If Serena Williams only played tennis, there's a good chance she'd burn out, get hurt or both. "Any workout done exclusively can lead to an overuse injury and decreased results," Holland says. "Cross-training, engaging in an activity with different cardiovascular demands and muscle activation patterns, can increase endurance, strength and flexibility while allowing you to continue favorite activities with less risk."
How to cross-train if you're a...
- Runner: Spin to boost your aerobic capacity, without added pounding on joints.
- Cyclist: Take a Pilates class to stretch your low back and strengthen abs, two spots that can suffer on a bike.
- Yogi: Add two weekly strength workouts with bands or weights to build muscle.
- Boot Camper: Do a weekly long, slow jog to build endurance and offset intervals.