Biomedical subjects

Angus M Hunter

Publications and source records attributed to Angus M Hunter.

3 recordsLinked to original sources

PubMed2002

The effect of selective beta1-blockade on EMG signal characteristics during progressive endurance exercise.

This study analysed the effect of selective beta(1)-blockade on neuromuscular recruitment characteristics during progressive endurance exercise. Ten healthy subjects ingested a selective beta(1)-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 VO(2), 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 beta(1)-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 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 x l(-1) vs 7.1 (4.1) mmol x 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 beta(1)-blockers. This study has shown significant shifts to the upper end of the EMG frequency spectrum after beta(1)-blocker ingestion, which could be caused by a change in neuromuscular recruitment strategy to compensate for the impaired submaximal exercise performance.

Acebutolol↗

PubMed2002

Electromyographic (EMG) normalization method for cycle fatigue protocols.

PURPOSE: To determine the most effective electromyographic (EMG) normalization method for cycling fatigue protocols. METHODS: Ten healthy subjects performed two 5-s isometric knee extension maximal voluntary contractions (MVC) at a knee joint angle of 60 degrees, two fixed cycle pedal contraction at knee joint angles of 60 degrees (60 degrees A) and 108 degrees (108 degrees A), and a dynamic single maximal revolution of a cycle pedal (1REV). Integrated EMG (IEMG) data were recorded for all contractions and power output recorded during MVC and 1REV. RESULTS: Mean IEMG for MVC was significantly (P < 0.01) greater than 60 degrees C, 108 degrees C, and 1REV. There were no significant differences between MVC and 1REV power output/EMG relationship. CONCLUSIONS: MVC will record a higher IEMG than 60 degrees A, 108 degrees A, and 1REV. As IEMG was greatest during MVC, and the relationship between IEMG and power output was not different between MVC and 1REV, normalization against maximal possible recruitment potential is most likely during MVC.

Adult↗

PubMed2002

Caffeine ingestion does not alter performance during a 100-km cycling time-trial performance.

This study analyzed the effect of caffeine ingestion on performance during a repeated-measures, 100-km, laboratory cycling time trial that included bouts of 1- and 4-km high intensity epochs (HIE). Eight highly trained cyclists participated in 3 separate trials' placebo ingestion before exercise with a placebo carbohydrate solution and placebo tablets during exercise (Pl), or placebo ingestion before exercise with a 7% carbohydrate drink and placebo tablets during exercise (Cho), or caffeine tablet ingestion before and during exercise with 7% carbohydrate (Caf). Placebo (twice) or 6 mg.kg(-1) caffeine was ingested 60 min prior to starting 1 of the 3 cycling trials, during which subjects ingested either additional placebos or a caffeine maintenance dose of 0.33 mg.kg(-1) every 15 min to trial completion. The 100-km time trial consisted of five 1-km HIE after 10, 32, 52, 72, and 99 km, as well as four 4-km HIE after 20, 40, 60, and 80 km. Subjects were instructed to complete the time trial and all HIE as fast as possible. Plasma (caffeine) was significantly higher during Caf (0.43 +/- 0.56 and 1.11 +/- 1.78 mM pre vs. post Pl; and 47.32 +/- 12.01 and 72.43 +/- 29.08 mM pre vs. post Caf). Average power, HIE time to completion, and 100-km time to completion were not different between trials. Mean heart rates during both the 1-km HIE (184.0 +/- 9.8 Caf; 177.0 +/- 5.8 Pl; 177.4 +/- 8.9 Cho) and 4-km HIE (181.7 +/- 5.7 Caf; 174.3 +/- 7.2 Pl; 175.6 +/- 7.6 Cho; p <.05) was higher in Caf than in the other groups. No significant differences were found between groups for either EMG amplitude (IEMG) or mean power frequency spectrum (MPFS). IEMG activity and performance were not different between groups but were both higher in the 1-km HIE, indicating the absence of peripheral fatigue and the presence of a centrally-regulated pacing strategy that is not altered by caffeine ingestion. Caffeine may be without ergogenic benefit during endurance exercise in which the athlete begins exercise with a defined, predetermined goal measured as speed or distance.

Adult↗