If sore knees have ruled out running, the pool deserves a look. Swimming builds aerobic fitness across nearly every muscle group while your joints carry almost nothing. The weak grade reflects thin long-term data, not signs of harm. Big studies are simply scarce.
One large British cohort anchors this entry. It followed 80,306 adults and compared six sport types, including swimming. Swimmers had lower risks than non-participants: deaths from any cause (hazard ratio 0.72, 95% CI 0.65 to 0.80) and cardiovascular deaths (0.59). That study is observational, and swimmers skew toward people with leisure time and income, so part of the advantage probably belongs to circumstance rather than to strokes. Fewer cohorts cover swimming than walking or cycling, and no trial has tested swimming against other exercise on mortality. It counts fully toward the 150 weekly minutes in WHO guidance, which is the sensible way to value it.
Doing it: Swim 20 to 30 minutes of comfortable laps two or three times a week, resting between lengths whenever you need to. A few technique lessons early repay themselves for decades. Pool walking counts too if laps feel out of reach at first.
Who it suits: People with joint pain, arthritis, old injuries or extra weight that makes land exercise uncomfortable, plus anyone who dislikes sweating. Non-swimmers should ask about adult beginner classes; pools usually run them cheaply.
Sources
- Oja et al., British Journal of Sports Medicine 2017; specific sports and mortality, cohort of 80,306 British adults (PMID 27895075)
- WHO Guidelines on physical activity and sedentary behaviour, 2020
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