Minimum effective plyometric training volume in sedentary individuals: Impact on lower limb viscoelastic properties and functional performance in a randomised controlled trial.

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.

Does the Position of the Ankle Matter During the Single Gluteal Bridge in Futsal Players? An Electromyographic Analysis.

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.

Test-Retest Reliability of 3 Specific Strength Tests in Professional Handball Players.

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.

Influence of the body positions adopted for resistance training on intraocular pressure: a comparison between the supine and seated positions.

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, ηp2 = 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, ηp2 = 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.

Effects of Power Training on Functional Capacity Related to Fall Risk in Older Adults: A Systematic Review and Meta-analysis.

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 I2 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.

Muscle Quality Index is inversely associated with psychosocial variables among Chilean adolescents.

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 (ß; -6.18, 95% CI; -10.11: -2.25, p = 0.003), anxiety (ß; -6.61, 95% CI; -9.83: -3.39, p < 0.001) and stress (ß; -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.

Impact of Starting Knee Flexion Angle on Muscle Activity and Performance during Plyometrics without Jumping.

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.

Vertical Versus Horizontal Training for Improving the Change of Direction Speed in Adult Basketball Players: A Systematic Review and Meta-analysis.

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.

Core training and performance: a systematic review with meta-analysis.

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.

Lifestyle mediates the relationship between self-esteem and health-related quality of life in Chilean schoolchildren.

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 (ß; 0.04, P = 0.49) and PA (ß; 1.15, P < 0.001) had positive association with HRQoL. By contrast,ST was linked in an inverse way to HRQoL (ß; -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.

Self-perceived cognitive function and neuropsychological performance in women with fibromyalgia.

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.

Depression is associated with lower levels of physical activity, body image dissatisfaction, and obesity in Chilean preadolescents.

Mental health during the preadolescent years may be determinant for later periods of life; therefore, the factors that influence it need to be studied deeply. The aim of this study was to determine the association between depressive symptoms with physical activity (PA), body image dissatisfaction and weight status in preadolescents. A total of 269 girls and 329 boys (age 12.02 ± 0.98 years) were included in this study. Body mass index (BMI), waist circumference, body image dissatisfaction, PA and depressive symptoms were assessed. The PA reported an inverse association with depression in girls (ß:-2.12, P < 0.0001) and boys (ß:-1.13, P = 0.001). Instead, BMI in girls (ß: 1.00, P < 0.0001) and boys (ß: 0.70, P < 0.0001), and body image dissatisfaction in girls (ß: 0.05, P = 0.017) and boys (ß: 0.04, P = 0.003) reported positive association with depression. In the same way, depression was associated with obesity (odds ratio [OR] = 2.05, P = 0.020), but, the boys had higher risk (OR = 18.4, P < 0.001) than girls. In conclusion, depression in Chilean preadolescents presented association with low levels of PA, obesity and body image dissatisfaction. Therefore, schools should target and promote PA to improve psychological and physical health in preadolescents, which may reduce the future burden of mental illness.

Relationship between anthropometric nutritional status and functional capacity in older adults living in the community.

BACKGROUND: The functional fitness of older people may be associated with their nutritional status. AIM: To assess the association between of anthropometric measures with functional fitness in older people. MATERIAL AND METHODS: Cross-sectional study conducted in 75 participants aged 65 to 89 years. Body mass index (BMI), waist-to-height ratio (WHtR), fat mass (FM) and skeletal muscle mass index (SMI) were calculated from anthropometric measures. The functional fitness was determined using the Senior Fitness Test battery. RESULTS: BMI and FM indicated obesity, and WHtR indicated cardiometabolic risk in 49%, 55% and 83% of participants, respectively. SMI indicated a low muscle mass in 91% of females. Performance standards of chair stand, arm curl, 2-min step test and 8-foot up-and-go tests were met in 1%, 8%, 1% and 89% of participants, respectively. Significant negative correlations were found between 2-min step test and BMI, WHtR and FM (r = -0.26, -0.31 and -0.48 respectively). Back scratch had a negative correlation with BMI (r = -0.23) and SMI (rho = -0.28). Significant positive correlations were found between 8-foot up-and-go, WHtR (rho = 0.28) and FM (rho = 0.23), and between 2-min step test and SMI (rho = 0.28). The coefficient of determination (R2) between 2-min step test with BMI, WHtR and FM were 0.05, 0.08 and 0.22, respectively, while the R2 between back scratch and BMI was 0.04. Multiple regression models indicated that FM affected the 2-min step test independently of BMI and WHtR (adjusted R2 = 0.22), however age and sex negatively influenced these associations. CONCLUSIONS: Functional fitness of older adults is influenced by nutritional anthropometric measures, particularly BMI, WHtR and FM for aerobic capacity, and BMI for upper limb flexibility.

The influence of cardiometabolic risk factors on cardiorespiratory fitness in volunteer Chilean firefighters.

OBJECTIVES: Maximum oxygen consumption (VO2max ) plays a fundamental role in firefighters' occupational activities due to the high intensity tasks they perform in their professional duties. In Chile, firefighters are volunteers (non-salary) and their lack of continuous and programmed physical activity may affect their physical fitness and health. The goal of this study was to determine the influence of anthropometric parameters and cardiometabolic risk (CMR) factors on the cardiorespiratory fitness (CRF) of volunteer Chilean firefighters. METHODS: Seventy-six volunteer male firefighters (median [5-95 percentiles]) aged 27.5 years [26-56], body mass index (BMI) 27.7 kg m-2 [19.9-35], and VO2max 44 mL kg-1 min-1 [36-56]) participated in the study. The following variables were assessed: BMI, fat mass%, body density, waist circumference (WC), waist-to-hip ratio (WHR), blood pressure, blood glucose, and VO2max . RESULTS: In total, 68% of the samples were overweight or obese. A total of 36% presented abdominal obesity (WC ≥102 cm). High blood pressure (HBP) was observed in 25% of firefighters and high blood glucose was found in about 20%. The presence of abdominal obesity was the strongest predictor of VO2max (OR = 12.35, 95% CI = 3.56-42.82, P < .001), followed by the WHR (OR = 11.5, 95% CI = 3.1-42.7, P < .001) and high blood glucose (OR = 2.87, 95% CI = 1.7-7.3, P = 0.019). CONCLUSION: This study showed that abdominal obesity in firefighters was the strongest predictor of low CRF. In addition, CRF was associated with CMR factors, except for HBP.

Feasibility of incorporating high-intensity interval training into physical education programs to improve body composition and cardiorespiratory capacity of overweight and obese children: A systematic review.

BACKGROUND/OBJECTIVE: High-intensity interval training (HIIT) can produce similar or improved results compare with traditional training, but the question as to whether HIIT can be used in the setting of physical education (PE) remains unanswered. The aim of this systematic review was to critically analyze the feasibility of incorporating HIIT programs into PE classes to improve the body compositions and cardiorespiratory fitness of overweight students. METHODS: We conducted database searches for literature dating between January 2012 and January 2017. Of the final six studies selected, three were conducted in children under 12 years old and three involved adolescents between 12 and 18 years old. RESULTS: The HIIT protocols consisted of 2-3 sessions per week, with intervals of 15 s and passive or active rests of 15 s, totaling up to 6 min of work with 4 min of rest. The duration of HIIT programs was 6-24 weeks. Significant changes were reported in body composition, body mass index, body fat (%), waist circumference, and sum of skinfolds; and increases in muscle mass were observed. The inclusion of HIIT programmes improved maximal oxygen uptake (VO2max), performance in the intermittent Yo-Yo test and maximal aerobic speed. CONCLUSIONS: The HIIT programmes showed improvements in the variables studied, with interventions two or three times weekly. Therefore, they can be used in schools, as a strategy to combat the childhood obesity pandemic and HIIT can be use alongside with existing PE activities within the same lesson or in specific periods during day school.

Adaptaciones al ejercicio físico en el perfil lipídico y la salud cardiovascular de obesos mórbidos.

OBJECTIVE: To assess the effects of a physical exercise program on the lipid profile, weight status and the cardiovascular health of obese candidates for bariatric surgery. METHOD: 22 morbidly obese patients participated in a 6-month physical exercise program. 16 formed the adherent group (attendance ≥ 80%; age: 37.81 ± 11.90 years) and six the non-adherent group (attendance < 80%; age: 45.83 ± 14.23 years). Before and 72 h after the last session were evaluated: weight, body mass index (BMI), contour waist, blood pressure, fasting, cardio respiratory fitness, cholesterol and triglycerides. RESULTS: Weight, BMI and WC showed significant changes (p < 0.05) in both groups, with the results of the adherent group being better. In the adherent group, cardiorespiratory capacity (p = 0.001) was also increased, while diastolic pressure (p = 0.011), basal glycemia (p = 0.021) and triglycerides decreased significantly (p < 0.001). The non-adherent group did not present significant changes in these variables (p ≥ 0.05). CONCLUSIONS: The intervention was feasible to perform without negative effects for the participants, and it is possible to recommend improving the cardiovascular health of these of patients.

Exploring lower limb muscle activity and performance variations during instrumented Sit-to-Stand-to-Sit in sedentary individuals: Influence of limb dominance and testing modalities.

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.

Reliability of two devices for shoulder strength assessment: Wii Fit Balance Board and hand-held dynamometer.

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.

Relationship between natural muscle oscillation frequency and lower limb muscle performance during instrumented sit-to-stand and stand-to-sit movements on a novel device in sedentary subjects.

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.

Strength characteristics in faster change of direction basketball players: A comparison across cutting angles.

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.