Serum hormone concentrations and physical performance during concurrent strength and endurance training in recreational male and female endurance runners

To investigate the effects of concurrent strength and endurance training on physical performance and serum hormone levels a total of 32 recreational endurance runners were trained for 18 weeks. Subjects were divided into four training groups separated by the strength training mode and gender. The groups were women’s and men’s combined maximal and explosive strength training group (WME; n=9 and MME; n=9), and women’s and men’s muscle endurance strength training group (WE; n= 8 & ME; n=8). The training was executed in three consecutive periods (I; 10 weeks, II; 4 weeks and III; 4 weeks). The endurance training in all groups was low-intensity (below lactate threshold) running throughout the whole experiment. The strength training was similar moderate-intensity resistance training for all groups during the training period I. During the training periods II and III, strength training differed between the groups (combined maximal and explosive vs. muscle endurance strength training). All groups performed two strength training sessions per week. Serum basal hormone levels, one repetition maximum (1RM), counter movement jump (CMJ), maximal oxygen consumption (VO2max) and maximal running velocity (Vmax) mere measured prior to the experiment and after each training period. Free testosterone increased in WE from Week 10 to Week 14 (20.1 ± 20.6 %, p < 0.05). No other changes in basal serum hormone levels were observed within or between the groups or genders. 1RM and CMJ improved significantly in all groups (p < 0.05-0.001) as well as Vmax (p < 0.05-0.001). No significant differences in the changes in 1RM, CMJ or VO2max were observed between the training groups. The increase in Vmax was significantly higher (p < 0.05) in the ME compared with the MME group (p < 0.05) during the differentiated strength training period. Additionally, ME had a significantly (p < 0.05) larger improvement in Vmax compared with WE (p < 0.05-0.001) during the experiment. In conclusion, hormonal responses to the present concurrent strength and endurance training seemed to be highly individual and mainly non-significant in the group level. No gender differences were observed in the hormonal responses. In addition, no gender differences were found in the changes in most of the selected physical performance variables except for the greater increase in the Vmax in ME compared to WE. Well designed concurrent strength and endurance training regimens resulted in improvements in strength and endurance in recreational endurance runners regardless of the strength training type used. However, improvements in strength and power were more systematic in the groups performing combined maximal and explosive strength training. The differences in the selected endurance performance variables were minimal except for the larger improvement in Vmax in the ME group compared with the MME group