The effect of selective beta1-blockade on EMG signal characteristics during progressive endurance exercise |
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| Authors: | Hunter Angus M St Clair Gibson Allan Derman Wayne E Lambert Michael Dennis Stephen C Noakes Timothy D |
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| Institution: | (1) MRC/UCT Research Unit of Exercise Science and Sports Medicine, Department of Human Biology, University of Cape Town, Cape Town, South Africa,;(2) Department of Sports Studies, University of Stirling, Stirling, FK9 4LA, Scotland, |
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| Abstract: | This study analysed the effect of selective β1-blockade on neuromuscular recruitment characteristics during progressive endurance exercise. Ten healthy subjects ingested
a selective β1-blocker, acebutolol (200 mg b.d.), for 7 days (for one of two cycling trials), with a 10-day wash-out period between trials.
On the last day of acebutolol ingestion subjects performed three successive 15-min rides at 30%, 50% and 70% of their peak
power output and then cycled at increasing (15 W min–1) work rates to exhaustion. Force output, heart rate, submaximal V˙O2, rate of perceived exertion (RPE), electromyographic (EMG) data and blood lactate were captured during the cycling activity.
Peak work rate 270 (111) W vs 197 (75) W, CON vs BETA, P <0.01], time to exhaustion 49.7 (23.2) min vs 40.3 (23.7) min, CON vs BETA, P <0.05] and heart rate mean, for the full ride 135.5 (38.3) beats min–1 vs 111.5 (30.0) beats min–1 CON vs BETA, P <0.05] were significantly lower for the group who ingested β1-blockade (BETA) compared to the control group (CON). Although not significant, submaximal V˙O2 was reduced in BETA during the ride, while RPE was significantly higher during the ride for BETA (P <0.01). Mean integrated electromyography was higher in the BETA group although these differences were not significant. Mean
power frequency values of the BETA group showed a significant (P <0.05) shift to the upper end of the spectrum in comparison to the control group. Lactate values 11.7 (3.5) mmol.l–1 vs 7.1 (4.1) mmol.l–1 CON vs BETA] were significantly lower (P <0.05) at exhaustion in BETA. Significant reductions in cycling performance were found when subjects ingested β1-blockers. This study has shown significant shifts to the upper end of the EMG frequency spectrum after β1-blocker ingestion, which could be caused by a change in neuromuscular recruitment strategy to compensate for the impaired
submaximal exercise performance.
Electronic Publication |
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| Keywords: | β 1-Blockade Fatigue Integrated electromyography Mean power frequency spectrum |
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