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BACKGROUND AND OBJECTIVE: Muscle strength imbalance can be an important factor in hamstrings muscle strain. The main purpose of this study was to investigate the effects of downhill running on hamstrings/quadriceps torque (H/Qtorque) and the electromechanical delay (H/QEMD) ratios. METHODS: Fifteen active male individuals performed two maximal voluntary isometric contractions of the knee extensors and knee flexors, from which the maximal muscle torque, EMD and H/Qtorque and H/QEMD ratios were extracted. Thereafter, the participants performed a 30-minute downhill run (−16%) at 70% VO2max. Dependent variables were assessed immediately before, immediately following and 48 hours after the effort. RESULTS: Maximal isometric torque decreased significantly immediately after the downhill run for both the extensors (pre: 271.8 ±45.9 N•m; post: 235.5 ± 55.7 N•m) and flexors (pre: 112.2 ±26.3 N•m; post: 97.7 ±27.2 N•m). No significant difference was identified over time for the EMD of the vastus lateralis and biceps femoris muscles. The H/Qtorque and H/QEMD ratios were not influenced by the downhill run. CONCLUSION: We have demonstrated that moderate intensity and volume downhill run does not impair knee joint stability at early (H/QEMD) and late phases (H/Qtorque) of quadriceps/hamstrings contraction. [ABSTRACT FROM AUTHOR]

We investigated the effectiveness of a resistance training (RT) protocol with lower volume and lower load in the body recomposition of postmenopausal women, and to determine whether changes in body recomposition induced by RT would be associated with changes in physical performance, independently of confounding factors. Participants were randomly assigned to one of three groups: I) Single set-high load (SSHL, n = 14, 1 set of 8 to 12 maximum repetitions), II) Single set-low load (SSLL, n = 15, 1 set of 25 to 30 maximum repetitions), and III) Multiple sets-high load (MSHL, n = 14, 3–6 sets of 8 to 12 maximum repetitions). The study extended over a duration of 27 weeks, encompassing 24 weeks of RT. We assessed body composition using dual-energy X-ray absorptiometry, physical performance using the Timed Up and Go and sit and stand tests, and muscle strength using the one-repetition maximum (1RM) test. We quantified body recomposition using a composite z score calculated as follows: (appendicular lean mass % delta z score) + (− 1 × fat mass delta % z score) / 2. Results showed significant improvements in physical performance (P < 0.001), significant reductions in visceral adipose tissue, total fat mass, and % fat (P = 0.003, P = 0.042, and P < 0.001, respectively), and increases in muscle mass and strength (P < 0.001), regardless of group assignment. Notably, the higher load groups (SSHL and MSHL) had significantly greater body recomposition compared to the lower load group (SSLL), particularly after adjusting for age, physical activity, and sitting time (P = 0.028). Therefore, the higher load of RT is a critical factor in the body recomposition of postmenopausal women. Furthermore, the positive effects of body recomposition induced by RT extend to physical performance and muscle strength. [ABSTRACT FROM AUTHOR]

Purpose: The torque–duration relationship in muscle group exercise is characterized by two parameters, the critical torque (CT) and the W prime (Wʹ), which define the limit of tolerance. These parameters have significant utility in assessing health and disease. However, there is a lack of information regarding the optimization of CT and/or Wʹ gains through manipulation of resistance training (RT) variables, especially in older adults. Therefore, this study aimed to investigate the impact of different intensities of RT, specifically higher intensity RT (HIRT) versus lower intensity RT (LIRT), on CT and Wʹ in postmenopausal women. Methods: The study spanned 12 weeks of RT. Postmenopausal women were randomized into three groups: control group (CG, n = 14), LIRT (loads necessary to perform 27–31 repetitions, n = 17), and HIRT (loads necessary to perform 8–12 repetitions, n = 14). Results: Compared to the CG group, the LIRT group exhibited a significant increase in CT (15%, P < 0.05), while the HIRT group showed a significant increase in Wʹ (36%, P < 0.05). Conclusions: Different intensities of RT result in distinct adaptations of torque–duration relationship parameters (Wʹ and CT) in postmenopausal women. [ABSTRACT FROM AUTHOR]

Purpose: The decline in physical performance, assessed by physical tests such as the timed up and go (TUG) test, is a consequence of reduced physiological reserves at higher levels of a hierarchical process. This occurs due to changes in muscle architecture, including atrophy and fat infiltration into the muscles, which in turn lead to changes in muscle function, resulting in reduced muscle strength and power and, consequently, affecting physical performance. This study investigated predictive factors for physical performance in breast cancer survivor (BCS), focusing on intramuscular adipose tissue (IMAT), quadríceps muscle area (QMA), and muscular power. Methods: This observational, analytical, and cross-sectional study included 23 women without a history of cancer (age, 58.5 ± 8.3 years; BMI, 27.2 ± 5.1 kg/m2) and 56 BCS (age, 58.5 ± 8.3 years; BMI, 27.2 ± 5.1 kg/m2). QMA and IMAT were assessed using computed tomography images. Muscular power and physical performance were measured using the 5-repetition sit-to-stand and TUG tests, respectively. Results: IMAT (r = 0.4, P < 0.01) and muscular power (r = − 0.4, P < 0.01) were associated with TUG performance in BCS, whereas QMA (r = − 0.22, P = 0.10) showed no significant association. QMA (r = 0.55, P < 0.01) was associated with muscular power, while no significant association was found between IMAT and muscular power (r = − 0.05, P = 0.73). Age explained 19% (P < 0.01) of TUG performance variability. Adding muscular power increased explanatory power by 12% (P < 0.01), and including IMAT further increased it by 7% (P = 0.02) for TUG performance. Collectively, age, muscular power, and IMAT accounted for 38% of the performance variance in the TUG test (age, B = 0.06, P = 0.043; muscular power, B = − 0.01, P = 0.002; IMAT, B = − 0.05, P = 0.020). Conclusions: Our findings suggest that IMAT and muscular power predict the physical performance of BCS, while QMA does not have the same predictive capability. [ABSTRACT FROM AUTHOR]

Background: The hyperbolic torque-duration curve depicts critical torque (CT) and W prime (W′), with the curve's asymptote representing CT as the boundary between heavy- and severe-intensity domains. W′, the curvature constant, indicates cumulative work beyond CT. This study investigated age-related reductions in W′, CT, and gait speed, and whether W′ and CT predict gait speed independently of muscle torque. Methods: three groups (adults, middle-aged, older) totaling 131 women were studied. W′ and CT were determined using 60 maximal isometric voluntary contractions of knee extensors. The fast gait speed was calculated in walking tests at 10 m, 400 m, and six minutes (6 MWT). Results: gait speed decreased (p < 0.05) with age, as did W′ and CT. Both W′ and CT correlated positively with gait speed at different distances (10 m, 400 m, 6 MWT). Adjusted for maximum muscle torque, only W′ maintained a positive association (p < 0.05) with all gait speed tests (10 m: β = 0.201, SE = 0.086; 400 m: β = 0.262, SE = 0.085; 6 MWT: β = 0.187, SE = 0.086). Conclusions: aging led to declines in W′, CT, and gait speed. W′, not CT, remained a significant predictor of gait speed, indicating its importance for older women's mobility. [ABSTRACT FROM AUTHOR]

The identification of young soccer players’ maturation level throughout puberty is crucial to verify the influence of aspects that interfere on sport performance, such as body height and physical capacities. The aim of the present study was to verify the differences in physical performance of young soccer players in maturation stages before and after peak height velocity. This study comprised 49 soccer players (14.49 ± 1.00 yrs) belonging to the youth teams of a club in the city of Fortaleza. Body weight, height and trunk-cephalic height were measured. Somatic maturation was estimated using distance in years from peak height velocity (DPHV). 10 Meters Sprint and 20 Meter Flying Sprint, Modified Illinois, Jump Height (CMJ), RAST and Yo Yo IRT 1 tests were applied. Standardized Mean Difference (SMD) and Confidence Intervals (CI = 90%) were used to compare the study variables (PRE-PHV vs POST-PHV). Our findings showed that POST-PHV group showed higher values in CMJ (3/3/97, Very likely) and RAST (peak, average, minimum power) and lower in the 20 Meter Flying Sprint (100/0/0, Most Likely) when compared to the PRE-PHV group. We concluded that young soccer players with somatic maturation after peak height velocity presented better capacity of lower limb strength, anaerobic power and speed. [ABSTRACT FROM AUTHOR]