Temperature dependence of soleus H-reflex and M wave in young and older women
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The purpose of this study was to investigate the effect of altered local temperature on soleus H-reflex and compound muscle action potential (M wave) in young and older women. H-reflex and M wave responses were elicited in 10 young (22.3 +/- 3.3 years) and 10 older (72.5 +/- 3.2 years) women at three muscle temperatures: control (34.2 +/- 0.3 degrees C), cold (31.3+/-0.5 degrees C) and warm (37.1 +/- 0.2 degrees C). H-reflex output, expressed as the ratio between maximal H-reflex and maximal M wave (H(max)/M(max)), was lower in the older, compared with the younger, group, regardless of temperature. In control temperature conditions, for example, the H(max)/M(max) ratio was 36.8 +/- 24% in the young and 25.4 +/- 20% in the older (P<0.05). Warming had no effect on the H-reflex output in either group, whilst cooling increased H-reflex output only in the younger group (+28%). In both groups, cooling increased (+5.3%), and warming decreased (-5.5%) the H-reflex latency. This study confirms that older individuals experience a reduced ability to modulate the reflex output in response to a perturbation. In a cold environment, for example, the lack of facilitation in the reflex output, along with a delayed reflex response could be critical to an older individual in responding to postural perturbations thus potentially compromising both static and dynamic balance.
|Number of pages||9|
|Journal||European journal of applied physiology|
|Publication status||Published - Aug 2005|
- Action Potentials, Adaptation, Physiological, Adult, Age Factors, Aged, Aging, Ankle Joint, Body Temperature, Electric Stimulation, Electromyography, Female, H-Reflex, Humans, Muscle Contraction, Muscle, Skeletal, Temperature