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.

Parental reaction and adaptability to the prenatal diagnosis of fetal defect or genetic disease leading to pregnancy interruption

The objective of the study was to evaluate the psychological reaction of two groups of parents to a pregnancy termination after they had undergone a prenatal diagnostic procedure. The analysis involved interviews with a study group of 76 patients who were at risk of giving birth to a child with a genetic disease or defect and a comparison group of 124 who had a pregnancy termination after a major anomaly had been detected by routine ultrasound and who were not at known risk for a genetic disease. Only patients in the study group had received counselling before the prenatal diagnosis and were aware that the fetus could be affected. The overall reaction of the comparison group was one of shock, denial of fetal abnormality, and guilt over 'abandoning the fetus'. A feeling of guilt was expressed by patients in the comparison group (73 per cent versus 29 per cent) in the period immediately following the interruption. One-third of patients in both groups felt obliged to undergo a therapeutic abortion. More patients in the study group than in the comparison group expressed the need to see a psychiatrist at the time of the study (19 per cent versus 7 per cent) and viewed future pregnancies as a replacement for the lost pregnancy (63 per cent versus 19 per cent). The recommendations of the study focus on information sessions to personnel, nursing support, analgesia during the expulsion period, an atmosphere of respect that should be present at the time that the fetus is viewed, the anticipation of mourning, and the long-term follow-up of the couple to ensure that counselling for future pregnancies and psychological support are provided when needed.

Lipoprotein lipase activity in white adipose tissue of rats subjected to exercise--rest cycles

This study was conducted to determine serum lipid levels and the activity of lipoprotein lipase in epididymal white adipose tissue of rats undergoing exercise training. During the 8-week period of treatment, one group of rats was kept sedentary and the remaining animals were exercise trained either continually (1 h of daily treadmill running) or intermittently (alternate weeks of daily running and inactivity). Exercise training, either continual or intermittent, decreased postprandial serum total and high-density lipoprotein cholesterol concentrations, which returned to sedentary levels in the intermittently trained animals following a week of rest. Lipoprotein lipase activity in whole epididymal adipose pad was lower in rats trained continually than in the sedentary group at the end of the treatment. The intermittent training program elicited large fluctuations in both the specific (per milligram of protein) and total (per tissue) activity of lipoprotein lipase in white adipose tissue. During rest periods, enzyme activity rose to levels that were higher than those of sedentary rats, whereas lipase activity was below that of sedentary animals following a week of running. In the last exercise--rest cycle, body weight gain of the intermittently trained rats was nearly abolished during the week of running, but it increased above that of sedentary animals during weeks of rest. The present results suggest that the modulation of lipoprotein lipase activity in white adipose tissue is one of the adaptations that take place to accommodate the fluctuations in the rate of energy deposition that occur in the rat during an intermittent training program.

Genetic effect in resting and exercise metabolic rates

Two studies dealing with the contribution of the genotype in individual differences for resting metabolic rate (RMR), thermic effect of a 4.2 MJ carbohydrate meal (TEM), and energy cost of submaximal exercise are reported. The genetic effect for RMR and TEM was studied in 31 pairs of parent-child, 21 pairs of dizygotic (DZ) twins, and 37 pairs of monozygotic (MZ) twins, whereas the heritability of the energy cost of submaximal exercise was determined from data on 22 pairs of DZ twins and 31 pairs of MZ twins. The heritability of RMR reached approximately 40% of the variance remaining after adjustment for age, gender, and fat-free mass, (FFM). The genetic effect for TEM was equivalent to at least 40% to 50% of the variation in the energy expended during four hours after the meal test. A highly significant genetic effect was found for fasting plasma glucose (greater than .72), but the results for fasting plasma insulin are unclear. No significant genetic variance was seen for the glucose and insulin response to the carbohydrate meal. Finally, heritability for the metabolic rate during cycle exercise was high (greater than or equal to .46) at low power output, but it became nonsignificant when the energy cost reached about 6 times the RMR.

Anaerobic performances of sedentary and trained subjects

The objective of this report was to compare the performance of sedentary individuals, physical education students, and athletes of various disciplines in 10 s and 90 s maximal cycle ergometer tests. The 10 s power was the highest power output in one second from the 10 s test, while capacities were defined as the total work output during the best 10 s trial and the 90 s test. ANOVA and Duncan multiple range test indicated that the mean values of the 10 S power and capacity and the 90 S capacity tests were significantly higher in sprinter than in sedentary groups. Sprinters performed significantly better than marathon runners only in the 10 s capacity and power. Bodybuilders and sedentary subjects had similar results in the 90 s capacity test. Mean performance values per kilogram of body weight in sedentary females reached about 60% of sedentary males while marathon runners, physical education students and sprinter females reached about 80% of the male performances for the three indicators. When expressed per kilogram of fat-free mass, females reached a higher proportion of the male values for all performances. These results indicate that: a) there are differences for the power and capacity measured in predominantly anaerobic tests between athletes from different disciplines and sedentary individuals, and b) gender differences exist for these anaerobic performance indicators, but they appear attenuated in trained subjects.

Estimation of the contribution of the various energy systems during maximal work of short duration

The aim of this experiment was to estimate the relative contribution of the various energy delivery systems during maximal exercise tests of short duration. Twenty-five males were submitted to a VO2max test and 10-, 30-, and 90-s maximal ergocycle tests. Expiratory gases were collected with a Douglas bag during the entire 30-s test and continuously monitored with an open-circuit system during the 90-s test. Estimates of the phosphagenic component represented approximately 55%-60% of the energy expenditure during the 10-s work performance. Results of the 30-s test indicated that the relative contributions of the energy systems were 23%, 49%, and 28% for the phosphagenic, glycolytic, and oxidative pathways, respectively. For the 90-s test, these estimates were 12%, 42%, and 46% for the three metabolic systems. The highest contribution of each system during the 90-s was obtained from 5 to 15 s for the phosphagenic component, from 16 to 30 s for the glycolytic, and from 61 to 75 s for the aerobic energy systems. During the 90-s test, VO2max was reached after approximately 60 s. It is concluded that the 30 and 90 s are not strictly anaerobic although they all have a large anaerobic component.

Hormonal response to exercise in humans: influence of hypoxia and physical training

Hypoxia and physical training alter the responses of glucoregulatory hormones to absolute work loads in opposite directions. These effects have tentatively been ascribed to changes in maximal O2 consumption (VO2 max) and ensuing changes in relative work loads. However, hypoxia as well as training may more specifically influence the hormonal response. We therefore differentiated the influence of hypoxia, training, and VO2 max, respectively, on the hormonal response to bicycle exercise. Responses to hypoxia in a low-pressure chamber (PB = 465 vs. 730 Torr) were studied at given absolute and relative (85% VO2 max) work loads in seven endurance-trained athletes (T) and 7 age and weight-matched sedentary subjects (C). Concentrations in plasma of norepinephrine, growth hormone, adrenocorticotropic hormone, and cortisol were always closely related to the relative work load. However, the epinephrine response in T, but not in C, was at the same relative work load higher during hypoxia (5.84 +/- 0.83 nmol/l) than during normoxia (4.26 +/- 0.44, P less than 0.05). These results indicate that the hormonal response is influenced by hypoxia and physical training, mainly via changes in the relative work load. However, in trained subjects both at rest and during exercise, an enhancing effect of hypoxia per se on the epinephrine response is seen, probably due to an increased adrenal medullary secretory responsiveness in long-term endurance-trained subjects.

Genetic and environmental sources of variation in physical fitness

The technique of path analysis was used to assess inherited and environmental variance components in physical fitness indicators measured in 1630 subjects from 375 families of French descent living in the greater Québec city area. For that purpose, submaximal power output (PWC150/kg), muscular endurance, muscular strength, reaction time and movement time were evaluated during a visit of the family to the laboratory. Inter-class correlations in various types of relatives were computed from scores adjusted for linear and non-linear effects of age and sex by a regression procedure (Y = age + sex + (age X sex) + age2). Correlations were then used in the path analytic BETA model which allows the partition of transmissible variance (t2) into genetic (h2) and cultural (b2) components. Results indicated that t2 accounted for 18% (movement time) to 63% (muscular strength) of the phenotypic variance. The contribution of genetic factors was found to be negligible for PWC150/kg and movement time, and accounted for about 20% of the phenotypic variance for reaction time and muscular endurance and 30% for muscular strength, while non-transmissible variance (1 - t2) accounted for 37% (muscular strength) to 82% (movement time) of the phenotypic variance. These results suggest that biological variation observed in the physical fitness level of a healthy population is mainly associated with non-transmissible environment factors and that the contribution of heredity is moderate and clearly lower than previously reported.

[Results of the integration of psychiatric services in general hospitals. Testimony after ten years of absence.]

The author traces the evolution of psychiatrie services in Montréal and the province of Québec up until 1977. Following this summary, the author describes what has been undertaken in the area of mental health since that year. He also recounts his observations in the course of visits made in the fall of 1986 to certain hospital centers catering to short term patients (centres hospitaliers de courte durée), at the request of the Harnois Committee. Among his findings, he points out that the projects started at the onset of the Bédard and Castonguay reforms have been implemented, if not in spirit by the book, and that the integration of the entire psychiatric services of the C.H.C.D. is about to be completed.

Effects of two high-intensity intermittent training programs interspaced by detraining on human skeletal muscle and performance

The purpose of this study was to investigate the effects of repeated high-intensity intermittent training programs interspaced by detraining on human skeletal muscle and performances. First, nineteen subjects were submitted to a 15-week cycle ergometer training program which involved both continuous and high-intensity interval work patterns. Among these 19 subjects, six participated in a second 15-week training program after 7 weeks of detraining. Subjects were tested before and after each training program for maximal aerobic power and maximal short-term ergocycle performances of 10 and 90s. Muscle biopsy from the vastus lateralis before and after both training programs served for the determination of creatine kinase (CK), hexokinase, phosphofructokinase (PFK), lactate dehydrogenase (LDH), malate dehydrogenase, 3-hydroxyacyl-CoA dehydrogenase (HADH) and oxoglutarate dehydrogenase (OGDH) activities. The first training program induced significant increases in all performances and enzyme activities but not in CK. Seven weeks of detraining provoked significant decreases in maximal aerobic power and maximal 90s ergocycle performance. While the interruption of training had no effect on glycolytic enzyme markers (PFK and LDH), oxidative enzyme activities (HADH and OGDH) declined. These results suggest that a fairly long interruption in training has negligeable effects on glycolytic enzymes while a persistent training stimulus is required to maintain high oxidative enzyme levels in human skeletal muscle. The degree of adaptation observed after the second training program confirms that the magnitude of the adaptive response to exercise-training is limited.

Heredity and muscle adaptation to endurance training

To determine whether sensitivity of muscle characteristics and aerobic performances to endurance training was genotype-dependent, 6 pairs of monozygotic (MZ) twins, 21 +/- 4 yr of age (mean +/- SD), took part in a 15-wk ergocycle endurance training program. Tests were performed before and after 7 and 15 weeks of training. A biopsy of the vastus lateralis muscle was obtained for the determination of fiber type composition and activities of creatine kinase, hexokinase, phosphofructokinase, lactate dehydrogenase, malate dehydrogenase, 3-hydroxyacyl CoA dehydrogenase, and oxoglutarate dehydrogenase. Maximal oxygen uptake was measured with a progressive maximal ergocycle test, while endurance performance was determined as the total work output during a 90-min maximal ergocycle test. Results indicated that maximal oxygen uptake X kg-1 and endurance performance X kg-1 increased significantly (14 and 31%, respectively) with training, and intra-pair resemblance (intra-class) in response to 15 wk of training ranged from 0.65 to 0.83. Hexokinase (31%), phosphofructokinase (37%), lactate dehydrogenase (21%), malate dehydrogenase (31%), and 3-hydroxyacyl CoA dehydrogenase (60%) were significantly increased with training whereas no mean change in fiber-type proportions, oxoglutarate dehydrogenase and creatine kinase activities and the phosphofructokinase/oxoglutarate dehydrogenase ratio was observed. Similarity within twin pairs in the response to enzyme activities was mainly detected in the second half of the training program. The present results confirm, therefore, that both maximal oxygen uptake and endurance performance responses to training are largely genotype-dependent.(ABSTRACT TRUNCATED AT 250 WORDS)

Aerobic performance in brothers, dizygotic and monozygotic twins

Forty-two brothers, 66 dizygotic twins of both sexes and 106 monozygotic twins of both sexes, 16 to 34 yr of age, took part in this study that was designed to investigate the effect of heredity in aerobic performance. Maximal oxygen uptake (VO2 max), maximal heart rate (HR max), maximal ventilation, and maximal oxygen pulse were obtained from a progressive ergocycle test to exhaustion. Total work output in a 90-min maximal ergocycle test was also determined in the twins. Fat-free weight was estimated from body density measurements obtained through underwater weighing. Aerobic performance scores were adjusted for age (brothers), and age and sex (dizygotic and monozygotic twins) by regression procedures. Dizygotic twins and brothers of same sibship exhibited about the same level of resemblance for all variables or were only slightly different, with the exception of HR max. Monozygotic pairs were generally more alike than the other sibs, as suggested by the intra-class coefficients. Twin data were used to compute the genetic effects. The within-pair estimate of genetic variance revealed that it was significant (P less than or equal to 0.05) for all variables except VO2 max X kg-1 fat-free weight X min-1. In the case of HR max, the among-pairs component estimate had to be used, and it also proved significant (P less than or equal to 0.01). The size of the genetic effect was computed from three different methods, and it reached about 40% for VO2 max X kg-1 X min-1, 50% for HR max, 60% for maximal oxygen pulse and maximal ventilation, and 70% for 90-min work output X kg-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Training increases the concentration of [3H]ouabain-binding sites in rat skeletal muscle

Exercise is associated with a net loss of K+ from the working muscles and an increased plasma K+ concentration, indicating that the capacity for intracellular reaccumulation of K+ is exceeded. Training reduces the exercise-induced rise in plasma K+, and an increased plasma [K+] may interfere with physical performance. Since the clearing of K+ from the extracellular space depends on the capacity for active K+ uptake in skeletal muscle, the effects of training and inactivity on the total concentration of (Na+ + K+)-ATPase was determined. Following 6 weeks of swim training, the concentration of [3H]ouabain-binding sites in rat hindlimb muscles was up to 46% (P less than 0.001) higher than in those obtained from age-matched controls. Whereas muscle Na+, K+ contents remained unchanged, the concentration of citrate synthase increased by up to 76% (P less than 0.001). Training induced no change in the [3H]ouabain-binding-site concentration in the diaphragm, but in the heart ventricles, the K+-dependent 3-O-methylfluorescein phosphatase activity increased by 20% (P less than 0.001). Muscle inactivity induced by denervation, plaster immobilisation or tenotomy reduced the [3H]ouabain-binding-site concentration by 20-30% (P less than 0.02-0.001) within 1 week. In conclusion, training leads to a significant and reversible rise in the concentration of (Na+ + K+)-ATPase in muscle cells. This may be of importance for the beneficial effects on physical performance by improving the maximum capacity for K+ clearance.

Genetic effects in human skeletal muscle fiber type distribution and enzyme activities

The purpose of the study was to estimate the genetic effect for skeletal muscle characteristics using pairs of nontwin brothers (n = 32), dizygotic (DZ) twins (n = 26), and monozygotic (MZ) twins (n = 35). They were submitted to a needle biopsy of the vastus lateralis for the determination of fiber type distribution (I, IIa, IIb) and the following enzymes were assayed for maximal activity: creatine kinase, hexokinase, phosphofructokinase (PFK), lactate dehydrogenase, malate dehydrogenase, 3-hydroxyacyl CoA dehydrogenase, and oxoglutarate dehydrogenase (OGDH). For the percentage of type I fibers, intraclass correlations were 0.33 (p less than 0.05), 0.52 (p less than 0.01), and 0.55 (p less than 0.01) in brothers and DZ and MZ twins, respectively. MZ twins exhibited significant within-pair resemblance for all enzyme activities (0.30 less than or equal to r less than or equal to 0.68). In spite of these correlations, genetic analyses performed with the twin data alone indicated that there was no significant genetic effect for muscle fiber type I, IIa, and IIb distribution and fiber areas. Although there were significant correlations in MZ twins for all muscle enzyme activities, the often nonsignificant intraclass coefficients found in brothers and DZ twins suggest that variations in enzyme activities are highly related to common environmental conditions and nongenetic factors. However, genetic factors appear to be involved in the variation of regulatory enzymes of the glycolytic (PFK) and citric acid cycle (OGDH) pathways and in the variation of the oxidative to glycolytic activity ratio (PFK/OGDH ratio). Data show that these genetic effects reach only about 25-50% of the total phenotypic variation when data are adjusted for age and sex differences.

Repeatability of fibre type and enzyme activity measurements in human skeletal muscle

In order to assess the variability in repeated determination of human muscle fibre type distribution, fibre area and enzyme activity measurements, two biopsies were taken within 10 days in the same vastus lateralis for 12 females and 13 males, and in the right and in the left muscles for 25 other subjects (13 females and 12 males). Within muscle, intraclass reliability coefficients were 0.88, 0.82 and 0.56 for type I, IIa and IIb per cent fibres, respectively, and ranged from 0.74 to 0.82 for fibre areas and from 0.71 to 0.90 for enzyme markers of different metabolic pathways. Correlations between right and left muscle measurements were also high for fibre areas (from 0.85 to 0.91) and enzyme activities (from 0.71 to 0.87), except for phosphofructokinase (r = 0.63). In contrast, the right and left thigh muscle correlation reached 0.67, 0.40 and 0.64 for type I, IIa and IIb fibre distribution, respectively. Thus, the variation in muscle sampling and technical procedures reached about 15% of the total variation (i.e. total differences between subjects) for the proportion of fibre type I and IIa and about 20-25% for fibre areas and enzyme activities. On the other hand, the technical error for the proportion of fibre type I and IIa is about 6-7%. This implies that differences brought about by any experimental treatment on these skeletal muscle characteristics in human studies have to be of a relatively large magnitude before being detectable. On the other hand, fibre areas and enzyme activities measured in single needle biopsy sample, from one of the vastus lateralis muscles, are quite representative of the other vastus lateralis. Similarity in fibre type proportion between right and left vastus lateralis cannot be postulated, however, without investigating both muscles.

Inheritance of human skeletal muscle and anaerobic capacity adaptation to high-intensity intermittent training

The role of heredity in the response of maximal anaerobic capacities and skeletal muscle histochemical and biochemical characteristics to a 15-week cycle ergometer training program involving both continuous and interval work patterns was investigated in 14 pairs of monozygotic twins. The training program consisted mainly of series of ergocycle supramaximal exercises lasting from 15 s to 90 s and performed 4 and 5 times a week. The subjects were submitted to 10 s and 90 s all-out ergocycle tests to estimate maximal anaerobic alactacid (AAC) and lactacid (ALC) capacities, respectively. Muscle fiber types and creatine kinase (CK), hexokinase (HK), phosphofructokinase (PFK), lactate dehydrogenase (LDH), malate dehydrogenase (MDH), 3-hydroxyacyl CoA dehydrogenase (HADH), and oxoglutarate dehydrogenase (OGDH) activities were determined in a biopsy from the vastus lateralis. Training increased AAC, ALC, fiber type I proportion, MDH, HADH, and OGDH (P less than 0.05) and decreased fiber type IIb proportion and the PFK/OGDH ratio. No significant change was observed for CK, HK, PFK, and LDH. Large interindividual differences in the response to training were observed for all variables. However, intraclass correlations indicated that the extent of the response of ALC and CK, HK, LDH, MDH, and OGDH activities and of the PFK/OGDH activity ratio to training were significantly similar within pairs of twins. Although the role of heredity appeared absent for the changes in fiber type proportions and in anaerobic alactacid capacity, the present results suggest that the response of anaerobic lactacid capacity and most enzyme activities to high-intensity intermittent training is significantly determined by the genotype.

Specificity of aerobic and anaerobic work capacities and powers

Thirty-three untrained subjects of both sexes, 18-31 years of age, performed several tests on cycle ergometers. Maximal aerobic power (MAP) was obtained in a progressive work test. Maximal aerobic capacity (MAC) was measured in a 90-min maximal test and was computed as the total work output during that period. Two all-out cycle ergometer work tests lasting 10 s and 90 s were used to estimate the anaerobic alactic capacity (AAC) and lactic capacity (ALC). Anaerobic alactic power (AAP) was computed as the highest output in 1 s in the AAC test and anaerobic lactic power (ALP) was obtained as the mean output during the last 5 s in an all-out test of 30 s. Correlation coefficients were computed between all measurements of capacity and power expressed per kg of body weight as well as with scores adjusted for sex differences. Common variances (r2 X 100) between measurements of power were either low (MAP-AAP, 40%) or moderate (MAP-ALP, 61%; AAP-ALP, 62%) while common variances between measurements of capacity were sometimes low (MAC-AAC, 49%) or higher (MAC-ALC, 76%; AAC-ALC, 77%). The common variances between tests of power and capacity reached high values when calculated with metabolic criteria of the same class (MAP-MAC, 81%; AAP-AAC, 92%). These results provide quantitative evidence to support the notion of specificity between the aerobic and the anaerobic work performances and support the distinction between capacity and power of the three energy systems.

Relationships between skeletal muscle characteristics and aerobic performance in sedentary and active subjects

Forty-eight sedentary and 39 quite active or well-trained men participated in this study. Muscle biopsy samples were taken from the vastus lateralis for the determination of fiber type composition (I, IIa, IIb), fiber type area, and assay of the following enzymes: malate dehydrogenase (MDH), 3-hydroxyacyl CoA dehydrogenase (HADH) and oxoglutarate dehydrogenase (OGDH). Maximal oxygen uptake (VO2max) was determined with a progressive cycle ergometer test, while endurance performance or maximal aerobic capacity (MAC) was defined as the total work output during a 90-min cycle ergometer test. Correlation analysis revealed no evidence of association between fiber type composition and VO2max kg-1 or MAC kg-1 in sedentary subjects, while active men exhibited significant correlation between % type I (r = 0.52), % type IIb (r = 0.31) and VO2max kg-1. Enzyme activities were not significantly correlated with MAC kg-1 and VO2max kg-1 in sedentary men while active men exhibited significant correlation for the three enzymes (0.37 less than or equal to r less than or equal to 0.51) with VO2max kg-1. These results show that the contribution of muscle fiber type and enzyme activities to aerobic performance may be inflated from a statistical point of view by the training status heterogeneity of subjects. They also suggest that variation in these muscle characteristics does not account for the individual differences in aerobic performance of subjects who have never trained before. Therefore, the assessment of muscle characteristics is not as useful as originally thought for the detection of individuals with a high potential for endurance performance among untrained subjects.

Human skeletal muscle fiber type alteration with high-intensity intermittent training

The response of muscle fiber type proportions and fiber areas to 15 weeks of strenuous high-intensity intermittent training was investigated in twenty-four carefully ascertained sedentary (14 women and 10 men) and 10 control (4 women and 6 men) subjects. The supervised training program consisted mainly of series of supramaximal exercise lasting 15 s to 90 s on a cycle ergometer. Proportions of muscle fiber type and areas of the fibers were determined from a biopsy of the vastus lateralis before and after the training program. No significant change was observed for any of the histochemical characteristics in the control group. Training significantly increased the proportion of type I and decreased type IIb fibers, the proportion of type IIa remained unchanged. Areas of type I and IIb fibers increased significantly with training. These results suggest that high-intensity intermittent training in humans may alter the proportion of type I and the area of type I and IIb fibers and in consequence that fiber type composition in human vastus lateralis muscle is not determined solely by genetic factors.

Skeletal muscle histochemical and biochemical characteristics in sedentary male and female subjects

The purpose of this study was to assess the relationship between muscle fiber type distribution and enzymatic characteristics in sedentary male and female subjects. Muscle biopsy samples from the vastus lateralis muscle of 38 females and 37 males were analyzed to determine the fiber type composition (I, IIa, and IIb), the fiber size, and maximal activities of enzyme markers of energy metabolic pathways. Significant correlations were found (p less than 0.05) between percent fiber type I area and hexokinase (r = -0.39), phosphofructokinase (r = -0.39), lactate dehydrogenase (r = -0.41), and oxoglutarate dehydrogenase (r = 0.33) activities, whereas such correlations with total phosphorylase (r = -0.02), malate dehydrogenase (r = 0.12), and 3-hydroxyacyl CoA dehydrogenase (r = 0.12) activities were not significant. The results of the present study also suggest the presence of a significant but low covariation of less than 30% between the fiber type distribution and muscle enzyme activities. They confirm the presence of an important metabolic heterogeneity independent of the muscle fiber type distribution in sedentary male and female subjects. Moreover, these results indicate that sedentary males exhibit a lower mean value of percent fiber type I and higher glycolytic enzyme activities than sedentary females.

Responses of maximal aerobic power and capacity to aerobic training

The purpose of this experiment was to investigate the individual differences and the specificity in the response of maximal aerobic power (MAP) and capacity (MAC) to a 20-week aerobic training program. Twenty-four subjects (25 +/- 4 years), ascertained as sedentary, including 13 women and 11 men, participated in this study. MAP was determined with a progressive maximal ergocycle test, while MAC was computed as the total work output accomplished during a 90-min maximal ergocycle test. A modified bicycle ergometer allowed the exact measurement of the distance and the load for the computation of the work performed during MAC. The aerobic training program enhanced mean MAP/kg and MAC/kg by 33% and 51%, respectively. Although MAP/kg response to training was similar in both sexes, there was a sex difference in the response of MAC/kg, men improving 50% more than women. Individual differences in the response to the standardized training program were considerable with training gains ranging from 5% to 88% for MAP/kg and from 16% to 97% for MAC/kg. Correlations between training increments in MAP/kg with those in MAC/kg were rather low ranging from 0.28 to 0.44. These results indicate that there is a sex difference in the trainability of aerobic capacity, but not of maximal aerobic power, under the same 20-week aerobic training program. Moreover, large individual differences in the response to similar aerobic training are observed in sedentary persons, suggesting that certain genotypes are more sensitive to training than others. Finally, there is a high level of specificity in the response to training of the power and of the capacity of the aerobic energy metabolism.

Submaximal power output in adopted and biological siblings

Submaximal power output was determined in relative steady state on a bicycle ergometer at a heart rate of 150 beats per minute (PWC150). PWC150 was measured in 880 individuals, 9 to 26 years of age, belonging to 46 sibships of adopted sibs, 66 sibships of unrelated individuals including adoptees, 33 sibships of first-degree cousins, 225 sibships of biological sibs, 56 sibships of DZ twins and 54 sibships of MZ twins. PWC150, PWC150/kg of body weight, PWC150/kg lean body mass, PWC150/cm of height and PWC150/m2 of body surface area were submitted to analysis of variance and correlation analysis after statistical control over age and sex of subjects. Few significant resemblances were found in PWC measurements for adoptive siblings, unrelated sibs and cousins. Sibling resemblance was, however, significant for the sibships of biological sibs, and of DZ and MZ twins. Interclass correlations reached significance only in pairs of biological brothers and sisters, and in pairs of DZ and MZ twins. Estimates of total genetic effect in PWC150/kg in a population of free-living children, adolescents and young adults vary from 0.30 to 0.48. It is concluded that submaximal power output is only moderately affected by the genotype.

A test of aerobic capacity: description and reliability

The purposes of this study were 1) to describe a maximal aerobic capacity (MAC) test and 2) to report on its reliability. Thirty subjects (16 males and 14 females) were tested for maximal aerobic power (MAP) with a progressive bicycle ergometer test and the ventilatory anaerobic threshold (VANT) was determined. MAC was measured as the amount of work that could be performed in 90 min on a bicycle ergometer at an intensity set individually from VANT. Subjects were asked to perform as much work as possible during this non-stop 90 min period. For females and males respectively, MAP reached 42.9 +/- 5.9 (mean +/- SD) and 56.0 +/- 4.7 ml O2/kg X min-1 (p less than .01), VANT 36.3 +/- 6.1 and 46.0 +/- 5.2 ml O2/kg X min-1 (p less than .01), max HR 198 +/- 8 and 195 +/- 9 (p greater than .05) and HR at VANT 187 +/- 9 and 180 +/- 10 (p greater than .05). The same subjects were tested twice for MAC within 7 days. Results expressed in kJ/kg reached 10.6 +/- 2.1 and 10.8 +/- 2.4 for females, 14.7 +/- 2.1 and 14.9 +/- 2.2 for males. Mean HR maintained during MAC were 174 +/- 11 and 174 +/- 9 for females and 169 +/- 10 and 170 +/- 10 for males. There was a non significant difference between means (p greater than .05) of the first and second test in total work performed in kJ/kg. This difference reached about 2% of the first test score, 32.7% of this difference occurring in the first 10 min.(ABSTRACT TRUNCATED AT 250 WORDS)

The significance of pregnancy among adolescents choosing abortion as compared to those continuing pregnancy

The significance of pregnancy for adolescent women is usually related to unconscious motivations. Some teenagers faced with the problem choose to abort, and others do not. Psychosocial status, contraceptive and sexual habits, attitudes towards pregnancy and environmental influences were studied in 50 teenagers who chose abortion. These young women were matched for age and parity with a control group of 50 who elected to carry their pregnancies to term. The results point to significant differences between the two groups, particularly as to the meaning of pregnancy and the decision-making process.

Tests of anaerobic alactacid and lactacid capacities: description and reliability

The purpose of this paper is 1) to describe maximal anaerobic alactacid (AAC) and lactacid (ALC) capacity test and 2) to determine their reliabilities in men and women. The subjects were submitted to either a 10-s (2 trials) or a 90-s (1 trial) all-out ergocycle test for AAC and ALC respectively. Thirty-four male and 24 female subjects were tested for AAC, while 21 males and 19 females took part in the ALC test. A modified bicycle ergometer allowed the exact measurement of the distance and the work load for the computation of the work performed. load for the computation of the work performed. Each subject was tested and retested within 7 days. In both AAC and ALC, male subjects performed more work than women. AAC was 108 +/- 16 (mean +/- SD) and 90 +/- 14 J/kg for males and females respectively while ALC was 486 +/- 50 and 377 +/- 34 J/kg. Although the work load was designed to be 0.09 kp/kg for the AAC and 0.05 kp/kg for the ALC tests, there were wide variations between subjects with respect to the optimal load (AAC: from 0.05 to 0.11; ALC: from 0.03 to 0.06 kp/kg). Reproducibility was consistently high, with intraclass correlations of 0.98 and 0.99 for AAC (AAC-Max) and ALC respectively, with no difference between the male and female subgroups. It is concluded that these AAC and ALC tests, designed under assumptions of face validity, allow for differences between males and females and are highly repeatable.

A method to assess energy expenditure in children and adults

A variety of studies has a need to estimate the amount and pattern of daily energy expenditure. To this end, a 3-day activity record was developed and is described. Every 15-min period over 3 days, including a weekend day, was qualified in terms of energy cost on a 1 to 9 scale corresponding to a range of 1.0 MET to 7.8 METs and higher. A reliability study of 61 subjects indicated a highly reproducible procedure as shown by an intraclass correlation of 0.96 for mean kcal of energy expenditure over 3 days. Repeatability was unchanged whether or not the hours of sleep were included in the record. Samples of 150 children and 150 adults were also drawn to investigate the relationship between energy expenditure, physical working capacity, and body fatness. Results support the hypothesis that mean energy expenditure per kg of body weight is significantly correlated with physical working capacity expressed per kg of body weight (r = 0.31; p less than 0.01). Mean energy expenditure per kg of body weight is negatively related to body fat (-0.08 less than or equal to r less than or equal to -0.13). It is concluded that the 3-day activity record is a procedure suitable to estimate energy expenditure in population studies.