Physical activity, genes, and lifetime predisposition to chronic disease

Table 1 Strengths and weaknesses of the study designs in physical activity/exercise and health research

Study design	Strengths	Weaknesses
Observational cohort studies	Large sample sizes	Unclear cause-and-effect evaluation
	Population-based samples	Unclear cause-and-effect evaluation
	Population-based samples	Healthy exerciser bias
	Long follow-ups	Healthy exerciser bias
Experimental mechanistic studies	Show in-detail effects of training on specific risk factors	Small sample sizes
Experimental mechanistic studies	Show in-detail effects of training on specific risk factors	Effects on true disease outcomes and disease progression unclear
(Randomized) controlled trials	Reliable evaluation of cause-and-effect	Small sample sizes
(Randomized) controlled trials	Reliable evaluation of cause-and-effect	Short follow-ups

ISSN: 1861-6909