The fibrinolytic response to acute resistance training in lean and obese women
Fibrinolysis is the process by which fibrin blood clots are dissolved. Fibrinolytic research is clinically relevant because decreased fibrinolytic potential is linked to increased risk of an ischemic event. Fibrinolysis is known to increase in response to aerobic exercise, however, few research studies have focused on the fibrinolytic response to resistance exercise. Furthermore, women are severely underrepresented in fibrinolytic research, and there are no current studies that focus on women and resistance exercise. Estrogen has been shown to affect basal fibrinolytic potential resulting in the need for fibrinolytic research focused on female subjects. Body composition is known to influence basal fibrinolysis leaving individuals with higher absolute amounts of body fat at risk for cardiovascular events due to decreased fibrinolytic potential. Little is known, however, about the influence of body composition on the fibrinolytic response to exercise. Purpose. The purpose of this study was to describe the fibrinolytic response to acute resistance training in young women, and further, to determine how body fat percentage affects fibrinolysis at rest and following resistance exercise. Methods. Twenty-three sedentary, healthy women (22.5 ± 4 yrs, 22.3 ± 3.0 kg•m 2) participated in the study. Body fat percentage and fat distribution were assessed using dual-energy X-ray absorptiometry (DEXA), and subjects were separated into two groups by body fat percentage: <30% (lean, n=12) and >30% (obese, n=11). Each subject performed 6 sets of 10 leg extension repetitions at an intensity associated with 70% of her one-repetition maximum. The two primary mediators of fibrinolytic potential, tissue plasminogen activator (tPA) and plasminogen activator inhibitor 1(PAI-1), were assessed at baseline and immediately after exercise in venous blood. Results. tPA activity increased in response to acute resistance exercise (p<0.05), however, there was no significant change in PAI-1 activity (p>0.05). A significant main effect of group was observed, indicating the lean women had higher tPA activity (p<0.05) and lower PAI-1 activity (p<0.05) than the obese group. A significant time x group interaction indicated that the tPA response was blunted in the obese group (p<0.05). Conclusions. Fibrinolytic potential increases in response to acute resistance exercise in young women due to increases in tPA activity. Obese women demonstrate a decreased fibrinolytic potential at rest and following acute resistance exercise compared to lean women. Given the relationship between fibrinolytic potential and outcomes of cardiovascular disease, these physiological responses suggest that overweight women may be at elevated risk of an adverse cardiovascular event both at rest and during exercise.