Marcel Ballin also argues that there are many different reasons for promoting physical activity. However, large-scale interventions or policy changes intended to apply to the entire population must be based on reliable estimates — otherwise there is a risk of expecting effects that have in fact been overestimated. “Our results should not be interpreted as if physical activity and exercise are ineffective or that you should not try to promote it. But to create a more nuanced understanding of how big the effects of fitness actually are on different outcomes, we need to use several different methods. If we just ask the question in the same way, we will always get the same answer. It’s only when we get the same answer to a question that we have asked in slightly different ways that we can be sure that the findings are accurate,” says Marcel Ballin.