Biomedical subjects

Michael Lambert

Publications and source records attributed to Michael Lambert.

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

Self-esteem of adolescents who were born prematurely.

OBJECTIVE: To determine whether there are any differences between the self-esteem of a cohort of adolescents who were extremely low birth weight (ELBW) in comparison with term controls (Cs); and to test the associations between self-esteem and several predefined predictor variables. BACKGROUND: Self-esteem is considered to play a significant role in psychological adjustment and scholastic success. Little information exists on how adolescents who were ELBW regard themselves. DESIGN/METHODS: Longitudinal follow-up of a regional cohort of 132/169 (78%) ELBW survivors and 127/145 (88%) sociodemographically matched Cs, born between 1977 and 1982. MEASURES: Harter Adolescent Self-Perception Profile (1988) with 9 dimensions, including Global Self-Worth, socioeconomic status (Hollingshead), height-for-age and weight-for-age z scores, and Wide Range Achievement Test---Revised (WRAT-R; Reading, Spelling, and Arithmetic). DATA ANALYSIS: General linear model multiple analyses of covariance were performed to determine whether significant relationships existed between the 9 self-esteem dimensions and the independent variables of birth weight status and gender, and the covariates of age, socioeconomic status, physical development, and academic achievement. RESULTS: Global Self Worth was similar for ELBW and Cs (means: 3.1 and 3.2). Multivariate effects revealed no interactions, but significant main effects emerged for birth weight status, gender, weight-for-age z scores, age in months, and for all 3 WRAT-R subtests, all effect sizes medium to large. Follow-up analysis of covariance revealed medium-size gender effects for athletic competence (means: 3.1 and 2.6), and physical appearance (means: 2.9 and 2.5), where boys rated themselves significantly higher on both domains; and age effects, where older teens rated themselves better for job competence. Significant but small effect sizes emerged for the following: 1) weight-for-age z scores, where heavier youth rated themselves higher on close friendships, 2) gender, where girls had higher ratings for close friendships, 3) birth weight, where Cs rated themselves higher on athletic competence, and 4) WRAT-R math effect, where children with higher math scores rated themselves better on scholastic competence. CONCLUSIONS: Overall, ELBW teenagers do not differ significantly from C teenagers on most dimensions of self-esteem. Gender effects emerged on some Harter domains.

Achievement↗