Author(s): FINCH, E., CAMERON, N., WALDRON, M., SCHOENMAKERS, P., KIDGELL, D., FRAZER, A., MAUDER, E., WATERWORTH, S., TALLENT, J., Institution: UNIVERSITY OF ESSEX , Country: UNITED KINGDOM, Abstract-ID: 1138

INTRODUCTION:
This study intended to quantify central and peripheral fatigue responses to incremental tests. Part A assessed neuromuscular fatigue and modality responses during cycling and running in triathletes. Part B explored the influence of exercise familiarity by comparing runners’ responses to accustomed (running) and unaccustomed (cycling) exercise.
METHODS:
Twenty-nine participants (15 triathletes, 14 runners; 13 female, 16 male) completed two laboratory visits involving randomised crossover incremental cycling and running peak oxygen uptake tests. Neuromuscular function was assessed using transcranial magnetic stimulation, peripheral nerve stimulation, and maximal voluntary quadricep contractions (MVC) during pre-exercise, following the lactate stage of the incremental test (peripheral measures only), immediately post-exercise, and 30-minutes post-exercise. A linear mixed model with baseline covariate adjustment was performed.
RESULTS:
Part A (triathletes), a modality effect was found in both MVC (P<0.001), and maximal compound muscle action potential (MMAX) amplitude (P=0.003) were higher in running following the incremental tests. No modality or time effects were observed for potentiated peripheral twitch, voluntary activation (VA), corticospinal excitability (CSE), short-interval intracortical inhibition, or intracortical facilitation. Time effects of half relaxation time (HRT) (P=0.012) and cortical silent period (cSP) (P=0.007), both showed prolonged durations 30-minute post-exercise compared to post lactate stage and immediately post-exercise. Part B (runners), Q.tw.pot showed a significant time*modality interaction (P<0.001), with higher values following running immediately post and 30 min post-exercise. A modality effect of MMAX showed higher amplitude in running (P<0.001), while cSP showed extended durations in running compared to cycling (P =0.03). Time effects were presented in cSP (P<0.001) and HRT (P=0.034) both increased at 30 min post-exercise versus immediately post-exercise.
CONCLUSION:
Comparing familiar and unfamiliar exercise modalities provides important insight into how task specificity influences neuromuscular fatigue. Exercise modality significantly shaped neuromuscular responses to incremental exercise, whereas task familiarity did not meaningfully alter central or peripheral fatigue. Cycling induced greater peripheral changes than running in triathletes. In both groups, modality effects changes were most evident in peripheral contractile properties function and cortical inhibition, while VA and CSE remained stable, suggesting preserved central drive. Transient, modality-independent reductions in cortical inhibition may reflect an adaptive central strategy to maintain motor output under fatigue. Overall, neuromuscular fatigue was driven by the mechanical and physiological demands of the exercise modality rather than prior task familiarity, highlighting the need for modality-specific fatigue assessment.