G-18 Free Communication/Poster - Muscle Performance and Fatigue: JUNE 2, 2007 7:30 AM - 11:00 AM ROOM: Hall E
There is good evidence for an increase in muscle length subsequent to bouts of eccentric contractions. Many studies have used torque measured at a single knee angle as an index of muscle function after eccentric bouts. However, muscle torque changes may be angle dependent.
PURPOSE: To determine the torque-angle relationship of the knee extensor muscles following eccentric muscle damage.
METHODS: Six healthy male volunteers (age 24±4 years, height 175.8±8.3 cm, weight 74.0±6.4 kg, all data are mean±S.D.) performed 150 maximal eccentric contractions of the knee extensors of a randomly selected leg on an isokinetic dynamometer. The study was originally designed to examine antioxidant treatment, but no differences were found for the parameters presented here and data from both treatment groups were combined. Maximal voluntary isometric torque was recorded at 10° intervals between 60-150° (internal knee angle, with the volunteer lying in a prone position) pre-bout, 2 and 5 days after the eccentric bout. Isometric force at 90° knee angle was recorded pre-bout, 0, 1,3, 5, 7, and 10 days after the bout with the volunteer sitting upright. Serum Creatine Kinase activity (CK) was measured using a commercial kit over the same time period. Data were examined using repeated measures ANOVA, P<0.05 was considered significant.
RESULTS: Isometric force at 90° declined after the eccentric bout to a minimum of 55.5±13.3% of pre-bout (P<0.001) force on day 3 and gradually increased to pre-bout force by day 10. CK gradually increased to a maximum of 13,359±18,222 U.L-1 (P<0.05, log activity) on day 5 and returned to basal activity by day 10. Torque was reduced at all angles on day 2 apart from 150°, and all angles on day 5 post eccentric exercise. On day 5 torque loss was greater at angles 110° to 70° (longer quadriceps lengths) compared to shorter quadriceps lengths (P < 0.05). Angle of peak torque changed from 107±5° pre-bout to 108±12° on day 2 (NS), and 120±6°onday 5 (P<0.01).
CONCLUSIONS: These data demonstrate greater torque loss at long muscle lengths, which may indicate a transient muscle shortening in the days following eccentric muscle damage.