A Polish research team conducted a study to evaluate the effect of long-term running training on muscle strength in two groups of men 50 years and older. The first group was physically active, the second was inactive. Men who had been running regularly had a significantly lower strength level. Results in the inactive group were determined to a great extent by significantly different body weights and a significantly higher body fat mass content. The symmetry index was statistically higher in the reference group. Long distance run training reduces body fat mass while maintaining a high level of muscle strength.
Am J Mens Health. 2019 May-Jun;13(3):1557988319859108. doi: 10.1177/1557988319859108.