The effects of a single bout of downhill running and ensuing delayed onset of muscle soreness on running economy performed 48 h later.

Delayed onset of muscle soreness (DOMS) is a common response to exercise involving significant eccentric loading. Symptoms of DOMS vary widely and may include reduced force generating capacity, significant alterations in biochemical indices of muscle and connective tissue health, alteration of neuromuscular function, and changes in mechanical performance. The purpose of the investigation was to examine the effects of downhill running and ensuing DOMS on running economy and stride mechanics. Nine, well-trained distance runners and triathletes participated in the study. Running economy was measured at three relative intensities [65, 75, and 85% of maximal aerobic capacity ( VO(2peak))] before (RE1) and 48 h after (RE2) a 30-min downhill run (-10%) at 70% VO(2peak). Dependent variables included leg muscle soreness, rate of oxygen consumption ( VO(2)), minute ventilation, respiratory exchange ratio, lactate, heart rate, and stride length. These measurements were entered into a two-factor multivariate analysis of variance (MANOVA). The analysis revealed a significant time effect for all variables and a significant interaction (time x intensity) for lactate. The energy cost of locomotion was elevated at RE2 by an average of 3.2%. This was coupled with a significant reduction in stride length. The change in VO(2) was inversely correlated with the change in stride length ( r= -0.535). Lactate was significantly elevated at RE2 for each run intensity, with a mean increase of 0.61 mmol l(-1). Based on these findings, it is suggested that muscle damage led to changes in stride mechanics and a greater reliance on anaerobic methods of energy production, contributing to the change in running economy during DOMS.