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.
Highlights
Fatigue can be defined as exercise-induced strength loss
Intense and/or repetitive eccentric contractions are well-known to induce ultrastructural disruption in skeletal muscle fibers, termed as exercise-induced muscle damage (EIMD), which is often quantified by the manifestation of delayed-onset muscle soreness (DOMS), increased plasma creatine kinase (CK), and strength loss[6,7]
Significant effects of time were observed for isometric peak torque (IPT) (F = 7.53, p = 0.003, ηp2 = 0.38), vastus lateralis EMG-root mean square (RMS) during
Summary
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). 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. In recreational or high-level sports activities, excessive fatigue development may compromise physical performance and increase susceptibility to injuries[3]. This impairment in muscle function depends on a variety of factors related to the exercise such as type of contraction, muscle groups involved, and exercise intensity and duration. After being exposed to EIMD, affected muscles become less susceptible to damage induced by a subsequent similar exercise, a phenomenon known as the repeated bout effect (RBE)[8]. The RBE extends to exercise bouts with similar m otions[8], it is still unclear if the protective effect conferred by a bout of DR can attenuate EIMD and fatigue following an extensive bout of level running
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