Local Muscle Cooling (LMC) as A New Blood Flow Restriction Technique: The Effect of 8-Weeks Resistance Training with LMC on Knee Extensor Muscle Thickness, Strength and Activation

Potential benefits of local cold application during exercise include reducing blood flow, delaying fatigue, and providing analgesic effects. The purpose of this study was to investigate the effect of 8-weeks local muscle cooling during resistance training on Knee Extensor (KE) strength, hypertrophy and muscle activation. In this experimental study, twelve recreationally-trained male and female (age, 24.1±3.5 years; weight, 69.3±18.8 kg; height, 175.2±12.7 cm) were divided equally into two groups: RT and RT-Cold. Both groups completed an eight-weeks progressively resistance training (seated Leg Curl and leg press, 4 sets, 6-12 rep, 70-85% 1RM, 3 sessions per week). A cold compression device (Cryo-cuff, Aircast) was placed on the subject's thigh for 25 min before and during resistance training with different temperatures (25° for RT and 10° for RT-Cold). Dynamic strength (1RM), knee extensor muscles cross-sectional area (CSA), and muscle activation (normalized RMS of EMG) were measured at baseline and after 8-week. Differences between the RT and RT-Cold groups were tested using analysis of covariance at the level of P≤0.05. The improvements in 1RM strength were not significantly different between RT and RT-Cold groups (P˃0.05). In terms of the muscle activation, there was not any significant difference in mean RMS of knee extensor muscles between groups. Ultrasound measurement of CSA also showed that the CSA of cooled limb in RT-Cold significantly greater than those in RT group. These results would indicate that local muscle cooling improve resistance training-induced hypertrophy, whereas this technique did not affect muscle strength and activation.