No abstract

We investigated the hypothesis that the pulmonary oxygen uptake (V O 2 ) slow component is related to a progressive increase in muscle lactate concentration and that prior heavy exercise (PHE) with pronounced acidosis altersV O 2 kinetics and reduces work efficiency. Subjects (n = 9) cycled at 75% of the peakV O 2 (V O 2 peak ) for 10 min before (CON) and after (AC) PHE.V O 2 was measured continuously (breath-by-breath) and muscle biopsies were obtained prior to and after 3 and 10 min of exercise. Muscle lactate concentration was stable between 3 and 10 min of exercise but was 2-to 3-fold higher during AC (P < 0.05 versus CON). Acetylcarnitine (ACn) concentration was 6-fold higher prior to AC and remained higher during exercise. Phosphocreatine (PCr) concentration was similar prior to exercise but the decrease was 2-fold greater during AC than during CON. The time constant for the initialV O 2 kinetics (phase II) was similar but theV O 2 asymptote was 14% higher during AC. The slow increase inV O 2 between 3 and 10 min of exercise during CON (+7.9 ± 0.2%) was not correlated with muscle or blood lactate levels. PHE eliminated the slow increase inV O 2 and reduced gross exercise efficiency during AC. It is concluded that theV O 2 slow component cannot be explained by a progressive acidosis because both muscle and blood lactate levels remained stable during CON. We suggest that both theV O 2 slow component during CON and the reduced gross efficiency during AC are related to impaired contractility of the working fibres and the necessity to recruit additional motor units. Despite a pronounced stockpiling of ACn during AC, initialV O 2 kinetics were not affected by PHE and PCr concentration decreased to a lower plateau. The discrepancy with previous studies, where initial oxidative ATP generation appears to be limited by acetyl group availability, might relate to remaining fatiguing effects of PHE.

The aim of this study was to compare short- (0-4 months) and long-term (0-10 months) effects of high-intensive Exercise on Prescription (EoP) intervention (counseling and supervised exercise) implemented in primary healthcare in a number of Danish counties with a low-intensive intervention (counseling) using maximal oxygen uptake (VO(2max)) as the primary outcome. The study was conducted as a randomized trial in 2005-2006 with a high and a low-intensive group. All the patients referred to the EoP scheme by their GP in the counties of Vejle and Ribe, Denmark, were eligible for the trial. The high-intensive EoP group received 4 months of group-based supervised training and attended five motivational counseling sessions. The low-intensive group only attended four motivational counseling sessions. Three hundred and twenty-seven patients entered the EoP scheme, and 52 (16%) volunteered for the randomized trial. No short- or long-term differences were found between the high and the low-intensive groups for VO(2max) (short-term 95% CI -1.1; 4.4 mL O(2)/(kg min), long-term 95% CI -1.6 to 2.1). The present study did not demonstrate any significant clinical outcome for the high-intensive EoP intervention as opposed to the low-intensive intervention.

Exercise on prescription can contribute to improvements in physical activity level and health-related quality of life in physically inactive patients with or at increased risk of developing lifestyle diseases. An acceptable number of participants achieved and maintained improvements in physical activity level and health-related quality of life.

Background: In many countries exercise prescriptions are used in an attempt to initiate a physically active lifestyle in sedentary populations. Previous studies have primarily evaluated low intensive exercise prescription interventions and found moderately positive effects on physical activity and aerobic fitness. In a highly intensive Danish exercise prescription scheme called 'Exercise on Prescription' (EoP) the general practitioners can prescribe EoP to sedentary patients with lifestyle diseases. The aim of this randomized trial is to assess the short-and long-term effects of the EoP scheme. Thus, the aim of this paper is to describe the randomized controlled trial designed for evaluating effectiveness of EoP, and to present results from validations of outcome measures.