Application of the neuromuscular fatigue threshold treadmill test to muscles of the quadriceps and hamstrings

Purposes The purposes of the present study were (1) to determine if the physical working capacity at the fatigue threshold (PWC FT ) model that has been used for estimating the onset of neuromuscular fatigue in the vastus lateralis (VL) during incremental treadmill running could also be applied to the vastus medialis (VM), biceps femoris (BF), and semitendinosus (ST) muscles and (2) if applicable, to compare the running velocities associated with the PWC FT among these muscles. Methods Eleven subjects (21.7 ± 1.8 years) performed an incremental treadmill test to exhaustion with electromyographic signals recorded from the VL, VM, BF, and ST. Results The results indicated there were no significant ( p > 0.05) mean differences in the running velocities associated with the PWC FT for the VL (14.4 ± 2.0 km/h), VM (14.3 ± 1.9 km/h), BF (13.8 ± 1.8 km/h), and ST (14.7 ± 2.3 km/h). In addition, there were significant inter-correlations ( r = 0.68 – 0.88) among running velocities associated with the PWC FT of each muscle. Individual results also indicated that 9 of the 11 subjects exhibited identical PWC FT values for at least 3 of the 4 muscles, but there were no uniform patterns for any intra-individual differences. Conclusion The findings of the present study suggested that the PWC FT test is a viable method to identify neuromuscular fatigue in the quadriceps and hamstrings during incremental treadmill exercise and results in consistent PWC FT values among these muscles.