The Effect of Selective ß1-blockade on Emg Signal

Running Head:-ß1-blockade and EMG signal during exercise. ABSTRACT Aim: This study analysed the effect of selective ß1-blockade on neuromuscular recruitment characteristics during progressive endurance exercise. Methods: Ten healthy subjects ingested a selective ß1-blocker, acebutolol (200mg 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 VO 2 , rate of perceived exertion (RPE), electromyographic (EMG) data and blood lactate was captured during the cycling activity. P < 0.05) and heart rate (mean, for the full ride 135.5 + 38.3 b.min-1 vs 111.5 + 30.0 b.min-1 CON vs BETA, P < 0.05) were significantly lower for the group who ingested ß1-blockade (BETA) compared to the control group (CON). Although not significant, submaximal VO 2 was reduced in BETA during the ride, while RPE was significantly higher during the ride for BETA (P < 0.01). Mean integrated electromyography (IEMG) was higher in the BETA group although these differences were not significant. Mean power frequency values (MPFS) 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. 3 Conclusions: Significant reductions in cycling performance were found when subjects ingested ß1-blockers. This study has shown significant shifts to the upper end of the EMG frequency spectrum after ß1-blocker ingestion, which could be caused by a change in neuromuscular recruitment strategy to compensate for the impaired maximal exercise capacity.