Jes Bak Sørensen

Exercise on prescription in general practice: A systematic review

‘Exercise on Prescription’ (EoP) is used for initiating physical activity among sedentary patients with signs of lifestyle diseases. EoP is personalized secondary prevention in primary healthcare. This review addresses EoP using a Health Technology Assessment perspective and aims to answer the following questions: (1) Does EoP increase physical activity level or physical fitness, and is more intensive EoP more effective than less intensive? (2) Is EoP acceptable and feasible in general practice? (3) Is EoP acceptable to and feasible for sedentary patients? (4) Is EoP cost-effective? EoP studies were searched using Medline thesaurus topic, Medline WinSPIRS, reference lists of recent reviews, and NLM Gateway Locator plus. A total of 22 studies were included in the review. Most studies reported moderate improvements in physical activity or physical fitness for 6–12 months. Among patients receiving EoP 10% more had improved physical activity level compared with controls and mean aerobic fitness was improved by 5–10% among EoP patients compared with controls. Little evidence existed in support of the hypthesis that more intensive EoP is more effective. EoP was acceptable and feasible to GPs and patients volunteering for EoP. However, little is known about non-completers, patients declining EoP, and GPs not highly motivated for using EoP. Only one study addressed health economic issues. It found EoP cost-effective, but comparisons with other interventions have not been performed. Even though most studies in this review presented favourable results for EoP there is a lack of evidence in several fields. In particular we lack high-quality studies evaluating EoP schemes that are sustainable in everyday use in general practice.

Prior heavy exercise eliminates slow component and reduces efficiency during submaximal exercise in humans

We investigated the hypothesis that the pulmonary oxygen uptake slow component is related to a progressive increase in muscle lactate concentration and that prior heavy exercise (PHE) with pronounced acidosis alters kinetics and reduces work efficiency. Subjects (n= 9) cycled at 75% of the peak for 10 min before (CON) and after (AC) PHE. 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 initial kinetics (phase II) was similar but the asymptote was 14% higher during AC. The slow increase in 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 in and reduced gross exercise efficiency during AC. It is concluded that the slow component cannot be explained by a progressive acidosis because both muscle and blood lactate levels remained stable during CON. We suggest that both the 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, initial 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.

Exercise on prescription: a randomized study on the effect of counseling vs counseling and supervised exercise

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 (VO2max) 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 VO2max (short‐term 95% CI −1.1; 4.4 mL O2/(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.

Muscle fiber type distribution and nonlinear Vo2-power output relationship in cycling

PURPOSE We examined whether reported deviations from linearity of the oxygen uptake (.VO(2))-to-power output (W) relationship during intense cycling exercise correlated with the percentage Type II fibers in the exercising muscle. METHODS Twelve trained young men with known fiber type distribution in the vastus lateralis muscle performed step-increment exercise (40 W.3 min(-1)) to exhaustion. RESULTS .VO(2) increased linearly with W up to about 50% .VO(2max) with a regression equation of .VO(2) (mL.min-1) = 661 + 9.73 W and a correlation coefficient (r) of 1.000. Subsequent .VO(2) values were all greater than corresponding linear estimates (P < 0.001 or 0.0001). Peak exercise excess .VO(2) (measured minus estimated .VO(2) assuming linearity) averaged (SD) 434 (192) mL O(2).min-1 or 10.3 (4.7) % .VO(2max). A comprehensive curvilinearity index defined as the sum of measured minus estimated .VO(2) at the four highest completed exercise trials averaged 973 (460) mL O(2).min-1 or 21.5 (9.4) % .VO(2max). Correlations between percentage Type II fibers and either of the two expressions of curvilinearity were nonsignificant. Delta [H+] (arterialized capillary blood) from basal level to peak exercise correlated with the submaximal curvilinearity index (r = 0.59-0.64; P < 0.05) but not with peak excess .VO(2). There was a trend toward a correlation between delta La and curvilinearity index in % .VO(2max)(r = 0.52; P < 0.10) but not with any of the other curvilinearity expressions. The relative ventilatory activity expressed as .V(E)-to-.VO(2) ratio tended to correlate with peak excess .VO(2) (P < 0.10) but not with curvilinearity index. Signals from motion sensors indicate that coactivation of upper-body musculature coincided with deviation from linearity in the .VO(2)-W relationship. CONCLUSION VO2 during step-increment cycling increases linearly with power output up to about 50% .VO(2max)and then curvilinearly. The degree of curvilinearity is not related to muscle fiber type distribution in the vastus lateralis, and only marginally and insignificantly related (P < 0.10) to the relative degree of hyperventilation or to lactate response. Acidosis, on the other hand, correlated significantly with curvilinearity index. The inclusion of isometrically working, upper-body muscular groups during high-intensity cycling may also contribute to the overshoot in oxygen cost.