The heterogeneity in reported effects was reduced in higher quality studies , when physical activity was self-directed with some professional guidance and when there was on-going professional support .
Our review suggests that physical activity interventions have a moderate effect on self reported physical activity and cardio-respiratory fitness , but not on achieving a predetermined level of physical activity .
Due to the clinical and statistical heterogeneity of the studies , only limited conclusions can be drawn about the effectiveness of individual components of the interventions .
BACKGROUND Little is known about the effectiveness of strategies to enable people to achieve an increase in their physical activity .
OBJECTIVES To assess the effects of interventions for promoting physical activity in adults aged 16 years and older , not living in an institution .
Work Ability, Physical Activity, and Cardiorespiratory Fitness: 2-year Results From Project Active
An adequate level of physical activity may maintain or promote work ability in aging workers . Project Active is a r and omized trial comparing a Lifestyle physical activity program with a Structured exercise program in sedentary but healthy adults aged 35 to 60 years . Subjects in both groups received 6 months of intensive intervention followed by 18 months of active follow-up .  The total number of subjects was 235 , from which 80 subjects participated in the work ability assessment . Primary outcome measures were energy expenditure ( kcal · kg−1 · day−1 ) , cardiorespiratory fitness ( peak oxygen uptake in ml · min−1 · kg−1 ) , and the Work Ability Index . At 6 months , daily energy expenditure had increased significantly over baseline ( mean ± SD , from 33.0 ± 0.9 to 34.4 ± 1.8 kcal · kg−1 · day−1 ) and was maintained over baseline at 24 months ( 34.0 ± 2.5 kcal · kg−1 · day−1 ) . The significant increase in energy expenditure was observed particularly in moderate levels of activity . The average percentage of body fat was significantly higher at baseline compared with 6 months and 24 months . Peak oxygen uptake increased from baseline significantly during the first 6 months ( from 29.6 ± 5.7 to 30.6 ± 6.3 ml · min−1 · kg−1 ) and decreased to the baseline level ( 29.1 ± 5.5 ml · min−1 · kg−1 ) at 24 months . At baseline , the average Work Ability Index was 44.2 ± 4.0 , and it remained unchanged at 6 months ( 44.4 ± 3.9 ) and at 24 months ( 44.2 ± 3.1 ) . In conclusion , a 2-year physical activity intervention increased daily energy expenditure , reduced body fat , and maintained peak oxygen uptake in healthy , middle-aged , sedentary subjects .  The average Work Ability Index score at baseline was excellent and did not change during the 2-year physical activity interventions
The heterogeneity in reported effects was reduced in higher quality studies , when physical activity was self-directed with some professional guidance and when there was on-going professional support .
Our review suggests that physical activity interventions have a moderate effect on self reported physical activity and cardio-respiratory fitness , but not on achieving a predetermined level of physical activity .
Due to the clinical and statistical heterogeneity of the studies , only limited conclusions can be drawn about the effectiveness of individual components of the interventions .
BACKGROUND Little is known about the effectiveness of strategies to enable people to achieve an increase in their physical activity .
OBJECTIVES To assess the effects of interventions for promoting physical activity in adults aged 16 years and older , not living in an institution .