Eur J Appl Physiol. 2025 Jul 2. doi: 10.1007/s00421-025-05879-y. Online ahead of print.ABSTRACTThis study compared the responses of arm-cycling during triceps surae neuromuscular electrical stimulation (NMES) on torque-time integral (TTI) and neuromuscular fatigue in healthy young adults. Achilles tendon vibration (VIB) (110 Hz) coupled with wide-pulse (WP) (1 ms) NMES (WP + VIB) of triceps surae alone or in combination with arm-cycling exercise (ARM-CYC) was delivered in two separate sessions in a randomised order (n = 22; 20 men; 29.9 ± 4.4 years). NMES intensity was set to elicit 20% of maximal voluntary isometric contraction (MVC) force. The stimulus pattern was comprised of four sets of 20 repetitions (5 s On and 5 s Off) superimposed to ongoing VIB with a 1-min inter-set interval. Time-torque integral (TTI) was measured for each NMES condition. MVC, voluntary activation level (VAL), peak twitch torque (Peaktwitch), and peak soleus (EMGSOL), medial (EMGMG), and lateral gastrocnemius (EMGLG) electromyography were measured before and immediately after each condition. No significant differences were observed for TTI (P = 0.371) between ARM-CYC and WP + VIB protocols. MVC force and Peaktwitch torque decreased (P < 0.001) immediately after both conditions. No changes were observed for VAL (P = 0.418) and EMGSOL, EMGLG, and EMGMG amplitudes (P = 0.061, 0.484, and 0.135), respectively. Rhythmic arm-cycling in combination with triceps surae NMES did not increase TTI compared to WP + VIB. This was accompanied with similar levels of peripheral fatigue with no indicative of central fatigue across both protocols. The lack of an ARM-CYC effect on torque output likely reflects the low intensity adopted, WP + VIB-induced ceiling effects, and/or enhanced inhibitory input to the triceps surae during combined tasks.PMID:40601011 | DOI:10.1007/s00421-025-05879-y