What is the best way to keep my legs strong without gaining muscle?

What is the best way to keep my legs strong without gaining muscle? I’m built like a sprinter and I build muscle very easily. I run, bike, inline-skate, ski, and play squash and tennis. I want to prevent injuries without adding muscle. I’ve had two knee surgeries and over 40. Jay Liverpool, New York

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Many endurance athletes are on a constant quest to improve leg strength and leg speed, but increased size is usually counterproductive to their major goals. In order to most effectively improve your athletic endeavors while minimizing the risk of injury, your strength program should include exercises that closely mimic the movements, speeds, and resistances that you encounter in your activities. This can be difficult to do in the weight room, but often you can improve strength while performing your chosen sport. Uphill running is one example that would likely save your knee joints. Low-cadence, high-resistance cycling would be another way to build sport-specific strength for athletes who don’t have knee issues to work around. But even pure cyclists often use a winter running program to maintain and improve leg strength. Here are some tips to ensure safety and maximize gains from hill running.

Use an aerobic/endurance pace rather than a maximum effort
Shorten your stride when running uphill
Run more on your toes than normal
Choose a variety of grades and lengths when running hills
Jog slowly or walk when coming down; downhill running can contribute to joint pain and muscle soreness
Incorporate long continual hills at an endurance pace, as well as shorter, steeper hills for more intense interval work