Journal of Strength and Conditioning Research

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ISSN / EISSN : 1064-8011 / 1533-4287
Total articles ≅ 10,403
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, J. Jay Dawes, Joseph M. Dulla, Robin M. Orr
Journal of Strength and Conditioning Research; https://doi.org/10.1519/jsc.0000000000004268

Abstract:
Lockie, RG, Dawes, JJ, Dulla, JM, and Orr, RM. Extending research on law enforcement academy graduation and fitness: A research note on receiver operating characteristic curves. J Strength Cond Res XX(X): 000–000, 2022—Fitness level contributes to a law enforcement recruit's ability to graduate from a training academy. However, limited research has used receiver operating characteristic (ROC) curves to ascertain whether fitness tests can accurately predict academy graduation. The investigators analyzed archival data from 311 recruits (260 males and 51 females) across 4 academy classes from 1 law enforcement agency. A robust, broad battery of fitness test data included grip strength for both hands, vertical jump, 75-yard pursuit run (75PR), 2-kg medicine ball throw, push-ups, sit-ups, arm ergometer revolutions in 60 seconds, and 20-m multistage fitness test (20MSFT) shuttles. Recruits were split into those who graduated (n = 269) or those who separated (did not complete academy; n = 42). A univariate ANOVA, with sex as a control variable, determined between-group fitness differences. Receiver operating characteristic curves were plotted for each fitness test, and the area under the curve (AUC) determined accuracy. Except for grip strength, graduated recruits were superior in all fitness tests (p < 0.001). The 75PR (AUC = 0.708) and 20MSFT (AUC = 0.727) had fair accuracy in predicting academy graduation. The data suggested that, ideally, fitness tests should not be used for diagnostic purposes in relation to academy graduation potential. Fitness test data can be used to provide specific feedback to at-risk recruits. These results suggest that the 75PR (change-of-direction speed) and 20MSFT (aerobic fitness) could contribute to successful graduation in law enforcement recruits. Law enforcement training staff could use this information to provide targeted training for recruits lacking in these qualities.
, Andreas Konrad, Kazuki Kasahara, Riku Yoshida, Yuta Murakami, Shigeru Sato, Kodai Aizawa, Ryoma Koizumi, Jan Wilke
Journal of Strength and Conditioning Research; https://doi.org/10.1519/jsc.0000000000004263

Abstract:
Nakamura, M, Konrad, A, Kasahara, K, Yoshida, R, Murakami, Y, Sato, S, Aizawa, K, Koizumi, R, and Wilke, J. The combined effect of static stretching and foam rolling with or without vibration on the range of motion, muscle performance, and tissue hardness of the knee extensor. J Strength Cond Res XX(X): 000–000, 2022—Although the combination of static stretching (SS) and foam rolling (FR) is frequently used for warm-up in sports, the effect of the intervention order is unclear. This study compared mechanical tissue properties, pain sensitivity, and motor function after SS and FR (with and without vibration) performed in different orders. Our randomized, controlled, crossover experiment included 15 healthy male subjects (22.5 ± 3.3 years) who visited the laboratory 5 times (inactive control condition, FR + SS, FRvibration + SS, SS + FR, and SS + FRvibration) with an interval of ≥48 hours. In each session, subjects completed three 60-second bouts of FR and SS, targeting the anterior thigh. Pressure pain threshold, tissue hardness, knee flexion range of motion (ROM), maximal voluntary isometric (MVC-ISO), and concentric (MVC-CON) torque, as well as countermovement jump height, were determined before and after the intervention. All interventions significantly (p < 0.01) increased knee flexion ROM (d = 0.78, d = 0.87, d = 1.39, and d = 0.87, respectively) while decreasing tissue hardness (d = −1.25, d = −1.09, d = −1.18, and d = −1.24, respectively). However, MVC-ISO torque was significantly reduced only after FR + SS (p = 0.05, d = −0.59). Our results suggest that SS should be followed by FR when aiming to increase ROM and reduce tissue hardness without concomitant stretch-induced force deficits (MVC-ISO, MVC-CON, and countermovement jump height). Additionally, adding vibration to FR does not seem to affect the magnitude of changes observed in the examined outcomes.
, Ranald Joseph, Keng Y. Ong, Jei M. Tang, Timothy J. Suchomel
Journal of Strength and Conditioning Research; https://doi.org/10.1519/jsc.0000000000004276

Abstract:
Lum, D, Joseph, R, Ong, KY, Tang, JM, and Suchomel, TJ. Comparing the effects of long-term vs. periodic inclusion of isometric strength training on strength and dynamic performances. J Strength Cond Res XX(X): 000–000, 2022—This study compared the effects of including isometric strength training (IST) for consecutive 24 weeks (CIST) against a periodic inclusion (PIST) of this mode of training on strength and dynamic performances. Twenty-four floorball athletes (age: 23 ± 2.7 years, stature: 1.74 ± 2.08 m, and body mass: 72.7 ± 14.4 kg) were randomly assigned to the control (CON), CIST, or PIST group. Athletes completed 20-m sprint, countermovement jump (CMJ), and isometric midthigh pull (IMTP) during pre-test and were tested on weeks 6, 12, 18, and 24. All groups performed a similar strength training program twice per week. However, 2 sets of squats were replaced with isometric squat in CIST for all 24 weeks but only on weeks 1–6 and 13–18 for PIST. A significant main effect for time was observed for 5-, 10-, and 20-m sprint time, CMJ height, peak force, peak power, time to take-off, modified reactive strength index, IMTP peak force, relative peak force, and force at 200 milliseconds (p = <0.001–0.037). Isometric strength training for 24 consecutive weeks resulted in greater improvement in 5-m sprint time than CON at week 24 (p = 0.024, g = 1.17). Both CIST and PIST resulted in greater improvements in 10-m sprint time than CON at various time points (p = 0.007–0.038 and 0.038, g = 1.07–1.44 and 1.18, respectively). Isometric strength training for 24 consecutive weeks and PIST resulted in greater improvements in 20-m sprint time than CON at week 6 (p = 0.007 and 0.025, g = 1.65 and 1.40, respectively). The results showed that the inclusion of IST resulted in greater improvements in sprint performance than CON but no significant difference in all measured variables with PIST.
Annemiek J. Roete, Inge K. Stoter, Robert P. Lamberts, Marije T. Elferink-Gemser,
Journal of Strength and Conditioning Research; https://doi.org/10.1519/jsc.0000000000004271

Abstract:
Roete, AJ, Stoter, IK, Lamberts, RP, Elferink-Gemser, MT, and Otter, RTA. Introducing a method to quantify the specificity of training for races in speed skating. J Strength Cond Res XX(X): 000–000, 2022—The specificity of training for races is believed to be important for performance development. However, measuring specificity is challenging. This study aimed to develop a method to quantify the specificity of speed skating training for sprint races (i.e., 500 and 1,000 m), and explore the amount of training specificity with a pilot study. On-ice training and races of 10 subelite-to-elite speed skaters were analyzed during 1 season (i.e., 26 weeks). Intensity was mapped using 5 equal zones, between 4 m·s−1 to peak velocity and 50% to peak heart rate. Training specificity was defined as skating in the intensity zone most representative for the race for a similar period as during the race. During the season, eight 500 m races, seven 1,000 m races, and 509 training sessions were analyzed, of which 414 contained heart rate and 375 sessions contained velocity measures. Within-subject analyses were performed. During races, most time was spent in the highest intensity zone (Vz5 and HRz5). In training, the highest velocity zone Vz5 was reached 107 ± 28 times, with 9 ± 3 efforts (0.3 ± 0.1% training) long enough to be considered 500 m specific, 6 ± 5 efforts (0.3 ± 0.3% training) were considered 1,000 m specific. For heart rate, HRz5 was reached 151 ± 89 times in training, 43 ± 33 efforts (1.3 ± 0.9% training) were considered 500 m specific, and 36 ± 23 efforts (3.2 ± 1.7% training) were considered 1,000 m specific. This newly developed method enables the examination of training specificity so that coaches can control whether their intended specificity was reached. It also opens doors to further explore the impact of training specificity on performance development.
, John D. Ashley, Robert M. Skinner, Jose P. Polanco, Mason T. Walters, Brian K. Schilling, J.M. Kellawan
Journal of Strength and Conditioning Research; https://doi.org/10.1519/jsc.0000000000004233

Abstract:
Stone, BL, Ashley, JD, Skinner, RM, Polanco, JP, Walters, MT, Schilling, BK, and Kellawan, JM. Effects of a short-term heat acclimation protocol in elite amateur boxers. J Strength Cond Res XX(X): 000–000, 2022—Boxing requires proficient technical and tactical skills coupled with high levels of physiological capacity. Although heat and humidity negatively affect acute exercise performance, short-term exercise training in hot and humid environments can lead to physiological adaptations that enhance exercise performance in both hot and thermoneutral conditions. In highly trained endurance athletes, exercise-induced acclimation can occur in as little as 5 days (known as short-term heat acclimation [STHA]). However, the impact of a 5-day heat acclimation (5-DayHA) in combat athletes, such as elite amateur boxers, is unknown. The aim of the present investigation was to determine whether a 5-DayHA improves aerobic performance in a thermoneutral environment and causes positive physiological adaptations in elite boxers. Seven elite amateur boxers underwent a 5-DayHA protocol, consisting of 60-minute exercise sessions in an environmental chamber at 32 °C and 70% relative humidity. Repeat sprint test (RST) evaluated aerobic performance in a thermoneutral environment 24 hours before and after the 5-DayHA. Presession and postsession hydration status (urine specific gravity) and body mass were assessed. After a 5-DayHA period, boxers significantly improved RST performance (13 ± 7 to 19 ± 7 sprints, d = 0.92, p = 0.03) but not pre-exercise hydration status (1.02 ± 0.01 to 1.01 ± 0.01, d = 0.82, p = 0.07). Therefore, these findings suggest 5-DayHA enhances aerobic performance in elite-level amateur boxers and may provide a viable training option for elite combat athletes.
Alexandre K. G. Prado, Thais Reichert, Matheus O. Conceição, Rodrigo S. Delevatti, Ana Carolina Kanitz, Luiz Fernando M. Kruel
Journal of Strength and Conditioning Research, Volume 36, pp 1468-1483; https://doi.org/10.1519/jsc.0000000000001595

Abstract:
The effects of training in an aquatic environment on muscular strength are still contradictory in the literature. The aim was to conduct a systematic review and meta-analysis of randomized studies about muscle strength responses after a program of aquatic exercise. A systematic review followed the Cochrane and PRISmA recommendations. The search was performed between December 2015 and January 2016. There were no language restrictions and PUBmED, SCOPUS, Scielo, Cochrane and PEDro databases were consulted. An analysis of eligibility of the studies was done by two independent authors. The data extraction followed standard criteria, and an evaluation of methodological quality was performed. The statistical analysis was conducted in Review Manager 5.1 software. The statistical heterogeneity was assessed by means of Cochran’s Q test and by the inconsistency test (I2). The search found 2563 manuscripts, 27 were included, totaling a total n of 1006 participants. The analysis of the risk of bias demonstrated a lack of clarity of the randomization process, allocation concealment, blinding assessment, intention to treat analysis and calculation of the sample in 70% or more of the studies analyzed. Meta-analysis demonstrated a significant increase in handgrip strength, in isometric peak torque of knee unilateral extension and flexion and isokinetic peak torque (60°.s-1) of knee unilateral extension. Sensitivity analyses demonstrated that the positive effects of training in an aquatic environment may be dependent on factors such as age, velocity of movement and use of device. Land-based and aquatic exercises seem to lead to similar muscle strength gains. Aquatic exercise should be recommended as a strategy to improve muscle strength, but new studies with better methodological quality should be conducted.
, Masaaki Kanno, Shota Shidochi, Kazuhito Sakae, Norihiro Shima
Journal of Strength and Conditioning Research, Volume 36; https://doi.org/10.1519/jsc.0000000000002378

Abstract:
This study aimed at elucidating the characteristics of upper-limb physical strength required by female wrestlers by comparing the pull power, power endurance, and number of repetitions between female wrestlers at world and national levels. The subjects were 20 female wrestlers (8 Olympic- and/or world-class and 12 national-class top-ranking individuals). The subjects assumed a lying prone (face down) position on a bench and pulled a bar from arms length until contact with underside of bench. The weight load was increased in 10-kg steps and the upper-limb pull power was measured for each lift. To measure power endurance, the power to achieve the repetition maximum and the maximum number of repetitions were measured at the load at which they exerted their maximum power. All measurements were obtained using a GymAware power meter (Kinetic Performance Technology, Canberra, Australia). Pull power was greater at 20, 30, 40 and 50 kg in world-class wrestlers than in national-class wrestlers. No difference was observed in the time course of power endurance between the groups; however, the power in world-class wrestlers declined slower than in national-class wrestlers. Repetition maximum also tended to be higher in world-class wrestlers than in national-class wrestlers. Female wrestlers were observed to have greater upper-limb pull power in a range from low to high loads and were able to preserve repetition ability while maintaining high power. Their competitive performance appears to be related to these abilities.
, Jennifer Sanfilippo, Samantha Dawes, Andrew Watson
Journal of Strength and Conditioning Research; https://doi.org/10.1519/jsc.0000000000004259

Abstract:
Haraldsdottir, K, Sanfilippo, J, Dawes, S, and Watson, A. Contribution of lean mass distribution on aerobic fitness and performance in NCAA division I female rowers. J Strength Cond Res XX(X): 000–000, 2022—The purpose of this study was to determine the relative influence of total lean body mass (LBM), body fat percentage (BF%), upper extremity lean mass (ULM), lower extremity lean mass (LLM), and trunk lean mass (TLM) on maximal aerobic capacity (V̇o2max) and time to exhaustion (Tmax) in female collegiate rowers. One hundred seven female collegiate rowers (aged 18–22 years) performed maximal progressive rowing ergometer testing to determine V̇o2max and Tmax. Body mass, LBM, BF%, ULM, LLM, and TLM were determined by using dual-energy x-ray absorptiometry. Separate multivariable linear regression models were performed to predict V̇o2max and Tmax by using LBM and BF% as predictors. In addition, separate linear regression models were used to predict V̇o2max and Tmax with ULM, LLM, and TLM as covariates. Subjects were aged 20 ± 3 years. V̇o2max was significantly predicted by LBM (r2 = 0.29, p < 0.001), but not BF% (r2 = 0.002, p = 0.79). Similarly, Tmax was significantly predicted by LBM (r2 = 0.25, p < 0.001), but not BF% (r2 = 0.003, p = 0.19). V̇o2max was significantly predicted by LLM (r2 = 0.12, p < 0.01), but not ULM (r2 = 0.08, p = 0.68) or TLM (r2 = 0.09, p = 0.17), and Tmax was significantly predicted by TLM (r2 = 0.09, p = 0.02), but not ULM (r2 = 0.07, p = 0.89) or LLM (r2 = 0.08, p = 32). Among female collegiate rowers, whole body LBM is a significant predictor of both V̇o2max and Tmax. However, LLM is a stronger predictor of V̇o2max while TLM is a stronger predictor Tmax, although each of these relationships has a low coefficient of determination. These findings suggest that aerobic fitness and performance may be influenced by regions of lean mass differently.
Luis Miguel Fernández-Galván, Arturo Casado, Amador García-Ramos, Guy Gregory Haff
Journal of Strength and Conditioning Research; https://doi.org/10.1519/jsc.0000000000004255

Abstract:
Fernández-Galván, LM, Casado, A, García-Ramos, A, and Haff, GG. Effects of vest and sled resisted sprint training on sprint performance in young soccer players: A systematic review and meta-analysis. J Strength Cond Res XX(X): 000–000, 2022—The aim of the meta-analysis was to determine the effect of resisted sprint training (RST) on sprint performance in young (<20 years) soccer players and to analyze whether the training equipment (sled or vest) and magnitude of the resistive load (above or below 20% of body mass [BM]) influences the long-term adaptations in sprint performance. Resisted sprint training reduced the acceleration phase time [standardized mean difference (SMD) = −0.41], with greater reduction in sprint time occurring in response to applying resistance with a vest (SMD = −0.70) when compared with a sled (SMD = −0.27). Similar reductions were determined for resistive loads <20% (SMD = −0.55) and ≥20% of BM (SMD = −0.31). Full sprint time showed a small reduction after RST (SMD = −0.36), regardless of the training equipment (sled: SMD = −0.44; vest: SMD = −0.26) and resistive load (<20% of BM: SMD = −0.40 ≥ 20% of BM: SMD = −0.21). There was a small and nonsignificant reduction in the maximum-velocity phase after RST (SMD = −0.25), which was comparable when the training was performed with vest (SMD = −0.34) or sled (SMD = −0.22). No significant differences in the changes of the acceleration phase time (SMD = 0.05) or full sprint time (SMD = 0.08) were observed between the experimental (sled or vest RST) and control groups (only soccer or unresisted sprint training). In conclusion, RST is effective to improve sprint performance in young soccer players, but the improvements are not superior to unresisted sprint training.
, Witalo Kassiano, João Pedro Nunes, Gabriel Kunevaliki, Pâmela Castro-E-Souza, Paulo Sugihara Junior, Rodrigo R. Fernandes, Edilson Serpeloni Cyrino, Leonardo De Sousa Fortes
Journal of Strength and Conditioning Research; https://doi.org/10.1519/jsc.0000000000004042

Abstract:
Costa, BDV, Kassiano, W, Nunes, JP, Kunevaliki, G, Castro-E-Souza, P, Sugihara-Junior, P, Fernandes, RR, Cyrino, ES, and de Fortes, LS. Does varying resistance exercises for the same muscle group promote greater strength gains? J Strength Cond Res XX(X): 000–000, 2021—Two of the foremost principles of progression are progressive overload and variation. A way to vary within a resistance training (RT) program is to perform different exercises for the same muscle group; however, this strategy is still overlooked. The purpose of the present study was to compare strength adaptations between an RT routine that maintained the exercises fixed (N-VAR) and another that varied the exercises for the same muscle group during the weekly sessions (VAR). Twenty-three young men (23.3 ± 4.1 years) were randomly allocated to N-VAR (n = 11) and VAR (n = 12) conditions. The RT was performed 3 times a week for 9 weeks and consisted of a whole-body routine (3 sets of 8–12 repetitions). Maximum dynamic strength was assessed using the 1-repetition maximum test (1RM), and the isometric strength was assessed using an isokinetic dynamometer, before and after training. Following the training period, both groups increased the 1RM values in all exercises (p ≤ 0.002), without significant differences between them (p ≥ 0.20). In contrast, a greater increase (p = 0.02) in isometric knee extension strength was showed to N-VAR (+12%) compared with VAR (+7%). There was no significant increase in both groups for isometric knee flexion strength (N-VAR, p = 0.10; VAR, p = 0.18). Our findings indicate that maintaining or varying the exercises for the same muscle group promotes similar adaptations in the maximum dynamic strength. In contrast, for the isometric strength in knee extension, maintaining the fixed exercises seems to be more interesting.
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