Thirteen young men completed a ten-week exercise training program on bicycle ergometers. Training sessions were conducted five days per week, with eight men randomly assigned to low-effort (LE) and five to high-effort (HE) regimens. LE participants worked continuously at 50% of their maximal oxygen intake (exercise HR congruent to 135 BPM); HE participants performed two minutes alternating work-rest intervals at 80% of their maximal oxygen intake (exercise HR congruent to 170 BPM). Total work done was held constant for the two groups. LE and HE participants increased maximal oxygen intake (P < .01), but there was no difference in changes between the two groups. LE exercise training programs are more comfortable for participants and perhaps should be recommended over HE programs for most individuals, since improvements in physical fitness appear to be comparable.