PCOS and Muscle Strength

Abstract

Polycystic ovary syndrome (PCOS) is a very common endocrinopathy in reproductive-aged women, characterized by hyperandrogenism, chronic anovulation and polycystic ovaries on ultrasound. PCOS is also frequently associated with body fat excess and insulin resistance, factors that may limit physical performance. However, androgen excess could be an advantage, in these women, in terms of increased muscle strength and performance. To date, only few studies in overweight/obese women have addressed the possibility that PCOS may be associated with changes in muscle strength, with controversial results. PURPOSE: The aim of this preliminary study was to assess muscle strength in normal weight PCOS women, to avoid the confounder effect of excess body fat. METHODS: Eight sedentary women with PCOS and 10 age- and BMI-matched healthy controls, with a similar level of habitual physical activity, were recruited. The strength of the knee extensor muscle of the dominant leg was assessed by isokinetic dynamometry at two different rates of execution (30°/s and 120°/s) in concentric and eccentric phase, whereas muscle architectural characteristics (thickness, fascicle length and pennation angle) were analyzed by ultrasound scan of the vastus lateralis muscle. Anthropometric and metabolic features, serum total and free testosterone levels (as measured by LC-MS/MS and equilibrium dialysis) were also assessed. RESULTS: As expected, testosterone levels were higher in PCOS women compared with controls, while no significant differences were observed in body composition and metabolic features between PCOS women and controls. The PCOS group showed greater isokinetic muscle strength in concentric phase at slow rate of execution (30°/s) (difference between groups 17%, p=0.04), whereas borderline differences were observed at higher rates of execution. No differences in muscle architectural characteristics were found. CONCLUSION: This preliminary study suggests that women with PCOS may have increased muscle strength. Further research should assess whether this phenomenon may be related to the effects of hyperandrogenemia on muscle fiber expression.