Spinal modulations accompany peripheral fatigue during prolonged tennis playing.
To examine the time course of alteration in neural process (spinal loop properties) during prolonged tennis playing, 12 competitive players performed a series of neuromuscular tests every 30 min during a 3-h match protocol. Muscle activation (twitch interpolation) and normalized EMG activity were assessed during maximal voluntary contraction (MVC) of plantar flexors. Spinal reflexes and M-waves were evoked at rest (i.e., H(max) and M(max) , respectively) and during MVC (i.e., H(sup) , V-wave, M(sup) , respectively). MVC torque declined significantly (P<0.001) across the match protocol, due to decrease (P<0.001) in muscle activation and in normalized EMG activity. The impairment in MVC was significantly correlated (r=0.77; P<0.05) with the decline in muscle activation. H(max) /M(max) (P<0.001), H(sup) /M(sup) (P<0.01) and V/M(sup) (P<0.05) ratios were depressed with fatigue and decreased by ∼80%, 46% and 61% at the end of exercise, respectively. Simultaneously, peak twitch torque and M-wave amplitude were significantly (P<0.01) altered with exercise, suggesting peripheral alterations. During prolonged tennis playing, the compromised voluntary strength capacity is linked to a reduced neural input to the working muscles. This central activation deficit partly results from a modulation in spinal loop properties.
Girard
O
O
Research and Education Center, ASPETAR, Qatar Orthopaedic and Sports Medicine Hospital, Doha, Qatar. oliv.girard@gmail.com
Racinais
S
S
Micallef
J-P
JP
Millet
G P
GP
D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography; D015444:Exercise / Q000502:physiology; D005221:Fatigue / Q000503:physiopathology*; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D013131:Spine / Q000502:physiology*; D013715:Tennis / Q000502:physiology*; D055815:Young Adult