Purpose: When assessing neuromuscular fatigue (NMF) from dynamic exercise using large muscle mass (e.g. cycling), most studies have delayed measurement for 1-3 min after task failure. This study aimed to determine the reliability of an innovative cycling ergometer permitting the start of fatigue measurement within 1 s after cycling.
Methods: Twelve subjects participated in two experimental sessions. Knee-extensor NMF was assessed by electrical nerve and transcranial magnetic stimulation with both a traditional chair set-up (PRE and POST-Chair, 2 min post-exercise) and the new cycling ergometer (PRE, every 3 min during incremental exercise and POST-Bike, at task failure).
Results: The reduction in maximal voluntary contraction (MVC) force POST-Bike (63 +/- 12% PRE; P < 0.001) was not different between sessions and there was excellent reliability at PRE (ICC = 0.97; CV = 3.2%) and POST-Bike. Twitch (Tw) and high-frequency paired-pulse (Db100) forces decreased to 53 +/- 14 and 62 +/- 9% PRE, respectively (P < 0.001). Both were reliable at PRE (Tw: ICC = 0.97, CV = 5.2%; Db100: ICC = 0.90, CV = 7.3%) and POST-Bike (Tw: ICC = 0.88, CV = 11.9%; Db100: ICC = 0.62, CV = 9.0%). Voluntary activation did not change during the cycling protocol (P > 0.05). Vastus lateralis and rectus femoris M-wave and motor-evoked potential areas showed fair to excellent reliability (ICC = 0.45 to 0.88). The reduction in MVC and Db100 was greater on the cycling ergometer than the isometric chair.
Conclusion: The innovative cycling ergometer is a reliable tool to assess NMF during and immediately post-exercise. This will allow fatigue etiology during dynamic exercise with large muscle mass to be revisited in various populations and environmental conditions.
(C) 2017 American College of Sports Medicine