Effects of Preloaded Isokinetic versus Pure Isokinetic Training on Dynamic and Static Lumbar Muscle Strength and Endurance

A training study was conducted to investigate effects of two modes of exercise on the strength and endurance characteristics of the lumbar musculature. Twenty symptom free male subjects were divided into either a preloaded isokinetic (49 Nm preload) or a pure isokinetic training group. Both groups trained for five sets of 10 repetitions at 30°/s for 3 sessions per week for 1 month. Maximum preloaded isokinetic endurance and strength increased 26% (P < .001) and 20% (P = .001) for the preloaded isokinetic group and –1% (NS) and 3% (NS) for the pure isokinetic group. Maximum isometric strength and isometric endurance increased 11% (P < .001) and 3% (NS) for the preloaded isokinetic group and 9% (NS) and 18% (P = .024) for the pure isokinetic group. Both training regimes did not significantly change EMG spectral parameters. The preloaded isokinetic group exhibited retention of strength and endurance gains for as long as a year. The results indicated that the preloaded isokinetic group yielded superior gains in strength and endurance as compared with the pure isokinetic group except for isometric endurance. The observed retention of gains in the preloaded group during follow-ups may help direct rehabilitation to include eccentrics with isokinetic training.