ABSTRACT:Cleary, A, Winchester, JB, Cochrane-Snyman, KC, and McBride, JM. The relationship between the NBA draft combine tests, advanced performance metrics, and perceived performance in National Collegiate Athletic Association Division I men's basketball. J Strength Cond Res 40(3): 337-343, 2026-The NBA Draft Combine (NBADC) assesses an athlete's size, length, and athleticism. Advanced metrics such as player efficiency rating (PER) and Win Share/40 (WS/40) quantify basketball performance. This study explored relationships between NBADC metrics, performance metrics, and perceived performance in a National Collegiate Athletic Association DI Men's Basketball team. Thirteen scholarship athletes (age 20.1 ± 0.64 years, height 1.9 ± 0.1 m, mass 93.9 ± 10.9 kg) participated. Players and coaches ranked each player at their position, creating perceived performance rankings (player rank [PR] and coaches rank [CR]). A Spearman's rank correlation was performed using PER, WS/40, PR, and CR as dependent variables, with anthropometric and physical data as independent variables. Statistical significance was set a priori ≤0.05. Stepwise linear regression identified predictive relationships. Win Share/40 significantly correlated with maximum vertical jump (MVJ) ( ρ = 0.589, p ≤ 0.05). Maximum vertical jump explained 35% of WS/40 variability, and MVJ with body composition (BC) predicted 61.4%. Player efficiency rating and raw no-step vertical jump predicted 87.4% of WS/40. Coaches rank and standing reach explained 73.9% of WS/40, while CR alone explained 64.1% of PER. Results suggest lower body muscular power and body composition significantly relate to basketball performance. Coaches assessing players and projecting future contributions should prioritize vertical jump metrics and body composition over other NBADC assessments.

BACKGROUND:Several investigations have examined various methods of measuring hamstring strength to determine the effectiveness of these tests in predicting hamstring injury (HSI) risk in athletes. However, no previous studies have examined the effectiveness of hamstring strength and interlimb asymmetry utilizing a newly developed modified single leg isometric bridge test (SLIBT) versus a standard Nordic hamstring exercise (NHE) to predict HSI in professional baseball players. PURPOSE:To determine whether preseason hamstring strength and interlimb asymmetry measured using a modified SLBIT versus an NHE are associated with future HSI in professional baseball players, as well as if measures of hamstring strength and interlimb asymmetry using the SLIBT are correlated to values from the NHE. STUDY DESIGN:Cohort study; Level of evidence, 3. METHODS:Professional baseball players (n = 465) from 8 teams affiliated with a single Major League Baseball organization completed a preseason hamstring strength assessment as part of routine athlete monitoring before the 2019, 2021, and 2022 seasons. A total of 38 new HSI events were recorded among 36 players over 751 player-seasons included in the analysis. RESULTS:Lower hamstring strength levels in subsequent HSI limbs were observed compared with the 2-limb mean hamstring strength of healthy players for the SLIBT (365.1 ± 58.4 vs 390.9 ± 59.6 N; P = .014) and NHE (403.5 ± 90.4 vs 440.5 ± 76.0 N; P = .017). Players with NHE hamstring strength <377 N exhibited a significantly higher risk of HSI (RR, 2.49; 95% CI, 1.18-5.27; P = .027). Logistic regression indicated an inverse relationship between hamstring strength and HSI risk, with each 10-N increase in the SLIBT and NHE corresponding to a 7.4% and 6.2% risk reduction, respectively (with no interaction effects between tests). Interlimb asymmetry measures from both the SBILT and NHE were not indicative of subsequent HSI. Moderate significant correlations (r = 0.33-0.39) were observed for absolute and relative hamstring strength measured utilizing the SLIBT versus the NHE. No significant correlations were found between measures of interlimb asymmetry when assessed by the SBILT versus the NHE. CONCLUSION:The current investigation indicates that low levels of hamstring strength measured in both the SLIBT and NHE are associated with an increased risk of future HSI. Thus, these measures could be utilized to identify at-risk players and to develop mitigation strategies to limit the rate of HSI and maximize time at play.

ABSTRACT:McBride, JM, Bauer, EC, Kaufmann, NC, Triplett, NT, and Shanely, RA. Handgrip strength associated with leg strength, power, and muscle mass in 18-64-year-old males and females. J Strength Cond Res 39(6): 642-648, 2025-The purpose of this investigation was to determine the association between handgrip strength (HGS) and measures of leg strength, power, and muscle mass. Twenty-one men (age = 32.9 ± 11.4 years, height = 175.7 ± 8.3 cm, body mass = 83.6 ± 14.4 kg, body fat = 22.6 ± 6.2%) and 24 women (age = 35.5 ± 14.0 years, height = 164.6 ± 6.8 cm, body mass = 65.2 ± 8.6 kg, body fat = 30.0 ± 5.7%) performed a HGS test, a squat and leg press 1 repetition maximum (1RM), a countermovement jump (CMJ) on a force plate, and a dominant leg peripheral quantitative computed tomography thigh scan to calculate muscle cross-section area (CSA). Lean body mass was determined through dual x-ray absorptiometry. Jump height and impulse were calculated from force time curves from the CMJ as a representation of leg muscular power. Strong statistically significant correlations were found between HGS and squat 1RM ( r = 0.80, p ≤ 0.0001), leg press 1RM ( r = 0.79, p ≤ 0.0001), CMJ height ( r = 0.78, p ≤ 0.0001), CMJ impulse ( r = 0.84, p ≤ 0.0001), and thigh muscle CSA ( r = 0.75, p ≤ 0.0001 and lean body mass ( r = 0.79, p ≤ 0.0001). This study indicates that HGS could be used as a preliminary screening tool for determination of leg strength, power, and muscle mass. These variables have been determined to be components to overall fitness that increase quality of life and overall health. Thus, health care providers may be able to use this simple test as an early indication of possible risk factors for poor health and well-being.

Introduction: Several investigations have examined utilizing inertial measurement units (IMU) to estimate ground reaction force (GRF) during exercise. The purpose of this investigation was to determine the effect of inertial measurement units location on the estimation of ground reaction force during vertical jumping. Methods: Eight male subjects completed a series of ten countermovement jumps on a force plate (FP). The subjects had an inertial measurement units attached to the sacrum, back and chest. Ground reaction force was estimated from data from the individual inertial measurement units and by using a two-segment model and combined sensor approach. Results: The peak ground reaction force values for the sacrum, back, chest and combined inertial measurement units were 1,792 ± 278 N, 1,850 ± 341 N, 2,054 ± 346 N and 1,812 ± 323 N, respectively. The sacral inertial measurement units achieved the smallest differences for ground reaction force estimates providing a root mean square error (RMSE) between 88 N and 360 N. The inertial measurement units on the sacrum also showed significant correlations in peak ground reaction force ( p < 0.001) and average ground reaction force ( p < 0.001) using the Bland-Altman 95% Limits of Agreement (LOA) when in comparison to the force plate. Discussion: Based on assessment of bias, Limits of Agreement, and RMSE, the inertial measurement units located on the sacrum appears to be the best placement to estimate both peak and average ground reaction force during jumping.

PURPOSE The purpose of this study was to explore whether offset loading in the barbell squat altered ground-reaction force (GRF) and muscle activation in the dominant (D) and nondominant (ND) lower limb compared to traditional squats. METHODS Twelve well-trained men (age 26.4 [3.2] y; 10.3 [1.9] y experience) performed 3 sets of 10 repetitions at 60% of their previously measured 1-repetition maximum. Sets were quasi-randomized between traditional loading (TDL), dominant-side offset loading (OS-D), and nondominant-side offset loading (OS-ND). All repetitions were performed on a dual force plate with electromyography sensors on the prime mover muscles of the squat. GRF symmetry was assessed using the symmetry index (SI) to determine the direction (D [+] or ND [-]) and magnitude (%) of the asymmetry. Finally, the first 3 and final 3 repetitions of each set were compared for compensatory changes in symmetry. RESULTS OS-D induced a significant change in limb SI relative to TDL (5.21% vs 1.44%; P = .011); however, no significant difference in limb SI was seen between TDL and OS-ND (-0.66% vs 1.44%; P = .278). No asymmetries between D and ND muscle activation were present in any condition. TDL and OS-D squats exhibited significant improvements in limb SI between the first 3 and final 3 repetitions (P = .035 and .011, respectively); however, no such improvement was seen in OS-ND. CONCLUSIONS OS-D is capable of significantly altering GRF limb SI in a bilateral squat; however, OS-ND appears to exhibit no GRF or electromyography effects relative to TDL. Thus, the results of this study do not support the use of OS-ND in the pursuit of strengthening a weaker limb, suggesting that unilateral training may be a preferred mode of exercise for this desired outcome.

[This corrects the article on p. 1386 in vol. 13, PMID: 35414965.].

Polarization-sensitive optical coherence tomography (PS-OCT) derived birefringence values effectively identify skeletal muscle structural disruption due to muscular dystrophy and exercise-related muscle damage in animal models in ex vivo tissue. The purpose of this investigation was to determine if a PS-OCT needle probe inserted into the leg of a human subject could accurately identify various anatomical structures with implications for use as a diagnostic tool for the determination of skeletal muscle pathology. A healthy middle-aged subject participated in this study. A custom-built PS-OCT system was interfaced with a side-viewing fiber-optic needle probe inserted into the subject's vastus lateralis muscle via a motorized stage for 3D data acquisition via rotation and stepwise pullback. The deepest recorded PS-OCT images correspond to a depth of 6 mm beneath the dermis with structural images showing uniform, striated muscle tissue. Multiple highly birefringent band-like structures with definite orientation representing connective tissue of the superficial aponeurosis appeared as the depth of the needle decreased. Superficial to these structures the dominating appearance was that of adipose tissue and low birefringent but homogeneous scattering tissue. The data indicate that a PS-OCT needle probe can be inserted into live human skeletal muscle for the identification of relevant anatomical structures that could be utilized to diagnose significant skeletal muscle pathology.

Background A significant challenge that non-elite collegiate triathletes encounter during competition is the decline in running performance immediately after cycling. Therefore, the purpose of this study was to determine if performing a 40-km bout of cycling immediately before running would negatively influence running economy and mechanical efficiency of running during simulated race conditions in collegiate triathletes. Methods Eight competitive club-level collegiate triathletes randomly performed two trials: cycling for 40 km (Cycle-Run) or running for 5 km (Run–Run), immediately followed by a four-minute running economy and mechanical efficiency of running test at race pace on an instrumented treadmill. Blood lactate, respiratory exchange ratio, mechanical work, energy expenditure, and muscle glycogen were also measured during the four-minute running test. Results Mechanical efficiency of running, but not running economy, was significantly lower in Cycle-Run, compared to Run–Run (42.1 ± 2.5% vs. 48.1 ± 2.5%, respectively; p = 0.027). Anaerobic energy expenditure was significantly higher in the Cycle-Run trial, compared to the Run–Run trial (16.3 ± 2.4 vs. 7.6 ± 1.1 kJ; p = 0.004); while net (151.0 ± 12.3 vs. 136.6 ± 9.6 kJ; p = 0.204) and aerobic energy expenditure (134.7 ± 12.3 vs. 129.1 ± 10.5 kJ; p = 0.549) were not statistically different between trials. Analysis of blood lactate, respiratory exchange ratio, mechanical work, and changes in muscle glycogen revealed no statistically significant differences between trials. Conclusions These results suggest that mechanical efficiency of running, but not running economy, is decreased and anaerobic energy expenditure is increased when a 40-km bout of cycling is performed immediately before running in collegiate triathletes.

This publisher's notes amends the reference citations and the reference list of [Biomed. Opt. Express 13, 1386 (2022)]. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

The current investigation examined muscle-tendon unit kinematics and kinetics in human participants asked to perform a hopping task for maximal performance with variational preceding milieu. Twenty-four participants were allocated post-data collection into those participants with an average hop height of higher (HH) or lower (LH) than 0.1 m. Participants were placed on a customized sled at a 20º angle while standing on a force plate. Participants used their dominant ankle for all testing and their knee was immobilized and thus all movement involved only the ankle joint and corresponding propulsive unit (triceps surae muscle complex). Participants were asked to perform a maximal effort during a single dynamic countermovement hop (CMH) and drop hops from 10 cm (DH10) and 50 cm (DH50). Three-dimensional motion analysis was performed by utilizing an infrared camera VICON motion analysis system and a corresponding force plate. An ultrasound probe was placed on the triceps surae muscle complex for muscle fascicle imaging. HH hopped significantly higher in all hopping tasks in comparison to LH. In addition, the HH group concentric ankle work was significantly higher in comparison to LH during all of the hopping tasks. Active muscle work was significantly higher in HH in comparison to LH as well. Tendon work was not significantly different between HH and LH. Active muscle work was significantly correlated with hopping height (r = 0.97) across both groups and hopping tasks and contributed more than 50% of the total work. The data indicates that humans primarily use a motor-driven system and thus it is concluded that muscle actuators and not springs maximize performance in hopping locomotor tasks in humans.

BACKGROUND:Ankle dorsiflexion motion and plantarflexor stiffness measurement offer clinical insight into the assessment and treatment of musculoskeletal and neurologic disorders. We aimed to determine reliability and concurrent validity of an ankle arthrometer in quantifying dorsiflexion motion and plantarflexor stiffness.METHODS:Ten healthy individuals were assessed for dorsiflexion motion and plantarflexor stiffness using an ankle arthrometer with a 6 degree-of-freedom kinematic linkage system and external strain gauge to apply dorsiflexion torque. Two investigators each performed five loads to the ankle at different combinations of loads (10 or 20 Nm), rates (2.5 or 5 Nm/sec), and knee angles (10° or 20°). Anteroposterior displacement and inversion-eversion rotation were also assessed with arthrometry, and functional dorsiflexion motion was assessed with the weightbearing lunge (WBL) test.RESULTS:Good-to-excellent intrarater reliability was observed for peak dorsiflexion (intraclass correlation coefficient [ICC][2,k] = 0.949-0.988) and plantarflexor stiffness (ICC[2,k] = 0.761-0.984). Interrater reliability was good to excellent for peak dorsiflexion (ICC[2,1] = 0.766-0.910) and poor to excellent for plantarflexor stiffness (ICC[2,1] = 0.275-0.914). Reliability was best for 20-Nm loads at 5 Nm/sec. Strong correlations were observed between peak dorsiflexion and anteroposterior displacement (r = 0.666; P = 0.035) and WBL distance (r = -0.681; P = 0.036).CONCLUSIONS:Using an ankle arthrometer to assess peak dorsiflexion and plantarflexor stiffness seems reliable when performed to greater torques with faster speeds; and offers consistency with functional measures. Use of this readily available tool may benefit clinicians attempting to quantify equinus and dorsiflexion deficits in pathological populations.

ABSTRACT Purpose Given maladaptive neuroplasticity after musculoskeletal injury, interventions capable of restoring corticospinal excitability should be considered. We therefore aimed to determine if a 4-wk intervention of anodal transcranial direct current stimulation (aTDCS) with eccentric exercise would improve neural excitability, functional performance, and patient-reported function in individuals with chronic ankle instability (CAI). Methods Twenty-six individuals with CAI were recruited to undergo 4 wk of eccentric evertor strengthening. Subjects were randomized into aTDCS ( n = 13) and sham ( n = 13) groups, where the aTDCS group received 18 min of aTDCS (1.5 mA) over the primary motor cortex. Participants were assessed for cortical excitability, dynamic balance, muscle activation, functional performance, strength, and patient-reported function at baseline, week 2, week 4, and week 6. Results Twenty-two subjects completed the training and test sessions. Cortical excitability (resting motor threshold) to peroneus longus in aTDCS increased from baseline (36.92 ± 11.53) to week 6 (32.91 ± 12.33, P = 0.024), whereas sham increased excitability from baseline (36.67 ± 12.74) to week 2 (27.86 ± 14.69, P = 0.007), but decreased at week 4 (35.63 ± 13.10, P = 0.022) and week 6 (35.99 ± 13.52, P = 0.006). Dynamic balance and muscle activation also improved in the aTDCS group from baseline to week 6 ( P = 0.034). Functional performance on a side-hop test increased in all participants from baseline to week 2 ( P = 0.003). The aTDCS group had decreased perceived disablement from week 2 (18.09 ± 6.41) to week 4 (15.55 ± 4.82, P = 0.046), whereas the sham group reported increased disablement from baseline (17.91 ± 4.59) to week 2 (21.00 ± 8.52, P = 0.047). Conclusions Our results provide preliminary evidence that 4 wk of eccentric training with aTDCS improves cortical excitability, functional performance, and patient-reported function in individuals with CAI. These data are the first to show the efficacy of noninvasive brain stimulation therapies in patients with musculoskeletal injury, and demonstrate the link between improved neural excitability and functional outcomes.

Purpose: The mechanical properties of resistance-training machines are a variable that may help to optimize sports performance and injury prevention protocols. The purpose of this study was to examine two non-gravity-dependent training modalities on muscle structure and function. Methods: Eighteen professional handball players were randomly divided into two experimental groups: 1) iso-inertial flywheel training (FW) and 2) pneumatic resistance training (PN). Participants in both groups completed twelve training sessions in six weeks consisting of three movements (lateral raise, internal and external rotation). Four sets of seven repetitions for each movement were performed during each session. Before and after training subscapularis and deltoid (anterior, middle, posterior) muscle thickness was measured. Isokinetic torque and power during internal and external rotation at 60, 180, and 240 deg·s-1 was measured as well. Throwing speed was assessed before and after training while both sitting and standing situations. Results: Both groups showed similar significant increases in throwing speed and internal and external rotation peak torque, average and peak power at all angular velocities. Anterior and middle deltoid muscle thickness changes were greater after training in FW (20 and 22%) in comparison to PN (14 and 7%, respectively). Conclusions: In summary, both flywheel and pneumatic training resulted in similar increases in shoulder strength and power and throwing speed. However, flywheel training appeared to possibly result in a slightly greater level of muscle hypertrophy of the anterior and middle deltoid. Non-gravity dependent training appears to induce changes that would be beneficial to sports performance and perhaps injury prevention.

To better understand and define energy algorithms during physical activity as it relates to strength and movement strategy of the hip, knee and ankle, a model of increasing eccentric load was implemented in the current investigation utilizing a countermovement jump and a series of drop jumps from different heights (15, 30, 45, 60, 75 cm). Twenty-one participants were grouped by sex (men, n = 9; women, n = 12) and muscle strength (higher strength, n = 7; moderate strength, n = 7; lower strength, n = 7) as determined by a maximal squat test. Force plates and 3D motion capture were utilized to calculate work for the center of mass (COM) of the whole body and individually for the hip, knee and ankle joints. Statistically significant lower net work of the COM was observed in women and lower strength participants in comparison to men and moderate strength and higher strength participants respectively (p ≤ 0.05). This was primarily due to higher negative to positive work ratios of the COM in women and lower strength participants during all jumps. Furthermore, the COM negative work was primarily dissipated at the knee joint in women and in the lower strength group, particularly during the higher drop jump trials, which are representative of a demanding eccentric load task. A definitive energy algorithm was observed as a reflection of altering joint work strategy in women and lower strength individuals, indicating a possible role in knee joint injury and modulation of such by altering muscular strength.

Dear Editor-in-Chief, We read the article of Buckner et al. (1), hoping to find new insights on resistance training. Unfortunately, the article is a restatement of information contained in previously published reviews from this group. Here are our major concerns: HYPERTROPHY AND STRENGTH GAINS Buckner et al. believe that high-volume phases are unnecessary. Initial alteration in body composition (including myofibrillar hypertrophy) is conceptually (along with the more important increased work capacity) a tenet of resistance training periodization. The paradigm of first developing muscle cross-sectional area (CSA) is not new (2) and has substantial theoretical support. We believe there is sufficient evidence indicating that hypertrophy resulting from resistance training, along with other factors, enhances maximum strength (3). The degree of enhancement depends on several factors, including training methods and trained state. Although we agree that the impact can be relatively small, particularly in early phases of training in inexperienced trainees compared with neurological adaptations, and so on, total hypertrophy (myofibrillar) resulting from long-term resistance training substantially contributes to strength development (3). Evidence from both early muscle activation and CSA studies and later studies (4) indicates that initial gains (up to 6–8 wk) in hypertrophy (myofibrillar) are small and likely do not contribute markedly to increased strength. This evidence also suggests that later alterations (~4–8 wk) in CSA (myofibrillar) can begin to contribute to alterations in strength and related characteristics. TRAINING VARIATION Buckner et al. (5) suggest that there is minimal evidence supporting the use of variation in resistance training programming or periodization. It should be noted that individuals cannot tolerate high-volume and/or heavy multijoint exercise loading for extended periods without experiencing nonfunctional overreaching or overtraining syndrome. Altering fitness phase order (therefore programming) produces different outcomes, sometimes subtle, but different (6). Researchers in early studies examined programming variation versus various constant repetition programming schemes and demonstrated that the variation groups produced superior adaptations. Furthermore, a recent systematic review indicates that using the same training stimulus for >6 wk, especially in trained subjects and athletes can result in a plateau in maximal strength (7). TRAINING TO FAILURE The majority of studies and reviews indicate training to failure is unnecessary, and loading does make a difference (7). Evidence from both cross-sectional and longitudinal studies indicate selective hypertrophy can result from different loading schemes; training to failure, particularly with higher repetitions, tended to select type I motor units, whereas heavier loading and ballistic movements targeted type II motor units (8). These observations likely play an important role in the training and performance outcomes of athletes. MISREPRESENTATION OF THE LITERATURE Finally, selective use of references, careless editing of quoted statements, and what appear to be misrepresentations of literature in this review fosters misconceptions among readers. One particular example is that of Morehouse and Miller (2). We encourage interested readers to examine pages 59 to 60 and 244 to 246 to surmise what the authors actually stated; the meaning derived directly from the source text is substantially different than what was quoted. Hopefully, those interested will critically review the available literature in its entirety. Michael H. Stone Director, Exercise and Sport Science Lab Sports, Exercise, Recreation and Kinesiology Center of Excellence for Sport Science and Coach Education East Tennessee State University Johnson City, TN Kent Adams Kinesiology Department Exercise Physiology Lab CSU Monterey Bay, CA Seaside, CA Caleb Bazyler Sports, Exercise, Recreation and Kinesiology Center of Excellence for Sport Science and coach Education East Tennessee State University Johnson City, TN Clive Brewer Director of Performance Columbus Crew Columbus, OH George Beckham Assistant Professor, Kinesiology Department CSU, Monterey Bay Seaside, CA Kevin Carroll Sports, Exercise, Recreation and Kinesiology Center of Excellence for Sport Science and coach Education East Tennessee State University Johnson City, TN Robert D. Chetlin Department of Sports Medicine Mercyhurst University Erie, PA Paul Comfort Directorate of Psychology and Sport University of Salford Salford, Greater Manchester, UNITED KINGDOM Centre for Exercise and Sport Science Research Edith Cowan University Joondalup, AUSTRALIA Bret Comstock Department of Exercise Science Bloomsburg University Bloomsburg, PA Aaron Cunanan Sports Science Coordinator San Francisco Giants Brad DeWeese Sports, Exercise, Recreation and Kinesiology Center of Excellence for Sport Science and Coach Education East Tennessee State University Johnson City, TN Jacob E. Earp University of Rhode Island Kingston, RI Sandor Dorgo Department of Kinesiology The University of Texas at El Paso El Paso, TX Steven J. Fleck FlecksRx LL Andrew C. Fry Exercise Physiology Graduate Program Dir. of Research, Research & Coaching Performance Team Director Jayhawk Athletic Performance Laboratory University of Kansas Lawrence, KS Andrew Galpin Co-Director: Center for Sport Performance Director: Biochemistry & Molecular Exercise Physiology Lab California State University Fullerton, CA John Garhammer Professor Emeritius California State University Long Beach, CA Daniel Gahreman College of Health and Human Sciences Charles Darwin University Darwin, NT, AUSTRALIA Casuarina NT, AUSTRALIA Stuart Guppy Centre for Exercise and Sports Science Research Edith Cowan University Joondalup, WESTERN AUSTRALIA G. Gregory Haff Professor of Strength and Conditioning Course Coordinator Masters of Exercise Science (Strength & Conditioning) Edith Cowan University Joondalup, WESTERN AUSTRALIA Keijo Häkkinen Neuromuscular Research Center Biology of Physical Activity Faculty of Sport and Health Sciences University of Jyväskylä, FINLAND Disa Hatfield Department of Kinesiology University of Rhode Island Kingston, RI Cody Haun Speed Center Sport Science Coordinator Exercise Science Lagrange College LaGrange, GA Guy Hornsby Coaching and Performance Science College of Physical Activity and Sport Sciences West Virginia University Morganton, WV Chad Kersick Exercise Science Exercise and Performance Nutrition Laboratory School of Health Sciences Lindenwood University St. Charles, MO William J. Kraemer Department of Human Sciences Program Area: Kinesiology The Ohio State University Columbus, OH Hugh Lamont Department of Kinesiology Coastal Carolina University Conway, SC Jeff McBride College of Health Sciences Department of Health & Exercise Science Director: Neuromuscular & Biomechanics Laboratory Appalachian State University Boone, NC Satoshi Mizuguchi Sports, Exercise, Recreation and Kinesiology Center of Excellence for Sport Science and Coach Education East Tennessee State University Johnson City, TN Robert U. Newton Exercise Medicine, Exercise Medicine Research Institute Edith Cowan University Joondalup, WESTERN AUSTRALIA Kyle Pierce Kinesiology and Health Science Louisiana State University at Shreveport Michael W. Ramsey Department of Sport, Exercise, Recreation, and Kinesiology Center of Excellence for Sport Science and coach Education East Tennessee State University Johnson City, TN Nicholas Ratamess School of Nursing, Health, and Exercise Science The College of New Jersey Ewing, NJ Hugo Santana College of Education, Federal University of Mato Grosso Do Sul, Avenida Costa E Silva, Campo Grande, Mato Grosso do Sul, BRAZIL Margaret E. Stone Center of Excellence for Sport Science and Coach Education East Tennessee State University Johnson City, TN Timothy J. Suchomel Department of Human Movement Sciences Carroll University Dylan Suarez Sports, Exercise, Recreation and Kinesiology Center of Excellence for Sport Science and Coach Education East Tennessee State University Johnson City, TN Kyle Travis Sports, Exercise, Recreation and Kinesiology Center of Excellence for Sport Science and Coach Education East Tennessee State University, Johnson City Chris Taber Exercise Science College of Health Professions Sacred Heart University Fairfield, CT N. Travis Triplett Exercise Science Exercise Science Undergraduate Program Director Department of Health and Exercise Science Appalachian State University Boone, NC Jakob Vingren Chair Department of Kinesiology, Health Promotion and Recreation Professor of Exercise Physiology and Biological Sciences Co-Director Applied Physiology Laboratory University of North Texas Denton, TX John Wagle Performance Science/Player Development Kansas City Royals Surprise, AZ Dan Wathen Athletic Trainer Emeritus Youngstown State University Youngstown, OH

The primary purpose of this investigation was to determine whether strength-matched men and women exhibit a different magnitude and ratio of leg muscle activity during a maximal voluntary isometric squat. The secondary purpose was to assess the effect of normalization method on differences in strength between men and women. Thirty-two men (n = 16) and women (n = 16) were successfully strength-matched (≤10% difference) by maximal force produced during an isometric squat (IS) when normalized to body weight. Subjects first performed a maximal isometric knee extension (IKE) and knee flexion (IKF) followed by the IS and muscle activity (EMGmax) was recorded for the vastus medialis (VMO), vastus lateralis (VL), semitendinosus (ST) and biceps femoris (BF). Muscle activity during the IS was expressed relative to the maximums observed during the IKE and IKF (%EMGmax). The results indicate that VMO, VL, ST and BF %EMGmax were not significantly different (p > 0.05) between men and women during the IS (Men VMO = 136.7 ± 24.9%, Women VMO = 157.1 ± 59.8%, Men VL = 126.2 ± 38.2%, Women VL = 128.1 ± 35.5%, Men ST = 25.5 ± 13.6%, Women ST = 25.2 ± 21.8%, Men BF = 46.1 ± 26.0%, Women BF = 42.2 ± 24.8%). Furthermore, the VMO:VL and hamstring to quadriceps (H:Q) %EMGmax ratio were not significantly different between groups in the IS (Men VMO:VL = 1.15 ± 0.28, Women VMO:VL = 1.22 ± 0.26, Men H:Q = 0.28 ± 0.14, Women H:Q = 0.24 ± 0.20). This investigation indicates that the magnitude of muscle activity and the ratios examined are not significantly different between men and women in a maximal voluntary isometric squat when matched for normalized strength. Future investigations should consider subject strength and normalization procedures in the experimental design to elucidate possible sex differences in neuromuscular performance capabilities.

Field-based sprint performance assessments rely on metrics derived from a simple model of sprinting dynamics parameterized by 2 constants, v0 and τ, which indicate a sprinter's maximal theoretical velocity and the time it takes to approach v0, respectively. This study aims to automate sprint assessment by estimating v0 and τ using machine learning and accelerometer data. To this end, photocells recorded 10-m split times of 28 subjects for three 40-m sprints while wearing an accelerometer around the waist. Features extracted from the accelerometer data were used to train a classifier to identify the sprint start and regression models to estimate the sprint model parameters. Estimates of v0, τ, and 30-m sprint time (t30) were compared between the proposed method and a photocell method using root mean square error and Bland-Altman analysis. The root mean square error of the sprint start estimate was .22 seconds and ranged from .52 to .93 m/s for v0, .14 to .17 seconds for τ, and .23 to .34 seconds for t30. Model-derived sprint performance metrics from most regression models were significantly (P < .01) correlated with t30. Comparison of the proposed method and a physics-based method suggests pursuit of a combined approach because their strengths appear to complement each other.

The aim of this study was to examine bone, muscle, strength and stretch-shortening cycle (SSC) performance in young and elderly individuals with an ankle model to elucidate potential effects of ageing that have been suggested to influence fall risk. Moderately active young (n=10; age=22.3±1.3 yrs) and elderly (n=8; age=67.5±3.3 yrs) males completed a peripheral quantitative computed tomography scan on the dominant lower leg, maximal voluntary isometric plantarflexions (MVIP) and SSC tasks: a countermovement hop and drop hops from three different heights. Bone stress-strain index at 14% of the lower leg and muscle density, muscle cross-sectional area and muscle+bone cross-sectional area at 66% of the lower leg were all significantly greater (p≤0.05) in younger males than elderly males. Younger males also had significantly greater rate of force development and peak force during the MVIP when compared to the elderly. Younger males achieved significantly higher forces, velocities and hop heights during all SSC tasks than elderly males. Such information provides support for greater specificity in exercise interventions that prevent lower leg morphological and functional decrements in the ageing population.

The assessment of sprint velocity is useful for evaluating performance and guiding training interventions. In this paper, we describe an adaptive filtering algorithm to estimate sprint velocity using a single, sacrum-worn magneto-inertial measurement unit. Estimated instantaneous velocity, average 10 m interval velocity, and peak velocity during 40 m sprints from the proposed method were compared to a reference method using photocell position-time data. Concurrent validity of the proposed method was assessed using mean absolute error and mean absolute percent error for all velocity estimates. The significance of the mean error was assessed using a factorial ANOVA for average interval velocity and a paired-samples t test for peak velocity. Reliability was assessed using Bland–Altman 95% limits of agreement for repeated measures. Average interval velocity was underestimated early in the sprint (− 0.25 to − 0.05 m/s) and overestimated later (0.13 m/s) with mean absolute error between 0.20 m/s (3.95%) and 0.62 m/s (7.78%). The average mean absolute error was 0.45 m/s (7.02%) for instantaneous velocity and 0.63 m/s (7.84%) for peak velocity. The limits of agreement grew progressively wider at greater distances (− 0.59 to 0.34 m/s for 0–10 m and − 1.32 to 1.59 m/s for 30–40 m). The estimation error from the proposed method is comparable to other wearable sensor-based methods and suggests its potential use to assess sprint performance.