Maximal and submaximal oxygen uptake during running: how should body mass be accounted for?

Oxygen uptake during running, i.e., the running economy, is an important factor in determining running performance in endurance events. The relation to performance is particularly strong when the aerobic running capacity is calculated, i.e., when running economy is related to the maximal oxygen uptake. There is considerable interindividual variation in running economy, and the reason for this is only partly understood. To some extent, this may be due to the way in which the oxygen uptake during running is usually expressed. This may expecially be true when subjects with different or changing body masses are compared. Several lines of evidence, including earlier animal studies as well as more recent human studies, favor the expression of submaximal and maximal oxygen uptake during running in terms of ml · kg^−0.75· min⁻¹ rather than as ml · kg⁻¹· min^−1.     

Aerobic exercise capacity at sea level and at altitude in Kenyan boys, junior and senior runners compared with Scandinavian runners

The aim of this study was to characterize Kenyan runners in regard to their oxygen uptake and blood and ammonia responses when running. Untrained Kenyan boys (14.2±0.2 years) and Scandinavian runners were included for comparison. The studies were performed at altitude (～2.000 m.a.s.l.) and, for several Kenyan and Scandinavian runners, at sea level as well. At altitude sedentary adolescent Kenyan boys had a mean maximal oxygen uptake (Vo_2max) of 47 (44–51) ml · kg^?1· min^?1, whereas similarly aged boys regularly walking or running but not training for competition reached above 62 (58–71) ml · kg^?1· min^?1 in Vo^2max. Kenyan runners in active training had 68±1.4 ml · kg^?1· min^?1 at altitude and 79.9±1.4 ml · kg^?1· min^?1 at sea level, with individuals reaching 85 ml · kg^?1· min^?1. The best Scandinavian runners were not significantly different from the Kenyan runners in Vo_2max both at altitude and at sea level, but none of the Scandinavians reached as high individual values as observed for some Kenyan runners. The running efficiency, determined as the oxygen cost at a given running speed, was less in the Kenyan runners, and the difference became more pronounced when body weight was expressed in ml · kg^?0.75 min^?1. Blood lactate concentration was in general lower in the Kenyan than in the Scandinavian runners, and the Kenyans also had extremely low ammonia accumulation in the blood even at very high exercise intensities. It is concluded that it is the physical activity during childhood, combined with intense training as teenagers that brings about the high Vo_2max observed in some Kenyan runners. Their high aerobic capacity, as well as their good running economy, makes them such superior runners. In addition, their low blood lactate and ammonia accumulation in blood when running may also be contributing factors.     

Malate-aspartate and alpha-glycerophosphate shuttle enzyme levels in human skeletal muscle: methodological considerations and effect of endurance training

The aim of the present study was to investigate whether the levels of the malate-aspartate and alpha-glycerophosphate shuttle enzymes in human skeletal muscle are affected by endurance training. The approach used was to compare six untrained and six endurance-trained subjects as well as through performing a longitudinal study of endurance training on eight untrained subjects. Biopsy samples were obtained from the lateral part of the quadriceps femoris muscle. The trained muscles were characterized by higher levels of oxidative enzymes (55%) as well as enhanced capillary supply (30%). In both the cross-sectional and longitudinal studies, the malate-aspartate shuttle enzyme levels were about 50% higher in the trained state (cytoplasmic malate dehydrogenase 36%, mitochondrial malate dehydrogenase 46%, cytoplasmic aspartate aminotransferase 52% and mitochondrial aspartate aminotransferase 48%). Contrary to this, the alpha-glycerophosphate shuttle enzyme levels did not differ significantly (cytoplasmic and mitochondrial glycerol-3-phosphate dehydrogenase: 10 and -4%, respectively). The activity ratios of the enzymes involved in respective shuttle did not differ significantly between the untrained and endurance-trained states. It is concluded that endurance training may induce increased levels of malate-aspartate shuttle enzymes in human skeletal muscle while the levels of the alpha-glycerophosphate shuttle enzymes are not affected. The study also includes results from several methodological experiments.     

The Maze operation for treatment of atrial fibrillation. Early clinical experience in a Scandinavian institution

The Maze operation is a potentially curative surgical option in patients with disabling atrial fibrillation (AF) refractory to conventional treatment. The aim of this study was to evaluate the initial 4-year Maze experience in our institution. The study included 26 patients (19 males, mean age 55 years) who had undergone the Maze (III) operation between 1994 and 1998. Nine patients had surgery for concomitant heart disease. Follow-up was 3-55 (median 18) months. No deaths or neurological complications occurred; 22 patients are at present in regular sinus-, or junctional rhythm, 2 patients have permanent atrial pacing for symptomatic sinus node dysfunction, and 2 patients have had persistent AF, post surgery. Sinus node dysfunctions were detected in five patients, though not requiring pacemakers. Out of the total 26 patients, 23 are free of anti-arrhythmic drugs. Echocardiographic signs of left atrial contraction were recorded in 50% of the patients. The Maze operation offers a safe alternative to conventional therapy, with attractive results justifying expansion in the use of this treatment for AF.     

Skeletal muscle and hormonal adaptation to physical training in the rat: role of the sympatho-adrenal system

The main purpose of the present study was to test the hypothesis that adrenergic stimulation of muscle fibres during exercise is a major stimulus for the training-induced enhancement of skeletal muscle respiratory capacity. Therefore, Sprague-Dawley rats either underwent bilateral surgical ablation of the adrenal medulla or were sham-operated. Furthermore, unilateral surgical extirpation of the lumbar sympathetic chain was performed. Half of the rats were then trained for 12 weeks by swimming (up to 5.5 h X day-1, 4 days X week-1) and the remaining rats were sedentary controls. In the gastrocnemius muscle, training significantly increased the mitochondrial enzymes citrate synthase, succinate dehydrogenase, cytochrome c oxidase, and 3-hydroxyacyl-CoA dehydrogenase. In sham-operated rats, the increases were 40%, 43%, 66%, and 25%, respectively, in legs with intact sympathetic innervation. The training-induced enzyme adaptation after adrenodemedullation and/or sympathectomy was not significantly lower than these control values. In sham-operated rats, training decreased resting plasma insulin and glucagon levels and increased liver glycogen content. Similar changes were induced by adrenodemedullation, but training did not augment these changes in adrenodemedullated rats. In conclusion, the data suggest that neither adrenomedullary hormones nor local sympathetic nerves are prerequisites for the training-induced increase in muscle mitochondrial enzymes. The training-induced decline in resting plasma insulin and glucagon levels in intact rats may be mediated by adrenomedullary hormones.     

Beta-adrenergic blockade and training in healthy men--effects on central circulation

The effect of chronic beta-adrenergic blockade on central circulatory adaptations to physical training was investigated. 16 healthy sedentary males (20-31 yrs) trained on cycle ergometers 40 min/day, 4 days a week for 8 weeks at a work load that during the last 5 weeks corresponded to 75% of the pretraining VO2 max. In a single blind way, 8 subjects were during the training period treated with the beta-adrenergic receptor blocker propranolol (160 mg/day), while the remaining 8 received placebo tablets. Pretraining tests were performed before the start of medication and posttraining tests were performed 6 days after the last day of training and medication. The training program resulted in a similar increase (8%) in VO2 max in both groups (p less than 0.01). The resting heart rate (-4 beats/min; p less than 0.05) as well as the exercise heart rate at a moderate work load (120 W: -11 beats/min; p less than 0.01) decreased with training, and no significant difference was seen between the 2 groups. At a high work load (180 W), however, the heart rate decreased significantly more with training in the placebo group as compared with the beta-blockade group (-19 vs. -7 beats/min; p less than 0.05). The oxygen pulse (VO2/HR) increased in both groups at 120 W (+6%; p less than 0.01). At 180 W the oxygen pulse increased only in the placebo group (+8%; p less than 0.05). The estimated stroke volume at 120 and 180 W, as determined by impedance cardiography, did not change significantly with training although there was a tendency towards an increase in the placebo group only. The resting left ventricular wall thickness and diameter, as determined by echocardiography, did not change significantly with training in either group.--In conclusion, the present study indicates that a moderate degree of beta-adrenergic blockade does not prevent or impair the training-induced increase in the maximal oxygen uptake. During submaximal work, however, the circulatory adaptation may be less apparent if training has been performed during partial blockade of the sympatho-adrenal system.     

Physical training in Syndrome X: physical training counteracts deconditioning and pain in Syndrome X

OBJECTIVES: The aim of this study was to evaluate the effects of exercise training and body-awareness training in female patients with Syndrome X. BACKGROUND: Patients with Syndrome X, defined as effort-induced angina pectoris, a positive exercise test and a normal coronary angiogram, suffer from a chronic pain disorder. We hypothesized that this disorder results in physical deconditioning with decreased exertional pain threshold. METHODS: Twenty-six patients were randomly assigned to two training groups (A, B) and a control group (C). Group A (n = 8) started, after baseline measurements, with eight weeks of body-awareness training followed by eight weeks of exercise training on a bicycle ergometer three times a week for 30 min at an intensity of 50% of peak work rate. Group B (n = 8) performed only eight weeks of exercise training. Group C (n = 10) acted as controls without any intervention whatsoever. The effects on exercise performance, hormonal secretion, vascular function, adenosine sensitivity and quality of life were evaluated. RESULTS: Body-awareness training did not change the pain response. The two training groups did not differ in effects of exercise training. Exercise capacity before training was below the gender- and age-matched reference range and improved by 34% with training to a level not different from the reference range. Onset of pain was delayed by 100% from 3 +/- 2 to 6 +/- 3 min (p < 0.05) while maximum pain did not change. Thus the pain-response-to-exercise curve was shifted to the right. Syndrome X patients showed a hypersensitivity to low-dose adenosine infusion compared to healthy age- and gender-matched controls (p < 0.0001) that did not change with exercise training. Endothelium-dependent blood flow increase was at baseline within reference range and tended to increase (p < 0.06) following training. In Group A the concentration of cortisol in urine decreased by 53% after body-awareness training (p < 0.05), and this change from baseline remained after physical exercise training (p < 0.05). A similar decrease occurred with only exercise training (Group B). CONCLUSIONS: Physical deconditioning with lower exertional threshold for pain is a prominent feature in Syndrome X. Physical training in Syndrome X results in an increased exercise capacity with lesser anginal pain. We suggest physical training as an effective treatment in Syndrome X.     

Physiological and morphological characteristics of world class fencers

Physiological and morphological characteristics of world class épée fencers were analysed. The results showed that épée fencers have a high maximal aerobic power and high maximal isometric and dynamic strength. The movement pattern of épée fencing results in an asymmetry of the body. Thus, weapon hand isometric elbow flexion and forward leg isometric and dynamic muscle strength were higher than the contralateral extremity. Finally, forward leg muscle mass--evaluated from computed tomography--was higher while the muscle fiber composition was not different from the contralateral leg.     

Blood sampling during continuous running and 30-second intervals on a treadmill

The aim of the study was to investigate whether results from lactate threshold tests on a treadmill would be influenced by collecting blood during 30-s intervals (INT) as compared to sampling during continuous running (CONT). Ten well-trained middle- and long-distance runners ran the two protocols randomly on separate days, with the same speed both times. Values of blood lactate, heart rate and ratings of perceived exertion (RPE) were compared. The results showed no significant difference in any of the variables comparing the two regimens. During CONT and INT, running speed at 4.0 mmol · l⁻¹ was 18.6 (±1.2) and 18.7 (±1.2) km · h⁻¹, HR 182 (±10.7) and 183 (±8.1) beats · min⁻¹, respectively. Also at the 2 and 3 mmol · l⁻¹ level there were no significant differences in running speed or heart rate. RPE values of legs and breathing at the final speed, just above the 4 mM level, showed no significant difference. It is concluded that, for well-trained middle- and long-distance runners, any of the two regimens can be chosen without affecting the lactate threshold results.     

Beat‐to‐beat QRS amplitude variability in elite endurance athletes

Results from variance electrocardiography, displaying the wide‐band, phase‐locked electrical micro‐variability during the depolarization phase, was analysed versus clinical data, echocardiographic structural and functional variables and myocardial scintigraphic findings in 174 elite orienteers compared with 37 age‐matched elite endurance athletes and 50 age‐matched, healthy medical students. PCA analysis identified a subgroup of five orienteers deviating from the rest of the study group and both control groups with regard to their QRS amplitude variability. No correlations were found between pathology by medical history or any of the echocardiographic and scintigraphic variables or by the variance electrocardiographic aberrations in any of the groups studied.