ABSTRACT
Loss of muscle strength is not only associated with loss of muscle mass, but also affected by neural factors. It is well known that facilitatory and inhibitory responses of spinal motor neurons occur with cutaneous stimulation via spinal interneurons. The purpose of this study was to examine the neural adaptations associated with low load resistance training utilizing skin cooling (SC). 10 men trained both legs and each side was randomly assigned to SC training (SC-T) and non SC training (NSC-T). Subjects performed 30 isometric ankle dorsiflexion repetitions at 35% maximum voluntary contraction (MVC) 3 times weekly for 6 weeks. The skin cooling condition was defined as when skin temperature was 25°C while repetitive resistance training was being performed. Dorsiflexor MVC significantly increased in both SC-T (n = 9) and NSC-T (n = 9) by 12.8 and 3.8%, respectively. A significant increase in root mean square of EMG (rmsEMG) was observed for 30 isometric ankle dorsiflexion repetitions in SC-T both pre- and post-training. Lower leg girths did not significantly increase post-training. Therefore, the results of this study suggest that muscle strength might increase via changes in neural activation and that SC-T may lead to greater increases in muscle strength compared with NSC-T because of improved muscle activation during resistance training with SC. Therefore, we suggest that low load resistance training with SC is an effective method to increase muscle strength.
ABSTRACT
<b>Object </b>: The purpose of this study was to test the response of the decline in heart rate (HR) induced by compression on the eyeball (eyeball pressure : EP) and voluntary non breath (VNB) after pedaling exercise. <b>Methods </b>: EP ; Nine male subjects performed exercise for 3 min in a supine position using a bicycle ergometer. Immediately after the exercise all subjects received EP for 10 seconds. After that, subjects undertook the same protocol without EP (CON-E). VNB ; Four male and two female subjects performed exercise for 5 minutes using a bicycle ergometer. Immediately after the exercise subjects received VNB for 7 seconds. After that subjects undertook the same protocol without VNB (CON-V). <b>Results </b>: The slope of the decline in HR recovery (HR<sub>DS</sub>) after exercise in EP increased significantly more than that in CON-E (p<0.05). However, time constant (HR<sub>TC</sub>) in CON-E declined faster than that in EP. Thereby, the relationship between HR<sub>DS</sub> in EP and HR<sub>TC</sub> in CON-E correlated (r=-0.562). The HR<sub>DS</sub> of VNB was greater than that of EP and CON-V. However the relationship between HR<sub>DS</sub> in VNB and HR<sub>TC</sub> in CON-V did not correlate. <b>Conclusion </b>: We suggest that EP affects vagal nervous activity and VNB affects strength of baroreflex sensitivity. Therefore HR<sub>DS</sub> of EP might evaluate vagal nervous activity.