Does muscle mass affect running performance in male long-distance master runners?

The aim of the present study was to investigate associations between skeletal muscle mass, body fat and training characteristics with running times in master athletes (age > 35 years) in half-marathon, marathon and ultra-marathon. We compared skeletal muscle mass, body fat and training characteristics in master half-marathoners (n=103), master marathoners (n=91) and master ultra-marathoners (n=155) and investigated associations between body composition and training characteristics with race times using bi- and multi-variate analyses. After multi-variate analysis, body fat was related to half-marathon (ß=0.9, P=0.0003), marathon (ß=2.2, P<0.0001), and ultra-marathon (ß=10.5, P<0.0001) race times. In master half-marathoners (ß=-4.3, P<0.0001) and master marathoners (ß=-11.9, P<0.0001), speed during training was related to race times. In master ultra-marathoners, however, weekly running kilometers (ß=-1.6, P<0.0001) were related to running times. To summarize, body fat and training characteristics, not skeletal muscle mass, were associated with running times in master half-marathoners, master marathoners, and master ultra-marathoners. Master half-marathoners and master marathoners rather rely on a high running speed during training whereas master ultra-marathoners rely on a high running volume during training. The common opinion that skeletal muscle mass affects running performance in master runners needs to be questioned.