Jan Svedenhag

Applied Physiology of Marathon Running

SummaryPerformance in marathon running is influenced by a variety of factors, most of which are of a physiological nature. Accordingly, the marathon runner must rely to a large extent on a high aerobic capacity. But great variations in maximal oxygen uptake V̇O2 max have been observed among runners with a similar performance capacity, indicating complementary factors are of importance for performance. The oxygen cost of running or the running economy (expressed, e.g. as V̇O2 15 at 15 km/h) as well as the fractional utilisation of V̇O2 max max at marathon race pace %V̇O2 ma × V̇O2 ma−1) [where Ma = mean marathon velocity] are additional factors which are known to affect the performance capacity. Together V̇O2 max, V̇O2 15 and %V̇O2 ma × V̇O2 ma−1 can almost entirely explain the variation in marathon performance. To a similar degree, these variables have also been found to explain the variations in the ‘anaerobic threshold’. This factor, which is closely related to the metabolic response to increasing exercise intensities, is the single variable that has the highest predictive power for marathon performance. But a major limiting factor to marathon performance is probably the choice of fuels for the exercising muscles, which factor is related to the %V̇O2 ma × V̇O2 ma−1. Present indications are that marathon runners, compared with normal individuals, have a higher turnover rate in fat metabolism at given high exercise intensities expressed both in absolute (m/sec) and relative %V̇O2 max terms. The selection of fat for oxidation by the muscles is important since the stores of the most efficient fuel, the carbohydrates, are limited. The large amount of endurance training done by marathon runners is probably responsible for similar metabolic adaptations, which contribute to a delayed onset of fatigue and raise the %V̇O2 ma × V̇O2 ma−1. There is probably an upper limit in training kilometrage above which there are no improvements in the fractional utilisation of V̇O2 max at the marathon race pace. The influence of training on V̇O2 max and, to some extent, on the running economy appears, however, to be limited by genetic factors.

Co-release of neuropeptide Y and catecholamines during physical exercise in man

Venous plasma levels of neuropeptide Y-like immunoreactivity (with chromatographic properties of synthetic neuropeptide Y) increased in parallel with catecholamines, heart rate and blood pressure during graded physical exercise in man. The plasma levels of neuropeptide Y correlated better with the levels of noradrenaline than adrenaline, suggesting release of a neural origin. Taken together with previous results, this suggests that neuropeptide Y is released together with noradrenaline upon sympathetic activation during physiological conditions in man. Determinations of plasma neuropeptide Y may therefore be valuable in the assessment of sympathetic nerve activity.

Changes in onset of blood lactate accumulation (OBLA) and muscle enzymes after training at OBLA

SummaryEight well-trained middle and long distance male runners added to their regular training program a weekly 20-min treadmill run at a velocity calculated to elicit a blood lactate concentration of 4 mmol×1−1.

Oxygen uptake during running as related to body mass in circumpubertal boys: a longitudinal study

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Increase in Skeletal Muscle Lipoprotein Lipase Following Endurance Training in Man

O2 max, the running velocity eliciting 4 mmol×1−1 blood lactate (VOBLA), and the activities of citrate synthase (CS), phosphofructokinase (PFK), lactate dehydrogenase (LDH) and LDH isozymes in the M. vastus lateralis were determined before and after 14 weeks of this training. Significant increases were observed in VOBLA and the relative fraction of heart-specific LDH, while the activity of PFK and the ratio of PFK/CS decreased after training. The change in VOBLA was negatively correlated to the mean rate of blood lactate accumulation during the last 15 min of the treadmill training runs, and positively correlated to the percentage of slow twitch fibers in the M. vastus lateralis. The data support the hypothesis that a steady state training intensity which approximates VOBLA will increase VOBLA, and will result in measureable local metabolic adaptations in the active skeletal muscles of well-trained runners without a significant change in maximal aerobic power. Muscle fiber type composition may be an indicator of the “trainability’ of the musculature.

Effect of muscle mass on lactate formation during exercise in humans.

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.

Beat-to-beat QRS amplitude variability during dobutamine infusion in patients with coronary artery disease

SummaryTo investigate the effect of endurance training on physiological characteristics during circumpubertal growth, eight young runners (mean starting age 12 years) were studied every 6 months for 8 years. Four other boys served as untrained controls. Oxygen uptake (