The effects of skin cold stimulation on quadriceps muscle activity during walking in older adults.

Purpose: Given that walking speed declines with ageing and decreasing walking speed restricts activities of daily living (ADL), it is important for the old to maintain walking speed in order to prevent affecting ADL. Although skin cold stimulation (SCS) facilitates instantaneous muscle activity, which occurs during walking, the effects of SCS on muscle activity during walking remain unclear. Thus, the present study aimed to investigate the effect of SCS during walking in older adults.Methods: Seventeen community-dwelling healthy older adults (73 ± 6 years old) participated in this study. Walking speed at a comfortable pace and the electromyographic (EMG) activity of the vastus lateralis (VL) and biceps femoris (BF) were measured. SCS, which maintains the skin temperature at 25 °C, was applied to the front of the thigh during the procedures. Walking speed, root mean square EMG (rmsEMG) and mean power frequency (MPF) were compared under SCS and control conditions.Results: SCS significantly increased the walking speed (p < 0.01) and the rmsEMG of the vastus lateralis (p = 0.032). No change in the rmsEMG of the BF was observed, and SCS had no effect on MPF of both the VL and BF. Furthermore, a significant relationship was observed between these changes (r = 0.619, p = 0.042).Conclusion: SCS increased the EMG activity of the VL while increasing walking speed. Our results suggest that SCS is an effective strategy that can be included in daily life in order to improve walking ability of older adults.

Increase in rate of force development with skin cooling during isometric knee extension.

Rate of force development (RFD) plays an important role when performing rapid and forceful movements. Cold-induced afferent input with transient skin cooling (SC) can modulate neural drive. However, the relationship between RFD and SC is unknown. The purpose of this study was to investigate whether SC increases RFD during isometric knee extension. Fifteen young healthy men (25 ± 8 yrs old) contracted their quadriceps muscle as fast and forcefully as possible with or without SC. Skin cooling was administered to the front of the thigh. Torque and electromyographic activity were measured simultaneously. Peak torque was not affected by SC. Skin cooling induced a significant increase in RFD at the phase 0-30 and 0-50 ms. The root mean square of the electromyography of vastus medialis, rectus femoris and vastus lateralis at the phases 0-30-50-100 ms increased significantly or tended to increase with SC. These results suggest that SC may increase neural drive and improve RFD in the very early phases of contraction.