European Journal of Applied Physiology and Occupational Physiology

French Antarctic territories harbor bases that are devoted to scientific and technical work. Living and working conditions during 1-year sojourns in such an environment are quite acceptable, but the confinement and the drop in ultraviolet B radiation exposure during winter months raise the problem of preservation of normal vitamin D status. Seasonal variations in 25-hydroxyvitamin D [25(OH)D] levels have been well documented, but the effect of sunshine deprivation on 1,25 dihydroxyvitamin D [1,25(OH)2D] levels is quite controversial. The aim of this study was to address this question under the exceptional conditions of lack of sunshine exposure. Fifteen male Caucasian subjects participating in a 1-year mission in Antarctica were investigated. They were subjected to seven blood samplings, one before and six during their sojourn. Serum levels of 25(OH)D, 1,25(OH)2D, osteocalcin, and ICTP were measured. We found that levels of 25(OH)D and 1,25(OH)2D significantly decreased in these subjects during the mission, minimum levels being observed 10 months after their departure from France. ICTP concentrations did not change throughout this study, but osteocalcin levels were found to be higher at the end of the sojourn than before departure, which could argue for the existence of bone remodeling changes. Further studies are now needed to fully investigate bone metabolism changes and to address the question of vitamin D supplementation during this kind of sojourn.

Thirteen conditioned athletes were studied before and 5 min after running 10,000 m. This distance was run in an average of 414 min. All runners lost weight and accompanying this weight loss was an increase in the serum osmolality in the six runners in which it was measured. There was a significant increase in serum glucose (9611 mg-% before run; 17048 mg-% after run) and this increase was inversely correlated with running time. There was also a small, but significant, increase in serum insulin (152 U/ml before run; 194 U/ml after run). There was no consistent effect of running 10,000 m on serum cholesterol and triglyceride levels and on plasma lipoprotein electrophoresis patterns.

The influence was examined of ultra-long-distance running (1000 km race lasting 20 days) on changes in serum lipids. The 110 participants received two types of diet, a conventional Western diet and a wholesome vegetarian diet. Of the 55 finishers the serum concentration of total cholesterol, low density lipoprotein (LDL)-cholesterol, apolipoprotein B and triglycerides decreased significantly during the first 8 days of the run, but rose again towards the end of the race without reaching pre-race levels. The high density lipoprotein (HDL)-cholesterol increased initially but decreased in the final days of the run. The values for apolipoprotein A-I were not correlated with HDL-cholesterol. The free fatty acids and free glycerol showed marked increases (five times the prerace concentration), falling towards the end of the run. Changes in serum lipids showed no correlation with changes in body mass. Similar changes were observed in both dietary groups.

Hyperbaric oxygen at pressures of 300 to 500 kPa has been shown to induce changed distribution of cerebral blood flow (QCBF) in rats, in places reducing the supply of the supplementary O2. Thus, in the present study, the effect of hyperoxia at 101 (group 1, n = 9) and 150 (group 2, n = 9) kPa O2 on cerebral blood flow distribution and central haemodynamics was tested in conscious, habituated rats. During the control period the systolic arterial pressure (BPs), heart rate (fc), breathing frequency (fb), cardiac output (Qc), arterial acid-base chemistry and glucose, as well as QCBF distribution (rQCBF) were similar in the two groups of animals. During O2 exposure, the acid-base chemistry remained unchanged. The haemoglobin decreased in group 2, but remained unchanged in group 1. The fc decreased rapidly in both groups during the change in gas composition, after which fc remained constant both in group 1 and in group 2, for whom pressure was increased. The Qc and fb decreased and BPs increased similarly in the two groups. Total QCBF and rQCBF decreased to the same extent in both groups, and the rQCBF changes were equally scattered. In group 1, breathing of pure O2 did not increase the O2 supply to any cerebral region except to the thalamus and colliculi after 60 min, whereas the O2 supply to the hypothalamus decreased and remained low. In group 2, the O2 supply was unchanged compared to the control period in all regions. These findings agree with previous observations during exposures to higher O2 pressures. In air after O2 exposure the acid-base chemistry remained normal. The fc and fb increased to higher levels than during the control period. The BPs remained high. The brain blood flows were increased, inducing elevated O2 supply to several brain regions compared to the control period. In conclusion, O2 supply to the central nervous system was found to be in the main unchanged during breathing of O2 at 101 kPa and 150 kPa.

The ventilatory equivalent for CO2 defines ventilatory efficiency largely independent of metabolism. An impairment of ventilatory efficiency may be caused by an increase in either anatomical or physiological dead space, the latter being the most important mechanism in the hyperpnoea of heart failure, pulmonary embolism, pulmonary hypertension and the former in restrictive lung disease. However, normal values for ventilatory efficiency have not yet been established. We investigated 101 (56 men) healthy volunteers, aged 16–75 years, measuring ventilation and gas exchange at rest (n = 64) and on exercise (modified Naughton protocol, n = 101). Age and sex dependent normal values for ventilatory efficiency at rest defined as the ratio ventilation:carbon dioxide output (V˙ E:V˙CO2), exercise ventilatory efficiency during exercise, defined as the slope of the linear relationship between ventilation and carbon dioxide output (V˙ E vs V˙CO2 slope), oxygen uptake at the anaerobic threshold and at maximum (V˙O2AT,V˙O2max, respectively) and breathing reserve were established. Ventilatory efficiency at rest was largely independent of age, but was smaller in the men than in the women [V˙ E:V˙CO2 50.5 (SD 8.8) vs 57.6 (SD 12.6) P<0.05]. Ventilatory efficiency during exercise declined significantly with age and was smaller in the men than in the women (men: (V˙ E vs V˙CO2 slope = 0.13 × age + 19.9; women: V˙ E vs V˙CO2 slope = 0.12 × age + 24.4). The V˙O2AT and V˙O2max were 23 (SD 5) and 39 (SD 7) ml O2 · kg · min−1 in the men and 18 (SD 4) and 32 (SD 7) in the women, respectively, and declined significantly with age. The V˙O2AT was reached at 58 (SD 9)% V˙O2max. Breathing reserve at the end of exercise was 41% and was independent of sex and age. It was concluded from this study that ventilatory efficiency as well as peak oxygen uptake are age and sex dependent in adults.

This study examined the correlations between isokinetic muscle strength of knee and elbow flexors and extensors with vertebral and femoral bone mineral density in a population of 106 women between the ages of 44 and 87 years. The absolute value of muscle strength correlated significantly with bone mineral density; muscle strength of the upper limb appeared to be more closely correlated with bone mass, while muscle strength in the lower limb was more specific for femoral mineral bone density. The most important finding that these results demonstrated was a concomitant decline in muscle strength of the upper limb and bone mineral density between the 5th and 6th decades. In contrast, they also showed a decline in muscle strength of the lower limbs after the 6th decade, occurring before the decline in bone mineral density observed between the 7th and 8th decades. From these results it would appear that other studies are required to examine the relationship between the essentially hormonal role in postmenopausal decline in muscle strength and the decline in physical activity during the senile period. These elements are important because they must be taken into account in physical exercise programmes designed to prevent osteoporosis.

The predictability of maximal oxygen uptake was tested on 123 normal, healthy children (80 boys and 43 girls) aged 11-12 years. Submaximal and maximal heart rate and maximal oxygen uptake were measured. VO2 max was calculated using the Astrand and Ryhming nomogram. The calculated values for VO2 max (without correction for differences in maximal heart rate) were lower than when measured directly, the average differences being 26% in boys and 23% in girls. Accuracy of the calculated maximal oxygen uptake can be increased by using the proposed regression equations: Girls Y = 1.299 +0.502 predicted VO, max (r = 0.82) 1/min, Boy Y - 1.444 + 0.522 predicted VO2 max (r = 0.52) l/min.

Nineteen boys were tested annually from age 11 to 15 years. Recovery O2 (or O2 debt in l and ml X kg-1) and blood lactate ([La], mmol X l-1) were measured following supramaximal treadmill tests (20% grade) designed to stress the anaerobic energy systems maximally. The purpose was to describe the rate of development of anaerobic capacity (AnC) from pre-puberty to adolescence. AnC improved from age 11 to 15 years, as indicated by a tripling of recovery O2 (l), 80% increase in recovery O2 per kg and 45% in [La]. Changes were similar from year to year with average yearly increments in recovery O2 of 0.8 l or 9 ml X kg-1 and in [La] of 0.9 mmol X l-1. Individual data also were plotted in relation to age of peak height velocity (PHV, 12.9 +/- 1.2 years). Changes in the measures of AnC were not significantly different when related to biological rather than chronological age. Development of AnC did not show a growth function curve and was not closely correlated with size, nor was the development of AnC enhanced immediately following maturation. Thus, in this longitudinal study, recovery O2 and [La] as measures of AnC showed large increases from age 11 to 15 years, but the gains were similar year to year rather than related to size growth, per se, or hormonal influences at maturation postulated to induce qualitative changes in glycolytic potential of muscle.

Heart rate (HR) was monitored in 66 French pubertal boys (B, n = 28) and girls (G, n = 38) aged 11-16 years to evaluate habitual physical activity (HPA) over a 1-week period in the winter. The HR and the percentage of heart rate reserve (%HRR) were taken to be indexes of the metabolic activity for the whole day and for the different parts of the day. The HPA was evaluated from the time spent each day below 50%HRR, between 50%-70%HRR and above 70%HRR, which related to the time spent in no or low physical activity (NLPA), moderate physical activity (MPA) and vigorous physical activity (VPA), respectively. No sex differences were observed in the average %HRR each day [%HRRmean, [B 30 (SD 4)%; G 32 (SD 4)%]] or in NLPA [B 715 (SD 61) min, G 711 (SD 81) min] and VPA [B 19 (SD 16) min, G 21 (SD 21) min] throughout the week. During school days, daily %HRRmean was 7% smaller in 14-16 year olds compared to 11-13 year olds. This was linked to a decrease in MPA and a concomitant increase in NLPA (P < 0.05). Daily %HRRmean varied significantly during the week (range: 28-34% HRR). There were significant differences among the periods of the day (P < 0.05). The HR was the greatest during physical education lessons [128 (SD 11) beats x min(-1)], recreation [113 (SD 15) beats x min(-1)] and lunch break [108 (SD 12) beats x min(-1)] and the lowest during the evening [94 (SD 10) beats x min(-1)]. It was only during the lunch breaks that %HRRmean was greater (P < 0.05) on school days than on free days. Of all the teenagers studied 32% were considered active during the week.

The purpose of the study was to investigate to what extent the physical activity pattern in adulthood can be predicted by physical characteristics, performance and activity in adolescence. A group of 62 men and 43 women completed a questionnaire concerning physical activity during their leisure time at the ages of 16 and 27 years. An activity index produced from the questionnaire. At the age of 16 years, the subjects were also tested for strength (strength test battery) and running performance (9-min run). Maximal oxygen uptake (VO2max) was estimated from a submaximal test and a muscle biopsy specimen was taken and analysed for fibre types (percentages of types I, IIA, IIB). The proportion of subjects engaged in some kind of physical activity during their leisure time was approximately 70% among the women and 80% among the men at both ages. The time spent on physical activity (minutes per week) decreased with age for the men but not for the women. The women devoted less time to physical activity than the men both at age 16 and 27 years. The attitude to endurance activities had changed to a more positive attitude among the women and to a less positive attitude among the men at age 27 years. The aerobic potential (VO2max and percentage of type I fibre), running performance, strength performance, physical activity and marks in physical education at age 16 years explained 82% of the physical activity level in adulthood for the women and 47% for the men.(ABSTRACT TRUNCATED AT 250 WORDS)

Ninety-six boys aged 11--13 years were tested at submaximal and maximal loads on a bicycle ergometer. Submaximal and maximal heart rates and maximal oxygen uptake were measured. A function predicting VO2max from age, height, and steady state heart rate at submaximal work load was developed using multiple regression analysis.

Under hyperbaric conditions (11 ata) obtained with normoxic O2-N2 mixtures spontaneous EMG activity disappears, as do reactions to noise, but this phenomenon is reversible after the substitution of Helium for Nitrogen in the mixture. Analysis of EMG responses to sciatic nerve excitation has revealed no difference between the EMG tracings recorded under normobaric pressure and those obtained under hyperbaric conditions (O2-N2 or O2-He, 11 ata), and hyperbaric conditions do not seem to interfere with neuro-muscular synaptic transmission. Furthermore, the effect of Pavulon (an antidepolarising, acetyl-cholino-competitive curare-mimetic drug) is similar under normal and hyperbaric conditions: hyperbaria changes neither the onset of neuro-muscular blockage nor its intensity or duration. The absence of a specific effect on synapse function of a change in the diluting gas from nitrogen to helium suggests that there was no change in post-synaptic receptor function. This result is not in accordance with the hypothesis that inert gas pressures of less than 10 ata modify molecular structures particularly at the neuro-muscular synapse level.

The relationships between \(\dot V_{O_2 } \) at rest, \(\dot V_{O_{2max} } \) and \(\dot V_{O_2 } \) during submaximal work on a treadmill with body weight, height and lean body mass assessed by densitometry were analyzed annually in 39 boys aged 11 to 18 years. Interindividual differences in \(\dot V_{O_2 } \) at rest and \(\dot V_{O_{2max} } \) during growth depended in the first place on interindividual differences in lean body mass, to a lesser extent on differences in body weight and least on differences in height. Intersubject differences in \(\dot V_{O_2 } \) during submaximal work were primarily conditioned by differences in body weight, due to the fact that, at a given running speed, energy output depends on body weight. The differences in submaximal \(\dot V_{O_2 } \) depended to a lesser extent on differences in lean body mass and least on differences in height. The relationships between \(\dot V_{O_2 } \) increments and increases in body dimensions were somewhat different in 90 boys between the ages of 11 and 15 years: \(\dot V_{O_{2max} } \) increments were determined primarily by changes in body weight and height, changes in lean body mass being of secondary importance. Increases in submaximal \(\dot V_{O_2 } \) were influenced decisively by increments in body weight, followed by increments in lean body mass and least by increments in height. In the equation y=a·x b expressing the relationship of \(\dot V_{O_{2max} } \) at the ages of 14 and 15 years were 0.87 and 0.88 in relation to body weight, 2.63 and 2.72 in relation to height. These values are significantly higher than the theoretical values of 0.67 for body weight and 2.00 for height. Similar significant differences from these theoretical values were found for all values between the ages of 11 and 15 years.

Twenty-three girls and 19 boys performed the handgrip and standing long jump (SLJ) tests. Their total forearm and leg volumes were calculated from circumference and length measurements and the lean volumes (bone + muscle) were calculated by making allowance for skinfold thickness. Although the boys were older than the girls (12.8 and 12.4 years), there was no significant difference in their heights or body masses. The absolute performances of the boys were superior to those of the girls in both tests (handgrip 234 and 205 N and SLJ 1.53 and 1.34 m), but when jumping performance was expressed as distance x body mass, there was no significant difference. In both tests, performance in terms of unit lean limb volume showed no significant gender difference. When performance was related to lean limb volume, both boys and girls showed a linear relationship in the two tests, with no significant difference between them. This absence of a gender difference contrasts with the results of a previous study on young adults and comparison shows that the relationships between lean limb volume and performance in the two tests for both boys and girls lie just below those of the young, adult females. The difference between the girls and the young adult females was just significant in the handgrip (p less than 0.05), but not significant in the SLJ (p greater than 0.25), whereas the differences between the boys and young adult males were significant (p less than 0.01) in both tests. Thus it would appear that a gender difference in the performance of skeletal muscle develops during adolescence and possible contributory factors are discussed.

The aim of the present study was to compare the influence of drinking water, a carbohydrate-electrolyte solution, containing additional free glucose (Glucose) or the same carbohydrate-electrolyte solution containing additional fructose (Fructose), on running performance. Twelve endurance-trained recreational runners volunteered to take part in this study; 9 completed the three and all 12 completed two trials. The subjects were randomly assigned to one of the three trials: Water, Glucose or Fructose. In each trial the subjects were required to run 30 km as fast as possible on a motorized treadmill, instrumented so that they could control its speed. The carbohydrate-electrolyte solutions contained a total of 50 g carbohydrate, 20 g as a glucose polymer. The Glucose solution contained an additional 20 g free glucose and the Fructose solution contained an additional 20 g fructose rather than glucose. The osmolality of the Glucose and Fructose solutions was approximately 300-320 mosmol and the energy equivalent of both solutions was 794 kJ.l-1. The subjects ingested 1 l fluid throughout each run. The running times were not significantly different, being 129.3 (+/- 17.7) min, 124.8 (+/- 14.9) min and 125.9 (+/- 17.9) min for Water, Glucose and Fructose respectively. There was a decrease (P less than 0.05) in running speed over the last 10 km of the Water trial from 4.14 (+/- 0.55) to 3.75 (+/- 0.86) m.s-1, which did not occur in the carbohydrate trials. Blood glucose concentrations during the Water trial decreased from 15 km onwards and at the end of the run they were significantly (P less than 0.05) lower than the value recorded at 15 km.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of a 120-day 6° head-down tilt (HDT) bed rest with and without countermeasures on the mechanical properties of the human triceps surae muscle was studied in eight healthy young women subjects. One group [n = 4, mean age 31.5 (SEM 1.7) years] underwent a 120-day HDT only and a second group [n = 4; mean age 28.0 (SEM 1.1) years] underwent HDT with countermeasures (physical training). The results showed that the contractile properties of the skeletal muscle studied changed considerably. After HDT without countermeasures the maximal voluntary contraction (MVC) had decreased by 36% (P < 0.05), and the electrically evoked tetanic tension at 150 Hz (P o) and isometric twitch contraction (P t) had decreased by 24% (P < 0.02) and 12% (P < 0.05), respectively. Time- to-peak tension (TPT) of the twitch had significantly increased by 14% (P<0.05), but half-relaxation time (1/2RT), and total contraction time (TCT) had decreased by 19% (P<0.05) and 18% (P<0.05), respectively. The difference between P o and MVC expressed as a percentage of P o and referred to as force deficiency (FD), was also calculated. The FD had increased by 40% (P<0.001). The rate of increase of voluntary contractions calculated according to a relative scale had significantly reduced, but for the electrically evoked contraction no substantial changes were observed. After HDT with countermeasures TPT, 1/2RT and TCT of the twitch had decreased by 4%, 7%, 19%, respectively in relation to the control condition. Training had caused a decrease of 3% (P>0.05) in MVC, and P t, and in P o of 14%, and of 9% (P>0.05), respectively. The FD had decreased significantly by 10% (P<0.02). The rate of increase of electrically evoked tetanic tension did not change significantly during HDT with countermeasures but the rate of increase in isometric voluntary tension development was increased. Physical training provided a reserve of neuromuscular function, which attenuated the effect of bed rest. The experimental findings indicated that neural as well as muscle adaptation occurred in response to HDT with countermeasures.

The aim of this study was to determine the relative exercise intensity (oxygen uptake during the march/maximal oxygen uptake, V˙O2 march/V˙O2max ) during a long-distance march in subjects or over 70 years of age. Secondly, the effect of hypertension, cardiovascular and pulmonary diseases on the relative exercise intensity was evaluated. One hundred and fifty-three subjects, 97 men aged 76.7 (4.6) years and 56 women aged 72.8 (3.6) years who completed the 1993 Nijmegen–day long-distance march (30 km · day−1 on 4 consecutive days) participated in the study. Oxygen uptake (V˙O2) during walking at different velocities () was measured in a subgroup of nine men and nine women, selected randomly from the population under study. With these data, regression equations describing the relationship between V˙O2 and \(\) were made. V˙O2 march was estimated with the obtained regression equations from an average of the march measured in all participants. V˙O2max was determined using incremental cycle ergometry in all subjects. V˙O2 march was 13.7 (1.8) ml · kg−1 · min−1 in men and 15.2 (1.3) ml · kg · min−1 in women at a mean \(\) of 5 km · h−1 in both sexes. This corresponded to 52% of V˙O2max in men and 63% in women. In both sexes subjects with cardiovascular and/or pulmonary diseases walked at a slower \(\) and thus lower V˙O2 march compared to subjects without these diseases. Due to the lower V˙O2max in subjects with these diseases there was no difference in the relative exercise intensity between the groups. A multiple linear regression analysis showed that and not age on the prevalence of hypertension, cardiovascular and/or pulmonary that V˙O2max was the most important predictor of the variance in self-selected march. This study demonstrates that these active people aged over 70 years could maintain a high relative exercise intensity during endurance walking on 4 subsequent days. Furthermore, it shows that the relative exercise intensity of marching is within the range recommended for improving fitness and reducing the risk of cardiovascular diseases. Finally, these results demonstrate that V˙O2max has a more important influence on performance than does age or chronic diseases in active elderly people.

The purpose of this study was to investigate the force-producing characteristics of boys aged 13 years in relation to fatigue of elbow flexor muscles. Maximal voluntary force in elbow flexion was measured before and after a muscle endurance test (MET) by using an isokinetic dynamometer isometrically, concentrically and eccentrically at three velocities, i.e. 0.21, 0.52, and 1.05 rad.s-1. The MET consisted of maximal concentric and eccentric muscle actions performed alternately at 0.52 rad.s-1 for 50 consecutive trials. Muscle cross-sectional area (CSA) of elbow flexor muscles (biceps brachii and brachialis) was measured by a B-mode ultrasound apparatus. Although eccentric force showed significantly higher values than concentric force during MET, there was no significant difference in the rate of decline in force between the two actions. There was no significant difference in the rate of decline in force after MET for each velocity and muscle action. Isometric, concentric and eccentric force before MET was significantly related to muscle CSA whereas, after MET, concentric force significantly correlated with muscle CSA but there was no significant correlation between muscle CSA and isometric or eccentric force. From our study, it is therefore suggested that in development to maturity, isometric, concentric and eccentric force decrease at the same rate with advancing muscle fatigue; however, there might be differences among muscle actions in factors affecting force development.

Maximal oxygen uptake was assessed in 101 randomly selected 8 and 13 year old children. In both age groups a significantly higher aerobic capacity was found in boys than in girls, both in absolute terms and when maximal oxygen uptake was related to body weight, lean body mass and lean leg volume. Among girls, maximal oxygen uptake per kg body weight was lower in the older than in the younger (p less than 0.05). Estimation of spontaneous physical activity, by means of a questionnaire and the actometry method, indicated that physical activity was greater in children with a high than in those with a low aerobic capacity.

Isometric muscle strength of the hand-grip and of trunk flexion and extension, and isokinetic torque of elbow and knee flexion and knee extension were assessed in a random sample of 8 and 13 year old Swedish children. The results were compared with respect to sex and age in absolute terms and relative to weight, height2 and estimates of lean body mass and cross-sectional muscle area. Daily physical activity was also estimated. The muscle strength variables were in general found to be very similar in the 8 year old boys and girls. In the 13 year old group the boys were generally stronger than the girls, in both absolute and relative terms, except for similar torque values during knee extension. The absolute and relative muscle strength and torque values were higher in the older than in the younger children, with the exception of trunk strength per unit of body weight and of lean body mass, which were similar in boys of both ages and significantly lower in the older than in the younger girls. No significant correlation was found between the estimates of physical activity and isometric and isokinetic muscle strength and torque.

The effects of exercise on gastric emptying remain controversial, with some workers reporting that heavy exercise inhibits it to varying degrees whereas others report no effects up to an intensity of 70% maximal oxygen consumption (VO2max). The state of hydration of the subjects and the environmental conditions may influence the rate of gastric emptying during exercise. To understand further the effects of a 3-h, 16-km walk/run carrying 30 kg of equipment under field conditions at 39 degrees C, we estimated gastric emptying using a [13C]acetate breath test method. Breath samples were collected at intervals after giving 150 mg of [13C]acetate. The effects of giving a standard volume (530 ml) of water or dextrose (7.5 g x 100 ml(-1)) with electrolytes or fructose/corn solids (7.5 g 100 ml(-1)) at rest before exercise were compared with those of exercise and of recovery after exercise with or without extra fluids (400 ml each 20 min). At rest, after a standard 530-ml load, gastric emptying times [mean (SE)] were: 37 (2) min (water), 46 (3) min (dextrose/electrolytes) and 47 (5) min (fructose/corn solids) and were significantly slower (P < 0.05) than those occurring after extra fluid ingestion, i.e. 32 (3), 39 (2) and 41 (3) min respectively. After a standard 530-ml load, emptying times during exercise were almost identical to those at rest but, during exercise, extra fluid speeded up gastric emptying more than at rest to 24 (2), 26 (1) and 27 (5) min (P < 0.05) respectively. During resting recovery without extra fluids, gastric emptying was significantly slowed to 60 (2), 71 (5) and 78 (3) min, respectively. Although emptying times during recovery from exercise with extra fluid were faster [49 (6), 55 (2) and 58 (4) min, respectively], they were still slower than before exercise. The results suggest that: (1) extra fluid increases gastric emptying more during exercise than at rest, and (2) gastric emptying during resting recovery from exercise is slower than at rest before exercise whether or not fluid has previously been taken.

The aim of this study was to investigate heart rate threshold (HRT) related exercise intensities by means of two endurance cycle ergometer tests using blood lactate concentration [La], pulmonary ventilation (VE), oxygen uptake (VO2), heart rate (HR) and electromyogram (EMG) activity of working muscle. Firstly, 16 healthy female students [age, 21.4 (SD 2.8) years; height, 167.1 (SD 5.1) cm; body mass 62.7 (SD 7.1) kg] performed an incremental exercise test (10 W each minute) on an electrically braked cycle ergometer until they felt exhausted. The HRT and lactate turn point (LTP) were assessed by means of computer-aided linear regression break point analysis from the relationship of HR or [La] to power output. No significant difference was found between HRT and LTP for all the variables measured. Secondly, two endurance tests (ET) of 20 min duration were performed by 7 subjects. The first (ET I) was performed at an exercise intensity which was about 10% lower than the power output at HRT [61.2 (SD 3.1)% maximal oxygen uptake (VO2max)], the second (ET II) at an exercise intensity about 10% higher than the power output at HRT [79.2 (SD 3.4) % VO2max]. The parameters measured showed a clear steady state in ET I. All mean values were lower than values at HRT [power, 138.7 (SD 18.9) W; HR, 172.1 (SD 4.7) beats.min-1; VO2, 2.2 (SD 0.3) l.min-1; VE, 54.0 (SD 9.1) l.min-1; [La], 3.7 (SD 1.1) mmol.l-1; EMG, 81.1 (SD 24.0) microV] except HR which was the same.(ABSTRACT TRUNCATED AT 250 WORDS)

The purpose of this study was to test the hypothesis that the well-documented changes in background 13C enrichment of expired CO2 observed in response to exercise and carbohydrate ingestion, in subjects living on a North American diet, are not present in subjects living on a Western European diet. The experimental protocol used by Pirnay et al. in 1977 and by Krzentowski et al. in 1984 in subjects living on a Western European diet (4 h of exercise on a treadmill at approximately 50% VO2max with ingestion of 100 g of glucose in 400 ml of water) was duplicated as closely as possible in six subjects living on a North American diet. The actual amounts of exogenous glucose oxidized, computed with a high artificial 13C enrichment of glucose (+189.7/1000 delta 13C PDB-1) which allows one to neglect the 1-2/1000 delta changes in 13C background, were [mean (SEM)] 54.7 (5.4) and 84.2 (3.4) g over 2 h and 4 h of exercise, respectively. These values compare well with data computed by Pirnay et al. [56.6 (13.1) and 94.9 (4.2) g] and by Krzentowski et al. [55.0 (6.2) and 88.0 (4.5) g] using a natural enrichment of glucose (-11.21 and -10.63/1000 delta 13C PDB-1, respectively) assuming no change in 13C background in their Western European subjects. Under the same assumption and using a natural enrichment of glucose (-11.30/1000 delta 13C PDB-1) the oxidation of exogenous glucose was overestimated by 30-40% in our North American subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

In an attempt to measure gastric emptying of carbohydrate solutions after exercise, we used the 13C acetate breath test to differentiate the gastric emptying of three approximately isoenergetic carbohydrate solutions (i.e. glucose, glucose polymer and sucrose) from each other and from water. On four separate occasions, six post-absorptive subjects walked on an inclined treadmill at 70% maximum oxygen uptake for 1 h and were then given 330 ml of one of the solutions in which 150 mg of sodium 1-[13C] acetate had been dissolved. Breath samples were collected at regular (2-30 min) intervals over the next 3.5 h for analysis of expired 13CO2 by isotope ratio mass spectrometry. When water was given, all subjects reached peak breath enrichment after 30 min, and had a mean (SE) gastric emptying time of 33.2 (1.6) min. Peak breath enrichment occurred later for sucrose and glucose polymer at 54.3 (3.1) min and 59.0 (2.1) min respectively (P < 0.01), and for glucose this was even later, at 62.3 (1.0) min (P < 0.05). Calculated gastric emptying times for sucrose and glucose polymer were almost identical [66.5 (2.5) and 69.8 (2.9) min respectively], whereas that for glucose was significantly slower [76.8 (3.2) min; P < 0.02], probably reflecting the effects of increased osmolality. The gastric emptying of all carbohydrates were significantly longer than for water (P < 0.01). These results show that in the post-exercise state the 13C acetate breath test can be used to differentiate the gastric emptying rates of water and carbohydrate solutions of different properties.

In 13CO2 breath tests, based on 13C:12C ratio measurements, the appearance of 13C in exhaled CO2 was monitored after the administration of a 13C-labelled compound. Independently of the substrate used, the existence of a bicarbonate pool into which the CO2 produced enters before being exhaled, imposes a delay on the appearance of changes in the 13C:12C ratio. To estimate the nature and magnitude of this delay, we applied a two-compartment model to describe the kinetics of the body bicarbonate pool and we evaluated the 13C:12C ratio of CO2 entering that pool from the measured 13C:12C ratio in the exhaled CO2 after an oral intake of "naturally labelled" 13C-glucose. Our results demonstrated that discrepancies between total and exogenous glucose oxidation in relation to the peak occurrence time, as well as the absolute quantities, could be adequately explained by the interference of the bicarbonate stores.

White high school girls (n = 120) and boys (n = 120) aged 14–17 years, selected from 9th, 10th, 11th and 12 grades of a northern, midwest U.S. high school performed running exercise on a motor driven treadmill for determinations of maximal O2 uptake (\(\dot V\)O2 max). The mean \(\dot V\)O2 max for all age groups was 40.8±4.0 and 54.7±5.6 ml/kg·min−1 for girls and boys respectively. The difference in \(\dot V\)O2 max across age groups varied only from 40.2–41.2 ml/kg·min−1 for girls and 54.0–56.3 ml/kg·min−1 for boys. These differences were not significant (P>0.05). The reported \(\dot V\)O2 max data are compared with those reported in other studies for bicycle ergometer and treadmill exercise using similar age groups.

The isokinetic forces, during 50 repeated maximal knee extensions with a constant velocity of 3.14 rad · s−1, and muscle cross-sectional area (CSA) of the quadriceps femoris muscles were measured for boys aged 14 years (n = 26) and young adult men (n = 26). As representative scores in the maximal session, the mean values of force (\(\bar F\)) of every five consecutive and all trials were calculated. The CSA was measured by using a B-mode ultrasound technique at the midpoint of the thigh length (l t). The average values of\(\bar F\) at the 1st–5th contractions were 193 (SEM 12) N for the boys and 303 (SEM 13) N for the young adults. The average decline of\(\bar F\) with 50 contractions, expressed as a percentage of the value in the 1st–5th trial, was higher in the young adults than in the boys:\(\bar F\) for the young adults was reduced by 48 (SEM 2.9)%, for the boys by 36 (SEM 3.1)%. The\(\bar F\) of every five consecutive and all trials were significantly correlated to the product of CSA andl t (CSA ·l t) in separate groups: for the boysr = 0.762–0.894 (P < 0.01), for the young adultsr = 0.598–0.837 (P < 0.01). In a trial range between the 1st–5th and 11th–15th contractions, the young adults showed significantly higher values in the ratio of\(\bar F\) to CSA ·l t (\(\bar F\) · CSA−1 ·l t) than the boys. However, the difference between groups of the ratio on and after the 16th–20th trial and for all trials became insignificant. Thus, at least for 50 maximal repeated knee extensions, the 14-year-old boys were inferior to the young adults in their ability to produce force during the earlier sessions even when the difference in muscle size was allowed for. The inferiority in the boys might be attributed to a lower reliance on glycolysis as pointed out in previous biochemical studies.

To examine the effects of exhaustive swimming in normal and myopathic hamsters on muscle mitochondrial Ca2+ metabolism, sedentary normal and BIO 14.6 dystrophic Syrian hamsters swam individually in 35 degree C water until exhaustion occurred. Although the normal hamsters swam three times longer than did the BIO 14.6 hamsters, both swimming groups had a comparable two-fold increase in blood lactate. Contrary to exhaustive running, exhaustive swimming did not significantly affect mitochondrial Ca2+ uptake in either cardiac or skeletal muscle, regardless of the disease state. However, in general, the coefficients of variation for mitochondrial Ca2+ metabolism increased as a function of exercise, with the BIO 14.6 swimmers more variable than the normal swimmers. This suggests that the mitochondrial Ca2+ uptake process may be affected in some manner by exhaustive swimming, so that deviations from the norm are more apparent. The results provide further evidence that mitochondrial Ca2+ metabolism adapts to the specific type of exercise utilized to produce exhaustion.

The effects of growth and pubertal development on bio-energetic characteristics were studied in boys aged 6-15 years (n = 144; transverse study). Maximal oxygen consumption (VO2max, direct method), mechanical power at VO2max (PVO2max), maximal anaerobic power (Pmax; force-velocity test), mean power in 30-s sprint (P30s; Wingate test) were evaluated and the ratios between Pmax, P30s and PVO2max were calculated. Sexual maturation was determined using salivary testosterone as an objective indicator. Normalized for body mass VO2max remained constant from 6 to 15 years (49 ml.min-1.kg-1, SD 6), whilst Pmax and P30s increased from 6-8 to 14-15 years, from 6.2 W.kg-1, SD 1.1 to 10.8 W.kg-1, SD 1.4 and from 4.7 W.kg-1, SD 1.0 to 7.6 W.kg-1, SD 1.0, respectively, (P less than 0.001). The ratio Pmax:PVO2max was 1.7 SD 3.0 at 6-8 years and reached 2.8 SD 0.5 at 14-15 years and the ratio P30s:PVO2max changed similarly from 1.3 SD 0.3 to 1.9 SD 0.3. In contrast, the ratio Pmax:P30s remained unchanged (1.4 SD 0.2). Significant relationships (P less than 0.001) were observed between Pmax (W.kg-1), P30s (W.kg-1), blood lactate concentrations after the Wingate test, and age, height, mass and salivary testosterone concentration. This indicates that growth and maturation have together an important role in the development of anaerobic metabolism.

There are no studies on oxygen uptake of groups of physically active subjects aged over 70. This study describes the maximal oxygen uptake (VO2max) of 153 elderly people who completed the Nijmegen annual 4-day march (at least 30 km.day-1) in 1993. A total of 97 men with a mean age of 76.7 (SD 4.6) and 56 women with a mean age of 72.8 (SD 3.6) years participated in the study. The VO2max was determined using incremental cycle ergometry; 91 men and 49 women completed a maximal exercise test. Criteria for maximal performance were respiratory exchange ratio equal to or greater than 1.00, vertilatory equivalent for oxygen equal to or greater than 30.00 and maximal heart rate equal to or greater than (beats.min-1) 210 minus age (years). Mean maximal power output was 148.2 (SD 27.2) W and 120.4 (SD 20.5) W, mean VO2max.body mass-1 was 26.8 (SD 4.9) ml.kg-1.min-1 and 24.6 (SD 4.7) ml.kg-1.min-1, mean maximal heart rate was 152 (SD 18), and 157 (SD 14) beats.min-1 in men and women respectively. The mean VO2max.body mass-1 was about 20% higher than reported in other studies on subjects over 70 years of age. Mean maximal heart rate was about 10 beats.min-1 higher than predicted from the equation 220-age. The negative effect of chronic disease on VO2max.body mass-1 was smaller than in a sedentary reference population. The mean decline in VO2max.body mass-1 with age was 0.46 and 0.38 ml.kg-1.min-1 per year in the men and women respectively, which is the same rate as found in younger subjects. It was concluded that regular exercise might substantially increase aerobic power in the physically active elderly, even when they have chronic disease, and that it is unlikely that there is an accelerated loss of aerobic power in physically active elderly people aged over 70 year.

A random sample of schoolchildren, 119 boys and 153 girls, was tested in the fall of 1983. The data presented here are anthropometric data (height, weight, fat % and vital capacity) and oxygen uptake directly measured on a bicycle ergometer. The mean height and weight for boys were 179.1 cm and 67.7 kg, and those for girls were 168.0 cm and 59.6 kg. The mean fat content was 9.1% for boys and 19.1% for girls, and their mean vital capacities were 4.91 and 3.61 respectively. The boys had a high maximal oxygen uptake (51.7 ml X kg-1 X min-1) showing no reduction over the age span studied. The girls' maximal oxygen uptake was lower (overall mean 40.0 ml X kg-1 X min-1) with a small reduction from 16 to 19 years of age. When comparing maximal oxygen uptake per kg lean body mass in the two sexes, the boys had 18.4% higher values than the girls, indicating that girls of this age have the lower fitness level. The results of maximal aerobic power measurement in the boys compare well with findings from other investigations using direct measurements, indicating that the fitness of teenage boys is kept at a high level. Comparable data from various countries for girls show different pictures, but it appears that in general they have a low fitness level.

The force in maximal voluntary isometric contraction of elbow flexors, knee extensors, trunk flexors, and trunk extensors was measured in a representative sample of Danish school children 16-19 years of age (128 boys and 165 girls). The 16 year old boys were 177.8 cm in height, with a mean increase of 1.4 cm per year up to 19 years, and they weighed 66.0 kg, with a mean increase of 1.8 kg per year up to age 19. The girls were 168.0 cm in height with no increase up to age 19, and their mean weight was 59.6 kg, which increased by 1.8 kg per year up to age 19 (p greater than 0.05). The strength in the four muscle groups for boys a girls respectively was 281 N and 182 N for elbow flexors, 574 N and 419 N for knee extensors, 601 N and 404 N for trunk flexors and 664 N and 499 N for trunk extensors. An increase in strength in the elbow and trunk flexors and a decrease in strength in the trunk extensors in relation to values obtained in 1956 was seen, and a difference in strength per kg lean body mass between the boys and the girls was also observed. The estimated strength per unit cross-sectional area of muscle was 38 N X cm-2 in both boys and girls.

The peak oxygen uptake (VO2(peak)) of 196 healthy children and adolescents aged 8-16 years, and 187 children and adolescents (in the same age range) with congenital heart disease (CHD), was measured using a graded treadmill test (Oslo-protocol). The healthy population was tested to assess the reference values that were to be used in the interpretation of the results obtained from patients with CHD. The results revealed that patients with CHD exhibited lower VO2(peak) values, with declining values for boys after the age of 12-13 years. When separated into different diagnostic groups, on average, patients with a chronic pressure overload of the left ventricle and patients with tetralogy of Fallot have lower VO2(peak) values, but make approximately the same progress with age as healthy subjects. Patients with transposition of the great arteries, however, displayed a marked decline in VO2(peak) after the age of 12-13 years. Whether exercise testing should be included in routine follow-up in patients with CHD, especially those between the ages of 10 and 16 years, when the condition of some patients deteriorates, requires special attention.

Eight healthy male college students were selected and eight noise exposure conditions were planned. The noise exposure time of all the experiments was 14 h. Measurement of the TTS growth at 4 kHz was investigated during these 14 h. Saliva collected every 3 h was also examined for cortisol throughout the 24-h period. The exposure noises used in this experiment were pink noise and pure tone of 3 kHz. The time patterns of trapezoidal noise were as follows. The rise and decay times were 1 s respectively and the peak level was 1 s for the (A I type), being 500 ms and 1.5 s respectively for the (A II type). Three measurement were made: TTS Under intermittent noise exposure at 80 dB(A), exposure of 20% of the on fraction induced significant TTS growth, but exposure of 13% of the on fraction did not induce TTS growth. Under exposure at 75 dB(A), exposure of 66% of the on fraction did not induce TTS growth. Under pure tone exposure of 3 kHz at 75 dB(A), exposures of 20% and 30% of the on fraction did not induce TTS growth. There was a significant difference between the TTS induced by a steady state of 73 dB (A) (Leq of Exp. 2) and that of Exp. 2. Urinary 17-OHCS Level During the noise exposure period (14 h), there was a statistically significant difference between the urinary 17-OHCS level of the control condition and that of Exp. 3. In addition, there was no statistically significant difference among the urinary 17-OHCS levels of post-noise exposure. Saliva Cortisol With intermittent “pink noise” of 75 or 80 dB(A) (Exp. 2, 3, and 4), however, temporary elevation of the saliva cortisol level occurred only at the initial stage of exposure, and lasted for only one hour. Moreover, with steady state noise exposure, evanescent elevation occurred at the lower level of 71 dB(A).

A wet suit may not provide adequate thermal protection when diving in moderately cold water (17-18 degrees C), and any resultant mild hypothermia may impair performance during prolonged diving. We studied heat exchange during a dive to a depth of 5 m in sea water (17-18.5 degrees C) in divers wearing a full wet suit and using closed-circuit oxygen breathing apparatus. Eight fin swimmers dived for 3.1 h and six underwater scooter (UWS) divers propelled themselves through the water for 3.7 h. The measurements taken throughout the dive were the oxygen pressure in the cylinder and skin and rectal temperatures (Tre). Each subject also completed a cold score questionnaire. The Tre decreased continuously in all subjects. Oxygen consumption in the fin divers (1.40 l.min-1) was higher than that of the UWS divers (1.05 l.min-1). The mean total insulation was 0.087 degree C.m2.W-1 in both groups. Mean body insulation was 37% of the total insulation (suit insulation was 63%). The reduction in Tre over the 1st hour was related to subcutaneous fat thickness. There was a correlation between cold score and Tre at the end of 1 h, but not after that. A full wet suit does not appear to provide adequate thermal protection when diving in moderately cold water.

One hundred and thirty-five females were tested in order to: produce some normative percentage body fat (% BF) data on an Australian sample which represented a cross-section of physical activity patterns, cross-validate existing multiple regression equations which predict body density (BD) from anthropometric measurements, and if necessary develop population specific equations. Measurements were taken of 10 girths, 3 widths and 7 skinfolds. Body density was measured by underwater weighing with the residual volume (RV) being determined by helium dilution. The Siri equation was then used to convert BD to % BF. The % BF scores had an overall mean of 23.4 (range 10.8–49.2). The very active group (n=45) had a significantly lower (p<0.05) relative body fat (X=20.6% BF) than either the active (n=45; 23.5% BF) or sedentary groups (n=45; 26.2% BF). Previously published equations were found to have limited applicability to Australian subjects. A stepwise multiple regression was therefore used to develop the following equation (R = 0.893): BD(g·cm−3) = 1.16957-0.06447 (log10 ∑ triceps, subscapular, supraspinale, front thigh, abdominal and calf skinfolds in mm)-0.00081 (gluteal girth in cm)+ 0.0017 (forearm girth in cm) + 0.00606 (biepicondylar humerus breadth in cm). Only those predictors which resulted in a statistically significant increase inr (p⩽0.05) were included. The standard error of estimate of 0.00568 g · cm−3 was equivalent to 2.6% BF at the mean.

The relationships between physical working capacity (PWC), level of habitual activity, relative leanness-fatness, isometric strength and motor ability have been examined in 85 17 and 18 year-old school boys. Level of habitual activity was found to be significantly related to PWC and to the strength and motor ability scores, whilst relative leanness-fatness was not significantly related to any of the other variables studied. Some of the apparent association between PWC and the strength and motor ability scores was due to a common dependence on body size, but the relationship between PWC and four performance variables remained significant when the influence of differences in size of the subjects was removed. It is suggested that differences in the level of habitual activity of post adolescent male school boys influence the physical working capacity but not relative leanness-fatness. The association between level of habitual activity and strength and motor ability scores suggests that the latter variables may possibly influence the level of habitual activity in this type of subject.

Dual energy x-ray absorptiometry (DEXA) offers the possibility of assessing regional soft tissue composition, i.e. lean mass (LM) and fat mass : LM may be considered a measure of muscle mass. We examined age-related differences in LM, percentage fat (%fat) and muscle strength in 100 healthy non-athletic women aged 18–87 years. Relationships between muscle strength and leg LM in 20 elite female weight lifters and in 18 inactive women with previous hip fractures were also studied. The LM and %fat of the whole body, trunk, arms and legs were derived from a whole body DEXA scan. Isokinetic knee extensor strength (KES) and flexor strength (KFS) at 30° · s–1 were assessed using an isokinetic dynamometer. The women aged 71–87 years had 35% lower KES and KFS than the women aged 18–40 years (P < 0.0001). Differences in LM were less pronounced. The LM of the legs, for instance, was 15% lower in the old than in the young women (P < 0.0001). In a multiple regression analysis with age, body mass, height and leg LM or KES as independent variables and KES or leg LM as the dependent variable, age was the most important predictor of KES (r partial = −0.74, P < 0.0001). The same applied to KFS. Body mass, not age, was the most important predictor of leg LM (r partial = 0.65, P < 0.0001) and of LM at all other measurement sites. The LM measured at different regions decreased equally with increasing age. The KES:leg LM ratio was negatively correlated with age (r = −0.70, P < 0.0001). The weight lifters had significantly higher KES:leg LM ratios than age-matched controls (+12%, P < 0.0001) and vice versa for the women with previous hip fractures (–36%, P < 0.0001). In conclusion, from our study it would seem that in healthy nonathletic women, age is a more important determinant of muscle strength than is LM as measured by DEXA. Muscle strengthening exercises and inactivity seem to have a considerably stronger influence on muscle strength than on LM.

Estimates of energy expenditure using both isotope-labelled (2H2(18)O) water and dietary intake/body composition changes were made during an attempt by two men (MS and RF) to walk to the North Pole. The isotope-labelled water technique gave mean estimates of daily energy expenditure for the 48-day expedition of 28.05 MJ (MS) and 32.38 MJ (RF), which compared with estimates of 25.66 MJ (MS) and 24.86 MJ (RF) from the intake/body composition measurements. Fluid retention and peripheral oedema probably caused a considerable underestimate of the losses in body energy stores when applying the energy balance method, whereas in the isotope method, uncertainty in the measurements of isotopic background led to minimum errors of -4.9% to +4.0% of the means for MS and -12.7% to +8.2% for RF (95% confidence limits).

Heart diameters, heart volume (HV), PWC 130, \(\dot V\)O2 at 130 heart rate, and cardiorespiratory reactions during work at 3 kgm·s−1 were obtained in 237 boys ranging in age from 8–18 years. Results indicate that heart size, PWC 130, \(\dot V\)O130, and exercise HR, \(\dot V\)O2/HR, \(\dot f\)and SBP change significantly with age. On the other hand, HV·kg−1 and work \(\dot V\)O2, \(\dot V\) E and \(\dot V\) E/\(\dot V\)O2 remain rather stable throughout the growth period. Correlation analysis indicates that about 85% of the observed variation in the size of the heart during growth can be accounted for by body weight, while about 70% of the variation in light submaximal working capacity (\(\dot V\)O130) can be explained by HV alone. Holding age, height and body weight constant by partial correlation procedures yields significant relationships between HV and \(\dot V\)O130 (r = 0.461), and between HV·kg−1 and \(\dot V\)O130 (r = 0.414). Age, height, weight and size of the heart correlated simultaneously against \(\dot V\)O130 account for 75% of the variance in the dependent variable. It would seem important to suggest the need for study of the interactions between age, size and maturity, in addition to indicators of size and efficiency of the oxygen delivery system, and indices of muscle oxygen utilization efficiency. Such an approach will permit a more definite partitioning of the variance in submaximal aerobic capacity during growth, and would probably yield a more conservative estimate of the relationship between the size of the heart and submaximal working capacity during growth.

Male Wistar rats were subjected to 12.5 days of weightlessness aboard Cosmos 1887. Histomorphometric and biochemical analyses were investigated in soleus (SOL), plantaris (PL) and extensor digitorum longus (EDL) muscles of flight rats (group F) and compared with data from two groups of terrestrial controls: one group living free in a vivarium (group V) and another subjected to a flight simulation except for the state of weightlessness (group S). Relative to groups V and S, no alteration in the percentage distribution of fibres had occurred in SOL, PL or EDL, after the flight. In SOL muscles from group F animals, cross-sectional areas of all fibre types were reduced to a greater extent (-40%) than capillary to fibre ratio (-24%) leading to a higher capillary density (+33%) than in V and S groups. In PL, type I, IIA and IIB fibre cross-sectional areas were less decreased (-25%). In EDL, only fast-twitch fibre cross-sectional areas showed an average decrease of 30%. Capillary per fibre ratio was reduced by 15% and 28% respectively in PT and EDL muscles from group F rats compared to control groups V and S. Citrate synthase and 3-hydroxyacyl-coenzyme A dehydrogenase activities remained unchanged in SOL, PL and EDL following spaceflight. These findings indicate greater atrophy and functional alterations (capillarity) compared to those observed after 7 days of microgravity on Cosmos 1667.

Two men, R.F. and M.S., pulled sledges each with starting masses of 222 kg, 2300 km across Antarctica. Exercise was performed for approximately 10 h each day for 95 days. Despite an average energy intake of 21.3 MJ · day−1 both subjects lost more than 25% of body weight. Energy expenditure was measured using energy balance data (EB) and isotope-labelled water (2H218O). Isotope doses were taken on day 0 and day 50 of the expedition. During the first 50 days both methods gave reasonable agreement, giving energy expenditures of 38.3 (EB) and 35.5 (2H218O) MJ · day−1 in R.F. and 28.6 (EB) and 29.1 (2H218O) MJ · day−1 in M.S. The isotope data for days 20–30 yielded exceptional values of 44.6 MJ · day−1 in R.F. and 48.7 MJ · day−1 in M.S. Estimates of energy expenditure between day 51 and day 96 were much lower and although the methods were in agreement for R.F. – 24.1 (EB) and 23.1 (2H218O) MJ · day−1, there was poor agreement for MS – 26.8 (EB) and 18.8 (2H218O) MJ · day−1. However, some practical difficulties occurred during this second period and there were also problems arising from marked increases in body water that made estimates of body mass and composition change difficult to interpret. The latter problems were probably due to malnutrition, which may have also been responsible for surprising increases in urinary excretion of 2H and 18O observed in both men at around day 81. These increases may reflect the release of label incorporated into molecules other than water which do not normally freely exchange with the body water pool under the circumstances of marked malnourishment. Following the expedition, both men showed declines in maximal O2 consumption (V˙O2max , 53.6 to 41.2 ml O2 kg−1 · min−1 in R.F., 58.1–46.0 ml O2 kg−1 · min−1 in M.S.); maximal voluntary isometric force production in different muscle groups (up to 19.9% in R.F. and 55.8% in M.S.) and both cytoplasmic and mitochondrial skeletal muscle enzyme activities (up to 56% in R.F. and 63% in M.S.). Plasma samples taken during the expedition showed low glucose levels, inappropriately high insulin levels, and declines in testosterone and luteinizing hormone. Thyroxine, cholesterol, albumin and triglyceride levels remained normal.

In order to study possible changes in Swedish men between the approximate ages of 19 and 30, 55 men from the Stockholm area were re-examined 11 years after examinations made in connection with compulsory military duty. The most pronounced finding was a 11% increase in body weight accompanied by a 19% increase in waist circumference and a 25–41% increase in skinfold thickness. A 5% increase in work output at heart rate 170 (W 170) was observed but the ratio W 170/weight decreased by 5%. The observed changes were even more pronounced in a subgroup who had a low exercise level in their spare time at the age of 19 as well as 30. Growth was not quite completed at the age of 19. Of the increase in height amounting to 1.3 cm, 70% was due to growth in tibial length.

Mean values and standard deviations of total body volume, body density, height, weight, and a battery of 20 girth measurements of 200 Punjabi girls aged 10–19 years are presented. Selective stepwise multiple regression equations for predicting total body volume and body density from girth measurements are also given for different age groups. Hip girth was the most commonly selected measurement at the first step in most age groups and the values of ‘r’ between hip girth and total body volume ranged between 0.86–0.96 in different age groups. The values of multiple ‘R’ between total body volume and a combination of first four selected girth measurements varied from 0.96–0.99 in different age groups. The values of multiple ‘R’ between body density and a combination of four girth measurements selected up to fourth step ranged between 0.73–0.92 in different age groups.

The purpose of this study was to determine if pace changes similar to those experienced in competition could affect the relative contribution of aerobic and anaerobic processes to overall energy utilization during running. In particular, does a fast start in the mile race increase the energy supplied aerobically during the first three-quarters of a mile such that the lactate formation is reduced prior to the usual rapid last quarter? Eight subjects (middle and long distance runners) ran three-quarters of a mile on a treadmill according to a fast-medium-very slow (F-M-S) and a slow-medium-slow pace. The two paces were performed in a random order and the total running times were equal. No significant differences were found between the two paces for oxygen uptake during the runs, for the 15-min recovery oxygen and for the post-exercise peak lactate values. Although several world class milers have employed a fast-medium-slow-fast pace, the present data concerning the relative contribution of different energy sources do not explain why this might be the best pacing technique.

The purpose of this study was to measure the VO2max of trained cyclists on the treadmill (means +/- SD = 54.7 +/- 6.3 ml kg-1 min-1), while riding a bicycle on a velodrome track at 100 rpm (53.7 +/- 7.8) and on the bicycle ergometer at 60 rpm (62.4 +/- 8.1): VO2max beeing the highest in the latter case (p less than 0.05). The highest maximal HR, 188 +/- 6 beats min-1, was observed during the treadmill test, while estimates of 184 +/- 6 and 179 +/- 7 were obtained for the velodrome and the bicycle ergometer tests, respectively. No significant differences were observed in the blood lactate concentrations (treadmill: 10.35 +/- 4.01 bicycle ergometer: 10.25 +/- 2.29 velodrome: 10.95 +/- 1.51 mmol L-1. In conclusion, bicycle ergometer tests might not be specific enough to evaluate the ability of trained cyclists to perform an endurance or aerobic task on the track. Trained cyclists, as opposed to untrained ones, appear to achieve higher VO2max on the bicycle ergometer as compared to the treadmill.

The heart rate/work performance (f c/W) curve is usually S-shaped but a flattening at the top is not always seen. By means of radionuclide ventricular scintigraphy, the left ventricular ejection fraction (LVEF) of 15 sports students was investigated. The behaviour of the f c/W curve during cycle ergometry with increasing exercise intensities was examined. During exercise, the LVEF showed a distinct initial increase reaching roughly constant values at stress levels below-maximum, and sometimes even falling again. The inflections of the f c/W curve and left ventricular ejection fraction/performance curve (LVEFPC) were calculated from a second degree polynomial fit. From this function, the slopes of the tangents at the points of aerobic threshold and maximum performance were calculated together with the differences of the angles as a measure of the f c/W curve and LVEFPC inflections. It follows that the f c/W curve inflection became less pronounced or was even absent altogether when the decrease in LVEF towards the end of the ergometer exercise became more distinct. A significant negative correlation was found between the existence and extent of the f c/W curve inflection and the stress-dependent myocardial function, expressed as the inflection of the LVEFPC (P<0.01, r=0.673). Thus, it would seem that the absence of a f c/W curve inflection was related to a diminished stress-dependent myocardial function.

Reports from the literature and our own data on red cell 2,3-DPG and its importance for unloading O2 from Hb to the tissues during exhaustive exercise are contradictory. We investigated red cell metabolism during incremental bicycle ergometry of various durations. Furthermore changes in blood composition occurring during exercise were simulated under in vitro conditions. The effect of a moderate (11.2 mmol X l-1 lactate, pH = 7.127) and severe (18 mmol X l-1 lactate, pH = 6.943) lactacidosis on red cell 2,3-DPG concentration was compared with the effect of similar acidosis induced by HCl. Our data indicate that the concentration of 2,3-DPG in red cells depends on the degree of lactacidosis, but not on the duration of exercise. During moderate lactacidosis red cell 2,3-DPG remains unchanged. This can be explained by an interruption of red cell glycolysis on the PK and GAP-DH step caused by a lactate and pyruvate influx into the erythrocyte, as well as an intraerythrocytic acidosis and a drop in the NAD/NADH ratio. During severe lactacidosis and HCL-induced acidosis a decrease in 2,3-DPG due to an inhibition of 2,3-DPGmutase and other glycolytic enzymes can be found. Mathematical correction of the observed P-50 value for the decrease in 2,3-DPG occurring during severe lactacidosis showed that a decrease in Hb-O2-affinity during strenuous exercise depends on the degree of lactacidosis and temperature elevation.

A statistically significant 10% increase (p less than 0.005) in mean red cell 2,3-diphosphoglycerate (2,3-DPG) concentration, concomitantly with a mean 16% increase (p less than 0.001) in the predicted maximal oxygen uptake (VO2max) was observed in 29 recruits, who were studied during 6 months of physical training in military service. The increase in 2,3-DPG was higher, the lower the initial 2,3-DPG and VO2max levels. The mean initial 2,3-DPG level was higher in the subjects with a higher initial VO2max. A strenuous but highly aerobic 21-km marching exercise elicited a mean 9% increase (p less than 0.005) in red cell 2,3-DPG concentration. A significantly greater response of 2,3-DPG to marching exercise was observed in subjects with a lower pre-test VO2max than in those with a higher pre-test VO2max. During another more competitive march 2,3-DPG remained almost unchanged and was associated with a tendency towards a negative correlation with the acccompanying lactate response (r = -0.60, p less than 0.05). Red cell 2,3-DPG response to a standardized exercise is considered to be a suitable indicator for evaluating the effect of training on an individual.