are stable across multiple freeze-thaw cycles. J Strength Cond Res 37(4): 915–918, 2023—When processing salivary samples for biomarker analysis, avoiding multiple freeze-thaw cycles is generally recommended. However, confusing tissue handling instructions or challenges with collections in the field sometimes makes this problematic. Thus, the purpose of this study was to examine if the stability of salivary testosterone (T) and cortisol (C) hormones remains unchanged when exposed to multiple freeze-thaw cycles. Seven healthy recreationally active adults provided salivary samples at rest (i.e., 1600 hours) for analysis of T and C. Samples were separated into 4 aliquots for each hormone and underwent 4 freeze-thaw cycles (T1–T4 and C1–C4) before being analyzed by enzyme-linked immunosorbent assay. The overall analysis of variance model was significant for T (p = 0.008) and nonsignificant for C (p = 0.820). A follow-up post hoc comparison indicated significant differences in salivary hormonal concentrations between T1 and T4 (p = 0.029), T2 and T4 (p = 0.007), and T3 and T4 (p = 0.032). The findings of this study indicate that salivary steroid hormones seem to be relatively stable following multiple freeze-thaw cycles. However, C seems to be more stable when exposed to multiple freeze-thaw cycles, as T concentrations did reveal a significant decrease by the fourth thaw cycle. [ABSTRACT FROM AUTHOR]

While being an integral part of both the offensive and defensive segments of the game, the biomechanical parameters of setting motions remain understudied in the scientific literature. Thus, the purpose of the present study was to examine differences in kinetic and kinematic characteristics between: (a) three types of setting motions (i.e., front, middle, back); (b) two types of setting approaches (i.e., stationary, step-in); and (c) proficient (PRO) and non-proficient (N-PRO) volleyball players. Twenty recreationally active females performed five stationary and five step-in setting approaches to Zone 4–2 in a randomized order. Uni-dimensional force plate sampling at 1000 Hz and high-definition camera recording at 30 fps were used to obtain kinetic and kinematic variables of interest. The total number of setting attempts performed by each subject was 30, accounting for a grand total of 600 attempts. PRO setters had less knee flexion, shoulder flexion, and ankle dorsiflexion at the initial concentric phase of the volleyball setting motion when compared to the N-PRO setters. Moreover, significantly greater peak concentric and landing forces, impulse, rate of force development, and vertical jump height were observed for PRO setters compared to N-PRO setters, while no significant differences were found between different setting targets and approaches. [ABSTRACT FROM AUTHOR]

While the importance of optimal two-point and three-point jump-shooting performance for securing the desired game outcome on various levels of basketball competition has been well documented, there is a limited amount of scientific literature on what biomechanical adjustments in shooting technique comprise the success of each shooting attempt. Therefore, the purpose of the present study was to examine the difference in kinetic and kinematic characteristics during the preparatory and release phases of the shooting motion between made and missed jump shots. While standing on a force plate, twenty-nine recreationally active males with prior basketball playing experience attempted 10 two-point and 10 three-point jump shots, combining for a total of 580 attempts. Simultaneously, two high-definition cameras were used to capture kinematic characteristics of interest. Higher elbow positioning during the preparatory phase of the shooting motion, relative to the shooter's stature, was shown to be a critical kinematic adjustment that differentiated made from missed two-point jump shots. Alongside identical observations regarding the importance of the elbow placement, keeping the torso in a more erect position during the preparatory phase of the shooting motion, having a greater release angle and vertical jump height at the timepoint of the ball release, and attaining higher maximal trajectory height were critical kinematic adjustments that differentiated made from missed three-point jump shots. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to examine differences in game-related statistical parameters between National Basketball Association (NBA) regular and post-season competitive periods and to determine which variables have the greatest contribution in discriminating between winning and losing game outcomes. The data scraping technique was used to obtain publicly available NBA game-related statistics over a three-year span (2016–2019). The total number of games examined in the present investigation was 3933 (3690 regular season and 243 post-season games). Despite small to moderate effect sizes, the findings suggest that NBA teams' style of play (i.e., tactical strategies) changes when transitioning from the regular to post-season competitive period. It becomes more conservative (i.e., fewer field goal attempts, assists, steals, turnovers, and points scored), most likely due to greater defensive pressure. Discriminant function analysis correctly classified winning and losing game outcomes during the regular and post-season competitive periods in 82.8% and 87.2% of cases, respectively. Two key game-related statistics capable of discriminating between winning and losing game outcomes were field goal percentage and defensive rebounding, accounting for 13.6% and 14.2% of the total percentage of explained variance during the regular season and 11.5% and 14.7% during post-season competitive periods. Also, overall shooting efficiency (i.e., free-throw, 2-point, and 3-point combined) accounted for 23–26% of the total percentage of explained variance. [ABSTRACT FROM AUTHOR]

Detecting the magnitude of compression or shear events can provide valuable data to assess forces experienced by sensitive equipment or even the human body. Compression sensors have historically had limited use in fields such as wearable technology due to the large size of the sensors, lack of 3D sensing capacity, need for rigid components, or signal quality issues associated with the orientation or deformation of soft composites under compression. In particular, soft magnetic composites paired with a magnetometer to sense material deformation have been hindered by such issues. Here, experiments evaluated soft silicone‐magnetic powder composites of various shapes, sizes, magnetic filler concentrations, and orientations to a magnetometer to optimize sensor performance. Sensors with smaller diameter (≤2.5 mm) cylinder‐shaped magnetic elements exhibited a linear response to compression when paired with a 3 mm × 3 mm magnetometer. The soft magnetic elements composed of 80% magnetic powder by weight, the highest concentration tested, had the greatest sensitivity. Parameters from these studies are used to design a sensor integrated into a football helmet, which successfully recorded 3D force data from head impacts while being worn, demonstrating the potential for such sensors in wearable technology applications. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the acute effects of lower limb wearable resistance on maximal horizontal deceleration biomechanics, across two different assessments. Twenty recreationally trained team sport athletes performed acceleration to deceleration assessments (ADA), and 5-0-5 change of direction (COD) tests across three load conditions (unloaded, 2% of BW, 4% of body weight (BW)), with load attached to the anterior and posterior thighs and shanks. Linear mixed effect models with participant ID as the random effect, and load condition as the fixed effect were used to study load-specific biomechanical differences in deceleration mechanics across both tests. Primary study findings indicate that for the ADA, in the 4% BW condition, participants exhibited significantly greater degrees of Avg Approach Momentum, as well as significant reductions in deceleration phase center of mass (COM) drop, and Avg Brake Step ground contact deceleration (GCD) in both the 2% BW, and 4% BW condition, compared to the unloaded condition. In the 5-0-5 tests, participants experienced significant reductions in Avg Approach Velocity, Avg deceleration (DEC), and Stopping Time in the 4% BW condition compared to the unloaded condition. Similar to the ADA test, participants also experienced significant reductions in Avg Brake Step GCD in both the 2% BW and 4% BW conditions, and significant increases in Avg Approach Momentum in the 4% BW condition, compared to the unloaded condition. Therefore, findings suggest that based on the test, and metric of interest, the addition of lower limb wearable resistance led to acute differences in maximal horizontal deceleration biomechanics. However, future investigations are warranted to further explore if the use of lower limb wearable resistance could present as an effective training tool in enhancing athlete's horizontal deceleration and change of direction performance. [ABSTRACT FROM AUTHOR]

Lower-body strength and power are commonly measured performance qualities across a number of sports. In recent years, more attention has been given to relationships, primarily between lower-body strength and linear speed performance. While still limited, evidence is in agreement that lower-body strength positively contributes to linear speed performance. However, what is less well understood is if there comes a point in an athlete's development, at which, further working on increasing maximal strength may not fully compliment additional gains in speed performance. Within this study, authors aimed to provide practitioners with lower-body strength and power thresholds that can discriminate between slow and fast performers, within a group of collegiate American football players. The sample was further divided into a high-body and low-body weight group, and authors hypothesized that by using logistic regression, supplemented with receiver operator curve analyses, optimal cut-off points (i.e., relative lower-body strength thresholds) that are able to significantly discriminate between slow and fast linear speed performers may be identified. Findings indicate that optimal cut-off scores differed between the groups of athletes, as well as the lower body strength and power tests. All models were able to significantly distinguish between slower and faster performers, and area under the curve values ranged from 0.695 to 0.903. Although thresholds will likely vary based on factors such as sex, training age, and sport, findings from this investigation may be used to benchmark athletes and to further individualize training aimed at improving linear speed performance. [ABSTRACT FROM AUTHOR]

Fry, AC, Parra, ME, and Cabarkapa, D. Supplemental creatine modified with polyethylene glycol effectively loads skeletal muscle with lower doses. J Strength Cond Res 35(5): 1256-1261, 2021--The purpose of this study was to compare the efficacy of skeletal muscle uptake of creatine monohydrate (Cr H2O) with that of creatine bound to polyethylene glycol (Cr PEG). Healthy men (X6 SE; age = 23.5 6 1.0 years) were divided into control (Con, n = 9, 20 g·d-1 of Cr H2O) and experimental (Exp, n = 8, 10 g·d-1 of Cr PEG) groups. Blood samples and muscle biopsies were used to determine acute gastrointestinal absorption over = hours and muscle cellular uptake over = days. Both groups exhibited significantly (p, 0.05) elevated concentrations of muscle-free Cr (M·gdw -1; Con, pre=23.064.2, post=39.262.7; Exp pre=22.162.9, post=33.663.2), total Cr (M·gdw -1, Con pre=94.7 6 =.4, post = 114.8 ± 7.4; Exp pre = 92.6 ± 5.4, post = 106.6 ± 8.4), which were also elevated when these values were normalized for adenosine triphosphate using molar ratios. Circulatory uptake of Cr was significantly different between the groups, with blood concentrations (mg·dL-1) for the Con group peaking at 2 hours post-ingestion (25.99 ± 2.96), whereas the concentrations for the Exp group were lower and were still rising at = hours (4.0560.87). The integrated area under the curve for the 5-hour postingestion period was 7-fold greater for the Con group. Although total Cr ingested over the = days supplementation period was less for the Cr PEG group, skeletal muscle uptake of Cr PEG was similar to CrH2O. Based on circulating Cr concentrations, it seems that Cr PEG is cleared more slowly from the gastrointestinal tract. Thus, lower dosages of Cr may be ingested while maintaining optimal loading kinetics. [ABSTRACT FROM AUTHOR]

Sleeve gastrectomy (SG) induces weight loss-independent improvements in glucose homeostasis by unknown mechanisms. We sought to identify the metabolic adaptations responsible for these improvements. Nonobese C57BL/6J mice on standard chow underwent SG or sham surgery. Functional testing and indirect calorimetry were used to capture metabolic phenotypes. Tissue-specific glucose uptake was assessed by 18-fluorodeoxyglucose (18-FDG) PET/computed tomography, and RNA sequencing was used for gene-expression analysis. In this model, SG induced durable improvements in glucose tolerance in the absence of changes in weight, body composition, or food intake. Indirect calorimetry revealed that SG increased the average respiratory exchange ratio toward 1.0, indicating a weight-independent, systemic shift to carbohydrate utilization. Following SG, orally administered 18-FDG preferentially localized to white adipose depots, showing tissue-specific increases in glucose utilization induced by surgery. Transcriptional analysis with RNA sequencing demonstrated that increased glucose uptake in the visceral adipose tissue was associated with upregulation in transcriptional pathways involved in energy metabolism, adipocyte maturation, and adaptive and innate immune cell chemotaxis and differentiation. SG induces a rapid, weight loss-independent shift toward glucose utilization and transcriptional remodeling of metabolic and immune pathways in visceral adipose tissue. Continued study of this early post-SG physiology may lead to a better understanding of the anti-diabetic mechanisms of bariatric surgery. [ABSTRACT FROM AUTHOR]

Postactivation performance enhancement has been reported for multijoint resistance exercise, with both neural and intrinsic muscle mechanisms suggested as contributing factors. The purpose of this investigation was to examine whether regulatory light-chain (RLC) phosphorylation in a primary mover is associated with enhanced weightlifting performance. Nine male athletes performed 15 sets of 3 repetitions of a multijoint weightlifting activity (clean pull) at 85% 1 repetition maximum. Measures of performance, peak barbell velocity (PV), and average barbell power (AP) were determined by video analysis. Muscle biopsies were taken within 30-60 seconds of completion of the previous lifting set from the vastus lateralis before (PRE), during (MID), and after (POST) a training session. AP was significantly greater for sets 3, 4, and 5 compared with set 1, with large effect sizes (0.8-1.0). Increases in PV did not reach significance; however, the effect size increase for sets 3 and 4 versus set 1 was moderate (0.4). Relative change scores for AP and RLC phosphorylation were positively and negatively correlated at MID (r = 0.60; p = 0.05) and POST (r = -0.74; p = -0.01) exercise, respectively. These data suggest that RLC phosphorylation initially may be associated with postactivation performance enhancement during repeated multijoint exercise. [ABSTRACT FROM AUTHOR]

The purpose of this study was compare the effect of internal and external focus of attention instructions on force-time characteristics of the countermovement jump (CMJ) in collegiate student-athletes. Forty-three resistance-trained men (... ± SD; age = 20 ± 1.5 years) on an NCAA Division I baseball team volunteered to participate in this study. Each participant performed a total of 16 CMJs on a force platform while holding a wooden dowel on their shoulders to eliminate arm swing. Force and power parameters such as jump height (JH), peak velocity (PV), and mean concentric velocity (MCV) were calculated from force-time and position data. Paired-sample t-tests and Cohen's d effect sizes were used to examine differences between conditions. When subjects were instructed using an external focus, they demonstrated significantly (p < 0.05) greater JH, PV, and MCV compared with jumps performed with the internal focus (external JH = 48.0 ± 5.6 cm, internal JH = 46.4 ± 5.4 cm; external PV = 3.6 ± 0.3 m⋅s-1, internal PV = 3.5 ± 0.3 m⋅s-1; and external MCV = 2.31 ± 0.22 m⋅s-1, internal MCV = 2.25 ± 0.23 m⋅s-1). It is interesting to note that there was superior recall of the internal instructions during the manipulation checks that may suggest that the subjects consciously processed these instructions to a greater extent and reduced internal condition performance. These results indicate that instructions can alter the efficiency and performance of a skill. According to the literature and this study, if an optimum performance metric is desired, external focus of attention instructions should be used. [ABSTRACT FROM AUTHOR]

The purpose of the present study was (i) to explore the reliability of the most commonly used countermovement jump (CMJ) metrics, and (ii) to reduce a large pool of metrics with acceptable levels of reliability via principal component analysis to the significant factors capable of providing distinctive aspects of CMJ performance. Seventy-nine physically active participants (thirty-seven females and forty-two males) performed three maximal CMJs while standing on a force platform. Each participant visited the laboratory on two occasions, separated by 24–48 h. The most reliable variables were performance variables (CV = 4.2–11.1%), followed by kinetic variables (CV = 1.6–93.4%), and finally kinematic variables (CV = 1.9–37.4%). From the 45 CMJ computed metrics, only 24 demonstrated acceptable levels of reliability (CV ≤ 10%). These variables were included in the principal component analysis and loaded a total of four factors, explaining 91% of the CMJ variance: performance component (variables responsible for overall jump performance), eccentric component (variables related to the breaking phase), concentric component (variables related to the upward phase), and jump strategy component (variables influencing the jumping style). Overall, the findings revealed important implications for sports scientists and practitioners regarding the CMJ-derived metrics that should be considered to gain a comprehensive insight into the biomechanical parameters related to CMJ performance. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) force data from head impacts in football is important for understanding traumatic brain injuries (TBIs). Football helmets have not yet been instrumented with true 3D force sensors compelling the development of soft 3D force sensors that could be seamlessly integrated into existing helmet padding. PURPOSE: To develop and determine the accuracy and reliability of an in-helmet soft 3D force sensor in comparison to force plate data. METHODS: A force sensor was fabricated by embedding magnetic powder within a cylindrical rubber cushion which was affixed to a magnetometer. Prior to integration in a helmet, known compressive forces were slowly applied to the sensor to assess performance in a controlled setting. The sensor was then inserted and fixed into a cavity created on the forehead pad of a football helmet. The sensor was controlled by a microcontroller, which communicated data wirelessly to a nearby computer at a sampling rate of 29 Hz. Thirteen trials were performed in which the helmet, while being worn, impacted a vertically mounted 3D force plate from different angles. The reliability of the helmet sensor in relation to the force plate was assessed by the interclass correlation coefficient (ICC) of the peak force measured in the primary axis of the impact (i.e. z-axis for a straight impact, x-axis for an angled impact) from the helmet sensor and the force plate. RESULTS: The magnetometer's measurements of magnetic field strength exhibited a strong second order correlation to the force applied to the sensor (r2= 0.995). For the helmet-force plate impacts, the force vectors were clearly observable for all trials by analyzing the force-time curves of each of the three axes of the helmet sensor. The helmet sensor displayed excellent agreement with the force plate for peak force (ICC=0.981). In addition, peak forces for 8 of 13 impacts exhibited moderately low error (1-13%) when compared to the force plate, but the rest of the impacts had larger errors (25-51%). CONCLUSIONS: The sensor performed excellent in controlled studies and had high agreement with the force plate according to the ICC. Most impacts were accurately measured, but a higher sampling rate is needed for consistent and accurate quantification of impacts that contain higher frequency components. [ABSTRACT FROM AUTHOR]