Biomedical subjects

Jan Helgerud

Publications and source records attributed to Jan Helgerud.

6 recordsLinked to original sources

PubMed2005

Effective training for patients with intermittent claudication.

OBJECTIVE: Current guidelines for treatment of intermittent claudication (IC) do not include a specific recommendation for the intensity of exercise therapy. Thus, the purpose of this study was to determine the relative effectiveness of high versus low intensity exercise for patients with IC, and further to study the effect of such training on blood flow to the legs during exercise. DESIGN: The effect of eight weeks of supervised endurance training was examined in 16 patients with IC. The patients were randomly assigned to training at intensities corresponding to either 60% or 80% of their peak oxygen consumption (VO2peak), respectively. RESULTS: VO2peak and time to exhaustion increased significantly (9% and 16%, respectively) more in the high intensity group (p<0.05). Blood flow to the legs did not change after training in any of the groups. CONCLUSION: High intensity training gave larger improvements in VO2peak and time to exhaustion than low intensity training. As blood flow did not change after the exercise program, it is likely that the observed different increase of VO2peak was due to changed mitochondrial oxidative capacity and/or skeletal muscle diffusive capacity.

Aged↗

PubMed2004

High intensity aerobic interval exercise is superior to moderate intensity exercise for increasing aerobic capacity in patients with coronary artery disease.

BACKGROUND: Increased aerobic exercise capacity appears to reduce both all-cause mortality and cardiovascular disease mortality. Physical exercise to improve peak oxygen uptake (VO2peak) is thus strongly recommended, however evidence regarding the most efficient training intensity for patients with coronary artery disease (CAD) is still lacking. The purpose of this randomized study was therefore to assess the effects of high intensity aerobic interval exercise compared to moderate intensity exercise, representing the same total training load, for increasing VO2peak in stable CAD-patients. METHODS: Twenty-one stable CAD-patients were randomized to supervised treadmill walking at either high intensity (80-90% of VO2peak) or moderate intensity (50-60% of VO2peak) three times a week for 10 weeks. RESULTS: After training VO2peak increased by 17.9% (P=0.012) in the high intensity group and 7.9% (P=0.038) in the moderate intensity group. The training-induced adaptation was significantly higher in the high intensity group (P=0.011). CONCLUSIONS: High intensity aerobic interval exercise is superior to moderate exercise for increasing VO2peak in stable CAD-patients. As VO2peak seems to reflect a continuum between health and cardiovascular disease and death, the present data may be useful in designing effective training programmes for improved health in the future.

Coronary Artery Disease↗

PubMed2004

Atrioventricular plane displacement in untrained and trained females.

PURPOSE: Female athletes often demonstrate changes in cardiac dimensions that are less prominent than in male athletes, and results from longitudinal studies are conflicting. The atrioventricular plane displacement (AVPD) in the heart is used as an index of left ventricular systolic function with the assumption that it is a more sensitive method for measuring myocardial contractility compared with left ventricular ejection fraction. The aim of the present study was to determine the effect of a short period of endurance training on cardiac dimensions in sedentary female subjects and to measure the AVPD at rest and during submaximal workload. METHODS: Twelve sedentary female subjects (21.9 +/- 1.3 yr, 168.8 +/- 3.5 cm, 64.0 +/- 6.6 kg, and 42.6 +/- 2.9 mL x kg(-1) x min(-1) in maximal oxygen uptake) were examined with echocardiography before and after a period of interval training (varying from 2 to 5 min at 90-95% of maximal heart rate, 3 d x wk(-1), 8 wk). RESULTS: Maximal oxygen uptake increased by 18% to 50.4 +/- 3.1 mL x kg(-1) x min(-1) (P < 0.001). Left ventricular mass increased from 123.9 to 139.2 g (P = 0.007). There was a significant increase in posterior wall thickness but no change in cavity size. The AVPD did not change at rest but increased significantly from 15.6 to 17.6 mm (P < 0.001) during exercise at 85-90% of maximal heart rate. CONCLUSION: This study shows that a short period of aerobic endurance training induces changes in the female heart, both in cardiac dimensions at rest and in left ventricular systolic function at submaximal workload. AVPD during submaximal exercise discriminate well between the untrained and trained healthy heart.

Adaptation, Physiological↗

PubMed2004

Endurance and strength training for soccer players: physiological considerations.

Top soccer players do not necessarily have an extraordinary capacity in any of the areas of physical performance. Soccer training is largely based on the game itself, and a common recruitment pattern from player to coach and manager reinforces this tradition. New developments in understanding adaptive processes to the circulatory system and endurance performance as well as nerve and muscle adaptations to training and performance have given rise to more effective training interventions. Endurance interval training using an intensity at 90-95% of maximal heart rate in 3- to 8-minute bouts have proved to be effective in the development of endurance, and for performance improvements in soccer play. Strength training using high loads, few repetitions and maximal mobilisation of force in the concentric mode have proved to be effective in the development of strength and related parameters. The new developments in physical training have important implications for the success of soccer players. The challenge both for coaches and players is to act upon the new developments and change existing training practice.

Humans↗

PubMed2002

Maximal strength-training effects on force-velocity and force-power relationships explain increases in aerobic performance in humans.

Maximal strength-training with an emphasis on maximal mobilization during cross-country skiing increases exercise economy when double-poling. The aim of this experiment was to investigate whether the mechanism of this increase is a change in the force-velocity relationship and the mechanical power output. A group of 19 cross-country skiers having an average peak oxygen uptake of 255 ml x kg(-0.67) body mass x min(-1) or 61 ml x kg(-1) x min(-1) were randomly assigned to either a high resistance-training group (n=10) or a control group (n=9). Upper body endurance was tested on a ski ergometer. The high-resistance-training group trained for 15 min on three occasions a week for 9 weeks. Training consisted of three series of five repetitions using 85% of one repetition maximum (1RM), with emphasis on high velocity in the concentric part of the movement. Upper body exercise economy, 1RM and time to exhaustion increased significantly in the high resistance-training group, but was unchanged in the control group. Peak power and the velocities for a given load increased significantly, except for the two lowest loads. We conclude that the increased exercise economy after a period of upper body high resistance-training can be partly explained by a specific change in the force-velocity relationship and the mechanical power output.

Adult↗

PubMed2002

Ultrasound recorded axillary artery blood flow during elbow-flexion exercise.

PURPOSE: To characterize and evaluate the repeatability of ultrasound recorded blood flow in the axillary artery during one-arm dynamic elbow flexion. METHOD: 11 healthy women (23 +/- 0.9 yr, 168 +/- 1.7 cm, 63 +/- 1.1 kg) performed 90 degrees elbow flexion in supine position. Mean maximum blood velocity was recorded by ultrasound during and after two submaximal loads, representing 16 and 24% of maximal voluntary contraction, and after exhaustion (.VO(2peak))Axillary artery diameter was measured after each workload. Each subject was examined two times 8 wk apart. Oxygen uptake was measured during exercise. Values are mean +/- SE. RESULTS: Flow was not different in the two tests. Flow was 25% higher immediately after than during exercise at the submaximal workloads. Flow immediately after .VO(2peak) was 1420 +/- 79 mL.min(-1). Axillary artery diameter after .VO(2peak) was 8% larger than at rest. Coefficient of variation ranged from 11 to 23%, coefficient of repeatability ranged from 230 mL.min(-1) at rest to 940 mL.min(-1) after exercise. Coefficient of repeatability for artery diameter was 0.09 cm; coefficient of variation for diameter was about 4% at all recording times. CONCLUSION: The present study showed that ultrasound recordings of blood flow during dynamic elbow-flexion exercise were reproducible. The method can be used to study training-induced flow changes and can detect differences of about 130 mL.min(-1). Artery diameter seemed to increase as flow and load increased.

Adult↗