A single bout of downhill running attenuates subsequent level running-induced fatigue

Abstract

Fatigue can be defined as exercise-induced strength loss. During running, fatigue can be partially explained by repetitive low-intensity eccentric contractions-induced muscle damage (EIMD). Previous studies showed that a bout of downhill running (DR) attenuated subsequent EIMD. Thus, we tested if a 30-min DR bout would attenuate fatigue induced by subsequent 60-min level running (LR). Twenty-seven male college students were randomly allocated to an experimental (EXP) or a control (CON) group. All participants performed LR on a treadmill at 70% of the velocity (vVO₂peak) corresponding to peak oxygen uptake (VO₂peak). Only EXP performed a 30-min DR (- 15%) on a treadmill at 70% vVO₂peak fourteen days before LR. Indirect EIMD markers and neuromuscular function were assessed before, immediately and 48 h after DR and LR. Knee extension isometric peak torque (IPT) decreased (- 36.3 ± 26%, p < 0.05) immediately following DR with full recovery reached 48 h post-DR. Muscle soreness developed (p < 0.05) immediately (37 ± 25 mm) and 48 h (45 ± 26 mm) post-DR. IPT and rate of torque development (RTD) at late phases (> 150 ms) from the onset of muscle contraction decreased significantly (- 10.7 ± 6.1% and from - 15.4 to - 18.7%, respectively) immediately after LR for the CON group and remained below baseline values (- 5.6 ± 8.5% and from - 13.8 to - 14.9%, respectively) 48 h post-LR. However, IPT and late RTD were not significantly affected by LR for the EXP group, showing a group x time interaction effect. We concluded that a single DR bout can be used to attenuate fatigue induced by a LR performed fourteen days after.

Figure 1

Changes in (A) isometric peak torque, (B) vastus lateralis EMG-RMS during isometric peak torque, (C) quadriceps muscle soreness, and (D) serum creatine kinase (CK) activity following downhill run for experimental group. *p < 0.05 compared to pre-DR.

Figure 2

Changes in (A) knee extension isometric peak torque (IPT), (B) vastus lateralis EMG-RMS during isometric peak torque, (C) knee extensors muscle soreness, and (D) serum creatine kinase (CK) activity over time following 60-min of level run for control (CON) and experimental (EXP) groups. Brackets represent significant main effect of time; *p < 0.05 compared to baseline values for the same group. Analyses of variance of neuromuscular data (A,B) were performed with n = 12 for both groups due to missed assessment points.

Figure 3

Changes in RTD and normalized RTD, respectively, achieved at 30 ms (A,G), 50 ms (B,H), 100 ms (C,I). 150 ms (D,J), 200 ms (E,K) and 250 ms (F,L) over time following 60-min of level run for control (CON) and experimental (EXP) groups. *p < 0.05 compared to baseline values for the same group. Analyses of variance were performed with n = 12 for both groups due to missed assessment points.

Figure 4

Experimental design of the study. Dark-grey boxes represent assessments and intervention of experimental group (EXP) while light-grey boxes stand for assessments and intervention of both EXP and control (CON) groups. NMF neuromuscular function, DOMS delayed-onset muscle soreness, CK serum creatine kinases activity.