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Sedentary lifestyles reduce muscle mass, strength, power, and alter viscoelastic properties. Plyometric jump training (PJT) shows promise in countering these effects, but the optimal training volume for individuals with low athletic performance remains unclear. This study aimed to determine the minimal PJT volume required to improve muscle and tendon viscoelastic properties, strength, and power in sedentary individuals. A double-blind randomised controlled trial included 44 participants divided into three groups: Control Group (CG) ( n  = 16), Reduced Volume Training Group (RVTG) ( n  = 16), and Training Group (TG) ( n  = 12). The four-week PJT programme involved three weekly sessions with gradual volume increments; RVTG performed 50% less volume than TG. Baseline and follow-up assessments included the isokinetic standing up (SU) and sitting down (SD) phases at 15 cm/s and 5 cm/s, and myotonometer measurements. In the SU phase at 15 cm/s, significant differences were found ( p  = 0.01) with higher values in TG (10.0 ± 3.3 N/kg) compared to CG and RVTG. At 5 cm/s, differences in SD were observed ( p  = 0.002). For Achilles tendon properties in RVTG: stiffness ( p  = 0.04), decrement ( p  = 0.01), and relaxation ( p  = 0.02). A PJT volume of 2,414 jumps improved muscle strength, while 1,207 jumps altered tendon properties.

Change of directions (COD) involves multidirectional and complex actions, with performance influenced by multiple factors. As lower limb strength is one of the most determinant of COD performance, the present study aimed to (a) explore the differences in strength outcomes across different lower limb muscle actions between faster and slower basketball players in COD actions at different angles and (b) analyse the relationship between isometric, concentric and eccentric strength outcomes and COD performance at different cutting angles. Twenty-five basketball players (44% female) completed a battery of tests, encompassing isokinetic and isometric squat strength assessments, along with COD tests at 45°, 90° and 180°. Players were categorised as 'low-performance' and 'high-performance' groups based on execution time in COD, facilitating a comparison between performance groups. Results indicated that concentric strength showed the greatest differences between performance groups at 45° COD (effect size ≥ 0.813; p ≤ 0.034). Isometric and eccentric strength demonstrated a moderate-to-large relationship with 90° COD performance (Rho ≥ 0.394; p ≤ 0.045), and all muscle actions exhibited a large relationship with 180° COD (Rho ≥ 0.445; p ≤ 0.030). Moreover, the fastest players showed higher levels of concentric strength relative to eccentric strength, regardless of the cutting angle. These findings hold practical applications, suggesting that basketball coaches should train a specific kind of muscle action depending on the individual players' COD demands, focusing on improving the rapid eccentric force application while striving to reduce the eccentric/concentric ratio., (© 2024 The Author(s). European Journal of Sport Science published by Wiley‐VCH GmbH on behalf of European College of Sport Science.)

Purpose: to explore lower limb muscle activity concerning limb dominance, as well as variations in force and power during the standing up and sitting down phases of the instrumented sit-to-stand-to-sit test in sedentary individuals, across isokinetic and isotonic modalities., Methods: 33 sedentary individuals underwent testing using a functional electromechanical dynamometer in both isokinetic and isotonic modes, accompanied by surface electromyography., Results: In the isokinetic mode, the non-dominant gastrocnemius medialis and vastus medialis exhibited significantly (p < 0.05) higher muscle activity values during the standing up and sitting down phase compared to dominant counterparts. In the isotonic mode standing up phase, significant differences in muscle activity were noted for non-dominant gastrocnemius medialis, vastus medialis, and biceps femoris compared to their dominant counterparts. The sitting down phase in isotonic mode showed higher muscle activity for non-dominant vastus medialis compared to dominant vastus medialis. Regard to performance outcomes, significantly lower (p < 0.0001) values were observed for standing up (12.7 ± 5.1 N/kg) compared to sitting down (15.9 ± 6.1 N/kg) peak force, as well as for standing up (18.7 ± 7.8 W/kg) compared to sitting down (25.9 ± 9.7 W/kg) peak power in isokinetic mode. In isotonic mode, lower values were found for sitting down (6.5 (6.3-7.1) N/kg) compared to standing up (7.8 (7.3-8.9) N/kg) peak force and for sitting down (18.5 (13.2-21.7) W/kg) compared to standing up (33.7 (22.8-41.6) W/kg) peak power., Conclusions: Limb dominance influences lower-limb muscle activity during the instrumented sit-to-stand-to-sit test, and the choice of testing mode (isokinetic or isotonic) affects muscle engagement and performance outcomes., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Obesity is a major health burden worldwide. Although bariatric surgery (BS) is recognized as an effective strategy for weight loss and comorbidities improvement, its impact on muscle strength and quality is still unclear. We aimed to examine postoperative changes in muscle strength and quality and their relationship with body mass index (BMI) changes among adults undergoing BS. To this end, we systematically searched the WoS, PubMed, EBSCO, and Scopus databases. The meta-analyses, which included 24 articles (666 participants), showed that BS reduces absolute lower-limb isometric strength (ES = -0.599; 95% CI = -0.972, -0.226; p = 0.002). Subjects who experienced a more significant reduction in BMI after BS also suffered a higher loss of absolute muscle strength. Similarly, absolute handgrip strength showed a significant decrease (ES = -0.376; 95% CI = -0.630, -0.121; p = 0.004). We found insufficient studies investigating medium- and long-term changes in muscle strength and/or quality after BS. This study provides moderate-quality evidence that BS-induced weight loss can reduce the strength of appendicular muscles in the short term, which should be addressed in management these subjects. More high-quality studies are needed to evaluate the impact of BS on muscle strength and the different domains of muscle quality in the medium and long term (registered on PROSPERO CRD42022332581)., (© 2024 World Obesity Federation.)

Background: Despite the significance of muscle oscillation frequency, previous research has not established a correlation with muscle performance due to the challenges of applying resistance without altering natural motion during functional tests., Research Question: What is the correlation between muscle oscillation frequency and lower limb muscle strength, power, and work during an instrumented sit-to-stand and stand-to- sit (iSTS-TS) task among sedentary subjects?, Methods: In a cross-sectional study, the oscillation frequency of the gastrocnemius medialis (GM), biceps femoralis (BF), and vastus medialis (VM) muscles in both the dominant (D) and non-dominant (ND) legs was assessed with a handheld myotonometer in 34 sedentary individuals before performing the iSTS-TS task., Results: In the isokinetic mode, no significant correlations were found. In the isotonic mode, the BF muscle oscillation frequency in the D and ND legs exhibited significant positive correlations with peak force, peak power, and work during sitting down, as well as peak power and work during standing up. Positive correlations were observed in both legs between the GM oscillation frequency and sitting down peak force and work. Additionally, significant positive correlation was found with standing up work in the D leg. Muscle oscillation frequency of the VM exhibited a positive correlation with sitting down peak force in the ND leg., Significance: Due to a greater number of correlations found, it is advisable to use the isotonic mode when assessing muscle oscillation frequency in relation to muscle performance during functional iSTS-TS tasks in sedentary subjects., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflicts of interest., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

There is evidence that promoting school physical activity (PSPA) benefits children and adolescents, but little is understood about how this promotion may relate to academic achievement and school climate across varying levels of socioeconomic status (SES). Hence, the study aimed to address this knowledge gap by examining two main objectives: (1) determining the association between PSPA and academic achievement and school climate according to schools' SES and (2) exploring the potential mediating role of PSPA in the relationship between schools' SES and academic achievement and school climate. This cross-sectional study at the school level focused on 4,990 schools (including public, subsidized, and private schools) that participated in the National Educational Study 2018 (Chile), which was applied to primary schoolchildren (4th grade, aged 8-10 years). Schools were divided into non-PSPA ( n  = 4,280) and PSPA ( n  = 710) during the year 2018. Changes in academic achievement from 2017 to 2018 and school climate were considered. PSPA was associated with improvements in maths (low-SES OR: 1.80, p  < 0.001) and reading (middle-SES OR: 1.45, p  = 0.029; low-SES OR: 1.47, p  < 0.001). The indirect effect (IE) showed that PSPA partially mediated the relationship between SES and academic achievement in reading (IE = 1.017; SE = 0.12; 95%CI, -1.27, -0.77), maths (IE = -1.019; SE = 0.12; 95%CI, -1.25, -0.78), and school climate (IE = -0.46; SE = 0.52; 95%CI, -0.56, -0.35). In conclusion, PSPA was linked to positive changes in academic achievement, especially among low SES, and PSPA presented a potential mediating role in the relationship between SES of schools and academic achievement and school climate., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Delgado-Floody, Cristi-Montero, Jerez-Mayorga, Ruiz-Ariza, Guzmán-Guzmán, Álvarez, Gómez-López, Carter-Thuillier and Caamaño-Navarrete.)

Background: A greater motivation for coaches to be more involved in assessment could be the development of specific strength tests closer to specific handball tasks. Therefore, the aims were to determine the reliability of a handball specific strength test battery in young handball players using a functional electromechanical dynamometer (FEMD) and to evaluate the association between the strength test battery and performance measurements., Methods: Thirty-two young handball players (25% males and 75% females) performed a repeated-measurement design over four weeks. The players conducted one session per week, with each measurement consisting of two isometric tests to obtain isometric peak force, and four incremental tests. Moreover, performance handball tests (sprint and throwing velocity [TV]) were recorded., Results: The reliability of the whole handball specific strength tests was very high for the peak and mean strength (ICC=0.70-0.85; CV=8.49-13.99; SEM=0.44-0.67 kg). The step forward had a moderate association with 5 to 10 meters' time. The highest correlation between TVmean was found with the peak strength of standing lift and between TVpeak with peak strength of unilateral throw. The sprint total time could be explained by Body Mass Index and peak strength of the standing lift in the 40% and the TVpeak could be explained by arm span and mean strength of the standing lift in the 68%., Conclusions: The high reliability for all exercises and the significant correlation with handball performance (sprint time and TV) allow us to include these tests in handball team evaluation and training.

Background: The aim of this study was to compare the reliability and agreement between two devices - Wii Fit Balance Board (WBB) versus Hand-Held Dynamometer (HHD) to measure isometric strength during the athletic shoulder (ASH) test in healthy amateur rugby players., Methods: Fifteen males (23.73 ± 2.8 years) completed two testing sessions. Maximal isometric contractions using the dominant arm (D) and non-dominant arm (ND) against a WBB and HHD were assessed at three angles of abduction (180°, 'I'; 135°, 'Y' and 90°, 'T'), in a prone lying position., Results: The results indicate a very large correlation between the HHD and the WBB. WBB provides acceptable reliability at I-Test D (CV = 9.97%, ICC = 0.88) and HHD in the I-Test D (CV = 8.90%, ICC = 0.94), I-Test ND (CV = 8.60%, ICC = 0.95) in peak strength values. The HHD is most reliable in D ASH I-Y-T (CV = 10.94%) and WBB (CV = 11.05%). In the ND ASH I-Y-T test, the HHD is the most reliable (CV = 12.5%) compared to the WBB (CV = 14.43%)., Conclusions: These results suggest that WBB is a reliable device to assess strength in the ASH test with a very large correlation with the HHD. WBB and HHD are two affordable devices to assess isometric shoulder strength., Competing Interests: The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2022.)

Introduction: The purpose of this systematic review was: a) to determine the quality of evidence from studies assessing the effects of different lower limb strengthening protocols on muscle activity, strength, and power in sedentary and/or physically inactive subjects; and b) to determine the effectiveness of lower extremity strengthening protocols on muscle activity, strength, and power in sedentary and/or physically inactive subjects. Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) statements were followed using keywords associated with strength training, lower limb, sedentary, and physical inactivity. Four databases were used: Medline via PubMed, Web of Science, Scopus and SPORTDiscus. Methodological quality was assessed using the PEDro scale. A total of 164 articles were retrieved, six included in this review. Four studies were classified as fair methodological quality, and two were considered of good methodological quality. Due to the heterogeneity in methodological aspects and the limited number of articles including the variables under study, it was not possible to establish a measure of effectiveness of lower limb strengthening protocols on muscle activity, strength, or power. In conclusion, strength training in the lower limb seems to improve the levels of strength, power, and muscular activity in sedentary subjects. However, due to the limited number of articles, methodological variability, and training methods used, it is necessary to conduct new studies that control these variables.

Most of the existing research has focused on jump plyometrics, where landing reaction forces must be dissipated among lower limb articulations. In contrast, the investigation of resisted plyometrics without jumping, devoid of such landing forces, remains relatively limited. This study aimed to (i) investigate the impact of resisted plyometrics without jumping at two knee flexion angles (60 and 90 degrees) on vastus muscle activity relative to limb dominance and (ii) assess strength, power, and work during the concentric-eccentric phases of these exercises. Thirty-one healthy participants underwent quantification of lower limb muscle amplitude, strength, power, and work during resisted plyometrics without jumping from both 60° and 90° knee flexion positions. After anthropometric evaluations, participants used a dynamometer with a load equal to 80% of body weight while wireless surface electromyography electrodes recorded data. Statistical analyses utilized paired t-tests or nonparametric equivalents and set significance at p ≤ 0.05. Results showed significantly higher muscle activity in the vastus medialis (VM) (dominant: 47.4%, p = 0.0008, rs = 0.90; nondominant: 54.8%, p = 0.047, rs = 0.88) and vastus lateralis (VL) (dominant: 46.9%, p = 0.0004, rs = 0.86; nondominant: 48.1%, p = 0.021, rs = 0.67) muscles when exercises started at 90° knee flexion, regardless of limb dominance. Substantial intermuscle differences occurred at both 60° (50.4%, p = 0.003, rs = 0.56) and 90° (54.8%, p = 0.005, rs = 0.62) knee flexion, favoring VM in the nondominant leg. Concentric and eccentric strength, power, and work metrics significantly increased when initiating exercises from a 90° position. In conclusion, commencing resisted plyometrics without jumping at a 90° knee flexion position increases VM and VL muscle activity, regardless of limb dominance. Furthermore, it enhances strength, power, and work, emphasizing the importance of knee flexion position customization for optimizing muscle engagement and functional performance.

Abstract: Barrera-Domínguez, FJ, Martínez-García, D, Jerez-Mayorga, D, Chirosa-Ríos, LJ, Almagro, BJ, and Molina-López, J. Vertical versus horizontal training for improving the change of direction speed in adult basketball players: a systematic review and meta-analysis. J Strength Cond Res XX(X): 000-000, 2023-The ability to perform changes of direction (COD) is a complex skill that involves the application of multiple force-orientations, and its execution at maximum speed is crucial in basketball players. The present study aimed to synthesize findings from previous interventions classified according to force-orientation (vertical, horizontal, or mixed) and determine their magnitude of the effect on COD performance in basketball players. A systematic review of the literature was performed in several databases (Web of Science, Scopus, SPORTDiscus, and PubMed) following the PRISMA statement and reviewed the quality of the included papers according to the Cochrane Collaboration Guidelines Assessment. Sixteen articles with a total of 21 reports were included to analyze the role of force-orientations in COD performance. For the meta-analysis, the standardized mean differences with 95% confidence intervals (CIs) were calculated to determine the chronic changes induced by training and performed an effect size (ES) analysis with a random-effects model. The results showed that all force-orientations generated improvements in COD performance (ES = -0.47 [95% CI -0.57, -0.36], Z = 8.74 [p < 0.01]). It was a mixed force-orientation that produced the greatest changes (ES = -0.91 [95% CI -1.27, -0.55], Z = 4.96 [p < 0.01]), followed by vertical training (ES = -0.45 [95% CI -0.70, -0.20], Z = 3.51 [p < 0.01]). Horizontal training was the least studied and showed the smallest change (ES = -0.10 [95% CI -0.14, -0.07], Z = 5,71 [p < 0.01]). This meta-analysis demonstrates that mixed vertical and horizontally oriented training may be the most optimal because it offers a greater variety of multidirectional stimuli that better prepares the athlete to deal with complex COD in real-game situations., (Copyright © 2023 National Strength and Conditioning Association.)

A good muscle quality index (MQI) may have an inverse relationship with psychosocial variables of depression, anxiety, and stress in adolescents. Unfortunately, little scientific evidence has related MQI to psychosocial variables in this population. Therefore, this research aimed to determine the relationship between the MQI and psychosocial variables of depression, anxiety, and stress in Chilean adolescents. In this quantitative correlational design study, sixty adolescents participated voluntarily (mean ± standard deviation [SD]: age 15.11 ± 1.78 years). Anthropometric parameters, prehensile strength, MQI, and psychosocial variables were evaluated. The results showed that adolescents with high levels of MQI presented lower levels of depression (7.50 ± 6.06 vs. 10.97 ± 5.94), anxiety (5.64 ± 4.81 vs. 9.66 ± 5.12), and stress (6.79 ± 5.09 vs. 10 ± 5.58), in addition to reported lower abdominal obesity (WtHR, 0.47 ± 0.07 vs. 0.52 ± 0.07) than those with low levels of MQI. The group with high levels of MQI reported a higher prevalence of nonanxiety (81.3%, p = 0.031) and a lower prevalence of abdominal obesity (55.8%, p = 0.023). Likewise, a significant inverse association was evidenced between MQI and depression (β; -6.18, 95% CI; -10.11: -2.25, p = 0.003), anxiety (β; -6.61, 95% CI; -9.83: -3.39, p < 0.001) and stress (β; -4.90, 95% CI; -8.49: -1.32 p = 0.008). In conclusion, the results suggest that high levels of MQI are associated with a higher prevalence of nonanxiety in adolescents and a significant inverse association between MQI and levels of depression, anxiety, and stress., (© 2023. The Author(s).)

Context: Current devices to assess strength performance in handball may not be sufficiently sports-specific and reliable methods. Functional electromechanical dynamometry is a new technology that allows the development of accurate strength tests in athletes., Purpose: To determine the absolute and relative reliability and to compare the reliability of the right and left side, and mean and peak force of 3 specific strength tests in handball players with a functional electromechanical dynamometer: unilateral pullover, standing lift, and step forward., Methods: Fourteen male handball players of the first Spanish division (28.79 [4.81] y; 10.38 [4.63] y of professional experience) performed a repeated-measurement design. Three testing sessions were performed (one per week). The first measurement consisted of 4 isometric tests (right and left unilateral pullover, and right and left standing lift) to obtain isometric peak force, and in the second and third sessions, 6 incremental tests until failure (right and left unilateral pullover, and right and left standing lift, right and left step forward) were performed., Results: The tests provided high reliability or acceptable reliability for mean and peak strength of unilateral pullover, standing lift and step forward (intraclass correlation coefficient = .83-.97; coefficient of variation = 3.90-11.57). Effect side was negligible in any of the parameters, except for a small effect side in the left peak force for unilateral pullover and a small effect side on the left side for a step forward. Significant differences in reliability (coefficient of variation ratio > 1.15) were found between the right and left sides and peak and mean force in all exercises except peak force in unilateral pullover and step forward., Conclusion: These results confirm that the tests could be applied to assess physical performance in handball at the same time as regular gym training. Moreover, this is an excellent opportunity to individualize the player's weekly load.

Context: The aim of this study was to analyze the muscle activity of the hamstring muscles and the lateral gastrocnemius during different variants of the single-leg bridge (SLB) in futsal players., Design: Cross-sectional study., Methods: Twenty-two futsal players (age = 24.8 [3.9] y) volunteered to participate in this study. The participants performed 3 variations of the SLB with the knee flexed at 45°. The first position was performed with the ankle in plantar position with flat support, the second with the ankle in dorsiflexion (DF) with heel support, and the third with the ankle in DF and external rotation (ER) with heel support. The Wilcoxon rank-sum test assessed the difference between variables for samples with the rank-biserial correlation effect size. Spearman correlation coefficients were used to examine the associations of the percentage maximal voluntary isometric contraction for each muscle with peak force and rate of force development with 3 different variances of the SLB., Results: The variation of ankle DF and ER with heel support generated higher muscle activity in BF in concentric (P < .01, effect size [ES] = -0.613); isometric (P < .042, ES = -0.494); and eccentric (P < .005, ES = -0.668) contraction than ankle DF with heel support. In contrast, the variation of ankle DF and ER with heel support generated fewer muscle activity in lateral gastrocnemius in concentric (P < .001, ES = 0.779); isometric (P < .003, ES = 0.708); and eccentric (P < .014, ES = 0.589) contraction than ankle DF with heel support., Conclusions: The position of DF and ER was the best position in SLB to train the BF. It could be convenient to start rehabilitation of the BF with flat foot postition or ankle in DF with heel support and progress with the position of the ankle in DF and ER with heel support.

The purposes were to synthesize as much scientific evidence as possible to determine the effect of core training on balance, throwing/hitting velocity or distance, and jumping in healthy subjects, identify the possible differences between isolated and combined core training on performance and study training and sample variables related to performance. PRISMA guidelines were followed, and a systematic search was performed in the Scopus, Web of Science, Sports Discuss, and PubMed databases with no date restrictions until November 2022. The studies were considered for this meta-analysis following PICO; a) randomized control trials and randomized allocation studies with healthy subjects and > 12 years old b)isolated or combined core training programs with a minimum of 4 weeks in length; c) athletic performance outcomes for balance, throw/hit, and jump variables should be measured; d) sufficient data to calculate effect sizes. The Cochrane Collaboration Risk of Bias Tool and the Grading of Recommendations Assessment, Development, and Evaluation approach were used for assessing methodological quality. A total of 3223 studies were identified, 22 studies were included in the systematic review and 21 for the meta-analysis. We observed that core training improved balance outcomes (ES = 1.17; p < 0.0001), throwing/hitting velocity (ES = 0.30; p = 0.14), throwing/hitting distance (ES = 3.42; p = 0.03), vertical jumping (ES = 0.69; p = 0.0003), and horizontal jump (ES = 0.84; p = 0.01). Our findings indicate that core training improved different variables of performance such as balance, throw/hit, and vertical and horizontal jump., Competing Interests: All the authors declare that they have no conflicts of interest., (Copyright © Biology of Sport 2023.)

Objective: To evaluate the effects of exergames added to a conventional physical therapy (CPT) program on functional fitness and dynamometric muscle performance for the sit-to-stand (STS) maneuver in older adults and to compare their results concerning a CPT-only intervention. Materials and Methods: Fifty independent older adults were randomly assigned to CPT and exergames (CPT+ExG group; n  = 25; age = 71.8 ± 6.8 years) or CPT alone (CPT group; n  = 25; age = 71.3 ± 7.4 years). CPT was performed twice a week (60 min/session) for 8 weeks. The CPT+ExG group added exergames for 30 minutes in each session. The Senior Fitness Test was applied, considering the 30-second chair stand test as the primary outcome. Additionally, dynamometric muscle performance during the STS maneuver was assessed. Results: The CPT+ExG group improved the 30-second chair stand (lower body strength), back scratch (upper body flexibility), and 8-foot up-and-go (agility/dynamic balance) tests (all P  < 0.05). Both groups improved the kinetic dynamometric variables peak force, peak power, and total work (all P  < 0.05). Also, both groups improved the 30-second arm curl test (upper body strength) ( P  < 0.05), although the increase was higher in the CPT+ExG group compared with the CPT group (time × group; P  < 0.05). Conclusion: Adding exergames to a CPT program only significantly increases upper limb strength compared with CPT alone. The findings of this study have implications for the design of future exergame interventions focused on improving STS maneuver performance in older adults.

Objective: Functional capacity is 1 of the main risk factors for falls among older adults. The aim of this systematic review and meta-analysis was to determine the effect of power training on functional capacity test (FCT) related to fall risk in older adults., Data Sources: Systematic searches were conducted in 4 databases, including PubMed, Web of Science, Scopus, and SPORTDiscus, from inception to November 2021., Study Selection: Randomized controlled trials (RCTs) assessing the effect of power training on functional capacity compared with another type of training program or control group in older adults with the ability to exercise independently., Data Extraction: Two independent researchers evaluated eligibility and used the PEDro scale to assess risk of bias. The information extracted was related to article identification (authors, country and year of publication), participant characteristics (sample, sex, and age), strength training protocols (exercises/intensity/weeks), and the outcome of the FCT used related to fall risk. The Cochran Q statistic and I 2 statistics was used to assess heterogeneity. Random-effects model were conducted to pool the effect sizes expressed as mean differences (MD)., Data Synthesis: Twelve studies (478 subjects) were selected for systematic review. A meta-analysis comprised 6 studies (217 subjects) where the outcome measure was the 30-second Sit to Stand (30s-STS) test, and another comprised 4 studies (142 subjects) where the outcome measure was the timed Up and Go (TUG) test. There was an improvement in performance in favor of the experimental group in both the TUG subgroup (MD -0.31 s; 95% CI -0.63, 0.00 s; P=.05), and the 30s-STS subgroup (MD 1.71 reps; 95% CI -0.26, 3.67 reps; P=.09)., Conclusions: In conclusion, power training increases functional capacity related to fall risk further than other types of exercise in older adults., (Copyright © 2023. Published by Elsevier Inc.)

Background: Trunk rotator strength plays an important role in sports performance and health. A reliable method to assess these muscles with functional electromechanical dynamometer has not been described. Therefore, the objectives of this paper were (I) to explore the reliability of different strength variables collected in isokinetic and isometric conditions during two trunk rotator exercises, and (II) to determine the relationship of isometric and dynamic strength variables collected in the same exercise., Methods: A repeated measures design was performed to evaluate the reliability of the horizontal cable woodchop (HCW) and low cable woodchop (LCW) exercises. Reliability was assessed using t -tests of paired samples for the effect size, the standard error of measurement, the coefficient of variation (CV) and the intraclass correlation coefficient (ICC). The Pearson's ( r ) correlation coefficient was used to explore the association between isometric and isokinetic tests., Results: HCW exercise is more reliable than LCW exercise in assessing trunk rotator muscles. The strength manifestation that should be used is the average strength, and the most reliable evaluation was the HCW at 0.40 m·s -1 concentric (ICC = 0.89; CV = 10.21%) and eccentric (ICC = 0.85; CV = 9.33%) contraction and the dynamic condition that most correlated with the isometric was LWC at 0.50 m·s -1 ( r = 0.83; p < 0.01)., Conclusion: HCW is a reliable exercise to measure trunk rotator muscles.

The main objective of this study was to determine the differences in energy expenditure (EE) according to sex during and after two different squat training protocols in a group of healthy young adults. Twenty-nine Sports Sciences students volunteered to participate in this study. They attended the laboratory on four different days and completed four sessions: two sessions with 3 sets of 12 repetitions at 75% of their one-repetition maximum (RM) and two sessions with 3 sets of 30 repetitions at 50% of their 1RM. Energy expenditure was evaluated using an indirect calorimeter. Males consistently demonstrated higher EE in all sessions and intensities. The linear regression model identified a significant association between sex, BMI, and total EE across all sessions and intensities. In conclusion, males exhibited higher EE in both protocols (50% and 75% of 1RM) throughout all sessions. Furthermore, sex and BMI were found to influence EE in healthy young adults. Therefore, coaches should consider sex when assessing EE, as the metabolic response differs between males and females.

Objectives: A variety of factors are known to mediate on the intraocular pressure (IOP) response to resistance training. However, the influence of the body position adopted during resistance training on IOP remain unknown. The objective of this study was to determine the IOP response to the bench press exercise at three levels of intensity when performed in supine and seated positions., Methods: Twenty-three physically active healthy young adults (10 men and 13 women) performed 6 sets of 10 repetitions against the 10-RM (repetition maximum) load during the bench press exercise against three levels of intensity (high intensity: 10-RM load; medium intensity: 50% of the 10-RM load; and control: no external load) and while adopting two different body positions (supine and seated). A rebound tonometer was employed to measure IOP in baseline conditions (after 60 s in the corresponding body position), after each of the 10 repetitions, and after 10 s of recovery., Results: The body position adopted during the execution of the bench press exercise significantly affected the changes in IOP (p < 0.001, η p 2  = 0.83), with the seated position providing lower increases in IOP levels compared to the supine position. There was an association between IOP and exercise intensity, with greater IOP values in the more physically demanding conditions (p < 0.001, η p 2  = 0.80)., Conclusions: The use of seated positions, instead of supine positions, for the execution of resistance training should be prioritized for maintaining more stable IOP levels. This set of findings incorporates novel insights into the mediating factors on the IOP response to resistance training. In future studies, the inclusion of glaucoma patients would allow to assess the generalizability of these findings., (© 2023. The Author(s).)

Background: Muscle quality index (MQI) is an emerging health indicator obtained by dividing handgrip strength by body mass index (BMI) that needs to be studied in morbidly obese patients (defined by BMI ≥ 35 kg/m 2 )., Objective: To determine the association between MQI, metabolic syndrome (MetS) markers, and cardiorespiratory fitness (CRF), and as a second objective to determine the potential mediation role of MQI in the relationship between abdominal obesity and systolic blood pressure (SBP) in this sample., Methods: This cross-sectional study included 86 severely/morbidly obese patients (age = 41.1 ± 11.9 y, nine men). MQI, metabolic syndrome markers, CRF, and anthropometric parameters were measured. Two groups were developed according to MQI; High-MQI ( n = 41) and Low-MQI ( n = 45)., Results: The Low-MQI group reported higher abdominal obesity (High-MQI: 0.7 ± 0.1 vs. Low-MQI: 0.8 ± 0.1 WC/height; p = 0.011), SBP (High-MQI: 133.0 ± 17.5 vs. Low-MQI: 140.1 ± 15.1 mmHg; p = 0.048), and lower CRF (High-MQI; 26.3 ± 5.9 vs. Low-MQI; 22.4 ± 6.1 mL/kg/min, p = 0.003) than the High-MQI group. Waist-to-height ratio (β: -0.07, p = 0.011), SBP (β: -18.47, p = 0.001), and CRF (β: 5.21, p = 0.011) were linked to MQI. In a mediation model, the indirect effect confirms that MQI is a partial mediator of the association between abdominal obesity with SBP., Conclusions: MQI in morbidly obesity patients reported an inverse association with MetS markers and a positive association with CRF (VO2 max ). It mediates the relationship between abdominal obesity and SBP.

Screen time (ST) and abdominal obesity have a negative effect on health-related quality of life (HRQoL). However, there is little information regarding the mediating role of the muscle quality index (MQI) in these relationships. The aim of the present study was to investigate the association between HRQoL, physical status (i.e., anthropometrics and fitness), lifestyle (i.e., ST and physical activity), and the MQI, and then to determine the potential mediating role of the MQI in the relation of ST and abdominal obesity with HRQoL in Chilean schoolchildren. The cross-sectional study included 750 schoolchildren (girls, n = 332 and boys, n = 418) aged between 10 and 14 years (11.73 ± 1.08 y). MQI, lifestyle, fitness parameters, waist-to-height ratio (WtHR) and HRQoL were measured. HRQoL presented a significant correlation with WtHR (r: -0.19), VO2 max (r: 0.20), physical activity after school (r: 0.26), ST (r: -0.26) and MQI (r: 0.15). According to MQI, the high-MQI group reported higher HRQoL than the low-MQI group (low MQI: 36.10 ± 3.63 vs. high MQI: 37.43 ± 4.00, p < 0.001). In the mediation model, ST and abdominal obesity were negatively linked to HRQoL; the indirect effect confirmed that MQI is a partial mediator in the relation between ST and HRQoL (indirect effect = -0.04; SE = 0.02; 95% CI: -0.09, -0.01) and in the relation between abdominal obesity and HRQoL (indirect effect = -1.81; SE = 0.83; 95% CI: -3.41, -0.40). In conclusion, MQI is related to better HRQoL in schoolchildren, and the negative relation of ST and abdominal obesity with HRQoL is mediated by MQI.

Background: the main objective of this study was to evaluate the test-retest reliability of two different functional electromechanical dynamometry (FEMD)-controlled squat training protocols., Methods: twenty-eight healthy young adults volunteered to participate in this study. They attended the laboratory on four different days and performed four sessions: two of three sets of 12 repetitions at 75% 1RM and two of three sets of 30 repetitions at 50% 1RM. The range of movement (ROM), mean dynamic strength (MDS), peak dynamic strength (PDS), mean velocity (MV), peak velocity (PV), mean potency (MP), peak potency (PP), work (W), and impulse (I) were recorded. To evaluate the reliability of FEMD, the intraclass correlation coefficient (ICC), standard error of measurement (SEM), and coefficient of variation (CV) were obtained., Results: reliability was very high for ROM (CV: 3.72%, ICC: 0.95), MDS (CV: 1.09%, ICC: 1.00), PDS (CV: 1.97%, ICC: 1.00), and W (CV: 4.69%, ICC: 1.00) conditions at 50% 1RM and for ROM (CV: 3.90%, ICC: 0.95), MDS (CV: 0.52, ICC: 1.00), PDS (CV: 1.49%, ICC: 0.98), and W (CV: 4.14%, ICC: 1.00) conditions at 75% 1RM and high for the rest of variables at 50 and 75% 1RM., Conclusions: this study demonstrates that FEMD is a reliable instrument to measure ROM, MDS, PDS, MV, PV, PV, MP, MP, W, and I during both squat protocols (50 and 75% 1RM) in healthy young adults.

Background: Soccer is the most widely practiced sport in the world, demanding high-speed activities such as jumps, sprints and changes of direction. Therefore, having optimal levels of muscle strength improves performance and reduces the injury rate., Objectives: The objectives of our study were (i) to determine the dynamometric profile of hip muscle strength in young soccer players by position, evaluated at different isokinetic speeds, (ii) to describe the conventional and functional unilateral muscle strength ratios, (iii) to analyze the bilateral balance., Methods: Thirty-seven male soccer players (age 17.02 ± 0.92 years) participated in the study. Strength assessment was performed with a functional electromechanical dynamometer, and concentric and eccentric strength of abductors, adductors, extensors and hip flexors were measured bilaterally at 0.5 m/s and 1 m/s., Results: For eccentric right hip abduction at 0.5 m/s, defenders are significantly stronger than midfielders ( p = 0.013) and stronger than forwards ( p = 0.140). For eccentric right hip adduction at 0.5 m/s, defenders are significantly stronger than midfielders ( p = 0.005) and stronger than forwards ( p = 0.253), as for eccentric right hip adduction at 1 m/s, defenders are significantly stronger than midfielders ( p = 0.014) and stronger than forwards ( p = 0.084). There is a significant effect for the conventional strength ratio of left abduction/adduction at 1 m/s. The conventional strength ratio of forwards is significantly higher than that of defenders ( p = 0.045) and higher than that of midfielders ( p = 0.152)., Conclusions: Concentric and eccentric hip strength values differ according to playing position.

The main objective of this study was to test the relationship between shoulder internal rotation strength and standing throwing velocity. A repeated measures cross-sectional study was conducted with 20 professional handball players (mean ± SD; age: 19.28 ± 2.55 years, weight: 81.52 ± 9.66 kg, height: 185 ± 6 cm, BMI: 23.74 ± 1.69). The participants were instructed to perform eight standing throws from the 7 m line of the handball court at maximum velocity to calculate the mean and maximum throwing velocity. An incremental test was performed to calculate the repetition maximum (1-RM) of internal rotation shoulder strength. A Pearson's correlation analysis with a 95% confidence interval (95% CI) was performed to determine whether correlations existed between dominant arm internal rotation strength characteristics and maximum and mean ball-throwing velocity. There is no correlation between the internal rotation strength of the throwing shoulder and the velocity of the ball in the standing handball throw.

Background: Cognitive dysfunction is a common complain in patients with fibromyalgia (FM)., Aim: To assess the perceived cognitive function and cognitive performance in women with FM., Material and Methods: Cross-sectional study including 100 women with FM (FMG) and 100 healthy controls (CG). Self-perceived cognitive functioning was evaluated using the Functional Assessment of Cancer Therapy Cognition scale (FACT-Cogv3). The neuropsychological performance was assessed with the Trail Making Test (TMT-A, TMT-B), Digit Span test (DS), Barcelona test (DS-F/B) and the Frontal Assessment Battery (FAB-E), Spanish version test., Results: The mean scores of all cognitive self-perception factors and all neuropsychological tests were lower in the FMG (p < 0.001). Over 90% of the FMG took longer than the population mean (P50) to complete the TMT-A and TMT-B tests, while in the CG, 1/3 took longer than the P50 in both tests. The minimum expected scores for the DS-F and DS-B tests were not achieved by 40 and 9% of FMG participants, respectively. According to FAB-E, 54% and 24% of FMG were categorized as fronto-subcortical deficit and fronto-subcortical dementia, respectively., Conclusions: Women with FM have a higher perception of cognitive dysfunction and lower cognitive performance in objective tests than healthy women. More research is needed to explore the clinical, psychosocial, and sociodemographic characteristics that predispose to cognitive deficits in this group of patients.

Background: The trunk strength conventional ratio (CR) has been evaluated. However, the functional ratio and the ratio of strength to body weight (BW) or muscle mass (MM) have been poorly explored. Relative strength is a measure of muscle quality., Objectives: To analyze the trunk strength ratio normalized by BW and MM and compare the trunk's conventional and functional ratios collected in isokinetic and isometric conditions., Methods: Twenty-seven healthy males (21.48 ± 2.08 years, 70.22 ± 7.65 kg) were evaluated for trunk isometric and isokinetic strength using a functional electromechanical dynamometer., Results: The extensor's strength was greater than the flexors, with a CR of 0.41 ± 0.10 to 0.44 ± 0.10. Muscle quality was higher in eccentric contraction and high velocity for flexors and extensors. The functional flexor ratio (FFR) ranged between 0.41 ± 0.09 and 0.92 ± 0.27. The functional extensor ratio (FER) ranged between 2.53 ± 0.65 and 4.92 ± 1.26. The FFR and FER showed significant differences between velocities when considering the peak strength ( p = 0.001) and mean strength ( p = 0.001)., Conclusions: Trunk extensors were stronger than the flexors; thus, the CR was less than one. Muscle quality was higher at a high velocity. Unlike CR, FFR and FER behaved differently at distinct velocities. This finding highlights the need to explore the behavior of the functional ratio in different populations.

Background: Hypertension (HTN) is recognized as a significant public health problem in the world. The objective of this study is to evaluate emergent anthropometric indices as predictors of preHTN and HTN according to age and sex in a sample of Mexican adults., Methods: A cross-sectional study was conducted in 1,150 participants aged 18-80 years old. Anthropometric data and blood pressure measurements were analyzed. Comparisons between men and women were carried out by independent analysis. Cutoff points for each emergent anthropometric index were obtained using the values' upper second and third tertiles. Logistic regression models and receiver operating characteristics curve analyses were used to assess the association and the predictive value of several emergent anthropometric indices with the presence of preHTN and HTN., Results: The prevalence of preHTN and HTN was 29.74% and 14.35%, respectively. In a logistic regression analysis adjusted by age and sex, the body roundness index (BRI) (OR = 2.08, p < 0.001) and conicity index (CI) (OR = 1.37, p =0.044) were associated with preHTN, while CI (OR = 2.47, p < 0.001) and waist to height squared (W/Ht 2 ) (OR = 2.19, p < 0.001) were associated with HTN. Furthermore, in both sexes, BRI was the main predictor of preHTN (AUC: 0.634 and 0.656, respectively). Particularly, according to sex and age range, the predictive emergent anthropometric indices in men were the body shape index (ABSI) and waist to height cubic (W/Ht 3 ) (AUC = 0.777 and 0.771, respectively), whereas in women, the predictors were CI and ABSI (AUC = 0.737 and 0.729, respectively). In men ≤40 years old, central body fat indices were predictors of preHTN and HTN, but in men >40 years old, the predictor indices were W/Ht 3 and W/Ht 2 . In women ≤40 years, the pulse mass index (PMI) was the best main predictor (AUC = 0.909) of HTN., Conclusion: CI, PMI, W/Ht 3 , W/Ht 2 , and ABSI could represent differential predictors of preHTN and HTN between men and women according to age range., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2022 Oscar Zaragoza-García et al.)

A healthy lifestyle, including food habits, physical activity (PA) and screen time (ST), is an important factor for well-being. The main purpose of this study was to analyze the association between lifestyle (i.e., PA, ST and food habits), self-esteem and health-related quality of life (HRQoL). A second objective was to determine the association between self-esteem with HRQoL, considering the mediating effect of lifestyle. A descriptive and cross-sectional study was performed, involving both girls (n = 282, 11.86 ± 0.82 years) and boys (n = 352, 12.02 ± 0.87 years). Lifestyle, self-esteem, HRQoL and anthropometrics parameters were evaluated. The study reported that self-esteem (β; 0.04, P = 0.49) and PA (β; 1.15, P < 0.001) had positive association with HRQoL. By contrast,ST was linked in an inverse way to HRQoL (β; -1.82,, P < 0.001). According to the second objective, self-esteem had a significant association with HRQoL (total effect = 0.48, p < 0.01), and ST mediated this association negatively, instead, PA and food habits positively mediated this association. In conclusion, self-esteem presented association with HRQoL and lifestyle mediates this relationship positively (PA, MD adherence) and negatively (ST). Therefore, promoting healthy lifestyle among children should be a target of community- and school-based interventions to promote well-being.

Although bariatric surgery (BS) is recognized as an effective strategy for body weight loss, its impact on cardiorespiratory fitness (CRF) is still unclear. We aimed to examine postoperative changes in CRF (VO 2max/peak ) and its relationship with weight loss among adults undergoing BS. We systematically searched the WoS, PubMed, MEDLINE, and Scopus databases. Observational and intervention studies were selected reporting the presurgery and postsurgery CRF, measured by breath-by-breath VO 2 or its estimation. Eleven articles (312 patients) revealed that BS leads to a reduction in absolute VO 2max/peak in the short term (effect size, ES = -0.539; 95%CI = -0.708, -0.369; p < 0.001), and those patients who suffered a more significant decrease in BMI after BS also had a greater loss of absolute VO 2max/peak . However, VO 2max/peak relative to body weight increased after surgery (ES = 0.658; 95%CI = 0.473, 0.842; p < 0.001). An insufficient number of studies were found investigating medium and long-term changes in CRF after BS. This study provides moderate-quality evidence that the weight loss induced by BS can reduce CRF in the short term, which represents a therapeutic target to optimize BS outcomes. More high-quality studies are needed to evaluate the impact of BS on VO 2max/peak in the short, medium, and long term including normalized values for fat-free mass., (© 2021 World Obesity Federation.)

Introduction: Background: handgrip strength (HGS) is a health-status parameter associated with multicomorbidity in the adult population. Objective: the aim of the present study was to determine the association between HGS (i.e., absolute and relative) and abdominal obesity (AO), type-2 diabetes (T2D), and hypertension (HT), as well as to determine the association between low relative HGS with the presence of multicomorbidity (i.e., the co-occurrence of two or more comorbidities together) in a Mexican population. Methodology: a cross-sectional study was carried out in 860 participants from the south of Mexico (661 women and 199 men). The age range evaluated was from 18 to 65 years. Assessments were made of sociodemographic data, clinical history, anthropometric parameters, and measurement of maximal HGS. Results: the regression models adjusted by age show that the presence of comorbidities (i.e., AO, HT and T2D) was linked negatively to HGS (i.e., absolute and relative). Moreover, in men, a low relative HGS in both hands reported an association with the presence of three simultaneous comorbidities (right, RR: 17.2, p < 0.001; left, RR: 11.92, p = 0.020). In women the same association was found (right, RR: 10.42, p < 0.001; left, RR: 9.90, p < 0.001). Conclusion: lower levels of relative HGS were linked to the presence of simultaneous comorbidities (i.e., the joint presence of AO, T2D and HT). Furthermore, HGS (i.e., absolute and relative) presented an inverse association with individual anthropometric and clinical parameters related to cardiovascular risk in the Mexican population.

Background: The purpose of this systematic review was to determine the effect of antioxidant consumption on markers of oxidative stress and muscle damage after performing a muscle strength exercise., Methods: The Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) statements were followed. Four databases were used: Scopus, PubMed, WOS and SportDiscus. Methodological quality was assessed using the PEDro scale., Results: A total of 1709 articles were retrieved and following duplicate removal and application of exclusion criteria seven articles were reviewed. Supplementation with pomegranate juice alleviates oxidative stress, taurine reduces muscle damage, melatonin protects the skeletal muscles, blueberries decrease oxidation and oats mitigate muscle damage., Conclusions: Acute administration of antioxidants immediately before or during an exercise session can have beneficial effects, such as delay of fatigue and a reduction in the recovery period. Administration of antioxidant susbtances may reduce muscle damage and oxidative stress markers.

Background: Serratus anterior strengthening generally appears in shoulder rehabilitation protocols. This study's aim was to measure electromyographic activity of the serratus anterior, upper trapezius, and infraspinatus muscles during the Supine Scapular Punch exercise in healthy volunteers and those with unilateral shoulder pain., Methods: Fifty-four participants were included and grouped as without (n = 34, age = 25.8 years) or with unilateral shoulder pain (n = 20, age = 26.3 years, visual analogue scale = 4.15 cm). Electromyographic activity of the serratus anterior, upper trapezius, and infraspinatus muscles was assessed during Supine Scapular Punch (four phases: P1 = press up concentric, P2 = Supine Scapular Punch concentric, P3 = Supine Scapular Punch eccentric, P4 = press up eccentric) performed under two conditions, with and without additional load., Findings: Overall muscle activity during P1 and P4 was negligible (< 10% maximal voluntary isometric contractions). During P2 and P3, no statistically significant differences in serratus anterior and upper trapezius muscle activity were found between groups, with moderate to high serratus anterior activity (28.94% to 44.3%) and very low upper trapezius activity (< 6%). Upper trapezius/serratus anterior activity ratios ranged from 0.09 to 0.18. Overall infraspinatus muscle activity was always very low (< 10%)., Interpretation: The Supine Scapular Punch induces moderate to high serratus anterior muscle activity with very low upper trapezius and infraspinatus activation. Based on these results, the Supine Scapular Punch is a safe exercise that can be used in the early phases of shoulder rehabilitation., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Objective: The purpose was to determine the association of lifestyle (i.e., Mediterranean diet [MD] adherence, physical activity [PA], screen time [ST]) and fitness with abdominal obesity (AO) and excess weight in the Chilean and Colombian schoolchildren., Research Methods & Procedures: This cross-sectional study included 969 schoolchildren, girls (n=441, 5.24±0.80 years old) and boys (n=528, 5.10±0.78 years old) from Chile (n=611) and Colombia (n=358). The body mass index (BMI), waist circumference (WC), waist-to-height ratio (WtHR), MD adherence, PA, ST and cardiorespiratory fitness (CRF) were evaluated. The association of AO and anthropometric variables with lifestyle was estimated through multiple linear regression. To determine the association between AO and lifestyle, a logistic regression and the inclusion of odds ratios (ORs) with 95% confidence intervals (CIs) were used., Results: Worse CRF in Chilean children were positively correlated with WC. Excess weight in Chilean and Colombian children was positively associated with an unhealthy lifestyle. In Chilean children unhealthy lifestyle was also associated with AO based on WC≥85th percentile and AO based on WtHR≥85th percentile. In Chilean children, excess weight (BMI≥85th percentile) was positively associated with poor MD adherence., Conclusion: AO and excess weight were associated with an unhealthy lifestyle in Latin-American schoolchildren. Interventions to reduce the prevalence of AO should include promoting healthier lifestyle choices (i.e., increasing PA after school, reducing ST and improving CRF)., (Copyright © 2021 SEEN and SED. Published by Elsevier España, S.L.U. All rights reserved.)

Purpose: The objective of the study was to describe and compare the acute response of muscle oxygen saturation (SmO2) and hemoglobin concentration (Hgb) in the vastus lateralis (VL) during resistance exercise protocols until failure., Methods: Sixteen males were considered (mean ± SD, age = 36.12 ± 6.40 years). Two familiarization sessions and one evaluation session were carried out where three force protocols were executed in the VL, one of them was isometric load (P1) and two of dynamic load (P2 and P3). SmO2 [%] and Hgb [g/dL] were measured before and after each of these protocols. For P1, three series of 8 s of maximum isometric strength with the rest of 60 s between each set, the average isometric strength (AIS), and the isometric peak strength (IPS) were also recorded. After five minutes, P2 was performed, with an initial load of 40% of AIS. Then, at 30 minutes, P3 was performed considering an initial load of 40% of IPS., Results: The results suggest (I) minimum levels of SmO2 (66.31 ± 9.38%) and Hgb (12.22 ± 0.55 g/dL) during P2, (II) no significant differences were observed between the average loads of the respective protocols for SmO2 and (III) muscle Hgb differed significantly between rest with P1 and P3., Conclusions: Exercises of increasing intensity and of short duration do not significantly modify SmO2. However, Hgb increases substantially compared baseline values.

Purpose: This study aimed to examine the reliability of trunk extensor strength assessment with a functional electromechanical dynamometer (FEMD)., Methods: Thirty-one men performed strength assessment at different velocities (V) (V1 = 0.15 m⋅s-1 , V2 = 0.30 m⋅s-1,V3 = 0.45 m⋅s-1) and range of movement (R) (R1 = 25% cm; R2 = 50% cm), and isometric contraction at 90°. Reliability was obtained through the intraclass correlation coefficient (ICC), typical error (TE), and coefficient of variation (CV)., Results: The absolute reliability provided stable repeatability of the average eccentric strength in the V1R1 condition (CV = 9.52%) and the maximum eccentric strength in V1R1 (CV = 9.63%) and V2R2 (CV = 9.66%). The relative reliability of the trunk extensor's average strength was good (ICC = 0.77-0.83) for concentric and good (ICC = 0.78-0.85) and moderate (ICC = 0.67-0.74) for eccentric contraction. Also, good (ICC = 0.77-0.81) and moderate (ICC = 0.55-0.74) reliability of the maximum strength were obtained for concentric and eccentric contraction. The most reliable manifestation to evaluate the concentric (CV = 11.33%) and eccentric (CV = 9.52%) strength was the average strength in the V1R1 condition and the maximum strength (CV = 10.29%) to isometric assessment. The average concentric strength in the V2R2 condition (r = 0.69) and the maximum eccentric strength in the V1R1 condition (r = 0.65) were the best related to the maximum isometric strength., Conclusions: FEMD is a highly reliable device to evaluate trunk extensors strength.