Effects of running distance and training on Ca2+ content and damage in human muscle

Purpose: Muscle damage and soreness are well-known adverse effects of running, especially when covering distances in excess of habitual running activity. Loss of Ca2+ homeostasis is hypothesized to initiate the development of exercise-induced muscle damage. We tested the hypothesis that the Ca2+ content of vastus lateralis muscle increases after a 10- or 20-km run and studied the relations between Ca2+ accumulation and running distance, endurance training, and fiber type distribution. Methods: Twenty-four healthy young men and women were divided into two groups who ran either 10 or 20 km. Muscle biopsies and blood samples were collected before, immediately after, and in the days after the run. Results: The Ca2+ content in muscle biopsies increased from 0.70 +/- 0.02 to 0.93 +/- 0.04 mumol(.)g(-1) wet weight after the 20-km run (P < 0.001) and was still significantly elevated at 4 and 48 h after the run. In the 10-km runners, however, no significant increase in Ca2+ was found (0.81 +/- 0.03 vs 0.91 +/- 0.06 mumol(.)g(-1) wet weight, P = 0.08). Plasma levels of lactate dehydrogenase and creatine kinase increased after both running distances, the increase being greatest after the 20-km run. Eight of the 10-km runners completed an endurance-training program and subsequently repeated the 10-km run. The response to a new 10-km run with regard to muscle Ca2+ content and parameters of muscle damage was essentially unchanged by training. Conclusions: The degree of muscle damage depends on running distance, and a significant Ca2+ accumulation in muscle is seen after 20 km. Ten weeks of endurance training does not influence Ca2(+) homeostasis and muscle damage after 10-km running.