Conclusions Exercise-based cardiac rehabilitation is effective at reducing important clinical outcomes in patients with coronary heart disease .
While our analysis was constrained by the quality of included trials and missing information about intervention components , there appears to be little differential effect of variations in exercise intervention , particularly on mortality outcomes .
Background While the clinical benefits of exercise-based cardiac rehabilitation are well established , there is extensive variation in the interventions used within these trials .
It is unknown whether variations in individual components of these exercise interventions provide different relative contributions to overall clinical outcomes .
This study aims to systematic ally examine the relationship between individual components of the exercise intervention in cardiac rehabilitation ( such as intensity and frequency ) and clinical outcomes for people with coronary heart disease .
Complex interventions: how “out of control” can a randomised controlled trial be?
Complex interventions are more than the sum of their parts , and interventions need to be better theorised to reflect this Many people think that st and ardisation and r and omised controlled trials go h and in h and . Having an intervention look the same as possible in different places is thought to be paramount . But this may be why some community interventions have had weak effects . We propose a radical departure from the way large scale interventions are typically conceptualised . This could liberate interventions to be responsive to local context and potentially more effective while still allowing meaningful evaluation in controlled design s. The key lies in looking past the simple elements of a system to embrace complex system functions and processes . The suitability of cluster r and omised trials for evaluating interventions directed at whole communities or organisations remains vexed.1 It need not be.2 Some health promotion advocates ( including the WHO European working group on health promotion evaluation ) believe r and omised controlled trials are inappropriate because of the perceived requirement for interventions in different sites to be st and ardised or look the same.1 3 4 They have ab and oned r and omised trials because they think context level adaptation , which is essential for interventions to work , is precluded by trial design s. An example of context level adaptation might be adjusting educational material s to suit various local learning styles and literacy levels . Lead thinkers in complex interventions , such as the UK 's Medical Research Council , also think that trials of complex interventions must “ consistently provide as close to the same intervention as possible ” by “ st and ardising the content and delivery of the intervention.”5 By contrast , however , they do not see this as a reason to reject r and omised controlled trials . These divergent views have led to problems on two fronts . Firstly , the field of health promotion is being turned away from r and omised
Conclusions Exercise-based cardiac rehabilitation is effective at reducing important clinical outcomes in patients with coronary heart disease .
While our analysis was constrained by the quality of included trials and missing information about intervention components , there appears to be little differential effect of variations in exercise intervention , particularly on mortality outcomes .
Background While the clinical benefits of exercise-based cardiac rehabilitation are well established , there is extensive variation in the interventions used within these trials .
It is unknown whether variations in individual components of these exercise interventions provide different relative contributions to overall clinical outcomes .
This study aims to systematic ally examine the relationship between individual components of the exercise intervention in cardiac rehabilitation ( such as intensity and frequency ) and clinical outcomes for people with coronary heart disease .