Randomized controlled trials (RCTs) are the gold standard of research design and therefore provide the bedrock of evidence for claims regarding the health benefits of exercise training across the human lifespan. Nevertheless, there is substantial heterogeneity between RCTs regarding the outcomes of exercise training, as RCTs sometimes provide null or negative results regarding changes in outcomes, and positive results might even suffer from a lack of reproducibility by other scientists. This paper reviews the National Institutes of Health (NIH) Stage Model of Intervention Development and then identifies aligning research approaches and design considerations for informing and conducting RCTs of exercise training and its health benefits. The primary goal is the provision of a thoughtful and deliberate approach for designing RCTs that yield strong and reproducible research results regarding the health benefits of exercise training. This is necessary for strengthening the science behind the implementation and dissemination of evidence-based exercise training programs.