Electromyographic Study on the Inhibitory Effects of Local Cold- and Hot-Water Bathing of the Upper Limb on Finger Flexor α-Motor Neuron Activity

TL;DR

This study shows that cold water immersion temporarily reduces finger muscle activity and grip strength, possibly helping manage spasticity in stroke patients.

Contribution

The study demonstrates that cold stimulation inhibits α-motor neuron activity, primarily through pain, offering a potential cryotherapy approach for spasticity management.

Findings

Cold-water immersion significantly reduced grip strength, IEMG, and skin temperature while increasing pain perception.

Warm-water immersion had no significant effect on α-motor neuron activity or pain perception.

Cold stimulation's effect on motor neuron activity is temporary, with prolonged skin temperature drop observed.

Abstract

This study evaluated the inhibitory effects of cold and heat stimulation on α-ｍotor neuron activity and the associated pain, exploring their clinical applications.

Twenty-four healthy young adults participated, undergoing four conditions: (1) cold-water finger immersion, (2) warm-water finger immersion, (3) warm-water forearm immersion, and (4) a control condition. Assessments included grip strength, integrated electromyography (IEMG) of finger flexor muscles, skin temperature, and pain perception.

Cold-water finger immersion involved three sets of 5-second ice water immersion with 2-second breaks. Warm-water immersion (finger and forearm) lasted 10 min at 42°C. Measurements were taken before and at 5-minute intervals up to 20 min post-intervention, with pain assessed via the Numerical Rating Scale (NRS).

Cold-water finger immersion significantly reduced grip strength, IEMG, and skin temperature while increasing NRS scores. In contrast, warm-water immersion had no significant effect. The cold-water condition also showed a prolonged skin temperature drop. These findings confirm that cold stimulation inhibits α-motor neuron activity, primarily due to pain, though the effect is temporary.

Cold stimulation may improve range-of-motion (ROM) exercise performance, potentially preventing joint contractures. This suggests that cryotherapy could be a valuable approach for managing spasticity in post-stroke patients. Since finger flexor spasticity impairs activities of daily living (ADL) and quality of life (QOL), reducing spasticity is crucial for ROM exercises.

Figures