Effect of inherent muscle length on isometric plantar flexion torque in healthy women.

This study investigated the relationship between inherent muscle length and torque production in 59 healthy women. We recorded nondominant ankle range-of-motion values for each subject. These values were partitioned into quartiles for two knee positions. Women with "loose" plantar flexor muscles comprised the first quartile, and those with "tight" plantar flexor muscles the fourth quartile. Tight- and loose-muscle groups were established for the 0-degree (fully extended) and 90-degree (flexed) knee test positions for data analysis. Torque measurements were obtained using an isokinetic testing apparatus. We asked each subject to perform a maximal isometric (static) plantar flexion contraction at each of three ankle positions: 7 degrees of dorsiflexion (angle A), 0 degrees or neutral (angle B), and 30 degrees of plantar flexion (angle C). Data analysis was performed using an analysis of variance for repeated measures. Results indicated that torque produced by the tight-muscle groups was significantly greater than the torque produced by the loose-muscle groups at both knee positions (p less than .05). Additionally, the ankle ROM data obtained suggest normative data different from those currently prevalent in the literature. Findings of this study may prove valuable in the rehabilitation of ankle injuries and could be beneficial especially to physical therapists in understanding more about normal ankle function.