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August 24, 1999 Estrogen May Curb Women's Muscle Pain Women, who draw on energy reserves of fat more efficiently than men, frequently outperform men on ultraendurance events like the 85-kilometer marathon. Now, some researchers believe that women may have another edge. Recent studies suggest that estrogen might make them less prone to muscle soreness after exercise. For fitness enthusiasts, the dull pain and stiffness that sets in perhaps 6 to 12 hours after exercise can be a badge of honor, a symbol of a workout that pushed the limits. But for most people it is a consequence they would rather avoid. The soreness generally peaks 24 hours to 36 hours later, and causes a loss of strength and mobility, said Dr. Priscilla Clarkson, an exercise physiologist at the University of Massachusetts at Amherst. "Some soreness is good because it means that the muscle is growing in response to unaccustomed exercise," Dr. Clarkson said. "But if you are so sore that you cannot walk then you have exercised too intensely." The soreness is presumed to result from the body's reactions to exercise-induced microtears in the muscle tissue, she said. The consensus among exercise researchers is that damage most often occurs when the muscle is extended, as in the downward phase of biceps curls. Gender may play an important role in the susceptibility to soreness. "The animal data are very clear," Dr. Clarkson said. In studies, male rats showed much more muscle damage than female rats after exercises that emphasized muscle extensions, which specialists call eccentric contractions. "Estrogen seems to explain the difference," said Dr. Mark Tarnopolsky, a neuromuscular disease specialist at McMaster University Medical Center in Hamilton, Ontario, and the editor of "Gender Differences in Metabolism," published this year by CRC Press. When researchers gave male rats estrogen, they showed less damage, he said. Research is still in the early stages, and it is not known why estrogen might protect muscles. Dr. Clarkson hypothesizes that estrogen may be able to insert itself into cells, like muscle membranes, and stabilize them, which would protect them from tearing." Human studies are not as consistent as those with animals. In a study reported in the June issue of The Canadian Journal of Applied Physiology, Dr. Clarkson found that, compared with women who produce little or no estrogen, those on oral contraceptives, which contain estrogen, experienced less soreness after exercise, suggesting that estrogen does have a protective effect. And at an academic meeting of physiologists and biochemists in April, Dr. Tarnopolsky reported on a study in which men showed greater inflammation, an indicator of stress, two days after exercising, although men and women showed similar muscle tearing immediately after exercise. "The damage was the same for men and women, but the body's response seemed higher for men," Dr. Tarnopolsky said. On the other hand, more recent data collected by Dr. Clarkson showed no differences between men and women in the experience of soreness after repeated muscle extensions. The sex difference in soreness, if it holds up, suggests that women may be able to endure longer exercise sessions than men. "Women may accumulate less damage over the course of a long event, which would enable them to perform better," Dr. Tarnopolsky said. Soreness does have a positive side. It means that muscles have been stimulated to grow stronger as well as more resilient. "A single bout of eccentric trauma prepares muscles for subsequent bouts," said Dr. Brent Ruby, an exercise physiologist at the University of Montana. This "repeated bout effect" can protect muscles from further damage from similar exercise for up to six months, Dr. Clarkson's research showed. The best way to avoid soreness is to go easy. "Some soreness is inevitable when you exercise, but if you go slowly and progress gradually you won't get one bout that lays you up for a week," Dr. Ruby said. By NANCY STEDMAN Copyright 1999 The New York Times Company <http://www12.nytimes.com/library/national/science/082499hth-fitness-estrogen.html> janet paterson 52 now / 41 dx / 37 onset po box 171, almonte, ontario, canada, K0A 1A0 a new voice: http://www.geocities.com/SoHo/Village/6263/ [log in to unmask]