Efficacy of two intervention approaches on functional walking capacity and balance in children with Duchene muscular dystrophy

Objectives:Children with Duchene muscular dystrophy have weak muscles, which may impair postural adjustments. These postural adjustments are required for gait and dynamic balance during the daily living activities. The aim was to compare between the effect of bicycle ergometer versus treadmill on functional walking capacity and balance in children with Duchenne muscular dystrophy.Methods:Thirty boys aged from 6 to 10 years old diagnosed as Duchene muscular dystrophy participated in this study. Children were assigned randomly into two groups (A&B). Children in group (A) underwent a designed program of physical therapy plus aerobic exercise training in form of bicycle ergometer while, group (B) received the same program as group (A) and aerobic exercise training by treadmill for one hour, at three times a week for three successive months. Functional walking capacity and balance were assessed before and after treatment by using the 6-minute walk test and Biodex balance system equipment respectively.Results:The post treatment results revealed significant difference in all measured variables (P<0.05) as compared with its pre-treatment results. Post-treatment values indicated that there was a significant difference in all measured variables in favor of group B.Conclusions:treadmill training as an aerobic exercise can improve walking capacity and balance more effectively than bicycle ergometer in children with Duchenne muscular dystrophy.     

Response of erythrocytic 2,3-diphosphoglycerate to strenuous exercise.

Since increases of erythrocytic 2,3-diphosphoglycerate (2,3-DPG) have been shown to enhance the release of oxygen from hemoglobin, experiments were designed to evaluate the response of 2,3-DPG to two different work-loads in 13 fasted human subjects. No signficant mean change in 2.3-DPG was found following 16 min of strenuous exercise on a bicycle ergometer, but when the subjects were subjected later to a greater workload for 20 min, there was a significant mean decrease in 2.3-DPG despite much individual variation. In addition, there was a significant positive correlation of 2.3-DPG reduction with increases in postexercise lactate, and a significant inverse correlation of oxygen consumption during exercise with postexercise lactate. The data suggest that the 2.3-DPG mechanism may not be compensating in exercise when the workload requires a preponderance of anaerobic metabolism promoting lactacidaemia.     

Relationship between plasma renin activity and physical fitness in normal subjects

The relationship between plasma renin activity (PRA) at rest and physical fitness was studied in 40 normal young subjects on a liberal sodium intake. Plasma renin activity was measured in arterial blood withdrawn at the end of a 30-min period of rest in recumbency, while physical fitness was expressed by the highest oxygen uptake achieved during an uninterrupted graded exercise test performed in the sitting position on an electromagnetically braked ergometer bicycle (peak VO2). Log PRA correlated significantly and inversely with peak VO2 adjusted for body weight (r = -0.34; P less than 0.05) in single regression analysis. Using multiple regression and adjusted peak VO2, age, urinary sodium excretion and mean intra-arterial pressure as independent variables, no combination of two or more independent variables yielded significant partial correlation coefficients with log PRA. This correlation suggests that PRA at rest is inversely related to the subject's physical fitness.     

A study of passive weight-bearing lower limb exercise effects on local muscles and whole body oxidative metabolism: a comparison with simulated horse riding,bicycle, and walking exercise

Background

We have developed an exercise machine prototype for increasing exercise intensity by means of passively exercising lower limb muscles. The purpose of the present study was to compare the passive exercise intensity of our newly-developed machine with the intensities of different types of exercises. We also attempted to measure muscle activity to study how these forms of exercise affected individual parts of the body.

Methods

Subjects were 14 healthy men with the following demographics: age 30 years, height 171.5 cm, weight 68.3 kg. They performed 4 types of exercise: Passive weight-bearing lower limb exercise (PWLLE), Simulated horse riding exercise (SHRE), Bicycle exercise, and Walking exercise, as described below at an interval of one week or longer. Oxygen uptake, blood pressure, heart rate, and electromyogram (EMG) were measured or recorded during exercise. At rest prior to exercise and immediately after the end of each exercise intensity, the oxygenated hemoglobin levels of the lower limb muscles were measured by near-infrared spectroscopy to calculate the rate of decline. This rate of decline was obtained immediately after exercise as well as at rest to calculate oxygen consumption of the lower limb muscles as expressed as a ratio of a post-exercise rate of decline to a resting one.

Results

The heart rate and oxygen uptake observed in PWLLE during maximal intensity were comparable to that of a 20-watt bicycle exercise or 2 km/hr walking exercise. Maximal intensity PWLLE was found to provoke muscle activity comparable to an 80-watt bicycle or 6 km/hr walking exercise. As was the case with the EMG results, during maximal intensity PWLLE, the rectus femoris muscle consumed oxygen in amounts identical to that of an 80-watt bicycle or a 6 km/hr walking exercise.

Conclusion

Passive weight-bearing lower limb exercise using our trial machine could provide approximately 3 MET of exercise and the thigh exhibited muscle activity equivalent to that of 80-watt bicycle or 6 km/hr walking exercise. Namely, given the same oxygen uptake, PWLLE exceeded bicycle or walking exercise in muscle activity, thus PWLLE is believed to strengthen muscle power while reducing the load imposed on the cardiopulmonary system.

     

Correlation between heat tolerance during exercise and maximum aerobic work capacity

Observation of the physiological responses during exercise in a hot environment and measurement of maximal work capacity were made on eight young male subjects, ages 20--22. Exercise was performed on a bicycle ergometer at a constant work load of 450 kg . m/min at a cycling rate of 50 rpm for 30 min in a climatic chamber at 30 degree C with 70% relative humidity. The maximum work capacity was measured by bicycle ergometer exercise. Heat tolerance during exercise was assessed by the magnitude of physiological strain expressed by the combination of relative rise in rectal temperature, relative water loss and relative salt loss. Heat load during exercise was calculated using metabolic rates at rest and during exercise, assuming heat loss through the respiratory tract to be 10 percent of metabolic rate. Fairly good correlations were found between the ratio of work done to maximum work capacity and rise in rectal temperature, ratio of body weight loss to body weight and heat tolerance during exercise. Close correlations were found among relative heat load during exercise and rise in rectal temperature, relative body weight loss and heat tolerance. Heat tolerance during exercise in a hot environment correlated well to capacity of heat dissipation and maximum work capacity.     

训练专一性对无氧阈测定的影响

本文对以上肢训练为主的15名优秀皮划艇运动员和以下肢训练为主的14名优秀中长跑运动员在两种常规负荷方式下的无氧阈及最大吸氧量进行了测定分析,以探讨训练专一性对无氧阈测定的影响。采用踏车式功量计和活动平板方式逐级递增负荷,通过与Apple Ⅱ_E辅助联机的Jaeger EOS自动分析系统,以通气和气体交换指标的变化,无创性地测定无氧阈和最大吸氧量。结果表明,训练专一性会影响无氧阈测定结果。欲测得最高的无氧阈值,实验室测试手段就应当尽量模拟训练时的运动形式。此外,能敏感地反映出运动训练专一性适应的是无氧阈时的吸氧量绝对值(1/min),而不是无氧阈的相对值(％Vo_2max)。     

Supine lower body negative pressure exercise during bed rest maintains upright exercise capacity.

Bed rest and spaceflight reduce exercise fitness. Supine lower body negative pressure (LBNP) treadmill exercise provides integrated cardiovascular and musculoskeletal stimulation similar to that imposed by upright exercise in Earth gravity. We hypothesized that 40 min of supine exercise per day in a LBNP chamber at 1.0-1.2 body wt (58 +/- 2 mmHg LBNP) maintains aerobic fitness and sprint speed during 15 days of 6 degrees head-down bed rest (simulated microgravity). Seven male subjects underwent two such bed-rest studies in random order: one as a control study (no exercise) and one with daily supine LBNP treadmill exercise. After controlled bed-rest, time to exhaustion during an upright treadmill exercise test decreased 10%, peak oxygen consumption during the test decreased 14%, and sprint speed decreased 16% (all P < 0.05). Supine LBNP exercise during bed rest maintained all the above variables at pre-bed-rest levels. Our findings support further evaluation of LBNP exercise as a countermeasure against long-term microgravity-induced deconditioning.     

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.     

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.     

Functional Tests of Pulmonary Respiration

The duration of voluntary holding of external breathing (VHEB) on inspiration or expiration was measured in 300 18- to 22-year-old subjects of both sexes at rest and during bicycle ergometer exercise, in a sitting position or in the float posture, on land or immersed in water. The length of expiratory VHEB was found to depend on the residual lung volume, whereas inspiratory VHEB correlated with the functional residual lung capacity. Physical exercise increased the oxygen uptake and accelerated the consumption of lung oxygen reserves available on inspiration or expiration and decreased the duration of VHEB. Special formulas were proposed for calculating the theoretical length of VHEB and for its comparing the result with corresponding experimental values, as well as for determination of the lung volumes and oxygen consumption.     

The effect of brief physical exercise on free radical scavenging enzyme systems in human red blood cells

Eleven sedentary male students were studied, using a bicycle ergometer, for 30 min at about 75% of their maximal oxygen uptake, to observe the effects of brief physical exercise on free radical scavenging system enzymes of the erythrocytes. Of the enzymes examined, only total glutathione reductase activity showed a significant elevation immediately after exercise and appeared to remain high at 30 min after exercise. The results suggest that acute physical exercise has some effects on red blood cell glutathione reductase activity, which is related primarily to maintenance of reduced glutathione.     

Plasma testosterone and catecholamine responses to physical exercise of different intensities in men

Plasma testosterone, noradrenaline, and adrenaline concentrations during three bicycle ergometer tests of the same total work output (2160 J X kg-1) but different intensity and duration were measured in healthy male subjects. Tests A and B consisted of three consecutive exercise bouts, lasting 6 min each, of either increasing (1.5, 2.0, 2.5 W X kg-1) or constant (2.0, 2.0, 2.0 W X kg-1) work loads, respectively. In test C the subjects performed two exercise bouts each lasting 4.5 min, with work loads of 4.0 W X kg-1. All the exercise bouts were separated by 1-min periods of rest. Exercise B of constant low intensity resulted only in a small increase in plasma noradrenaline concentration. Exercise A of graded intensity caused an increase in both catecholamine levels, whereas, during the most intensive exercise C, significant elevations in plasma noradrenaline, adrenaline and testosterone concentrations occurred. A significant positive correlation was obtained between the mean value of plasma testosterone and that of adrenaline as well as noradrenaline during exercise. It is concluded that both plasma testosterone and catecholamine responses to physical effort depend more on work intensity than on work duration or total work output.     

Biomechanical evaluation of walking and cycling in children

Physical activity in children is important as it leads to healthy growth due to physiological benefits. However, a physiological benefit can be partially negated by excessive or unphysiological loads within the joints. To gain an initial understanding into this, the present study sought to compare joint loading between walking and cycling in children. With institutional ethical approval, 14 pre-pubertal children aged 8–12 walked on an instrumented treadmill and cycled on a stationary ergometer. Two methods were used to match physiological load. Cardiovascular loads between walking and cycling were matched using heart rate. Metabolic load was normalised by matching estimates of oxygen consumption. Joint reaction forces during cycling and walking as well as joint moments were derived using inverse dynamics. Peak compressive forces were greater on the knees and ankles during walking than during cycling. Peak shear peak forces at the knee and ankle were also significantly larger during walking than during cycling, independent of how physiological load was normalised. For both cycling conditions, ankle moments were significantly smaller during cycling than walking. No differences were found for knee moments. At equivalent physiological intensities, cycling results in less joint loading than walking. It can be speculated that for certain populations and under certain conditions cycling might be a more suitable mode of exercise than weight bearing activities to achieve a given metabolic load.     

Determination of cardiac output by the CO2 - rebreathing method in fifteen-year-old boys subjected to graduated loading.

The dynamics of cardiac output changes were studied in 23 15-year-old boys subjected to graduated loading up to maximum on an bicycle ergometer and relationships between cardiac output and other indexes of cardiorespiratory functions were determined. The correlation between cardiac output (Q in 1/min) and oxygen consumption (VO2 in 1/min) was Q = 6.84 + 5.64. VO2. CO2-rebreathing was found to be a suitable non-invasive method for determining cardiac output in loading tests in adolescents. Maximum cardiac output correlated with maximum oxygen consumption, maximum pulmonary ventilation, body weight, lean body mass and physical working capacity W 170 and did not correlate with systolic volume, the arteriovenous oxygen difference, the pulse rate and ballistocardiographic force. The absence of any statistically significant differences between the various functional indexes of the physical fitness of trained and untrained boys indicates that training was not very effective.     

Physiological reaction of women during exercise and recovery, in a comfortable environment and a hot environment

Physiological reaction and oxygen intake during exercise and recovery were measured in fourteen young female Japanese during the follicular phase of their menstrual cycle at 25 degree C with 50% relative humidity and at 35 degree C with 50% relative humidity. Subjects, clad in bathing suits only, performed a bicycle ergometer exercise at a constant work load of 600 kg . m/min at a cycling rate of 50 rpm for 20 min and recovered while remaining on the bicycle ergometer for 40 min. The mean values of sweat volume and skin temperature were significantly greater at 35 degree C than at 25 degree C. It has been shown that heart rate and rectal temperature during exercise were slightly higher at 35 degree C than at 25 degree C, while those during recovery were significantly higher at 35 degree C than at 25 degree C. Oxygen intake, oxygen debt, and the fall in diastolic blood pressure after exercise were considerably greater at 35 degree C than at 25 degree C. The increase in oxygen intake in a hot environment might result from an increased metabolism due to higher body temperature and increased energy requirement for heat dissipation such as profuse sweating, higher heart rate, and increased ventilatory volume. The increase in oxygen debt in a hot environment might reflect the increased metabolism caused by higher body temperature and the increased production of lactic acid in the working muscle as a result of an insufficient blood supply to the muscle. The increases in sweat volume, oxygen intake during exercise, and oxygen debt in women in a hot environment were considerably smaller than corresponding values for men. The smaller increase in sweat volume in women in a hot environment could reflect a smaller oxygen intake and a more marked dilation of skin vessels in women than in men.     

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.     

Sympathetic response to maximal bicycle exercise before and after leg strength training

Plasma catecholamine concentrations at rest and in response to maximal exercise on the cycle ergometer (278 +/- 15 watts, 6 min duration) have been measured on seven young active male subjects (19 +/- 1 years old; 80 +/- 3 kg; 176 +/- 3 cm) prior to and after a eight week leg strength training program (5RM, squat and leg press exercise). Strength training resulted in a significant increase in performance on squat (103 +/- 3 to 140 +/- 5 kg) and leg press exercise (180 +/- 9 to 247 +/- 15 kg) associated with a small significant increase in lean body mass (64.5 +/- 2.2 to 66.3 +/- 2.1 kg) and no change in maximal oxygen consumption (47.5 +/- 1.3 to 46.9 +/- 1.2 ml X kg-1 X min-1). Plasma norepinephrine (NE) and epinephrine (E) concentrations (pg X mL-1) were not significantly different before and after training at rest (NE: 172 +/- 19 vs 187 +/- 30; E: 33 +/- 10 vs 76 +/- 16) or in response to maximal exercise (NE: 3976 +/- 660 vs 4163 +/- 1081; E: 1072 +/- 322 vs 1321 +/- 508). Plasma lactate concentrations during recovery were similar before and after training (147 +/- 5 vs 147 +/- 15 mg X dL-1). Under the assumption that the "central command" is reduced for a given absolute workload on the bicycle ergometer following leg strength training, these observations support the hypothesis that the sympathetic response to exercise is under the control of information from muscle chemoreceptors.     

Reaction of the gastric glands in wrestlers aged 7–32 years to threshold-power bicycle ergometer exercise

Problems of quick adaptation of the gastric glands of wrestlers to threshold-power bicycle ergometer exercise during sports and postsports ontogeny are discussed. It has been established that threshold-power bicycle ergometer exercise may suppress, stimulate, or not affect the secretion of H₂O, HCl, and pepsinogen. The pattern of these shifts is aimed at optimizing the actual level of protein hydrolysis; it depends on the age, sports experience, and qualification and is correlated with the body weight.     

The relationship between anaerobic threshold and electromyographic fatigue threshold in college women

The purpose of this study was to investigate the relationship between anaerobic threshold (Th(an)) and muscle fatigue threshold (EMGFT) as estimated from electromyographic (EMG) data taken from the quadriceps muscles (vastus lateralis) during exercise on a cycle ergometer. The subjects in this study were 20 female college students, including highly trained endurance athletes and untrained sedentary individuals, whose fitness levels derived from their maximal oxygen consumption ranged from 24.9 to 62.2 ml.kg-1.min-1. The rate of increase in integrated EMG (iEMG) activity as a function of time (iEMG slope) was calculated at each of four constant power outputs (350, 300, 250, 200 W), sufficiently high to bring about muscle fatigue. The iEMG slopes so obtained were plotted against the exercise intensities imposed, resulting in linear plots which were extrapolated to zero slope to give an intercept on the power axis which was in turn interpreted as the highest exercise intensity sustainable without electromyographic evidence of neuromuscular fatigue (EMGFT). The Th(an) was estimated from gas exchange parameters during an incremental exercise test on the same cycle ergometer. The mean results indicated that oxygen uptake (VO2) at Than was 1.39 l.min-1, SD 0.44 and VO2 at EMGFT was 1.33 l.min-1, SD 0.57. There was no significant difference between these mean values (P greater than 0.05) and there was a highly significant correlation between VO2 at Than and VO2 at EMGFT (r = 0.823, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)