Occurrence of electromyographic and ventilatory thresholds in professional road cyclists

Abstract

The temporal relationship between the electromyographic (EMG) and ventilatory thresholds was investigated during incremental exercise performed by eight professional road cyclists. The exercise, performed on a cycloergometer, started at 100 W with successive increments of 26 Wx min(-1) until exhaustion. Gas exchange and the root mean square value of EMG (RMS) from eight lower limb muscles were examined throughout the exercise period. Professional cyclists achieved a maximal oxygen consumption, i.e. VO(2max), of 5.4 (0.5) l x min(-1) [74.6 (2.5) ml x min(-1) x kg(-1), range: 67.8-82.4 ml x min(-1) x kg(-1)] and a maximum power ( W(max)) of 475 (30) W (range: 438-516 W). Our results showed at least the occurrence of a first EMG threshold (EMG(Th1)) in 50% (gastrocnemius lateralis) of the subjects and a second EMG threshold (EMG(Th2)) in 63% (gastrocnemius medialis). EMG(Th1) occurred significantly before the first ventilatory threshold (VT(1)), i.e. at 52 (2)% and 62 (9)% of W(max), respectively. Inversely, no significant difference was observed between the occurrence of EMG(Th2) and the second ventilatory threshold (VT(2)), i.e. at 86 (1)% and 89 (7)% of W(max), respectively. These results suggest that the use of EMG may be a useful non-invasive method for detecting the second ventilatory threshold in most of the muscles involved in cycling exercise.