Acute hormonal and muscular responses and recovery : chronic adaptations to single session combined strength and endurance training with regard to order effect

Abstract

Combining both strength (S) and endurance (E) exercise loadings into a single training session can be considered to be of interest e.g. for time management purposes. However, the first loading in a combined session tends to produce notable acute fatigue responses, which can lead to the second loading being performed in a compromised state. Research on fatigue and recovery from a combined session with different loading orders is currently scarce, with even less attention given to the acute responses. Thus, this study investigated the long-term adaptations in the acute responses of a combined strength and endurance loading and whether or not there is an order effect. A total of 29 male subjects completed the study which consisted of 24 weeks of combined strength and endurance training. All subjects participated first in the basal measurements of strength and endurance and were then assigned to one of the two groups: performing endurance before strength (E+S) or vice versa (S+E). Measurements of acute responses and recovery took place in the first week of training (0 weeks) and at the end of the study (24 weeks). The acute loadings were completed in an assigned order. The endurance loading consisted of 30 minutes of continuous endurance exercise on a bicycle ergometer at 65% of Wmax. The strength loading consisted of 3x40% 1RM, 4x75-90% 1RM and 4x75-80% 1RM. Maximal voluntary isometric contractions (MVC) and force production in 500ms (MVC 0-500ms) as well as serum testosterone and cortisol concentrations from a venous blood sample were measured before the loading (Pre), after the first part (E or S) of the loading (Mid), after completion of the loading (Post) as well as during recovery (at 24h and 48h). Both groups experienced a significant (p<0.001) decline in MVC at 0 and 24 weeks at Post. A significant-between group (p<0.05) difference was observed at Mid-loading at 0 and 24 weeks. At 24 weeks S+E was significantly (p<0.05) more fatigued in terms of force production at Mid and Post compared to 0 weeks. In MVC 0-500ms a significant (p<0.05) between-group difference was found at Mid at 24 weeks. E+S was slightly more fatigued at 0 weeks Post than S+E (p<0.001 vs. p< 0.05). Both were equally fatigued at Post at 24 weeks (p<0.001). S+E was significantly (p<0.05) more fatigued at Post at 24 in comparison to 0 weeks. A significant (p<0.05) response in testosterone was observed at Mid for E+S (0 and 24 weeks). At 48h at 0 weeks E+S showed significantly (p<0.05) lowered testosterone levels. At Mid at both 0 and 24 weeks a significant (p<0.05) cortisol response in E+S and a significant (p<0.05) between-group difference was noted. Both groups experienced significant (p<0.001) increases in training induced changes in maximal dynamic 1RM. The findings provide some evidence for an order effect in terms of adaptations to the acute responses of a combined strength and endurance loading. However, no order effect was found for training induced adaptations in maximal dynamic 1RM.