Table 1

Strengths and weaknesses of randomized clinical trials versus observational studies of exercise and cancer risk

Randomized clinical trialsObservational studies
Strengths• Minimal bias• Relatively simple to administer
• Less measurement error
• Can measure high intensity• Inexpensive
• Can assess effect of change• No intervention required
• Minimize confounding• Ease of recruitment
• Determine pertinent aspects of movement• Subgroup analyses posible
• Avoid within-population homogeneity of exercise exposure
• Can focus on specific populations
• Can assess effect on intermediate endpoints and biomarkers
• Able to examine synergy with other factors
• Measure effects of exercise on multiple endpoints
Weaknesses• Expensive• Homogeneity of exposures (usually few high-intensity exercisers)
• Multidisciplinary team required
• Exercise facilities needed• Difficult to measure change
• Recruitment challenges• Bias in measurement
• Control group issues• Incomplete control of confounders
• Adherence/retention issues
• May require very large sample size and long-term follow-up to show definitive effects on disease endpoints• Colinear covariates