Alteration in neuromuscular function after a 5 km running time trial

Abstract

The aim of this study was to characterize the effect of a 5 km running time trial on the neuromuscular properties of the plantar flexors. Eleven well-trained triathletes performed a series of neuromuscular tests before and immediately after the run on a 200 m indoor track. Muscle activation (twitch interpolation) and normalized EMG activity were assessed during maximal voluntary contraction (MVC) of plantar flexors. Maximal soleus H-reflexes and M-waves were evoked at rest (i.e. H (MAX) and M (MAX), respectively) and during MVC (i.e. H (SUP) and M (SUP), respectively). MVC significantly declined (-27%; P < 0.001) after the run, due to decrease in muscle activation (-8%; P < 0.05) and M (MAX)-normalized EMG activity (-13%; P < 0.05). Significant reductions in M-wave amplitudes (M (MAX): -13% and M (SUP): -16%; P < 0.05) as well as H (MAX)/M (MAX) (-37%; P < 0.01) and H (SUP)/M (SUP) (-25%; P < 0.05) ratios occurred with fatigue. Following exercise, the single twitch was characterized by lower peak torque (-16%; P < 0.001) as well as shorter contraction (-19%; P < 0.001) and half-relaxation (-24%; P < 0.001) times. In conclusion, the reduction in plantar flexors strength induced by a 5 km running time trial is caused by peripheral adjustments, which are attributable to a failure of the neuromuscular transmission and excitation-contraction coupling. Fatigue also decreased the magnitude of efferent motor outflow from spinal motor neurons to the plantar flexors and part of this suboptimal neural drive is the result of an inhibition of soleus motoneuron pool reflex excitability.

Combining heat stress and moderate hypoxia reduces cycling time to exhaustion without modifying neuromuscular fatigue characteristics

“…In this study, strength losses in PF were relatively modest (~9 %) as compared to the losses induced by running exercises (~10–40 %; Girard et al 2012; Millet et al 2011; Perrey et al 2010; Racinais et al 2007) but were in accordance with the losses previously observed after a maximal cycling exercise (~8 %; Racinais and Girard 2012). Maximal EMG activity and twitch interpolation recordings obtained during MVC were used to assess the completeness of plantar flexors activation capacity.…”

Plantar flexor neuromuscular adjustments following match‐play football in hot and cool conditions

“…The present study found that PF fatigue induced by a football game is rather modest as evidenced by a nonsignificant reduction of ∼ 5% in MVC torque ∼30 min post game, which was restored near baseline after 24 h. Quite similar acute (∼7% reduction in MVC torque) and delayed (full recovery within 24 h) alterations in maximal torque production capacity of the same muscle group have been described after playing tennis for ∼2 h in temperate conditions (Périard et al., ). Larger reductions (ranging 10%–30%) in PF MVC torque have been documented after prolonged, moderate‐intensity treadmill tasks (60–90 min: Racinais et al., ; Kelly et al., ) and shorter runs performed at high (5‐km race: Girard et al., ) or maximal intensity (repeated‐sprint ability test: Perrey et al., ). In football, the fact that PF are not particularly prone to fatigue compared with other muscle group such as the quadriceps (Nédélec et al., ) after competitive games would suggest that PF torque production capacity impairments may only have a limited impact on running pattern or involvement with the ball as fatigue develops.…”

Fatigue Induced by Physical and Mental Exertion Increases Perception of Effort and Impairs Subsequent Endurance Performance

“…Endurance performance involves the prolonged maintenance of constant or self-regulated power/velocity (e.g., Girard et al, 2012; Jones et al, 2016; Smits et al, 2016) or torque/force (e.g., Froyd et al, 2013; Pageaux et al, 2015a; Angius et al, 2016). Traditionally, endurance performance is measured by completion of time to exhaustion tests (i.e., open loop exercises) or time trials (i.e., closed loop exercises).…”