Maximum concentric (CONC) and eccentric (ECC) strength of the ankle plantar flexor muscles were compared between middle-aged adults who regularly participated in resistance exercise training versus those who participated in weight-bearing endurance exercise. A total of 40 men and women with a mean age of 48.9 years (SD = 5.3) were tested for CONC and ECC plantar flexor (PF) strength, using an isokinetic device at 3 velocities: 30, 90 and 180 degrees/s. Mean strength values for the groups of men and women involved in resistance exercise were consistently higher than those involved in the endurance training for the CONC tests, where values ranged from 35% to 46% (avg. 41%, p < .01), but less between-group difference was observed for the ECC loading condition: 4% to 30% (avg. 18%). Thus ECC/CONC ratios, which rose with increasing velocity, were consistently higher for the endurance group vs. resistance-trained. Finally, since concentric PF torque values were found to be quite low for the middle-aged women who did only endurance training, this movement may require preventive strengthening exercises.