STRENGTH TRAINING EFFECTS ON REARFOOT MOTION IN RUNNING

The investigation examined isokinetic (IK) and nonisokinetic (NIK) str ength training programs for the inversion (INV) and eversion (EV) musc les on pronation during running. Seventy-seven volunteers were videota ped running on a treadmill at 3.8 m.s(-1) and total pronation (Delta b eta(PRO)) was computed. Eighteen heel-strike runners with the largest values of Delta beta(PRO) (X = 16.7 degrees) were selected as subjects . During the pre- and posttests, isokinetic muscle strength at 20 and 180 degrees.s(-1) was determined for the concentric (CON) and eccentri c (ECC) actions of the INV and EV muscle groups. The subjects also wer e videotaped running on a treadmill (3.8 m.s(-1)). The IK training gro up performed three sets of eight CON and ECC repetitions at 20, 90, an d 180 degrees.s(-1) for both muscle groups; and the NIK subjects did e xercises commonly used in ankle rehabilitation. Each group trained thr ee times weekly for 8 wk. The IK group showed significant (P less than or equal to 0.05) CON and ECC strength increases for all INV test con ditions and three of the four EV conditions (20 degrees.s(-1) CON and ECC, and 180 degrees.s(-1) CON). They also demonstrated significant de creases in the rearfoot (2.2 degrees) and pronation/supination (2.9 de grees) angles at heel strike and in Delta beta(PRO) (-2.2 degrees). Th e NIK group exhibited no change in rearfoot motion and only increased INV strength at the 180 degrees.s(-1) ECC test condition. The findings suggest that pronation can be decreased by an isokinetic strength tra ining program for the INV and EV muscles.