The 10–20% Rule: A Simple Way to Build Summer Fitness Without Breaking Down

One of the easiest ways to reduce your risk of injury during the summer is to avoid doing “too much, too soon.” A helpful guideline is the 10–20% rule: when increasing activity, try not to increase your total volume by more than about 10–20% per week. That could apply to running mileage, hiking distance, number of pickleball games, time spent walking hills, or even the amount of yard work you do in a weekend. The exact number does not have to be perfect — the bigger idea is to give your body time to adapt.

A common mistake is adding too many new variables at once. For example, someone might start running more often, add hills, increase speed, wear new shoes, and do a long hike all in the same week. Each of those things may be fine on its own, but stacking them together can overload the system. A better approach is to change one major variable at a time: distance, intensity, terrain, load, or frequency. This allows your muscles, joints, tendons, and nervous system to build capacity instead of constantly playing catch-up.

If you are returning to activity or ramping up for summer, think of the first few weeks as your “build phase.” Keep some days easy, add recovery days after harder efforts, and pay attention to soreness that lingers longer than expected. Mild muscle soreness can be normal. Sharp pain, swelling, limping, numbness, or pain that worsens as you continue are signs to back off and get assessed. Summer should be a season of more movement, not more setbacks.