Effects of eccentric-emphasized leg curl intervention on muscle strength imbalance markers in professional soccer players during pre-season.

BACKGROUND: The effects of strength training on muscle strength imbalance are unclear in professional soccer players. As a result, this study examined the effects of an 8-week strength training program comprising eccentric-emphasized prone leg curl adjusted according to the individual strength imbalance status. METHODS: Ten professional soccer players (26.0 ± 3.6 yrs) participated in the study. Players who had a ≥ 10% contralateral imbalance in knee flexors eccentric peak torque (n = 6) performed two additional repetitions per set in the low-strength limb (high-volume, HV) compared to the high-strength limb (low-volume, LV). Isokinetic concentric knee extension and concentric and eccentric knee flexion peak torque (PT) and derived contralateral imbalances and conventional and functional hamstring-to-quadriceps ratios (H:Q) were assessed at baseline and after 8 weeks. Differences at baseline were assessed using paired-sample T-tests, and a two-way (limb x time) repeated measures analysis of covariance (ANCOVA) for changes over time. RESULTS: A significant improvement in the eccentric knee flexion PT was observed in both limbs after 8 weeks (P < 0.05), with greater effects observed in the HV limb (25.0 N m, 95% CI: 15.1-34.9 N m). Significant decreases were also observed in the contralateral imbalances from concentric knee extension and flexion and eccentric knee flexion PT (P < 0.05). Differences were not observed in concentric knee extension and flexion PT (P > 0.05). CONCLUSIONS: A short-term eccentric-emphasized leg curl intervention adjusted by the initial knee flexors eccentric strength was an efficient method to improve knee flexors strength imbalance in professional soccer players.

Chronic effect of resistance training on blood pressure in older adults with prehypertension and hypertension: A systematic review and meta-analysis.

The chronic antihypertensive effect of resistance training (RT) has been widely recognized in mixed-aged populations. However, the specific effect of RT on blood pressure (BP) in older individuals (≥60 years) remains unknown. Therefore, this meta-analysis of randomized controlled trials explored the chronic effects of dynamic RT alone on BP in older people. The study followed the PRISMA statement, and the search was performed using MeSH terms "strength training", "blood pressure" and "aged" on MEDLINE (PubMed), SCOPUS, and Web of Science databases. From 1783 potential articles, 24 studies met all inclusion criteria resulting in 835 participants randomized into 26 RT interventions (n = 430) and 24 control groups (n = 405). Overall, BP reduction favoring RT was observed both in SBP (-6.88 [-10.02, -3.73] mmHg) and DBP (-3.37 [-4.71, -2.22] mmHg). Subgroup analysis revealed BP decreases in both participants with hypertension (SBP: -10.42 [-15.67, -5.17]; DBP: -3.99 [-5.76,-2.22] mmHg), and prehypertension (SBP: -4.87 [-7.76, -1.98]; DBP: -2.77 [-4.88, -0.66] mmHg). Improvement in BP was found in studies using traditional RT (free weights and machines) (SBP: -7.04 [-11.04, -3.05]; DBP: -2.60 [-3.72, -1.47] mmHg) and elastic band interventions (SBP: -2.79 [-3.72, -1.86]; DBP:-1.68 [-3.18, -0.18] mmHg). RT performed at moderate intensity (60-80 % 1RM) reduced SBP (-6.98, [-11.93, -2.03]mmHg) and DBP (-3.64 [-5.11, -2.18] mmHg). In conclusion, RT can reduce BP in older people at prehypertensive and hypertensive stage, with traditional RT performed with moderate loads leading to an effect estimate of approximately -7 mmHg for SBP and -4 mmHg for DBP.

Moderate volume of sprint bouts does not induce muscle damage in well-trained athletes.

INTRODUCTION: Understanding the recovery in response to different sprint protocols is important for optimizing neuromuscular gains and organizing training sessions in sports. The current study aimed to investigate acute neuromuscular changes following a moderate volume of sprint protocols with and without change-of-direction. METHODS: 26 well-trained male collegiate athletes from different sports were randomly allocated into straight-line group (SLG) or change-of-direction group (CODG). The protocols were 1 × 15 repetitions of 20-meter sprints in line (SLG) or with two changes in each repetition (CODG). Knee extension maximal and explosive strength, jump performance, serum creatine kinase, and quadriceps and hamstrings echo intensity were collected pre-, post- 0, 24, 48, and 72 h post-exercise. RESULTS: There were no significant changes in any of the variables at any time point after the exercise protocols in comparison with pre-exercise values (p > 0.05). CONCLUSIONS: The present study suggests that sprint training with moderate volume with or without change of direction does not induce neuromuscular or physiological changes during 72 h post-exercise. This information is especially important for sports staff in order to optimize training prescription and frequency.

Muscle quality and functionality in older women improve similarly with muscle power training using one or three sets.

The present study compared the effects of 12 weeks of muscle power training performing one or three sets on muscle quality assessed by echo intensity (MQEI) and index (MQindex), muscle power-related outcomes, and functional capacity in older women. Participants were randomly assigned into two groups: 1SET (n = 13) and 3SET (n = 13). Lower limb muscle power and vertical jump height were measured during a countermovement jump, maximal rate of torque development (MRTD), and root mean square (RMS) of electromyography signals and rate of rise (RER) of quadriceps maximal electromyography activation during unilateral knee extension at 0-50 and 0-200 ms, MQEI, MQindex (absolute muscle power/MQEI, and MRTD/MQEI) and functionally in both groups using timed-up-and-go were evaluated before and after training. There were significant and similar (p < 0.05) increases in muscle power, vertical jump height, MQEI, MQindex, and functionally (p ≤ 0.0001) in both groups. In contrast, MRTD increased only in 1SET (p ≤ 0.001), and the RMS0-200 and RER0-50 increased for 3SET only (p ≤ 0.05), with no difference between groups (p > 0.05). In conclusion, similar neuromuscular adaptations and improvements in the functional performance occurred in both groups.

Effects of resistance training on neuromuscular parameters in elderly with type 2 diabetes mellitus: A randomized clinical trial.

This study is a randomized controlled clinical trial that verified the resistance training efficacy on neuromuscular parameters, with muscle quality as primary outcome. Forty-four elderly with diabetes type 2 (69.7 ±â€¯6.9 years; 26 men) were randomly allocated to a 12-weeks resistance training group (RTG, 3 times a week), or an active control group with stretching classes (CG, once a week). Primary and secondary outcomes were assessed at baseline and after 12 weeks, as follow: quadriceps muscle thickness and rectus femoris muscle quality, maximal knee extension strength, rapid strength, functional performance, visceral adipose tissue, glycemic control, lipid profile and quality of life. Generalized estimating equations were used to analyses based on intention-to-treat and per-protocol approaches, which showed the same results. Among all outcomes measured there were improvements in the knee extension strength (P < 0.001) and quadriceps muscle thickness (P < 0.001) for RTG. The muscle quality did not improve for both groups (P = 0.98). For the secondary outcomes there were no improvements for functional performance, rapid strength, glycemic control, quality of life, visceral adipose tissue and lipid profile in both groups, with exception of triglyceride level reduction for RTG (P = 0.04).The resistance training program is an efficacious strategy for improve the neuromuscular health in elderly with T2DM, considering increases in lower limb strength and muscle mass, but the same was not found for muscle quality, rapid strength, functional performance and quality of life. Furthermore, the training program did not induce significant reduction in glycated hemoglobin values of patients who already had suitable glycemic control.

Higher muscle power training volume is not determinant for the magnitude of neuromuscular improvements in elderly women.

The aim of this study was to compare the effects of 12 weeks of muscle power training using one- and three-sets on neuromuscular adaptations in elderly women. Twenty six healthy elderly women were randomly assigned into two groups: one-set (n = 13) and three-sets (n = 13). Maximal dynamic and isometric strength, rapid force assessed as absolute and normalized rate of force development (RTD) and contractile impulse during unilateral leg knee extension at 0-50 and 0-200 ms, overall quadriceps muscle thickness, muscle power during a countermovement jump (CMJ), and functional performance using time-up-and-go and the timed stair climb tests were evaluated before and after training. After 12 weeks, one-set and three-sets groups exhibited significant (p ≤ 0.05) and comparable increases in dynamic and isometric strength, absolute RTD and contractile impulse at 0-50 and at 0-200 ms and in the performance of both functional tests. No significant differences between groups were evident for any measured parameters (p > 0.05). Furthermore, the normalized RTD did not increase for any group (p > 0.05). Over 12 weeks, the muscle power training performing one- or three-sets induced alike improvements in muscle function, mass and functionally. These evidences suggest that a low training volume is able to induce significant improvements in age-related neuromuscular changes.