INTRODUCTION The aim is to examine the effects of resisted and assisted butterfly swimming training on muscle activity patterns and magnitude by using surface electromyography(sEMG). The order of muscle activity and the control of muscle motion extent during swimming are very important for swimming performance, but due to device limitation, there was little research. METHODS Eight male college swimmers (age 20.50 ± 0.76yr; height 186.37 ± 6.02cm; weight 81.88 ± 4.85kg) participated in this study. Two GoPro underwater cameras(50Hz) were used to identify the stroke cycle. The subjects finished three 50m butterfly sprints by conditions of resisted (with a resistance parachute), assisted (with a towing tether) and normal butterfly swimming. All subjects were instructed to give maximal effort for each trial. Eight upper limb muscles activity were collected using Cometa sEMG system (2000Hz, Italy). RESULTS 1.There are significant difference in the whole stroke cycle and the stroke time among conditions.Time duration of resisted butterfly swimming was much longer than normal butterfly swimming (P<0.01)and time duration of assisted butterfly swimming was much shorter than normal butterfly swiming (P<0.01). 2.Resisted butterfly swimming showed similar muscle activity patterns compared with normal butterfly swiming. Assisted butterfly swimming also showed similar muscle activity patterns except latissimus dorsi, which was activated earlier than the pectoralis major. 3.The difference in RMS was also appeared in stroke phase. Compared with normal butterfly, RMS values of sEMG of pectoralis major (P<0.05), triceps (P<0.01), and latissimus dorsi (P<0.01) during resisted butterfly swimming were significantly greater than those during normal butterfly swimming. No significant difference in RMS values were observed between assisted and normal butterfly swimming. DISCUSSION There were no significant difference in muscle activity patterns of upper limb muscles, except latissimus dorsi, among resisted,assisted and normal butterfly swimming. Assisted swimming may have more benefits for trainng because it would maintain the muscle activity pattern as well as reducing the stroke time.
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