The Effect of Brief Skin Cooling on Isometric Muscle Strength and the Neuronal Mechanism Underlying This Effect

Cold application is frequently used in sports medicine and rehabilitation due to its beneficial effects on the neuromuscular system. Its main beneficial effects are facilitating muscle contraction (motor facilitation), increasing isometric muscle force formation and reducing spasticity. The motor effects of cold application may vary depending on the application time, cooling agent (ice, ice water, cooling spray, etc.) and subcutaneous fatty tissue thickness. Short-term cold application can increase contraction force through motor facilitation. As the duration of cold application increases, the effects of cold that inhibit motor functions, such as gamma motor neuron inhibition, muscle spindle inhibition, and muscle conduction block, come to the fore. With this effect, it is used in the treatment of spasticity.

Neurophysiological studies to explain the motor effects of cold application have generally focused on the monosynaptic muscle spindle-based reflex. The monosynaptic muscle spindle-based reflex activates muscle spindles and stimulates alpha motor neurons via Group Ia afferent nerves. This effect is also known as the servo-motor (servo-assistance) effect of the muscle spindle. The increase in the sensitivity of the muscle spindle can provide motor facilitation by strengthening the servo-assistance effect.

It has been shown that the muscle spindle has sympathetic innervation. It has been shown that the cold stress test can be an alternative to the classical autonomic nerve test and can be used to test sympathetic system activation. Additionally, studies have shown that cold stress test, mental arithmetic, isometric contraction and muscle ischemia cause an increase in muscle spindle sensitivity through increased sympathetic activity.

A literature review has shown that there is no study examining the mechanism underlying the effect of local cold application on motor facilitation. Demonstrating the effect of local cold application on increasing maximum contraction force through muscle spindle sensitivity is also important for clinical applications to be more effective and efficient. The aim of this study was to examine whether short-term local cold application increases isometric contraction force and, if there is an increase, whether this effect is related to muscle spindle activity.