Augmented supraspinal fatigue following constant-load cycling in the heat
Date
2015Author
Goodall, S.
Howatson, G.
Charlton, K.
Hignett, C.
Prichard, J.
Metadata
Show full item recordAbstract
The development of central fatigue is prominent follow-
ing exercise-induced hyperthermia, but the contribution
of supraspinal fatigue is not well understood. Seven
endurance-trained cyclists (mean ± SD peak O
2
uptake,
62.0 ± 5.6 mL/kg/min) completed two high-intensity
constant-load cycling trials (296 ± 34 W) to the limit of
tolerance in a hot (34 °C, 20% relative humidity) and, on
a separate occasion, for the same duration, a control con-
dition (18 °C, 20% relative humidity). Core body tem-
perature (T
c
) was measured throughout. Before and
immediately after each trial, twitch responses to
supramaximal femoral nerve and transcranial magnetic
stimulation were obtained from the knee extensors to
assess neuromuscular and corticospinal function, respec-
tively. Exercise time was 11.4 ± 2.6 min. Peak T
c
was
higher in the hot compared with control (38.36 ± 0.43 °C
vs 37.86 ± 0.36 °C; P = 0.035). Post-exercise reductions in
maximal voluntary contraction force (13 ± 9% vs
9 ± 5%), potentiated twitch force (16 ± 12% vs 21 ± 13%)
and voluntary activation (9 ± 7% vs 7 ± 7%) were similar
in hot and control trials, respectively. However, cortical
voluntary activation declined more in the hot compared
with the control (8 ± 3% vs 3 ± 2%; P = 0.001). Exercise-
induced hyperthermia elicits significant central fatigue of
which a large portion can be attributed to supraspinal
fatigue. These data indicate that performance decrements
in the heat might initially originate in the brain
URI
http://hdl.handle.net/10394/18689https://doi.org/10.1111/sms.12370
https://onlinelibrary.wiley.com/doi/10.1111/sms.12370/full