Complete recovery of quadriceps muscle peripheral fatigue after running in Olympic, but not Sprint, triathlon

This study compared central and peripheral fatigue development between the Sprint and Olympic distance triathlon. Fifteen male triathletes performed Sprint and Olympic triathlon simulations in a randomized and counterbalanced order. Central and peripheral fatigue was evaluated from changes in voluntary activation level (VAL) and twitch responses of quadriceps muscle (Q tw,pot ), respectively. Q tw,pot reduced from baseline to post-swimming similarly between triathlon simulations (Sprint,−17 11%; Olympic, −13 9%). In post-cycling, Q tw,pot further declined to a similar extent between triathlon distances (Sprint, −31 15%; Olympic, −28 11%). In post-running, Q tw,pot was fully recovered in the Olympic triathlon (−4 10%), whereas there was only a partial recovery of Q tw,pot in the Sprint triathlon (−20 11%). VAL was not reduced in post-swimming, but reduction was similar between triathlon distances in post-cycling (Sprint, −10 9%; Olympic, −8 8%) and post-running (Sprint, −15 14%; Olympic, −16 8%). In the Sprint triathlon, the swimming speed (1.07 0.13m.s −1 ) was above (p .001) critical speed (1.01 0.14m.s −1 ), the cycling power (179.7 27.2W) was below the respiratory compensation point (216.3 27.8W, p .001) and running speed (13.7 1.05km.h −1 ) similar to the respiratory compensation point (13.2 0.70km.h −1 , p .124). In the Olympic triathlon, swimming speed (1.03 0.13m.s −1 ) was similar to critical speed (p .392), and cycling power (165.3 27.3W) and running speed (12.6 1.05km.h −1 ) were below the respiratory compensation point (p .007). In conclusion, peripheral fatigue progressed until post-cycling regardless of triathlon distances. However, peripheral fatigue was fully recovered after running in Olympic but not in Sprint triathlon. The central fatigue started in post-cycling and progressed until post-running regardless of triathlon distances. Highlights The quadriceps muscle peripheral fatigue progresses similarly in Sprint and Olympic triathlons until post-cycling. The quadriceps muscle peripheral fatigue is completely recovered after running in the Olympic triathlon, whereas it is partially recovered in the Sprint triathlon. The central fatigue starts in post-cycling and progresses similarly until post-running in Sprint and Olympic triathlons, regardless of triathlon distances.