Aerobic work capacity of mentally retarded boys and girls in junior high schools.

The maximal oxygen uptake (Vo2 max) and ergometer load at a heart rate of 170 beats/min (PWC170) were determined in mentally retarded children (74 boys and 53 girls) of ages 12-15, whose IQ ranged from 36 to 91, and the results were compared with those for normal children. Mentally retarded boys and girls showed significantly inferior body height and weight, but no significant difference was found in skinfold thickness. The mean value of PWC170 for boys and girls was 14.34 kpm/kg/min and 11.31 kpm/kg/min, respectively, significantly less than that of the normal group. The mentally retarded boys had mean VO2 max per unit body weight of 42.4 ml/kg/min, which was significantly less than the 51.2 ml/kg/min of normal boys. The mentally retarded girls had a mean of 33.1 ml/kg/min which was also less than the 41.3 ml/kg/min of normal girls. The correlation coefficient between body weight and PWC170 (kpm/min) was 0.711 and 0.720 for boys and girls, respectively, while that between body weight and VO2 max (liter/min) was 0.641 for boys and 0.656 for girls. No significant correlation was found between IQ and PWC170 (kpm/kg/min) nor between IQ and VO2 max (ml/kg/min) both for boys and for girls. Similarly, no significant correlation was found between mental age and the VO2 max value (ml/kg/min).     

Effects of low calorie diet-induced weight loss on post-exercise heart rate recovery in obese men

[Purpose]

Heart Rate Recovery (HRR) after maximum exercise is a reactivation function of vagus nerve and an independent risk factor that predicts cardiovascular disease and mortality. Weight loss obtained through dietary programs has been employed as a therapy to reduce risks of cardiovascular disease and obesity.

[Methods]

Eighteen subjects of middle aged obese men (age 44.8 ± 1.6 yrs, BMI 29.7 ± 0.5 kg/m²) were selected for this study. As a weight loss direction, the nutritional direction of low-calorie diet mainly consisted of carbohydrate, protein, and fat has been conducted for 3 months. Blood pressure was measured after overnight fasting, and blood samples were collected from the antecubital vein before and after weight loss program. All the pre- and post-exercise ‘HRR decay constant’s were assessed by using values of HRR (heart recovery rate; 2 minutes) and HR measured after reached to the maximal oxygen uptake (VO₂max) exploited the bicycle ergometer.

[Results]

After the completion of weight loss program, body weight and BMI were significantly decreased, but the Heart Rate (HR) after maximum exercise and in steady state were not changed significantly (p > 0.05). The post-exercise HRR after the weight loss did not show significant changes in perspectives of 30 seconds (-16.6 ± 2.3 to -20.2 ± 2.1 beats/min, p > 0.05) and 60 seconds (-33.5 ± 3.4 to -34.6 ± 2.8 beats/min, p > 0.05) respectively but in perspectives of 90 seconds (-40.9 ± 2.6 to -48.1 ± 3.1 beats/min, p < 0.05) and 120 seconds (-48.6 ± 2.6 to -54.3 ± 3.5 beats/min, p < 0.05), they were decreased significantly. Pre-’HRR decay constant’s of 0.294 ± 0.02 %/second were significantly increased to post-values of 0.342 ± 0.03 %/second (p = 0.026). Changes in ‘HRR decay constant’ were significantly correlated with changes in blood glucose (r = -0.471, p < 0.05) and maximal oxygen consumption (VO₂max, r = 0.505, p < 0.05) respectively.

[Conclusions]

The low-calorie diet directed to obese middle aged men for 3 months significantly improved the HRR after maximum exercise, and this improvement in cardiovascular autonomic nerve system was estimated to be involved with improvements in blood glucose and maximal oxygen consumption.     

Effect of glucose polymer diet supplement on responses to prolonged successive swimming, cycling and running

Fifteen male endurance athletes were studied to determine the effect of a glucose polymer (GP) diet supplement on physiological and perceptual responses to successive swimming, cycling and running exercise. Thirty min of swimming, cycling and running at 70% VO2max, followed by a run to exhaustion at 90% VO2max was performed after one week of training under two dietary conditions: 1) GP (230 g of GP consumed daily) and 2) placebo (P, saccharin-sweetened supplement consumed daily). During GP, daily carbohydrate (CHO) intake was higher (p less than 0.05) by 173 g or 14% of energy intake than during P, but total energy intake was not significantly different. During 90 min of exercise, CHO utilization and blood glucose were significantly higher under GP than P by an average of 20.2% and 14.5%, respectively, but heart rate, ventilation, oxygen uptake, ratings of perceived exertion, and plasma lactate were not different. Run time to exhaustion at 90% VO2max was significantly longer by 1.2 min (23%) under GP. The results suggest that a GP diet supplement may be of value during endurance exercise by increasing the availability of CHO.     

Morning‐to‐Evening Differences in Oxygen Uptake Kinetics in Short‐Duration Cycling Exercise

This study analyzed diurnal variations in oxygen (O₂) uptake kinetics and efficiency during a moderate cycle ergometer exercise. Fourteen physically active diurnally active male subjects (age 23±5 yrs) not specifically trained at cycling first completed a test to determine their ventilatory threshold (T_vent) and maximal oxygen consumption (VO_2max); one week later, they completed four bouts of testing in the morning and evening in a random order, each separated by at least 24 h. For each period of the day (07:00–08:30 h and 19:00–20:30 h), subjects performed two bouts. Each bout was composed of a 5 min cycling exercise at 45 W, followed after 5 min rest by a 10 min cycling exercise at 80% of the power output associated with T_vent. Gas exchanges were analyzed breath‐by‐breath and fitted using a mono‐exponential function. During moderate exercise, the time constant and amplitude of VO₂ kinetics were significantly higher in the morning compared to the evening. The net efficiency increased from the morning to evening (17.3±4 vs. 20.5±2%; p<0.05), and the variability of cycling cadence was greater during the morning than evening (+34%; p<0.05). These findings suggest that VO₂ responses are affected by the time of day and could be related to variability in muscle activity pattern.     

Acute cardiorespiratory responses of hypertensive rats to swimming and treadmill exercise

The acute cardiorespiratory responses of spontaneously hypertensive rats (SHR) to swimming and running exercise was investigated because SHR populations are hyperresponsive to external stimuli, of the paucity of existing data, and of the uncertainty on the role of exercise stimuli for training adaptations to occur. Male rats were assigned to one of five groups (n = 5-6/group) and designated as controls (C), inexperienced or naive free swimmers (NFS), experienced free swimmers (FS), experienced weighted swimmers (WS) (attached weights equal to 2% of their body weight) or experienced runners (R) who ran at an intensity of 75% of their VO2max. After 75 min in the water, all groups were acidotic and hypercapnic with the WS experiencing the greatest changes. Heart rate (HR) was increased in all swimmers during the initial 10 min, but declined thereafter, and after 75 min, the HR of WS (348 +/- 1 beats/min) was significantly lower than the C group (416 +/- 22 beats/min). At the same time interval, mean arterial blood pressure (MAP) was decreased in all swimming groups to values lower than the C animals. In addition, an exaggerated diving reflex was frequently noted when the rats were submerged. When the magnitudes of the changes were evaluated in the swimming animals they were directly associated with their submergence times, i.e., during 65-75 min of the swim, NFS, FS, and WS were submerged for 43, 46, and 66% of their total swim time, respectively. In sharp contrast to the swimmers, the runners exhibited increases in HR and MAP with their blood gas measurements being indicative of hyperventilation. We concluded that swimming as an exercise mode for hypertensive rats is best served to study the combined effects of excitement, prolonged submergence, and the consequences of the diving reflex.     

中等强度有氧运动联合弹力带抗阻训练对稳定性冠心病患者血管内皮功能、心肺功能及运动耐力的影响

摘要 目的：探讨弹力带抗阻训练、中等强度有氧运动联合应用对稳定性冠心病患者心肺功能、血管内皮功能、运动耐力的影响。方法：选择2020年9月~2022年4月期间我院收治的稳定性冠心病患者70例,按照随机数字表法分为对照组（35例,中等强度有氧运动）和联合组（35例,对照组的基础上接受弹力带抗阻训练）。对比两组运动耐力、血管内皮功能指标[超声颈动脉内膜-中层厚度（IMT） 、内皮依赖性血管舒张功能（FMD）值、Crouse斑块积分]、心肺功能指标[左心室射血分数（LVEF）、心脏每搏输出量（SV）、最大摄氧量（VO₂max）和氧脉搏（O₂pulse）]、生活质量和心血管不良事件发生率。结果：干预后,两组6分钟步行试验（6MWT）升高,且联合组高于对照组（P<0.05）。干预后,两组LVEF、SV、VO₂max、O₂pulse升高,且联合组高于对照组（P<0.05）。干预后,两组生理/社会功能、躯体疼痛、生理/情感职能、精力、总体/精神健康各维度评分升高,且联合组高于对照组（P<0.05）。干预后,两组IMT缩小,FMD升高,Crouse斑块积分下降,且联合组的变化程度大于对照组（P<0.05）。两组心血管不良事件发生率对比无差异（P>0.05）。结论：稳定性冠心病患者采用弹力带抗阻训练和中等强度有氧运动联合干预可改善心肺功能和血管内皮功能,提高运动耐力及生活质量,具有较好的临床应用价值。     

Effects of one bout of endurance exercise on the expression of myogenin in human quadriceps muscle

The objective of this study was to investigate the cellular localisation of MyoD and myogenin in human skeletal muscle fibres as well as the possible alterations in the expression of MyoD and myogenin in response to a single bout of endurance exercise at 40% and 75% of maximum oxygen uptake (VO₂ max). Twenty-five biopsies (5 per subject) from the vastus lateralis muscle were obtained before exercise, from the exercising leg at 40% and 75% of VO₂ max and from the resting leg following these exercise bouts. The tyramide signal amplification-direct and the Vectastain ABC methods using specific monoclonal antibodies were used to determine the exact location of myogenin and MyoD, to identify muscle satellite cells and to determine myosin heavy chain (MyHC) composition. At rest, myonuclei did not express MyoD or myogenin. Following a single bout of exercise at 40% and 75% of VO₂ max, an accumulation of myogenin in myonuclei and not in satellite cells was observed in biopsies from the exercised leg but not in biopsies before exercise and from the resting leg. The number of myogenin-positive myonuclei varied among individuals indicating differences in the response to a single exercise bout. In conclusion, this immunohistochemical study showed that a rapid rearrangement of myogenin expression occurs in exercised human skeletal muscles in response to a single bout of exercise.     

Individual Responses to Completion of Short-Term and Chronic Interval Training: A Retrospective Study

Alterations in maximal oxygen uptake (VO₂max), heart rate (HR), and fat oxidation occur in response to chronic endurance training. However, many studies report frequent incidence of “non-responders” who do not adapt to continuous moderate exercise. Whether this is the case in response to high intensity interval training (HIT), which elicits similar adaptations as endurance training, is unknown. The aim of this retrospective study was to examine individual responses to two paradigms of interval training. In the first study (study 1), twenty active men and women (age and baseline VO₂max = 24.0±4.6 yr and 42.8±4.8 mL/kg/min) performed 6 d of sprint interval training (SIT) consisting of 4–6 Wingate tests per day, while in a separate study (study 2), 20 sedentary women (age and baseline VO₂max = 23.7±6.2 yr and 30.0±4.9 mL/kg/min) performed 12 wk of high-volume HIT at workloads ranging from 60–90% maximal workload. Individual changes in VO₂max, HR, and fat oxidation were examined in each study, and multiple regression analysis was used to identify predictors of training adaptations to SIT and HIT. Data showed high frequency of increased VO₂max (95%) and attenuated exercise HR (85%) in response to HIT, and low frequency of response for VO₂max (65%) and exercise HR (55%) via SIT. Frequency of improved fat oxidation was similar (60–65%) across regimens. Only one participant across both interventions showed non-response for all variables. Baseline values of VO₂max, exercise HR, respiratory exchange ratio, and body fat were significant predictors of adaptations to interval training. Frequency of positive responses to interval training seems to be greater in response to prolonged, higher volume interval training compared to similar durations of endurance training.     

Validity of heart rate and ratings of perceived exertion as indices of exercise intensity in a group of children while swimming.

The purpose of this study was to investigate the validity of heart rate (fc) and ratings of perceived exertion (RPE) as indices of exercise intensity in a group of children while swimming. Six healthy male swimmers, aged 10-12, swam tethered using the breast-stroke in a flume. The resistance started at 1.0 kg and increased in 1.0 kg steps up to the point of their exhaustion. The subjects swam for 5 min during each period, with a rest of 10-20 min until they had returned to their resting fc level. The last exercise intensity was with the maximal mass the subjects could support for 2 min. The last min of oxygen consumption (VO2) and 30 s of fc were measured during each exercise period. The subjects gave their RPE assessment at the end of exercise. The individual relationships between fc and VO2, and percentage maximal oxygen consumption (%VO2max) were linear with a high correlation r = 0.962-0.996 and r = 0.962-0.996, respectively. Therefore, it was concluded that fc was valid as an index of the exercise intensity of children while swimming. Compared to the results found in adults using a similar protocol, the children's fc were 8.3-26.9 beats.min-1 higher than those of the adults at the given %VO2max. The present study showed two different patterns in the relationship between VO2 and RPE in individuals. In two subjects the RPE increased linearly with VO2 while in the other four subjects the increase was discontinuous. If fc and RPE were to be applied to the setting and evaluation of exercise intensity during swimming, it would seem that fc would be a more useful guide than RPE for some children.     

Oxygen uptake during swimming in a hypobaric hypoxic environment

The purpose of this study was to determine oxygen uptake (VO2) at various water flow rates and maximal oxygen uptake (VO2max) during swimming in a hypobaric hypoxic environment. Seven trained swimmers swam in normal [N; 751 mmHg (100.1 kPa)] and hypobaric hypoxic [H; 601 mmHg (80.27 kPa)] environments in a chamber where atmospheric pressure could be regulated. Water flow rate started at 0.80 m.s-1 and was increased by 0.05 m.s-1 every 2 min up to 1.00 m.s-1 and then by 0.05 m.s-1 every minute until exhaustion. At submaximal water flow rates, carbon dioxide production (VCO2), pulmonary ventilation (VE) and tidal volume (VT) were significantly greater in H than in N. There were no significant differences in the response of submaximal VO2, heart rate (fc) or respiratory frequency (fR) between N and H. Maximal VE, fR, VT, fc, blood lactate concentration and water flow rate were not significantly different between N and H. However, VO2max under H [3.65 (SD 0.11) l.min-1] was significantly lower by 12.0% (SD 3.4)% than that in N [4.15 (SD 0.18) l.min-1]. This decrease agrees well with previous investigations that have studied centrally limited exercise, such as running and cycling, under similar levels of hypoxia.     

Cold-induced vasodilatation of finger and maximal oxygen consumption of young female athletes born in Hokkaido

To determine whether there is a direct correlation between endurance capacity and cold tolerance, maximal oxygen consumption (VO₂max), and cold-induced vasodilatation (CIVD), we measured these factors in 14 young female athletes born in Hokkaido, Japan's northernmost island. We determined the VO₂max by a standard incremental test on a cycle ergometer and measured the oxygen consumption (VO₂) by means of the Douglas-bag method. We determined the CIVD reaction by measuring the skin temperature of the left middle finger during immersion in cold water at 0°C for 20 min. The athletes showed significant positive correlations between VO₂max, expressed as l/min, and CIVD as well as other peripheral cold tolerance indexes (resistance index against frostbite and CIVD index). The body weight VO₂max (VO₂max/kg body weight) failed to correlate significantly with either the CIVD or with other cold tolerance indexes. These results suggest that CIVD in females may depend on factors other than those determined in this study, in addition to the functional spread of the vascular beds in peripheral tissues, including striated muscle; it is known that the size and the vascular bed in this tissue are affected by exercise training and that this results in the elevation of VO₂max and VO₂max/kg body weight.     

The Canadian Home Fitness Test as a predictor of aerobic capacity

The purpose of this study was to determine if maximum oxygen consumption (Vo₂ max) could be predicted from independent variables measured during the administration of the Canadian Home Fitness Test. Fifty-nine subjects between the ages of 15 and 74 years underwent the fitness test and a progressive exercise treadmill test for the direct determination of volitional Vo₂ max. The results indicated that Vo₂ max could be adequately predicted by the following regression equation: Vo₂ max (ml/kg·min) = 42.5 + 16.6(Vo₂) - 0.12(W) - 0.12(H) - 0.24(A), where Vo₂ is the average oxygen cost of the last completed exercise stage (in l/min), W is the body weight (in kg), H is the postexercise heart rate (in beats/min) and A is the age (in years).     

The aerobic scope of an antarctic fish,Pagothenia borchgrevinki and its significance for metabolic cold adaptation

Summary Resting weight-specific oxygen consumption of the cryopelagic Antarctic nototheniid Pagothenia borchgrevinki at 0°C was 39.6 ml kg^-1 · h^-1 for a 50 g fish, with oxygen consumption being described by the regression equation: log₁₀ VO₂(ml/h)=–1.104+0.825 log₁₀ M_b (g). These values are considerably below those raported by Wohlschlag (1964a,b). VO₂ max. in forced swimming was described by the regression equation: log₁₀ VO₂ max = –0.507+0.823 log₁₀ M_b. Despite low basal metabolism, factorial aerobic scope is similar to that reported for most other teleost fish, as is the cost of net transport. Myotomal muscles were used only at the highest swimming speeds and once they were recruited the fish fatigued rapidly. After swimming, oxygen debt was repaid rapidly, with a half-time of 20 min.     

Time course of O2-pulse during various tests of aerobic power.

The purpose of this study was to test the hypothesis that oxygen pulse typically reaches a maximum before maximal oxygen consumption by observing the time course of oxygen pulse throughout exercise to maximal stress and to discern those physiologic variables which might predispose an individual to reach a peak in oxygen pulse before achieving maximal oxygen consumption. Thirty male volunteers ranging in age from 18-25 (X = 20.5) years were recruited for this study. Maximal oxygen uptake was assessed on both bicycle ergometer and treadmill. Based upon the results of the exercise tests, subjects were classified into subgroups as a consequence of whether or not a maximal oxygen pulse or a plateau in oxygen pulse was demonstrated during submaximal exercise. The results indicate that submaximal peaking or at least the achieving of plateau values of oxygen pulse does in fact occur in some but not all indivuals. It was observed that this phenomenon occurs at a relatively high percentage of maximal heart rate and maximal oxygen consumption. It appeared that individuals who demonstrate low heart rates at low-work intensities, high maximal heart rates, and a disproportionate increase in R for a given ventilation are most likely to reach a submaximal peak in oxygen pulse. Oxygen pulse during submaximal exercise appears to provide a good indication of cardiorespiratory fitness.     

Cardiovascular responses to exercise as functions of absolute and relative work load

The roles of absolute and relative oxygen uptake (VO2 and percent of muscle group specific VO2 max) as determinants of the cardiovascular and ventilatory responses to exercise over a wide range of active muscle mass have not previously been defined. Six healthy men performed four types of dynamic exercise--one-arm curl, one-arm cranking, and one- and two-leg cycling at four different relative work loads--25, 50, 75, and 100% of VO2 max for the corresponding muscle group. VO2 during maximal one-arm curl, one-arm cranking, and one-leg cycling averaged 20, 50, and 75%, respectively, of that for maximal two-leg cycling. Cardiac output was linearly related to VO2 with a similar slope and intercept for each type of exercise. Heart rate at a given %VO2 max was higher with larger active muscle mass. In relation to %VO2 max, systemic resistance was lower and plasma catecholamine levels were higher with larger active muscle mass. The cardiovascular responses to exercise are determined to a large extent by the active muscle mass and the absolute oxygen uptake, with the principal feature appearing to be the tight linkage between systemic oxygen transport and utilization.     

Cardiorespiratory mobilization and endurance performance.

Twenty subjects performed for 11 min on a bicycle ergometer 30 sec following 5 min of prior exercise (PE) at each of four different intensities. PE was adjusted to maintain a heart rate of 110, 140, and 170 beats/min. The 4th treatment was no PE. Heart rate was an estimate of the mobilization of the cardiorespiratory system during exercise. The criterion task (CT) included cycling for 10 min against 3 kg resistance at 68 rpm followed by 1 min of an all-out work bout where subjects tried to complete as many rpm's as possible against 3 kg. The 11th minute was used to assure the complete exhaustion of energy reserves following the paced part of the task. Overall performance following PE-170 was significantly worse than that following no PE, PE-110, and PE-140, which was probably due to a build up of anaerobic metabolites such as lactate during the PE. Total work appeared to be greatest following PE-110, which showed a slight tendency toward better performance especially after the 6th minute. However, no clear cut evidence was produced to support the hypothesis that light to moderate PE would sufficiently improve performance by mobilizing the cardiorespiratory system, thereby reducing the initial oxygen deficit in the CT and thus allowing more work to be performed.     

Comparison of cardiopulmonary responses to two types of dry-land upper-body exercise testing modes in competitive swimmers

In this study we compared cardiopulmonary responses to upper-body exercise in 12 swimmers, using simulation of the front-crawl arm-pulling action on a computer-interfaced isokinetic swim bench and arm cranking on a modified cycle ergometer. Subjects adopted a prone posture; exercise was initially set at 20 W and subsequently increased by 10 W. min(-1). The tests were performed in a randomised order at the same time of day, within 72 h. The highest (peak) oxygen consumption (VO(2peak)), heart rate (HR(peak)), blood lactate ([la(-)](peak)) and exercise intensity (EI(peak)) were recorded at exhaustion. Mean (SEM) peak responses to simulated swimming were higher than those to arm cranking for VO(2peak) [2.9 (0.2) vs 2.4 (0.1) l x min(-1); P = 0.01], HR(peak) [174 (2) vs 161 (2) beats x min(-1); P = 0.03], and EI(peak) [122 (6) vs 102 (5) W; P = 0.02]. However, there were no significant differences in [la(-)](peak) [9.6 (0.6) vs 8.2 (0.6) mmol x l(-1); P = 0.08]. Thus simulated swimming is the preferred form of dry-land ergometry for the assessment of swimmers.     

Comparison of Peak Cardiopulmonary Performance Parameters on a Robotics-Assisted Tilt Table,a Cycle and a Treadmill

Robotics-assisted tilt table (RATT) technology provides body support, cyclical stepping movement and physiological loading. This technology can potentially be used to facilitate the estimation of peak cardiopulmonary performance parameters in patients who have neurological or other problems that may preclude testing on a treadmill or cycle ergometer. The aim of the study was to compare the magnitude of peak cardiopulmonary performance parameters including peak oxygen uptake (VO_2peak) and peak heart rate (HR_peak) obtained from a robotics-assisted tilt table (RATT), a cycle ergometer and a treadmill. The strength of correlations between the three devices, test-retest reliability and repeatability were also assessed. Eighteen healthy subjects performed six maximal exercise tests, with two tests on each of the three exercise modalities. Data from the second tests were used for the comparative and correlation analyses. For nine subjects, test-retest reliability and repeatability of VO_2peak and HR_peak were assessed. Absolute VO_2peak from the RATT, the cycle ergometer and the treadmill was (mean (SD)) 2.2 (0.56), 2.8 (0.80) and 3.2 (0.87) L/min, respectively (p < 0.001). HR_peak from the RATT, the cycle ergometer and the treadmill was 168 (9.5), 179 (7.9) and 184 (6.9) beats/min, respectively (p < 0.001). VO_2peak and HR_peak from the RATT vs the cycle ergometer and the RATT vs the treadmill showed strong correlations. Test-retest reliability and repeatability were high for VO_2peak and HR_peak for all devices. The results demonstrate that the RATT is a valid and reliable device for exercise testing. There is potential for the RATT to be used in severely impaired subjects who cannot use the standard modalities.     

Preconditioning with hydrogen peroxide (H2O2) or ischemia in H2O2-induced cardiac dysfunction

To assess whether allantoin levels in serum and urine are influenced by exhaustive and moderate exercise and whether allantoin is a useful indicator of exercise-induced oxidative stress in humans, we made subjects perform exhaustive and moderate (100% and 40% VO₂max) cycling exercise and examined the levels of allantoin, thiobarbituric acid reactive substances (TBARS) and urate in serum and urine. Immediately after exercise at 100% VO₂max, the serum allantoin/urate ratio was significantly elevated compared with the resting levels while the serum urate levels was significantly elevated 30 min after exercise. The serum TBARS levels did not increase significantly compared with the resting levels. Urinary allantoin excretion significantly increased during 60 min of recovery after exercise, however, urinary urate excretion decreased significantly during the same period. The urinary allantoin/urate ratio also rapidly increased during 60 min of recovery after exercise. Urinary TBARS excretion decreased during the first 60 min of the recovery period and thereafter significantly increased during the latter half of the recovery period. On the contrary, after 40% VO₂max of exercise, no significant changes in the levels of urate, allantoin and TBARS in serum or urine were observed. These findings suggest that allantoin levels in serum and urine may reflect the extent of oxidative stress in vivo and that the allantoin which appeared following exercise may have originated not from urate formed as a result of exercise but from urate that previously existed in the body. Furthermore, these findings support the view that allantoin in serum and urine is a more sensitive and reliable indicator of in vivo oxidative stress than lipid peroxidation products measured as TBARS.     

Heart rate during exercise with leg vascular occlusion in spinal cord-injured humans.

Feed-forward and feedback mechanisms are both important for control of the heart rate response to muscular exercise, but their origin and relative importance remain inadequately understood. To evaluate whether humoral mechanisms are of importance, the heart rate response to electrically induced cycling was studied in participants with spinal cord injury (SCI) and compared with that elicited during volitional cycling in able-bodied persons (C). During voluntary exercise at an oxygen uptake of approximately 1 l/min, heart rate increased from 66 +/- 4 to 86 +/- 4 (SE) beats/min in seven C, and during electrically induced exercise at a similar oxygen uptake in SCI it increased from 73 +/- 3 to 110 +/- 8 beats/min. In contrast, blood pressure increased only in C (from 88 +/- 3 to 99 +/- 4 mmHg), confirming that, during exercise, blood pressure control is dominated by peripheral neural feedback mechanisms. With vascular occlusion of the legs, the exercise-induced increase in heart rate was reduced or even eliminated in the electrically stimulated SCI. For C, heart rate tended to be lower than during exercise with free circulation to the legs. Release of the cuff elevated heart rate only in SCI. These data suggest that humoral feedback is of importance for the heart rate response to exercise and especially so when influence from the central nervous system and peripheral neural feedback from the working muscles are impaired or eliminated during electrically induced exercise in individuals with SCI.