Muscle soreness but not neuromuscular fatigue responses following downhill running differ according to the number of exercise bouts

Repeated sessions of eccentric‐biased exercise promote strength gains through neuromuscular adaptation. However, it remains unclear whether increasing the number of these sessions can mitigate the extent of neuromuscular fatigue and exercise‐induced muscle damage (EIMD) in response to a standardised eccentric‐biased bout. Twelve healthy untrained adults (five females and seven males; 25.1 ± 4.9 years; and : 49.4 ± 6.2 mL kg −1 min −1 ) completed two blocks of five downhill running (DR) sessions on a motorised treadmill at a speed equivalent to 60%–65% for 15–30 min. Knee extensor maximal voluntary isometric torque (MVT), electrically evoked measures of neuromuscular fatigue (peripheral and central components), and lower‐limb perceived muscle soreness (PMS) and perceived load (RPE × session duration) were assessed before and immediately after a 15 min standardised DR bout at baseline and after 5 and 10 DR sessions. MVT decreased following a standardised DR bout ( p < 0.01) similarly at all three time points (−14%, −11% and −9%; p > 0.05). The same observations were found for all peripheral and central neuromuscular fatigue indicators after 0, 5 and 10 DR sessions. Quadriceps (but not plantar flexor or gluteus ) PMS was lower after 10 DR sessions (8.7 ± 8.5 mm) compared to baseline (29.6 ± 22.2 mm and p = 0.01), but no difference was observed after 5 DR sessions (15.4 ± 11.9 mm and p = 0.08). Ten repeated sessions of eccentric‐biased exercise led to a reduction in quadriceps femoris PMS following a standardised DR bout but neither 5 nor 10 sessions altered the central or peripheral fatigue responses to the same standardised DR bout. These findings suggest distinct physiological adaptations to repeated eccentric‐biased exercise regarding EIMD and neuromuscular fatigue.