Effects of a 4-day low-intensity run after downhill running on recovery of muscle damage and running economy

This study examined whether a short period of either low-intensity running (LIR) exercise or passive rest following downhill running (DHR) would enhance the recovery of muscle damage and running economy (RE). Twenty-four active males participated in the study, and were randomly assigned into LIR (n = 12) and control (CON; n = 12) groups. Both groups performed one bout of DHR for 30 minutes on a treadmill with an incline of -26% and at the intensity of 70% of peak oxygen consumption (VO_2peak), The LIR group performed a 30-minute bout of running at a 0% incline and an intensity of 35% of VO _2peak, 30 minutes after the DHR. The 30-minute bout of LIR was repeated each day for 4 days by the LIR group, while the CON group passively rested during the same time period. RE was measured by rate of VO₂, minute ventilation, respiratory exchange ratio, heart rate, rating of perceived exertion, and stride frequency during a 5-minute bout of level running at 85% of VO_2peak performed before DHR, and at 2, 5 and 7 days thereafter. Blood lactate concentration was measured before and at 3 minutes after a 5-minute bout of level running (performed before DHR, and at 2, 5 and 7 days thereafter). Maximal isometric voluntary strength of the knee extensor, vertical jump, the level of muscle soreness, plasma creatine kinase activity, and myoglobin concentration were assessed before, immediately after, and every day for 7 days after DHR. All criterion measures were significantly changed (p < 0.05) following the DHR for both groups. In addition, the recovery of all criterion measures for the LIR group after DHR was not significantly different (p > 0.05) from that of the CON group. These results suggest that a 30-minute bout of LIR every day for 4 days following DHR did not improve the recovery of muscle damage or alter RE.