This study evaluated the effect of passive-heat stress on the neuromuscular properties of the wrist flexor
muscles, which are commonly used in manual labour hand tasks. A combination of techniques were utilised,
involving nerve stimulation and paired-pulse transcranial magnetic stimulation to assess changes in muscle strength,
contractile properties, fatigue-resistance and central activation as well as indices of intracortical excitability in
10 healthy humans who were exposed to a passive heat stress protocol as well as a normothermia control protocol.
Passive-heat stress increased core body temperature 1 C (37.2+0.4 to 38.2+0.4 C ; p<0.01), mean skin
temperature (34.5+0.7 C to 37.3+1.1 C; p<0.01), and heart rate (79.5+20.0 to 110.0+23.0 beats/min;
p=0.04). No effect was observed on muscle strength, contractile properties, muscle fatigability, central activation
or indices of intracortical excitability (p40.05). These data indicate that allowing internal temperatures of workers
to increase ~1.0 C does not affect neuromuscular properties of the wrist flexors.
Exercise-heat stress has been shown to reduce human performance and exacerbate muscle fatigue. However,
less is known about passive-heat stress, especially during milder heat stress encountered in many occupational
settings. Accordingly, the effect of occupationally relevant passive-heat stress on the neuromuscular properties of
the wrist flexors was examined.