Neuromuscular Fatigue After Repeated Jumping With Concomitant Electrical Stimulation.
OBJECTIVE
To evaluate the etiology and extent of neuromuscular fatigue induced by 50 squat jumps performed with and without neuromuscular electrical stimulation (NMES) of the knee extensors.


METHODS
Nine healthy, recreationally active men (24 ± 2 y) took part in 2 experiments. These consisted of 50 squat jumps performed with stimulation (NMES) or without (CON). Maximal voluntary contraction (MVC) force, maximal voluntary activation level (VAL), and forces evoked by single and double (10 and 100 Hz) stimulations were recorded before and after the 50 jumps. NMES was delivered at the maximal tolerated intensity.


RESULTS
Despite average jump height being ∼16% lower in the NMES than in the CON session, a reduction over time in jump height was only found in the NMES condition (-6%). After the 50 jumps, MVC force was reduced to a greater extent in NMES than in CON (-25% ± 11% vs -11% ± 12%). Similarly, forces evoked by single stimulations, as well as by 10-Hz and 100-Hz paired stimulations, were reduced to a greater extent in NMES (-33% ± 12%, -42% ± 15%, and -25% ± 13%) than in CON (-21% ± 6%, -30% ± 9%, and -14% ± 11%). VAL was not significantly altered by either condition.


CONCLUSIONS
Performing repeated squat jumps with concomitant NMES induced a greater fatigue than squat jumps performed alone and might potentially represent a stronger training stimulus.
Daria
D
Neyroud
Jimmy
J
Samararatne
Bengt
B
Kayser
Nicolas
N
Place
D000328:Adult; D004558:Electric Stimulation; D004576:Electromyography; D016552:Ergometry; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007717:Knee; D008297:Male; D009119:Muscle Contraction; D018763:Muscle Fatigue; D018482:Muscle, Skeletal / Q000502:physiology*; D063806:Myalgia / Q000503:physiopathology; D055815:Young Adult
M wave; evoked force; maximal voluntary contraction; neuromuscular electrical stimulation; squat jump