BOSCO, C., R. COLLI, R. BONOMI, S. P. VON DUVILLARD, and A. VIRU. Monitoring strength training: neuromuscular and hormonal profile. Med. Sci. Sports Exerc., Vol. 32, No. 1, pp. 202-208, 2000.
Purpose: This study investigated changes induced by a single heavy resistance training session on neuromuscular and endocrine systems in trained athletes, using the same exercises for training and testing.
Methods: Five different groups volunteered: track and field male sprinters (MS, N = 6), track and field female sprinters (FS, N = 6), body builders (BB, N = 6), and weight lifters performing low-repetition exercise (WLL, N = 4) and high-repetition exercise (WLH, N = 4). In training, the work performed during half and full squat exercise was monitored for mechanical power output as well as EMG analysis on leg extensor muscles of the subjects belonging to the MS, FS, and BB groups. Just before and immediately after the training session, venous blood samples were obtained for RIA determination of testosterone (T), cortisol (C), lutropin (LH), human prolactin (PRL), and follitropin (FSH) in FS and MS. In the other three groups (BB, WLH, and WLL), the hormonal profile was limited to T and human growth hormone (hGH) only.
Results: After training the power developed in full squat demonstrated a statistically significant decrease (P < 0.01) in MS and no changes in FS. The EMG activity remained constant during the training session. Consequently, the EMG/Power ratio increased in both MS and FS, although only in MS a statistical significance was noted (P < 0.05). In MS immediately after the session the levels of C, T, and LH were significantly lower (P < 0.05). No changes were found in FS. In both groups and in BB significant negative correlation was found between changes in T level and EMG/Power ratio in half squat performance.
Conclusions: It is likely that adequate T level may compensate the effect of fatigue in FT fibers by ensuring a better neuromuscular efficiency.
Intensive prolonged strength training is known to induce specific neuromuscular (26) and hormonal (17) adaptive responses in the human body. However, little is known about the hormonal changes that occur during a single strength training session (15). Furthermore, even less knowledge is available with respect to fatigue, relative strength loss, and hormonal changes during acute exercise in both male and female subjects (16). In addition, inappropriate control of the intensity and duration of the training session has contributed to relatively large variation in results. It is noteworthy to mention that in the classic training programs the concept of intensity has been misused. The term intensity has been used to define the magnitude of the load employed rather than the rate of the work performed (3). In addition, whenever the effect of acute training session has been examined, no specific muscular evaluation test has been employed. In fact, in spite of using the same machine for training and testing (27), evaluation of muscular function has been performed with a complete different activation pattern (e.g., isometric or isokinetic) than was used for training (isotonic) (16). The present study was designed to investigate changes induced by a single heavy resistance training session on neuromuscular as well as on endocrine systems in male and female well-trained athletes using the same exercises for training and testing. In addition, the athletes were kept informed during training of the magnitude of the power developed during each repetition and for the whole training session period through audio-visual biofeedback.