Reliability of lower limb strength assessment in female team sport athletes.

BACKGROUND: Lower limb injury rates have increased dramatically in line with increased female sport participation levels. Muscle strength is a modifiable lower limb injury risk factor, guiding performance monitoring and rehabilitation. OBJECTIVES: The aim of this study was to investigate the test-retest reliability of isokinetic and isometric lower limb peak torque to body mass of muscles acting on the hip, knee, and ankle in female team sport athletes. It was hypothesised the test-retest reliability would be good (intraclass correlation coefficients (ICC) ≥ 0.75). METHODS: Thirty-eight female athletes (Australian Rules Football = 18, netball = 12, soccer = 8) aged 16-35 years participated in this study. Participants performed isokinetic (60°/s and 120°/s) and isometric testing on a Biodex Isokinetic Dynamometer on three separate days. RESULTS: Poor to good reliability was demonstrated for all joint movements (ICC = 0.38-0.88) with small to moderate effect sizes (0.00-0.43) and typical errors (5.65-24.49). CONCLUSION: Differences in peak torque to body mass were observed between sessions one and two and/or one and three, demonstrating a learning effect. Therefore, three testing sessions, and/or the inclusion of a familiarisation session, is recommended for future assessments in populations unfamiliar with dynamometry.

Does kinesio tape alter muscle strength in athletes? - Systematic review and meta-analysis.

BACKGROUND: Kinesio tape (KT) is still a matter of debate and the results of studies that evaluated its effects on muscle strength in athletes are still contradictory and inconclusive. OBJECTIVES: To analyze randomized clinical trials (RCT) to compare the effects of KT on muscle strength with the control/placebo group among athletes with and without musculoskeletal injury. METHOD: The search involved the databases: PubMed, Web of Science, LILACS, PEDro, The Cochrane Library, Medline, Scopus, SPORTDiscus and Embase, without filter and included RCTs evaluating the effects of KT on muscle strength in athletes with or without musculoskeletal injury, comparing it to a control/placebo intervention. The following were excluded: studies with duplicate information; who used instruments for indirect assessment of muscle strength; involving a different population of athletes. Meta-analysis calculations were performed using post-intervention muscle strength data in the Review Manager (RevMan) program. RESULTS: 10 articles were eligible, among which 5 studies were included in the meta-analysis. In the primary analysis, no relevant clinical effect was found (immediate post-intervention <24h: Z = 1.97 CI95% = 0.35[0.00-0.70]; p = 0.05 I2 = 0% and late post-intervention ≥24h: Z = 1.47 CI95% = 0.59[-0.20-1.38]; p = 0.14 I2 = 69%) when comparing the KT group with the control/placebo groups for muscle strength of lower limbs in participants with and without musculoskeletal injury and in the subgroup analysis (including only individuals without injury), there was also no clinical effect (Z = 1.50, 95%CI = 0.31[-0.10-0.71] p = 0.13, I2 = 0%) of KT for muscle strength. CONCLUSIONS: KT does not contribute to muscle strength gain in athletes with and without musculoskeletal injuries. PROSPERO: CRD42020139822. (https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=139822) (29 July 2020).

The Effects of Near-Infrared Phototherapy Preirradiation on Lower-Limb Muscle Strength and Injury After Exercise: A Systematic Review and Meta-analysis.

OBJECTIVE: To assess near-infrared preirradiation effects on postexercise lower-limb muscle damage and function and determine optimal dosage. DATA SOURCES: PubMed, Embase, Cochrane Library, EBSCO, Web of Science, China National Knowledge Infrastructure, and Wanfang Data were systematically searched (2009-2023). STUDY SELECTION: Randomized controlled trials of near-infrared preirradiation on lower-limb muscles after fatigue exercise were incorporated into the meta-analysis. Out of 4550 articles screened, 21 met inclusion criteria. DATA EXTRACTION: The included studies' characteristics were independently extracted by 2 authors, with discrepancies resolved through discussion or by a third author. Quality assessment was performed using the Cochrane risk of bias tool and the Grading of Recommendations, Assessment, Development, and Evaluation System. DATA SYNTHESIS: In 21 studies, near-infrared preirradiation on lower-limb muscles inhibited the decline in peak torque (standardized mean difference [SMD], 1.33; 95% confidence interval [CI], 1.08-1.59; p<.001; increasing 27.97±4.87N·m), reduced blood lactate (SMD, -0.2; 95% CI, -0.37 to -0.03; p=.272; decreasing 0.54±0.42mmol/L), decreased creatine kinase (SMD, -2.11; 95% CI, -2.57 to -1.65; p<.001; decreasing 160.07±27.96U/L), and reduced delayed-onset muscle soreness (SMD, -0.53; 95% CI, -0.81 to 0.24; p<.001). Using a 24-hour cutoff revealed 2 trends: treatment effectiveness depended on power and energy density, with optimal effects at 24.16 J/cm2 and 275 J/cm2 for energy, and 36.81 mW/cm2 and 5495 mW/cm2 for power. Noting that out of 21 studies, 19 are from Brazil, 1 from the United States, and 1 from Australia, and the results exhibit high heterogeneity. CONCLUSIONS: Although we would have preferred a more geographic dispersion of laboratories, our findings indicate that near-infrared preirradiation mitigates peak torque decline in lower-limb muscles. Influenced by energy and power density with a 24-hour threshold, optimal energy and power densities are observed at 24.16 J/cm2, 275 J/cm2, 36.81 mW/cm2, and 5495 mW/cm2, respectively. Laser preirradiation also reduces blood lactate, creatine kinase, and delayed-onset muscle soreness.

The Attallah screw: Where safety meets robustness in posterior subaxial cervical instrumentation.

Posterior fixation of the subaxial cervical spine (SCS) commonly relies on the application of lateral mass screws (LMS), with pedicle screws being a less prevalent alternative. The present study provides another option: A recently introduced novel approach, the Attallah screw, intended to ensure a safety profile comparable to that of LMS, combined with a strength profile similar to that of pedicle screws. The focus of the present study is the comparative analysis of peak insertion torques for these three screw types. Employing standard surgical techniques and instruments, Attallah screws were scheduled for insertion on the right side of the SCS in 15 cadavers, pedicle screws on the left side in 8 cadavers, and LMS on the left side in the remaining 7 cadavers. The peak insertion torque was recorded using an electronic torque screwdriver. The results revealed that the peak insertion torques were similar in the pedicle and the Attallah screw at C3, C4 and C7, but differed at C5 (mean ± SD; pedicle, 79.5±19.6 cNm; Attallah, 56.7±18.5 cNm; P=0.029) and C6 (pedicle, 85.4±28.7 cNm; Attallah, 49.8±17.9 cNm; P=0.004) in favor of the superior pedicle screw measurements. The peak insertion torques of the pedicle screw were superior to the corresponding data from the LMS from C4 to C7. By contrast, the peak insertion torques of the Attallah screw were only superior to those of the LMS at C7 (Attallah, 69.5±24.5 cNm; lateral mass, 40.5±21.4 cNm; P=0.030), although similar trends were observed at the other cervical levels. On the whole, the findings presented herein indicate the level-dependent superior robustness of the Attallah screw as a posterior cervical fixation method compared to the LMS. However, from a biomechanical perspective, the pedicle screw remains the preeminent choice for fixation within the C5-C6 range.

Kinesio Taping Increases Peak Torque of Quadriceps Muscle After Arthroscopic Meniscectomy, Double-Blinded RCT.

Purpose: This study was conducted to release the debate and examine the short-term impact of KT on the quadriceps muscle following arthroscopic surgery for partial meniscectomy. Patients and Methods: As part of a double-blind, randomized controlled trial, 40 people who had an arthroscopic partial meniscectomy (APM) were randomly put into two groups, A and B. Group A received Kinesio tape (KT) for the superficial heads of the quadriceps muscle, while group B received placebo KTk. After 10 minutes of KT application, the peak torque of both groups was measured using a Biodex isokinetic dynamometer. Results: Peak torque showed a significant increase in group A in comparison with group B during angular velocity 60◦/Sec. (F (1, 130) = 58.9, p <0.001, ƞ2 =0.31) and during angular velocity 180◦/Sec. (F (1, 38) = 25.0, p <0.001, ƞ2 =0.40). Conclusion: After APM, individuals experienced an immediate and significant improvement in the quadriceps' peak torque following KT application to the Rectus femoris, Vastus medialis, and Vastus lateralis muscles from origin to insertion.

The Effect of Combining Blood Flow Restriction with the Nordic Hamstring Exercise on Hamstring Strength: Randomized Controlled Trial.

(1) Background: It is a matter of curiosity what effect the blood flow restriction (BFR) method, which is usually combined with low-intensity resistance exercises, will have when used with high-intensity eccentric exercises. (2) Methods: The present study examined the effects of combining BFR with nordic hamstring exercises (NHEs) on hamstring muscle strength, bilateral deficit (BLD), and training volume. Thirty young female volleyball players, who trained three times a week, participated voluntarily in the study. These players were stratified into three groups, each comprising ten individuals: a control group (CG), an NHE group, and an NHE + BFR group. Hamstring muscle strength and BLD values were determined using an H-BORD device, while training volume was measured in terms of sets and repetitions. (3) Results: Statistical analysis revealed that there were no statistically significant differences in non-dominant and dominant leg peak torque parameters in the exercise groups (F = 2.65; p = 0.097; ηp2 = 0.17; F = 1.15; p = 0.0334; ηp2 = 0.084), while the total training volume was lower in the NHE + BFR group. (4) Conclusions: As a result, it was seen that adding the BFR method to NHE did not provide additional gains. However, due to the low training volume of BFR + NHE, it may be recommended to apply BFR together with NHE to athlete groups.

Correlation between hip muscle strength and the lower quarter Y-balance test in athletes following anterior cruciate ligament reconstruction.

INTRODUCTION: The lower quarter Y-balance test (YBT-LQ), which measures dynamic postural control, has been reported to be predictive of lower limb injuries in athletes. It requires subjects to control their body while maintaining a single-leg stance, which necessitates sufficient strength of the hip muscles to maintain stability. The purpose of the study was to investigate the correlation between the performance of the YBT-LQ and the hip abductor or extensor muscle strength in athletes following anterior cruciate ligament reconstruction surgery (ACLR). METHODS: Fifteen athletes with post-ACLR participated in this cross-sectional study. The participants completed the YBT-LQ, followed by isokinetic measurement of the hip abductor and extensor muscles of both the legs. The peak and average torque of the hip abductor and extensor muscles were tallied with the composite score of the YBT-LQ for each limb. RESULTS: No correlation was found between the strength of the hip muscles and the YBT-LQ composite score in both injured and non-injured limbs at all velocities except for the eccentric hip abductor and concentric hip extensor torques. The eccentric hip abductor average torque is strongly associated with the YBT-LQ (r = 0.663, p = 0.010) at a speed of 180°/s. The concentric hip extensor peak torque was weakly correlated with balance (r = 0.540, p = 0.046) at a speed of 180°/s. CONCLUSION: Our study demonstrated a positive correlation between the YBT-LQ and eccentric hip abduction and concentric hip extension at higher velocities. This shows the importance of implementing velocity-oriented rehabilitation in an athletic population following ACLR.

Effects of Plyometric-Based Hydro-Kinesiotherapy on Pain, Muscle Strength, Postural Stability, and Functional Performance in Children with Hemophilic Knee Arthropathy: A Randomized Trial.

AIM: To explore how plyometric-based hydro-kinesiotherapy (Plyo-HKT) would affect pain, muscle strength, postural stability, and functional performance in a convenience sample of children with hemophilic knee arthropathy (HKA). METHODS: Forty-eight children with HKA (age: 8-16 years) were randomly allocated to the Plyo-HKT group (n = 24; underwent the Plyo-HKT for 45 min, twice/week over 12 wk in succession) or the comparison group (n = 24; performed the standard exercise rehabilitation at an equivalent frequency and duration). Pain, peak concentric torque of quadriceps and hamstring (produced at two angular velocities: 120 and 180 o/sec), dynamic limits of postural stability (DLPS), and functional performance [Functional Independence Score in Hemophilia (FISH) and 6-Minute Walk Test (6-MWT)] were assessed pre- and post-intervention. RESULTS: In contrast with the comparison group, the Plyo-HKT group achieved more favorable pre-to-post changes in pain (p = .028, η2p = 0.10), peak torque of quadriceps [120°/sec (p = .007, η2P = 0.15); 180°/sec (p = .011, η2P = 0.13)] and hamstring [120°/sec (p = .024, η2P = 0.11); 180°/sec (p = .036, η2P = 0.09)], DLPSdirectional [forward (p = .007, η2P = 0.15); backward (p = .013, η2P = 0.12); affected side (p = .008, η2P = 0.14); non-affected side (p = .002, η2P = 0.20)], DLPSoverall (p < .001, η2P = 0.32), and functional performance [FISH (p < .001, η2p = 0.26); 6-MWT (p = .002, η2p = 0.19)]. CONCLUSION: Plyo-HKT is likely helpful for reducing pain, improving strength, enhancing postural stability, and boosting functional capabilities in children with HKA. Physical rehabilitation practitioners should, therefore, consider this intervention strategy.

Fatigue effects on the knee flexors neuromuscular parameters during repeated sprinting.

BACKGROUND: To identify at which point fatigue on neuromuscular parameters occurs in the knee flexors during a repeated sprint protocol. METHODS: Physical active males without previous hamstring strain injury were recruited. Neuromuscular parameters such as peak torque (PT) and rate of torque development (RTD) were assessed after every two sprints in a 5 × (2 x 30 m) repeated sprint protocol. RESULTS: Twenty physical active males participated in the study. A significant effect of sprint number was found (p < 0.001; η2p = 0.643) with a decreased sprint speed by 6.9% from fastest to slowest sprint. No significant differences were observed in the time between finishing the sprint and performing the first MVIC (46.3 ± 4.7s; p = 0.423), nor in the time between finishing a set and starting the next set (121.2 ± 7.6s; p = 0.503). Regarding neuromuscular parameters, the only significant difference found was in PT between before and after two sprints (117.95 ± 5.61 N⋅m vs. 110.64 ± 5.71 N⋅m; p = 0.048, d = 0.289) and on RTD 0-50ms before and after ten sprints (465.78 ± 223.76 N⋅m/s vs. 382.30 ± 189.56 N⋅m/s; p = 0.008; η2p = 0.149). CONCLUSIONS: A recovery time of 46s between sprints and testing neuromuscular parameters (due to experimental design) seems sufficient to restore the neuromuscular system. Therefore, it can be suggested that time recovery is the principal factor in detecting fatigue on neuromuscular parameters.

New prediction equations for knee isokinetic strength in young and middle-aged non-athletes.

BACKGROUND: This study aimed to develop alternative prediction equations to predict isokinetic muscle strength at 60°/s based on anthropometric characteristics, including body mass, height, age, and sex for young and middle-aged non-athlete populations. METHODS: Three hundred and thirty-two healthy non-athletic participants (174 females, 158 males) between 20 and 59 years underwent a 60°/s isokinetic knee joint concentric contraction test. Forty people were randomly selected for retesting to assess the reliability of the isokinetic instrument. Multivariate linear regression was used to establish extension peak torque (EPT) and flexion peak torque (FPT) prediction equations. Sixty extra participants were used individually to validate the prediction equations, and Bland Altman plots were constructed to assess the agreement of predicted values with actual measurements. RESULTS: The result demonstrated that the instrument we used has excellent reliability. The multivariable linear regression model showed that body mass, age, and sex were significant predictors of PT (EPT: Adjusted R2 = 0.804, p < 0.001; FPT: Adjusted R2 = 0.705, p < 0.001). Furthermore, the equations we established had higher prediction accuracy than those of Gross et al. and Harbo et al. CONCLUSION: The equations developed in this study provided relatively low bias, thus providing a more suitable reference value for the knee isokinetic strength of young and middle-aged non-athletes.

The reference values for muscle mass and strength in healthy Indian adults using whole-body potassium counter and isokinetic dynamometer.

The study aims to define the sex-based reference data for muscle mass and strength among healthy young Indians and to compare the data from the present study with available literature. Healthy Indian adults (n = 100) aged between 18 and 40 years were recruited. The assessment of muscle mass and strength was performed. The body cell mass (BCM), fat-free mass, and muscle strength parameters were significantly higher among males compared to females (P < 0.001). A comparison of the current study data with the available literature showed that though BCM was comparable, Indians demonstrated a significantly lower isometric peak torque (P < 0.001 for both sexes). These findings suggest that Indians tend to have a lower muscle strength compared to the Western population, despite having a comparable BCM content.

Effects of eight week core stability training on stable- and unstable-surface on ankle muscular strength, proprioception, and dorsiflexion in athletes with chronic ankle instability.

BACKGROUND: Chronic ankle instability (CAI) is a common injury among athletes. Research has reported reduced dorsiflexion range of motion, impairment of proprioception, and decreased muscle strength of the ankle in people with CAI. The aim of this research was to examine the effects of 8-week core stability training on stable and unstable surfaces on ankle muscular strength, proprioception, and dorsiflexion range of motion (ROM) in athletes with CAI. METHODS: Thirty-six athletes with CAI (age 22.42 ± 2.76 years; height 169.11 ± 3.52 cm; weight 68.46 ± 2.75 kg) participated in this study. They were divided into three groups: unstable-surface group (UG) (n = 12), stable-surface group (SG) (n = 12), and control group (CG) (n = 12). The UG and SG performed the core stability exercise protocol for 8 weeks, 3 sessions per week. The CG received their usual care and daily activities. Outcomes were measured pre-sessions and post-sessions. RESULTS: The peak torque showed significant increases in the UG and SG compared with the CG during plantar flexion, dorsiflexion, inversion, and eversion (P < 0.05). There were also significant increases in UG compared with SG (P < 0.05). The proprioception showed significant decreases in UG compared with SG and CG (P < 0.05). The dorsiflexion ROM showed significant increases in UG and SG compared with CG. There were also significant increases in UG compared with SG (P < 0.05). CONCLUSIONS: It seems that core stability exercises on trampoline surface helps improve the measured parameters in athletes with ankle instability. Therefore, this type of training is recommended as a therapeutic option for Individuals with CAI.

Comparison of unilateral and bilateral strength ratio, strength, and knee proprioception in older male fallers and non-fallers.

BACKGROUND: Asymmetry of lower limb muscle strength and knee proprioception have been linked with risk of falling among elderly with and without history of falling. OBJECTIVE: This study aimed to determine the comparison of hamstrings to quadriceps strength ratio (CSR) and bilateral knee strength ratio, hamstrings and quadriceps muscles' strength and knee proprioception in elderly male fallers and non-fallers. METHODS: Sixty older adults, 65 years and older were recruited into faller (fell twice in the last six months) and non-faller groups. Then, the knee extension and flexion strength and proprioception at 45° knee flexion for the dominant leg (DL) and non-dominant legs (NDL) were measured with a Biodex Isokinetic Dynamometer. RESULTS: The strength of quadriceps and hamstring muscles showed significantly higher values in DL by 5.4 %, 9.2 % and NDL by 11.7 %, 15.5 % in the non-faller compared to the faller (p < 0.05). Significantly greater bilateral asymmetry (>10 % difference) was observed with the quadriceps (p = 0.014, -7.9 %, ES = 0.76) and hamstrings (p < 0.001, -18.4 %, ES = 1.5) as well as reduced CSR (<72 %) by 7.6 % in DL (ES = 0.64) and 11.3 % in NDL (ES = 0.81) with fallers versus non-fallers. Significantly less knee proprioception was found with the DL by -1.5 % (ES = 1.15) and NDL (ES = 1.50) by -2.1 % (p < 0.001) in non-faller compared to faller. CONCLUSION: It concluded that non-fallers have better strength symmetry, bilateral and unilateral knee strength ratios as well as more sensitive knee proprioception than fallers. It is suggestive that older adult fallers may need to improve bilateral knee strength symmetry and proprioception to prevent the risk of falling.

Low Pre-Season Hamstring-to-Quadriceps Strength Ratio Identified in Players Who Further Sustained In-Season Hamstring Strain Injuries: A Retrospective Study from a Brazilian Serie A Team.

A common pre-season injury prevention assessment conducted by professional football clubs is the hamstring-to-quadriceps (H:Q) strength ratio calculated by peak torque (PT). However, it is debatable whether players that present low pre-season H:Q ratios are more susceptible to further sustaining in-season hamstring strain injuries (HSI). Based upon retrospective data from a Brazilian Serie A football squad, a particular season came to our attention as ten out of seventeen (~59%) professional male football players sustained HSI. Therefore, we examined the pre-season H:Q ratios of these players. H:Q conventional (CR) and functional (FR) ratios, and the respective knee extensor/flexor PT from the limbs of players further sustaining in-season HSI (injured players, IP) were compared to the proportional number of dominant/non-dominant limbs from uninjured players (UP) in the squad. FR and CR were ~18-22% lower (p < 0.01), whereas quadriceps concentric PT was ~25% greater for IP than UP (p = 0.002). Low scores of FR and CR were correlated (p < 0.01) with high levels of quadriceps concentric PT (r = -0.66 to -0.77). In conclusion, players who sustained in-season HSI had lower pre-season FR and CR compared to UP, which appears to be associated with higher levels of quadriceps concentric torque than hamstring concentric or eccentric torque.

Serum Adiponectin and Leptin Is Not Related to Skeletal Muscle Morphology and Function in Young Women.

Adipokines secreted from adipose tissue, such as adiponectin and leptin, enhance skeletal muscle metabolism. Animal studies have shown that adipokine knockout leads to a reduction in muscle function. Muscle function is determined by muscle size and quality; therefore, it is speculated that lower adipokine levels affect skeletal muscle size and quality, eventually leading to lower muscle function. This study aimed to investigate the relationship between adipokines and skeletal muscle morphology and function in young individuals. A total of 21 young women participated in this study. Adiponectin and leptin levels were analyzed using fasting blood samples from all participants. B-mode ultrasound images of the thigh and calf were obtained, and the muscle thickness and echo intensity were measured in the vastus lateralis (VL) and medial gastrocnemius (MG). The shear modulus was measured from the VL and MG using shear wave elastography. Knee extension and plantar flexion peak torques were measured as muscle functions. Adiponectin and leptin were not related to echo intensity, shear modulus, and muscle thickness in the VL and MG (rs = -0.26-0.37, P > .05). Furthermore, no relationship was observed between adiponectin, leptin, knee extension, and dorsiflexion peak torque (rs = -0.28-0.41, P > .05). These negative results suggest that adiponectin and leptin levels in young women are not associated with muscle size and quality, nor are they related to muscle function.

Sex hormone-mediated change on muscle activation deactivation dynamics in young eumenorrheic women.

The goal of the study was to characterize muscle activation/deactivation dynamics across the menstrual cycle in healthy young women. Twenty-two healthy eumenorrheic women (age: 27.0 ± 4.4 years; mean ± SD) were tested every other day for one menstrual cycle. Serum estradiol and progesterone were quantified at the time of testing. Peak torque (PT), time to peak torque (TPT), and half relaxation time (HRT) of soleus muscle twitch were measured. Muscle twitch was elicited by delivering 1 ms width electrical pulses to the tibial nerve at an intensity that generated a maximum motor response (S-100) and at supramaximal intensity (S-120; 1.2 × S-100). The analyses were performed for each menstrual cycle phase: 1) the follicular phase to analyze the effect of estradiol while the progesterone concentrations remained at low concentrations; 2) the luteal phase to analyze the effect of progesterone with background estradiol concentrations. In the follicular phase, there was no association of estradiol for PT, TPT, and HRT. In the luteal phase, while estradiol had no association on PT, TPT, and HRT, progesterone expressed a significant association with HRT reduction but no association on PT or TPT. Also, there was a significant estradiol and progesterone interaction for HRT. However, the regression parameters are nearly zero, suggesting that the change in HRT may not have an impact on muscle performance across the menstrual cycle but implications on other women's health conditions with elevated sex hormone concentrations, such as pregnancy, may prove critical.

Comparison of Knee Muscular Strength Balance among Pre- and Post-Puberty Adolescent Swimmers: A Cross-Sectional Pilot Study.

Muscular weakness and strength imbalance between the thigh muscles are considered risk factors for knee injuries. Hormonal changes, characteristic of puberty, strongly affect muscle strength; however, it is unknown whether they affect muscular strength balance. The present study aimed to compare knee flexor strength, knee extensor strength, and strength balance ratio, called the conventional ratio (CR), between prepubertal and postpubertal swimmers of both sexes. A total of 56 boys and 22 girls aged between 10 and 20 years participated in the study. Peak torque, CR, and body composition were measured using an isokinetic dynamometer and dual-energy X-ray absorptiometry, respectively. The postpubertal boys group presented significantly higher fat-free mass (p < 0.001) and lower fat mass (p = 0.001) than the prepubertal group. There were no significant differences among the female swimmers. Peak torque for both flexor and extensor muscles was significantly greater in postpubertal male (p < 0.001, both) and female swimmers (p < 0.001 and p = 0.001, respectively) than in prepubertal swimmers. The CR did not differ between the pre- and postpubertal groups. However, the mean CR values were lower than the literature recommendations, which brings attention to a higher risk of knee injuries.

Characterization of Static Strength, Vertical Jumping, and Isokinetic Strength in Soccer Players According to Age, Competitive Level, and Field Position.

Muscular strength is strongly related to speed and agility tasks, which have been described as the most decisive actions preceding goals in the soccer game. This study aimed to characterize the players' strength indicators and to analyze the variation associated with age, competition level, and positional role. Eighty-three male soccer players from A team (n = 22), B team (n = 17), U-23 (n = 19), and U-19 (n = 25) participated in this study. Handgrip strength was assessed using a hand dynamometer (Jamar Plus+), countermovement jump (CMJ) and the squat jump (SJ) were evaluated using Optojump Next, and a Biodex System 4 Pro Dynamometer was used to assess the isokinetic strength of knee extension/flexion. Team A players showed increased lower-body strength compared to their peers, mainly through their increased vertical jumping capacity (i.e., CMJ and SJ; ps < 0.019), and superior performance in isokinetic assessments (i.e., peak torque, total work, and average power). Overall, older players outperformed their younger peers regarding vertical jumping, static strength, and average power in isokinetic strength (ps < 0.005). This study emphasizes the superior strength levels of professional soccer players compared with their lower-division peers, even after controlling by age. This information is of great value to sports agents and coaches, underlining the need to design and include strength-specific content during soccer training.

Contribution of Hip Abductors Muscles on Bone Mineral Density and Functionality in Older Women.

BACKGROUND: Despite the well-established role of muscle in maintaining bone mass and physical performance, there are still few studies that assess the relationship between muscle groups and specific bone sites and its contribution to physical function in older people. The aim of the study is to verify the association between hip and knee's muscle strength and bone mineral density of the femoral neck (BMD-FN) and investigated which muscle strength that are related with BMD-FN is associated with physical function in older women. METHODOLOGY: This is a cross-sectional study of 94 women over the age of 60 years, physically independent. Muscle strength of the hip and knee was evaluated using an isokinetic dynamometer (Biodex, USA) to obtain peak torque (PT). The BMD-FN was obtained using dual-energy x-ray absorption densitometry (DXA). Physical function was evaluated by the Timed Up and Go (TUG), gait speed (GS), five times stand to sit (5TSS) and single-leg stance (SS). To verify the association between muscle strength (independent variable) and the BMD-FN (dependent variable) and the relationship between muscle strength (independent variable) and clinical tests (dependent variable), the multiple linear regression was carried out, adjusted for age, time of menopause, height and level of physical activity. All of the analyses were carried out by the SPSS 17.0 software, with a level of p < 0.05 significance. RESULTS: We found an association between the hip abductors PT and the BMD-FN and between hip abductors PT and all clinical tests. CONCLUSION: We observe that hip abductor muscle strength contributes to BMD-FN and to performance in several clinical tests in older women. These findings reinforce the importance of this musculature not only for improving balance and gait, but also it can be a strategy to maintain/improve bone mass in the femoral neck in this population.

Diagnostic accuracy of the five times stand-to-sit test for the screening of global muscle weakness in community-dwelling older women.

BACKGROUND: Although the 5 times stand-to-sit test (5TSST) is indicated for screening for muscle weakness in older adults, its validity is based only on the correlation with quadriceps muscle strength or with the muscle strength of a few muscle groups of the lower limbs. Thus, the objective of the present study was to verify whether in independent older women, the 5TSST can really estimate global muscle strength, considering the sum of muscle strength of the trunk, hip, knee and ankle, which are important for functional activities. METHODS: 119 independent older women participated in this cross-sectional study, undergoing the 5TSST and an isometric muscle strength assessment of the trunk, hip, knee and ankle, using an isokinetic dynamometer. The accuracy of the 5TSST for the discrimination of older women with reduced global muscle strength was evaluated by the ROC curve. RESULTS: The ROC curve showed that the 5TSST may discriminate older women with reduced global muscle strength with moderate accuracy (AUC = 0.783; 95 % CI = 0.681-0.886; p < 0.001). The 5TSST score with the best accuracy (sensitivity: 80.0 % and specificity: 61.8 %) to evaluate global muscle strength was 11.64 s. CONCLUSION: 5TSST can be used to identify reduced global muscle strength in independent older women, standing out as an accessible tool for the screening of muscle weakness.