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Biomedical subjects

M R Boulay

Publications and source records attributed to M R Boulay.

At least 19 recordsLinked to original sources
PubMed2000

Specificity of treadmill and cycle ergometer tests in triathletes, runners and cyclists.

The objective of this study was to evaluate the viability of using a single test in which cardiorespiratory variables are measured, to establish training guidelines in running and/or cycling training activities. Six triathletes (two females and four males), six runners (two females and four males) and six males cyclists, all with 5.5 years of serious training and still involved in racing, were tested on a treadmill and cycle ergometer. Cardiorespiratory variables [e.g., heart rate (HR), minute ventilation, carbon dioxide output (VCO2)] were calculated relative to fixed percentages of maximal oxygen uptake (VO2max; from 50 to 100%). The entire group of subjects had significantly (P < 0.05) higher values of VO2max on the treadmill compared with the cycle ergometer [mean (SEM) 4.7 (0.8) and 4.4 (0.9) l.min-1, respectively], and differences between tests averaged 10.5% for runners, 6.1% for triathletes and 2.8% for cyclists. A three-way analysis of variance using a 3 x 2 x 6 design (groups x tests x intensities) demonstrated that all factors yielded highly significant F-ratios (P < 0.05) for all variables between tests, even though differences in HR were only 4 beats.min-1. When HR was plotted against a fixed percentage of VO2max, a high correlation was found between tests. These results demonstrate that for triathletes, cyclists and runners, the relationship between HR and percentage of VO2max, obtained in either a treadmill or a cycle ergometer test, may be used independently of absolute VO2max to obtain reference HR values that can be used to monitor their running and/or cycling training bouts.

Adult↗
PubMed2000

A polymorphism in the alpha2a-adrenoceptor gene and endurance athlete status.

PURPOSE: In a case control study, we examined the allelic frequencies and genotype distributions of two restricted fragment length polymorphisms (RFLP) in the alpha-2A-adrenoceptor gene (ADRA2A) and beta-2-adrenoceptor gene (ADRB2) among elite endurance athletes (EEA) and sedentary controls (SC). METHODS: The EEA group included 148 Caucasian male subjects recruited on the basis that they had a VO2max > 74 mL O2 x kg(-1) x min(-1). The SC group comprised 149 unrelated sedentary male subjects, all Caucasians, from the Quebec Family Study. After digestion with the restriction enzymes Dra I (ADRA2A) and Ban I (ADRB2), Southern blotting and hybridization techniques were used to detect the mutations in the two ADR genes, which are encoded on chromosomes 10 (q24-26) and 5 (q31-32), respectively. RESULTS: For the Dra I ADRA2A RFLP, we observed a significant difference in genotype distributions between the two groups (P = 0.037). A higher frequency of the 6.7-kb allele was observed in the EEA group compared with the SC group (P = 0.013). No statistically significant difference was found between groups for the Ban I ADRB2 polymorphic site. Genotype frequencies for both genes in both groups were in Hardy-Weinberg equilibrium. CONCLUSIONS: In summary, we found evidence that ADRA2A gene variability detected with Dra I is weakly associated with elite endurance athlete status, and we conclude that genetic variation in the ADRA2A gene or a locus in close proximity may play a role in being able to sustain the endurance training regimen necessary to attain a high level of maximal aerobic power.

Alleles↗
PubMed2000

No association between the angiotensin-converting enzyme ID polymorphism and elite endurance athlete status.

Several studies have reported that the insertion (I) allele of the angiotensin-converting enzyme (ACE) I/deletion (D) polymorphism is associated with enhanced responsiveness to endurance training and is more common in endurance athletes than in sedentary controls. We tested the latter hypothesis in a cohort of 192 male endurance athletes with maximal oxygen uptake >/=75 ml. kg(-1). min(-1) and 189 sedentary male controls. The ACE ID polymorphism in intron 16 was typed with the three-primer polymerase chain reaction method. Both the genotype (P = 0.214) and allele (P = 0.095) frequencies were similar in the athletes and the controls. Further analyses in the athletes revealed no excess of the I allele among the athletes within the highest quartile (> 80 ml. kg(-1). min(-1)) or decile (>83 ml. kg(-1). min(-1)) of maximal oxygen uptake. These data from the GENATHLETE cohort do not support the hypothesis that the ACE ID polymorphism is associated with a higher cardiorespiratory endurance performance level.

Alleles↗
PubMed1998

Three mitochondrial DNA restriction polymorphisms in elite endurance athletes and sedentary controls.

This study examined the associations between elite endurance athlete (EEA) status and three mitochondrial DNA (mtDNA) restriction fragment length polymorphisms (RFLPs) in the subunit 5 of the NADH dehydrogenase (MTND5) locus and one in the D-loop region. A group of 125 Caucasian male EEA well endowed with the phenotypic expression of VO2max (78.9 +/- 3.8 mL x kg(-1) x min(-1), mean +/- SD) and 65 sedentary controls (SCON: VO2max = 39.8 +/- 8.2 mL x kg(-1) x min(-1)) participated in the study. VO2max was determined during an incremental exercise test on a cycle ergometer or a motor-driven treadmill. mtDNA was extracted from white blood cells or lymphoblastoid cell lines and specific regions were amplified by the polymerase chain reaction. The Pearson Chi-square statistic test and Fisher exact test revealed no significant association (P > 0.05) between any of the three mtDNA RFLPs and EEA status. The MTND5-BamHI RFLP at bp 13,470 (morph 3) was found in 12.8% of the EEA and 12.3% of the SCON (chi2 = 0.009, P = 0.92). The prevalence of the MTND5-Ncil RFLP at bp 13,364 (morph 2) was 12.9% and 14% for the EEA and SCON, respectively (chi2 = 0.043, P = 0.83). The D-loop-KpnI RFLP at bp 16,133 (morph 1) was found in 5.8% of the EEA and in 1.6% of the SCON (Fisher exact test = 1.80, P = 0.18). The MTND5-HincII RFLP at bp 12,406 (morph 1) was not present in this study sample. These results indicate no evidence for a difference in the frequency of two polymorphic restriction sites in the subunit 5 of the NADH dehydrogenase gene of mtDNA and one in the D-loop region between elite endurance athletes and sedentary controls.

Adolescent↗
PubMed1997

Time course of training-induced changes in maximal exercise of short duration in men and women.

The purpose of the present study was to test the hypothesis that gender differences are present in the extent and time course of exercise training-induced changes in maximal 10- and 90-s performance test. Thirty-six sedentary subjects (19 women and 17 men) were submitted to 15 weeks of training involving both continuous and interval ergocycle exercise sessions, while 13 other subjects (5 women and 8 men) served as a control group. Maximal power output after 10 s (P10) and 90s (P90) of cycling exercise was measured before and at each 5-week interval of the 15-week training period in both groups. Significant (p < 0.01) training-induced increases in performance were noted after 5 weeks, 10 weeks and 15 weeks of training for P10, and after 5 and 10 weeks for P90 in both genders. P10 and P90 were significantly increased in both genders (about 25% in men and 35% in women) following the 15-week training program and overall absolute increases were not statistically different between men and women. Slight increases (about 5%) in performance tests were observed in control subjects, but only during the first 5-week interval. P10 and P90 of women expressed as a percentage of that of men remained the same throughout the 15-week program. No significant relationship between pre-training values of P10 and their responses to training was found in men and women. In conclusion, results of the present study indicate that women have the same capacity to increase maximal short-term performance in response to training in comparison to men.

Adult↗
PubMed1997

Monitoring high-intensity endurance exercise with heart rate and thresholds.

Ventilatory and lactate thresholds have been proposed as tools to establish the highest steady-state intensity sustainable during prolonged physical exercise. The purposes of this study were to clarify whether the intensity at the ventilatory threshold could be sustained during prolonged high-intensity exercise and if the corresponding work rate, pulmonary ventilation, and blood lactate concentration could also be maintained. Fifteen young and healthy male subjects were submitted to a VO2max test on ergocycle and a 90-min high-intensity ergocycle endurance exercise test. During the 90-min exercise test, subjects were able to maintain an intensity corresponding to a heart rate 5 beats.min-1 lower than that predetermined from the ventilatory threshold. Heart rate, FeO2, and FeCO2 were stable during the period from 20 to 80 min, VO2 was constant from 30 to 80 min, while work output, pulmonary ventilation, blood lactate, and VCO2 decreased significantly over the 90-min performance. These results show that physiological parameters near the ventilatory threshold are not interchangeable and that some cannot be used to monitor high-intensity long term exercise. Moreover, they clearly demonstrate that the blood lactate concentration fluctuates substantially during a 90-min endurance performance and cannot predict the highest work intensity that can be sustained during prolonged exercise without fatigue. However, heart rate and VO2 at the ventilatory threshold seem to be more suitable markers for that purpose.

Adult↗
PubMed1997

Muscle-specific creatine kinase gene polymorphisms in elite endurance athletes and sedentary controls.

The purpose of this study was to investigate the association between elite endurance athlete (EEA) status and two restriction fragment length polymorphisms (RFLPs) at the muscle-specific creatine kinase (CKMM) gene locus. Genomic DNA was extracted from white blood cells or lymphoblastoid cell lines of 124 unrelated Caucasian male EEA (VO2max > 73 mL.kg-1.min-1) and 115 unrelated Caucasian sedentary male controls (SCON). The genetic polymorphism at the CKMM locus was detected by the polymerase chain reaction and DNA digestion with the NcoI and TaqI restriction endonucleases. The allelic frequencies for the NcoI and TaqI RFLPs were not different (P > 0.05) between EEA and SCON subjects. The three expected genotypes for CKMM-NcoI (1170/1170 bp, 1170/985 + 185 bp, and 985 + 185/985 + 185 bp) and CKMM-TaqI (1170/1170 bp, 1170/1020 + 150 bp, and 1020 + 50/1020 + 150 bp) were observed in the EEA and SCON groups. These genotype frequencies were in Hardy-Weinberg equilibrium, but they were not significantly (P > 0.05) different between the EEA and SCON. A strong (P < 0.001) linkage disequilibrium was detected among the NcoI and TaqI RFLPs in both EEA and SCON. These findings indicate that the skeletal muscle CK-NcoI and CK-TaqI gene polymorphisms are not associated with the elite endurance athlete status.

Adult↗
PubMed1996

Electrical stimulation-induced changes in performance and fiber type proportion of human knee extensor muscles.

The purpose of the present study was to look at the changes in the performance of human knee extensor muscles (KEM) induced by 6 weeks of low-frequency (8 Hz) electrical stimulation (LFES). KEM performance of 20 sedentary (before and after stimulation), ten active, and five endurance-trained subjects was evaluated during 25 consecutive 10-s isometric contractions, each separated by a rest period of 5 s. The mean force maintained during six consecutive 10-s contractions was expressed as a relative percentage of that of the first contraction. The mean performance of the first series of six contractions was not altered in response to stimulation, whereas that of the other four series was significantly increased. No significant difference was noted among the three groups in terms of KEM performance during the first series of six contractions. However, after the first series of six contractions, KEM performance of endurance-trained subjects was better in comparison to the other groups. Citrate synthase (CS) activity, capillary number per type IIA and IIB fibers, and the percentage of type IIA muscle fibers determined from vastus lateralis samples were significantly increased in response to the stimulation protocol. No significant change was observed in the proportion or capillary number of type I fibers, or in the areas of type I, IIA, and IIB fibers. The present study provides evidence that resistance to fatigue of human skeletal muscle can be significantly altered in response to 6 weeks of transcutaneous low-frequency electrical stimulation. The improvement in KEM resistance to fatigue of the sedentary subjects was such that, at the end of the stimulation protocol, resistance to fatigue was similar to that of active subjects. However, the ability of endurance-trained subjects to withstand fatigue was still superior compared to that of the other untrained or active subjects.

Adult↗
PubMed1996

Kinematics of cross-country ski racing.

This study investigated the evolution of skiing velocity, cycle length, and cycle rate in elite and subelite skiers during cross-country ski races. Senior male cross-country skiers engaged respectively in a 30-km skating race (N = 34) or a 50-km classical race (N = 27) were videotaped as they skied two different sections of 30 m, a 7 degrees uphill, and a flat section. In the skating race, most skiers used the offset technique on uphill and the 2-skate on flat, while the preferred techniques during the classical race were the diagonal stride for uphill and double-poling on flat. Results demonstrated that faster skiers had longer cycle lengths than slower skiers except for the flat sections of the classical race. Cycle rate was not different between skiers of different performance levels in any circumstances or races. Decreased velocity observed during the second half of the skating race was almost entirely due to a decrease in cycle length. We conclude that slower athletes should emphasize extending cycle length during their technical training. Therefore, skiers should place an emphasis on strength and power training to increase their kick and pole pushes and enhance cycle length.

Biomechanical Phenomena↗
PubMed1995

Effect of drafting on work intensity in classical cross-country skiing.

The purpose of this study was to compare the heart rate responses during cross-country skiing as a leading skier, as well as in a drafting situation, three meters behind the leader. Eight male and two female cross-country ski racers, paired for skiing ability, skied a 2 km course (two loops of 1 km) using the diagonal stride and double-poling techniques at a fixed speed (4.75 m.s-1 and 4.45 m.s-1 for males and females respectively) on two different occasions, once as a leading skier, the other as a drafter. A recovery period of 30 minutes was allowed between the two trials. Heart rates (HR) were registered every five seconds during all performances. Results revealed that HR were significantly lower (165 vs 172 beats.min-1) when skiing behind another skier as opposed to leading. Results also revealed that projected frontal areas appeared to influence the effects of drafting such that the HR differences between the leading and the drafting situations were larger for smaller skiers drafting behind larger skiers. These results showed that skiing behind another skier in a classical cross-country ski race would be very advantageous when the situation is encountered and could help racers using this energy saving strategy.

Adult↗
PubMed1995

Changes in plasma electrolytes and muscle substrates during short-term maximal exercise in humans.

This study compared the effects of 3 short-term maximal exercise tests lasting 10, 30, and 90 sec upon blood volume, plasma electrolytes, glucose, glycerol, lactate and skeletal muscle ATP, PC, glycogen, and lactate concentrations. Seven sedentary male subjects were recruited and 5 of them were randomly assigned to each of the 3 protocols. The tests were performed on a modified ergocycle at workloads of 0.9, 0.075, and 0.05 kp.kg-1 body mass, respectively. Muscle biopsies were taken from the vastus lateralis before and immediately after each exercise. Venous blood samples were collected before, immediately after, and during the recovery (5, 20, 60, and 120 min). Plasma volume decreased during the 30- and 90-sec tests and was increased in all tests after 60 min of recovery. Plasma K+ increased during all tests and returned to normal values 5 min postexercise, except after the 90-sec test where it fell below resting values. Plasma Na+ and Cl- were unaffected. Blood lactate increased in all tests, glucose increased after the 90-sec test, and glycerol increased after the 30- and 90-sec tests. All 3 tests brought relatively similar changes in muscle ATP, PC, and glycogen while muscle lactate changes were related to exercise duration. These results suggest that a normal hydration status is important for a subject undergoing short training bouts, and that high-intensity tests of short duration do not require a special nutritional regimen to enhance glycogen reserves.

Adenosine Triphosphate↗
PubMed1995

Effect of slope variation and skating technique on velocity in cross-country skiing.

The purpose of the present study was to investigate the effect of slope variations upon the maximal velocity attainable by cross-country ski racers using three skating techniques (V-1, V-2, and Gunde). Nine (2 females, 7 males) junior ski racers (16.0 +/- 0.4 yr of age, mean +/- SEM) exhibiting strong technical skills participated in the study. The subjects were required to skate at maximal velocity over five different courses (length 120-200 m) with mean slopes of -1, 0, 6, 9, and 12%. Video analysis was used to determine skiing velocity, cycle length, and cycle rate. Heart rate was monitored to verify intensity of exertion. Results indicated that intensities were similar to those observed while racing. Velocities for the three techniques were not different for -1, 0, and 6% slopes. However V-1 was significantly faster (P < 0.01) at 9% and 12% inclines. Velocity was highly correlated to cycle length (P < 0.01) but unrelated to cycle rate. Cycle length was significantly different between techniques (P < 0.01) and varied across slopes. Cycle rate was significantly different between techniques (P < 0.01) but did not vary across slopes. Thus, our results indicate that any of the three techniques is adequate on flat and rolling terrain, but V-1 should be used at slopes of 9% and above. It is also concluded that during short trials skied at maximal velocity, skiing velocity is highly dependent on cycle length and independent of cycle rate.

Adolescent↗
PubMed1995

Upper-body testing of cross-country skiers.

The purpose of this study was to evaluate maximal oxygen uptake during treadmill running and double-poling with a ski ergometer twice during the competitive season. A progressive double-poling power test was also performed to measure maximal power output. The athletes were five male and five female cross-country ski racers. Testing was done in December and April. Results showed that for both male and female skiers, no difference was observed during the competition season. Athletes were then divided into two subgroups according to whenever they had their peaking period early (December-January) or late (March-April) during the season. Skiers peaking early had significantly higher values for all measurements during the upper-body VO2peak test in December compared to April. Values for the upper-body VO2peak test of the skiers peaking late significantly increased from December to April, in accordance with their fitness state. Furthermore, results of the upper-body power test showed that there was no difference for the skiers peaking early for both testing periods, while power output increased significantly from December to April for the skiers peaking late. Thus specific upper-body tests appear to be more related to the fitness state of cross-country skiers than a running VO2max test.

Adult↗
PubMed1994

Energy expenditure measurement in male cross-country skiers: comparison of two field methods.

The purpose of this study was to compare estimations of daily energy expenditure (DEE) made with a physical activity journal (PAJ) and a heart rate monitoring method (HR-VO2) in endurance athletes. Seven male cross-country skiers (21 +/- 5 yr of age, mean +/- SD) with high aerobic power (70.4 +/- 7.2 mlO2.kg-1.min-1) and eight lean and moderately active males serving as controls (22 +/- 1 yr; 50.9 +/- 9.9 mlO2.kg-1.min-1) were tested. VO2max, resting metabolic rate (RMR), energy cost of standardized activities, PAJ, HR monitoring, and food diaries for measurement of daily energy intake (DEI) were measured in October, before the specific training period. Results indicated that the skiers had a higher RMR (P < 0.05) than the controls (8.2 +/- 1.6 vs 6.9 +/- 0.6 MJ.d-1), as measured by indirect calorimetry. DEE estimates made with the PAJ and the HR-VO2 methods were similar in the controls subjects but the HR-VO2 method yielded significantly higher results in the skiers (17.0 +/- 4.0 vs 13.1 +/- 2.1 MJ.d-1). DEI measurements were similar to HR-VO2 DEE in both groups. Thus, it appears that the PAJ, which was established with a sedentary population, underestimated DEE in trained cross-country skiers. Thus, the physical activity status of subjects has to be investigated before using a physical activity diary.

Adult↗
PubMed1994

Effect of drafting on heart rate in cross-country skiing.

The purpose of this study was to compare the heart rate responses during cross-country skiing as a leading skier, as well as in a drafting situation, 2 m behind the leader. Six male cross-country ski racers, paired for VO2max skied a 2-km course (two loops of 1 km) using the skating techniques at a fixed speed (5.6 m.s-1) on two different occasions, once as a leading skier, the other as a drafter. A recovery period of 30 min was allowed between the two trials. Heart rates (HR) were monitored every 5 s during all performances. Capillary blood lactate concentrations were taken before and at 5 min posttrial. Results revealed that HR were significantly lower (154 vs 163 beats.min-1) when skiing behind another skier as opposed to leading. Lactate concentrations were not significantly different between the two trials. Results also revealed that projected frontal areas appeared to influence the effects of drafting such that the HR differences between the leading and the drafting situations were larger for smaller skiers drafting behind larger skiers. These results showed that skiing behind another skier in a ski race would be very advantageous when the situation is encountered and that coaches should use the drafting situation in training so that athletes can practice this energy-saving strategy.

Adult↗
PubMed1993

Mitochondrial DNA sequence polymorphism, VO2max, and response to endurance training.

Mitochondrial DNA sequence variation was determined in 46 sedentary young adult males who took part in ergocycle endurance training programs in two laboratories to assess whether mitochondrial DNA variants were associated with individual differences in maximal oxygen uptake (VO2max) and its response to training. VO2max was obtained from a progressive ergocycle test to exhaustion. White blood cell mitochondrial DNA was characterized with the restriction fragment length polymorphism (RFLP) technique using 22 restriction enzymes and human mitochondrial DNA as a probe for hybridization. Multiple mitochondrial DNA variants were detected with 15 of the enzymes. Some subjects exhibited many RFLPs, while others showed no variation. These RFLPs (morphs) were generated by base substitutions located in gene regions coding for mitochondrial proteins as well as in the noncoding regions. Carriers of three mitochondrial DNA morphs, two in the subunit 5 of the NADH dehydrogenase gene and one in the tRNA for threonine, had a VO2max (ml.kg-1.min-1) in the untrained state significantly higher than noncarriers, while carriers of one mitochondrial DNA morph in subunit 2 of NADH dehydrogenase had a lower initial VO2max. Endurance training increased VO2max by a mean of 0.5 l of O2, with individual differences ranging from gains of 0.06 to 1.03. After adjustment for training site and initial VO2max, a lower response was observed for three carriers of a variant in subunit 5 of the NADH dehydrogenase detected with HincII (mean gain of 0.28 l; P < 0.05). These results suggest that sequence variation in mitochondrial DNA may contribute to individual difference in VO2max and its response to training.

Adolescent↗
PubMed1993

Using maximal and submaximal aerobic variables to monitor elite cyclists during a season.

The purpose of this study was to identify sensitive physiological indicators for monitoring the progress in training state of elite cyclists throughout a training and competition season. Seven elite male cyclists performed maximal oxygen consumption (VO2max) tests and submaximal tests on three or four different occasions during their training and competition season. The submaximal test consisted of three successive 16-min bouts at 150, 200, and 250 W interspersed with rest periods between each load. Pedalling rate varied progressively from 50-120 rpm. Results showed that maximal heart rate (HR), ventilation (Ve), gross mechanical efficiency (MEG), and VO2max did not change during the season. Moreover, ventilation threshold (VT) did not change during the season, nor did HR, Ve, and VO2 at VT. However, changes were found in physiological variables during the submaximal test. HR decreased significantly during the season, as did VO2 (P < 0.05) for a standardized workload. On the other hand, at the higher power outputs (200 W and 250 W) MEG increased during the season. These results suggest that VO2max may not be a good indicator of enhanced capacity in elite cyclists. Rather, a standardized efficiency test during which submaximal variables such as HR, VO2, and MEG are monitored might be a more sensitive indicator of the progress in the training state of elite male cyclists during a training and competition season.

Adaptation, Physiological↗