Torque–velocity and power–velocity relationships during isokinetic trunk flexion and extension

Background. No study has reported the possibility of establishing torque–velocity and power–velocity relationships for both flexor and extensor trunk muscles. The present study therefore sought to assess these relationships during isokinetic exercise.Methods. Nine healthy male subjects performed series of isokinetic trunk flexions and extensions at six different velocities ranging from 45° s−1 to 120° s−1. Trunk flexor and extensor muscles were, respectively, assessed on two separate days. All experiments used a Biodex dynamometer.Findings. Torque–velocity relationships were significantly well described by a linear relationship for both trunk flexor (P < 0.01; r = 0.92–0.99) and extensor muscles (P < 0.05; r = 0.82–0.97) in all subjects. Power–velocity relationships exhibited a parabolic shape for all subjects (P < 0.05; r = 0.96–0.99) for both muscle groups.Interpretation. Results showed that trunk muscle torque– and power–velocity relationships can be assessed during isokinetic exercise. The findings were in agreement with previous studies of lower and upper limbs. This kind of measurement can therefore be applied in assessing low-back pain patients during rehabilitation.