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Increased passive torque and muscle swelling in human ankle extensors after eccentric exercise N
Whitehead*, C Holdstock, D Morgan & U Proske Eccentric exercise has been shown to cause muscle damage and delayed onset muscle soreness (DOMS). Associated with these changes are an increase in the passive stiffness of the muscle and swelling (Howell et al., 1993). The main purpose of this study was to investigate the effect of eccentric exercise on passive torque and swelling, and to determine whether a relationship existed between these parameters. The procedure involved measuring passive torque of the triceps surae muscle group of both legs over a range of ankle angles (50-90 degrees), while the subject sat completely relaxed. Leg volume below the knee was measured using a perspex water-filled container. Passive torque and leg volume measurements were taken 2-3 times prior to a test bout of eccentric exercise of one leg. The test bout required subjects to step backwards on an inclined treadmill for a period of one hour. Measurements, including soreness ratings, were made immediately and 2 hours post-exercise, as well as on each of the following 4 days. Passive torque increased immediately after the exercise for the exercised muscle and reached peak values at 72 hours post-exercise. This increase was significant when compared with pre-exercise values and the unexercised leg (P<0.05). Mean swelling after the exercise had a biphasic time course; increasing until 24 hours post-exercise, decreasing at 48 hours and increasing again at 72 hours. Swelling was significant for the exercised leg (P<0.05) while the unexercised leg showed no change. Muscle soreness was also significant for the exercised leg (P<0.05). Regression analysis revealed a significant relationship between passive torque and swelling for the eccentrically exercised leg (P<0.01). It was concluded that there was a likely causal relationship between swelling and the rise in passive torque following eccentric exercise. References:
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