Objective: To measure the activity of the core muscles and the middle trapezius in T54 class wheelchair racers during full-effort over ground sprinting and to determine its association with propulsion velocity. Material and Method: Eightmale international wheelchair racershaving normal upper limband partial to normaltrunk function(T54 class athletes) propelled their racing wheelchairs on 400-m competition trackwith maximal effort. Electromyography(EMG)of the rectus abdominis (RA), iliocostalis lumborum (IL), longissimus thoracis (LT) and middle trapezius (MT) were recorded at each 100-m reach using a wireless surface EMG recorder. Percentage of maximal voluntary contraction (%MVC)was measuredand correlated with propulsion velocity. Results:Median %MVC of RA, IL, LT and MT were 54.2, 43.9, 30.6 and 35.6% respectively. Positive associationto propulsion velocity was found in RA (p = 0.04, r = 0.73). Negative association to propulsion velocity was also found in MT (p = 0.03, r = -0.77). Conclusion: Abdominal function wasactivated most andassociated with propulsion velocity in male T54 class wheelchair racers. In addition, optimizing scapularretraction may benefit propulsionvelocity.
To characterize physiological stress response against simulated short-distance sprints among world-class paddlers. Thirteen dragon boat gold medalists performed 200-m and 500-m simulated race trials on a kayak ergometer in a randomized, counter-balanced, crossover fashion. During the 200-m and 500-m sprints, oxygen consumption (VO2) increased from 8.7 to 31.2 ml/kg/min and from 8.0 to 32.7 ml/kg/min within 60 s, respectively. A plateau of 35 ml/kg/min below maximal VO2(VO2max) (39.7 ± 6.3 ml/kg/min) was reached at 75 s during the 500-m sprint. Respiratory exchange ratio dropped from 1.21 ± 0.16 to 1.07 ± 0.12 and 1.28 ± 0.13 to 1.06 ± 0.16 at 45 s, and resurged to 1.17 and 1.28 at the end of 200-m and 500-m sprints with lactate concentration reached 13 ± 2 and 15 ± 2 mM. Aerobic energy contribution to paddling power increases from ~10% for the first 15 s to ~80% for the last 15 s during the 500-m trial. Postexercise plasma thiobarbituric acid reactive substances increased by 376% and 543% above baseline after 200-m and 500-m trials (P < 0.001, between trials), respectively, followed by quick returns to baseline in 30 min (P < 0.001). Increased plasma creatine kinase (+48%) was observed only after the 500-m trial (P < 0.001, between trials), not 200-m trial. Our data suggest that muscle damage occurred only when maximal sprinting exceeding 2 min, highlighting an importance of volume than intensity on exercise-induced muscle damage.
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