Individual differences in the responses to endurance and resistance training

Large individual differences in the responsiveness of cardiorespiratory fitness (VO_2peak) to endurance training have been observed in healthy subjects. We tested the hypothesis that subjects with a poor responsiveness to endurance training might benefit from resistance training in terms of aerobic fitness. The study population consisted of sedentary healthy male and female subjects (n=91, 42±5 year) assigned to either a training (n=73) or a control group (n=18). The randomized cross-over study design included a 2-week laboratory-controlled endurance or resistance training period with a 2-month detraining period between the interventions. Large individual differences were observed in the changes of VO_2peak (ΔVO_2peak) after both the endurance (average 8±6 %, P<0.001, range −5 to +22%) and resistance training (average 4±5%, P<0.001, range −8 to +16%). The average increase in ΔVO_2peak between genders was similar after both the endurance (8±6% for both genders, P=ns) and resistance training (3±5% for males and 5±6% for females, P=ns). There was no linear relationship between the changes in VO_2peak after each training intervention (r=−.09, P=ns). On the contrary, when the study group was divided into quartiles according to the endurance training response (1±3, 6±1, 9±1, and 16±3% increase in VO_2peak), the group with the lowest response to endurance training increased VO_2peak after the resistance training intervention (ΔVO_2peak 7±5%, P<0.001). The individual responsiveness of VO_2peak to exercise training is related to the mode of training. The healthy males and females whose training response is low after endurance training seem to result in a marked improvement in their cardiorespiratory fitness by resistance training.