The effects of a 16-week training period (2 days per week) of resistance training alone (upper- and lower-body extremity exercises) (S), endurance training alone (cycling exercise) (E), or combined resistance (once weekly) and endurance (once weekly) training (SE) on muscle mass, maximal strength (1RM) and power of the leg and arm extensor muscles, maximal workload (W(max)) and submaximal blood lactate accumulation by using an incremental cycling test were examined in middle-aged men [S, n = 11, 43 (2) years; E, n = 10, 42 (2) years; SE, n = 10, 41 (3) years]. During the early phase of training (from week 0 to week 8), the increase 1RM leg strength was similar in both S (22%) and SE (24%) groups, while the increase at week 16 in S (45%) was larger (P < 0.05) than that recorded in SE (37%). During the 16-week training period, the increases in power of the leg extensors at 30% and 45% of 1RM were similar in all groups tested. However, the increases in leg power at the loads of 60% and 70% of 1RM at week 16 in S and SE were larger (P < 0.05) than those recorded in E, and the increase in power of the arm extensors was larger (P < 0.05) in S than in SE (P < 0.05) and E (n.s.). No significant differences were observed in the magnitude of the increases in W(max) between E (14%), SE (12%) and E (10%) during the 16-week training period. During the last 8 weeks of training, the increases in W(max) in E and SE were greater (P < 0.05-0.01) than that observed in S (n.s.). No significant differences between the groups were observed in the training-induced changes in submaximal blood lactate accumulation. Significant decreases (P < 0.05-0.01) in average heart rate were observed after 16 weeks of training in 150 W and 180 W in SE and E, whereas no changes were recorded in S. The data indicate that low-frequency combined training of the leg extensors in previously untrained middle-aged men results in a lower maximal leg strength development only after prolonged training, but does not necessarily affect the development of leg muscle power and cardiovascular fitness recorded in the cycling test when compared with either mode of training alone.