Effects of a 30-min running performed daily after downhill running on recovery of muscle function and running economy

This study investigated the effects of a 30-min level running performed daily for 6 days after downhill running (DHR) on indicators of muscle damage and running economy (RE). Fifty men were placed into five groups - control (CON), 40%, 50%, 60% and 70% (10 subjects per group) - by matching the baseline maximal oxygen consumption (over(V, ̇) O_{2 max}) among the groups. Subjects in the 40%, 50%, 60% and 70% groups had a treadmill (0°) run for 30 min at 40%, 50%, 60% and 70% of the pre-determined over(V, ̇) O_{2 max}, respectively, at 1-6 days after a bout of 30-min DHR at -15% (-8.5°). Maximal voluntary isometric strength of the knee extensors, muscle soreness, plasma creatine kinase and lactate dehydrogenase activities were measured before, immediately after and every day for 7 days after DHR. RE was assessed by oxygen consumption, minute ventilation, respiratory exchange ratio, lactate, heart rate and rating of perceived exertion during a 5-min level running at 85% over(V, ̇) O_{2 max} performed before and at 2, 5 and 7 days after DHR. All muscle damage markers changed significantly (P < 0.05) after DHR without significant differences among the groups. The RE parameters showed a significant decrease in RE for 7 days after DHR, but no significant differences in the changes were evident among the groups. These results suggest that the daily running performed after DHR did not have any beneficial or adverse effects on recovery of muscle damage and RE regardless of the intensity.