Evidence in Physical Activity

The evidence that physical activity improves health is among the most consistent in medicine, but most of it on lifetime activity and long-term disease is observational.

Randomised trials provide causal evidence for shorter-term clinical and physiological outcomes. The reasons the rest is observational are practical:

• •Participants cannot be blinded to whether they went for a run
• •Exposure is measured imprecisely
• •People who exercise differ systematically from those who do not
• •The outcomes that matter most accrue over decades

A sport and exercise medicine (SEM) clinician needs to know what the guidelines say and why the evidence behind them looks the way it does: where it is strong and where it is weak.