Evaluation of acute hormonal responses to concentric, eccentric and concentric-eccentric muscle actions in healthy young men
Physiology and Pharmacology
* Introduction: Resistance exercise considerably increases the concentrations of circulating hormones such as growth hormone (GH) and testosterone. Conventional resistance exercise is performed using sequential concentric (CON) and eccentric (ECC) contractions that are performed on an external constant load. The aim of this study was to determine hormonal and metabolic responses to CON, ECC and CON-ECC muscle actions in order to develop appropriate resistance exercise protocols and equipment
... ls and equipment for both athletes and patients recovering from injury. In the present study, we have examined the endocrine system responses to six different upper and lower body exercises utilizing the CON, ECC and CON-ECC contractions. Methods: In this study, we examined acute hormonal responses of GH, total testosterone (TT), free testosterone (FT) and cortisol in 10 young men who had the experience of non-professional resistance exercise. The exercise protocol included 6 resistance exercises, Which 3 of them were upper body and the other 3 were lower body exercises. The participants performed 3 contraction actions in 3 different days with at least one week interval and at the same time of the day. The exercise protocol included 4 sets in each exercise session and 90 seconds of rest between the sets. Each set included 10 repetitions. CON and ECC actions performed at intensity of 80% CON 10-RM and 80 % (120% CON 10-RM), respectively. Considering to the counterbalanced force design and on the calculations was done, the intensity of CON-ECC action was 88% CON 10-RM. Blood samples were collected before the exercise, immediately after as well as 15 and 30 minutes after each exercise session. Results: GH was increased after CON, ECC and CON-ECC contraction exercise but this increase reached significance only after CON and CON-ECC trials. TT and FT increased significantly after all 3 types of exercise, while cortisol had a significant decrease after all types of exercise. Conclusion: Although we observed a significant increase in TT and FT and a significant decrease in cortisol levels after CON, ECC and CON-ECC contraction exercise, we did not find any significant difference among various types of exercise. This indicates that these hormonal responses after exercise is not influenced by the type of exercise. On the other hand, acute GH response after contractions depended on the type of exercise protocol, which indicates that GH response depends not only on the intensity and quantity of exercise, but also on the type of muscle contraction and degree of the motor units recruitment.