Abstract
This study compared muscle (vastus lateralis) excitation, muscle activation, and neuromuscular fatigue in response to low-load resistance exercise with blood flow restriction (LLBFR), medium-load resistance exercise with blood flow restriction (MLBFR), and high-load resistance exercise (HLRE) in resistance-trained (RT; n = 15) and untrained (UT; n = 14) college-aged males. Muscle excitation and activation were measured using surface electromyography (sEMG) and defined as the maximal root mean square amplitudes (RMS AMP) and the integrated area under the sEMG curve (iEMG) per repetition. Neuromuscular fatigue was defined as the reduction in peak torque measured during the postexercise knee extensor maximal isometric contractions (MVIC) relative to the pre-exercise MVIC. The LLBFR sessions showed 23.7% (p < 0.01) lower relative muscle excitation than the MLBFR and 26.7% (p < 0.001) lower than the HLRE. In contrast, LLBFR sessions showed 38.1% (p < 0.001) higher total muscle activation than the MLBFR and 19.3% (p < 0.05) higher than the HLRE. There were no differences between the RT and UT groups for percent change in peak torque or the RMS AMP measured during the knee extensor MVICs following the three exercise treatments (p > 0.05). However, the peak torque and maximal RMS amplitudes were higher in the RT group than in the UT group measured during the pre-exercise MVICs. Our data suggest that the LLBFR led to greater total muscle activation than MLBFR and HLRE despite lower relative muscle excitation independent of training status in our college-aged males.