Effects of Upper Body Eccentric versus Concentric Strength Training and Detraining on Maximal Force, Muscle Activation, Hypertrophy and Serum Hormones in Women

Effect of Tibialis Anterior Neuromuscular Electrical Stimulation-Induced Eccentric Contraction Training on Single-Leg Standing: A Pilot Study

This study explored the impact of a four-week Neuromuscular Electrical Stimulation (NMES)-induced eccentric contraction training on single-leg standing balance and muscle strength in 17 healthy adults. The unique training approach involved active antagonist muscle contraction during NMES. Post-training results revealed significant improvements in balance, with notable reductions in Center of Pressure (CoP) trajectory velocity (mean reduction: 0.07 ± 0.01 cm/s, p < 0.05) and range (mean reduction: 2.98 ± 0.53 cm, p < 0.05) on a firm surface. While increases in dorsiflexion force (mean increase: 21.43 ± 0.79 N, p < 0.05) and muscle activation were observed, these were not statistically significant. Changes in muscle pennation angles were also not significant (mean change: 0.43 ± 0.06 degrees, p > 0.05), underscoring the complexity of muscle adaptation processes. This study highlights NMES's potential in enhancing balance and proprioceptive sensing, suggesting its promising applications in neuromuscular rehabilitation. However, further research is needed to fully understand its impact.

Changes in hormonal profiles during competition preparation in physique athletes

PURPOSE

Physique athletes engage in rigorous competition preparation involving intense energy restriction and physical training to enhance muscle definition. This study investigates hormonal changes and their physiological and performance impacts during such preparation.

METHODS

Participants included female (10 competing (COMP) and 10 non-dieting controls (CTRL)) and male (13 COMP and 10 CTRL) physique athletes. COMP participants were tested 23 weeks before (PRE), one week before (MID), and 23 weeks after the competition (POST). Non-dieting CTRL participants were tested at similar intervals. Measurements included body composition (DXA), muscle cross-sectional area (ultrasound), energy availability (EA) derived by subtracting exercise energy expenditure (EEE) from energy intake (EI) and dividing by fat-free mass (FFM), muscle strength, and various serum hormone concentrations (ACTH, cortisol, estradiol, FSH, IGF-1, IGFBP-3, insulin, and free and total testosterone and SHBG).

RESULTS

During the diet, EA (p < 0.001), IGF-1 (p < 0.001), IGFBP-3 (p < 0.01), and absolute muscle strength (p < 0.01-0.001) decreased significantly in both sexes in COMP. Decreases in IGF-1 were also associated with higher loss in FFM. In males, testosterone (p < 0.01) and free testosterone (p < 0.05) decreased, while SHBG (p < 0.001) and cortisol (p < 0.05) increased. Insulin decreased significantly only in males (p < 0.001). Mood disturbances, particularly increased fatigue in males (p < 0.05), highlighted the psychological strain of competition preparation. All these changes were restored by increased EA during the post-competition recovery period.

CONCLUSION

Significant reductions in IGF-1 and IGFBP-3 during competition preparation may serve as biomarkers for monitoring physiological stress. This study offers valuable insights into hormonal changes, muscle strength, and mood state during energy-restricted intense training.

Testosterone/cortisol ratio: gender effect and prediction of podium results in beach sprint master rowers

Objective

The purpose of this study was to address the lack of data on the stress and motivation response in master athletes during competitions, as athletic performance in this age group can be significantly impacted by stress rather than appropriate training.

Methods

Coastal rowing beach sprint master athletes aged 43-57 years were examined to assess the saliva levels of stress biomarkers, cortisol, and testosterone. Specifically, samples were collected at awakening and before and after the boat race.

Results

Mean values of cortisol remained unchanged from awakening and raised at the end of the competition, while testosterone levels increased before the race, suggesting an aggressive/competitive behavior. Cortisol levels were significantly higher when comparing pre-race levels with post-race (p = 0.001) levels and early morning with post-race (p = 0.006) levels. No gender effect was observed in this case. Testosterone values did not demonstrate significance when compared between time points, not even when stratifying by gender. Considering the 24 athletes, a higher testosterone/cortisol ratio was correlated with a worse podium position (B = 3.705; p = 0.009). When stratified by gender, the testosterone/cortisol ratio demonstrated an association with a worse outcome of the race only in female rowers (B = 4.012; p = 0.022). Male athletes demonstrated no significant correlation between hormone ratio and race results (B = 3.288; p = 0.292).

Conclusion

It emerged from this study that the amateur rowers who approach competitive sport during adulthood may have problems in coping with the race-related stress and thus the outcome of their performance might be affected, as in adolescents.

Strength and power adaptations of the upper body following 20 training sessions on an eccentric arm-crank ergometer

PURPOSE

Eccentric strength training is an innovative and promising approach to improve exercise performance. However, most eccentric training studies in the past were performed with a focus on the lower extremities. The present study aimed to test the feasibility and effects on strength and power adaptations of a structured upper-body eccentric training program.

METHODS

Fourteen (median age (Q1-Q3) 29 years (27-32); 9 females, 5 males) healthy, regularly exercising individuals performed 20 progressive training sessions (2-3 sessions/week at 20-50% peak power for 8-14 min) on a symmetric eccentric arm-crank ergometer. Before and after the intervention, anaerobic peak power (PP) and maximal concentric aerobic power output (POmax) on an arm-crank ergometer as well as the one repetition maximum (1RM) for bench press were determined as main outcome parameters. A p-value ≤ 0.05 was considered statistically significant.

RESULTS

Significant improvements in PP (+ 4% (1-8), p = 0.007), POmax (+ 6% (0-8); p = 0.01), and 1RM (+ 12% (10-17); p < 0.001) were found. Exercise intensity was relatively low at 64% (55-70) of maximum heart rate.

CONCLUSIONS

Twenty progressive training sessions on a symmetric arm-crank ergometer are effective in inducing significant aerobic and anaerobic performance and strength improvements in the upper body. This intervention is safe and feasible, and can be performed at relatively low cardiovascular intensities. Therefore, this training method offers an interesting approach from elite sports to rehabilitation.

Skeletal muscle atrophy, regeneration, and dysfunction in heart failure: Impact of exercise training

This review highlights some established and some more contemporary mechanisms responsible for heart failure (HF)-induced skeletal muscle wasting and weakness. We first describe the effects of HF on the relationship between protein synthesis and degradation rates, which determine muscle mass, the involvement of the satellite cells for continual muscle regeneration, and changes in myofiber calcium homeostasis linked to contractile dysfunction. We then highlight key mechanistic effects of both aerobic and resistance exercise training on skeletal muscle in HF and outline its application as a beneficial treatment. Overall, HF causes multiple impairments related to autophagy, anabolic-catabolic signaling, satellite cell proliferation, and calcium homeostasis, which together promote fiber atrophy, contractile dysfunction, and impaired regeneration. Although both wasting and weakness are partly rescued by aerobic and resistance exercise training in HF, the effects of satellite cell dynamics remain poorly explored.

PAX7 and MyoD Proteins Expression in Response to Eccentric and Concentric Resistance Exercise in Active Young Men

OBJECTIVE

Satellite cells play an important role in muscle regeneration, which this process can be affected by different genes including PAX7 and MyoD. Exercise training known as an important strategy for mediating the satellite cell's function. Therefore, the main purpose of the present study is to investigate the changes in PAX7 and MyoD protein expression in response to eccentric and concentric resistance exercise in healthy young men.

MATERIALS AND METHODS

In this semi-experimental and cross-sectional study, 10 healthy men (age range 18-30 years old) participated. They were randomly divided into two equal groups (n=5) to perform one of two high-intensity eccentric or concentric knee extensions muscle contraction protocols. The contractions included a maximum of 12 sets of 10 repetitions, with a 30 second rest time interval between sets. PAX7 and MyoD protein expression was assessed using Immunohistochemistry analysis from the Vastus Lateralis muscle needle biopsy samples that have been taken 24 hours before and 3 to 4 hours after the end of the exercise protocol.

RESULTS

We observed that the PAX7 protein expression level increased significantly after eccentric (47.75%) and concentric (39.21%) (P=0.01) intervention. While, the MyoD protein expression level reduced (38.14%) significantly following acute eccentric resistance exercise (P=0.01).

CONCLUSION

It seems that eccentric or concentric muscular contraction modulates the expression of PAX7 and MyoD protein expression in the skeletal muscle, with further effects observed in eccentric resistance exercise.