Estimation of the neuromuscular fatigue threshold from an incremental cycling test using 1-minute exercise periods.

Abstract

The objectives of this study were: 1) to evaluate the method used for estimating the neuromuscular fatigue threshold from surface electromyographic amplitude (the PWCFT test) during a single incremental cycling workout using 1-minute exercise periods, and 2) to investigate the possible associations between PWCFT and metabolic (onset of blood lactate accumulation [OBLA]) and ventilatory (ventilatory threshold [VT] and respiratory compensation point [RCP]) variables. Sixteen cyclists performed incremental cycle ergometer rides to exhaustion with bipolar surface sEMG signals recorded from the vastus lateralis. Subsequently, participants performed one constant-workload exercise test at 100% of their PWCFT. During the incremental test, the power output at PWCFT was not correlated with that of OBLA (P>0.05), but it was positively correlated with those of VT and RCP (P<0.05). During the constant-workload test, heart rate and blood lactate increased progressively and significantly (P<0.05), whereas sEMG amplitude remained unchanged (P>0.05). The average duration of the constant-workload exercise was 8-9 minutes. The application of the PWCFT method using 1-min exercise periods could lead to overestimation of the neuromuscular fatigue threshold most likely because this stage duration allows insufficient time for the sEMG response to manifest.