Gender differences in muscle inflammation after eccentric exercise

Unaccustomed exercise is followed by delayed-onset muscle soreness and morp hological changes in skeletal muscle. Animal studies have demonstrated that women have an attenuated response to muscle damage. We studied the effect of eccentric exercise in untrained male (n = 8) and female (n = 8) subjects using a unilateral exercise design [exercise (Ex) and control (Con) legs]. Plasma granulocyte counts [before (Pre) and 48 h after exercise (+48h)] an d creatine kinase activity [Pre, 24 h after exercise(+24h), +48h, and 6 day s after exercise (+6d)] were determined before (Pre) and after (+24h, +48h, +6d) exercise, with biopsies taken from the vastus lateralis of each leg a t +48h for determination of muscle damage and/or inflammation. Plasma granu locyte counts increased for men and decreased far women at +48h (P < 0.05), and creatine kinase activity increased for both genders at +48h and +6d (P < 0.01). There were significantly greater areas of both focal (P < 0.001) and extensive (P < 0.01) damage in the Ex vs. Con leg for both genders, whi ch was assessed by using toluidine blue staining. The number of leukocyte c ommon antigen-positive cells/mm(2) tissue increased with exercise (P < 0.05 ), and men tended to show more in their Ex vs. Con leg compared with women (P = 0.052). Men had a greater total (Ex and Con legs) number of bcl-2-posi tive cells/mm2 tissue vs. women (P < 0.05). Atrophic fibers with homogeneou s bcl-2-positive staining were seen only in men (n = 3). We conclude that m uscle damage is similar between genders, yet the inflammatory response is a ttenuated in women vs. men. Finally, exercise may stimulate the expression of proteins involved in apoptosis in skeletal muscle.