Cross training involves playing a different sport or participating in another kind of physical activity besides your usual workout. Such training gives the body and mind a break from your primary sport’s continuous and repetitive movement, while simultaneously enhancing performance skills. By playing another sport or performing exercises you don’t normally do, you engage different muscles and ultimately improve athleticism or some aspect of your performance, like strength, speed and quickness.
For instance, volleyball athletes may play basketball, runners may swim laps and football players may play rugby or soccer. The key is to choose a sport or activity you enjoy, but also one that enhances your primary sport’s performance or skill.
The following ideas can help get you started:
Conditioning: Pool work, swimming and racket sports
All are great substitutes for running and other “high impact” sports (e.g., basketball, football and hockey) and activities that pound on the joints. Whether you swim, run or perform other exercises in the water, you can improve your aerobic capacity through long swims or your anaerobic capacity through interval training. The Michael Johnson Performance Center uses Hydro Training (underwater resistance training) one to two times a week to help athletes actively recover between training days. Watch video and learn how Detroit Lions’ Ndamukong Suh Hydro Trains.
Racket sports—racquetball, tennis and pingpong—are good cross-training choices for athletes constantly throwing or engaging in overhead contact, particularly baseball and volleyball. Racket sports involve alternating activity and recovery, delivering conditioning benefits that baseball and volleyball players need. The overhead motion of the racket swing helps with shoulder mobility, strength and range-of-motion, while tracking the ball develops hand-eye coordination.
Flexibility: Pilates, yoga, dance, dynamic warm-up
These activities promote functional fitness, meaning the body moves as a whole instead of moving muscles separately. Such cross-training can enhance performance and reduce injury by improving flexibility in all joints. It also helps with strength, mobility and stability in certain parts of the body that your usual training doesn’t work, such as traditional Squats and Presses or other exercises where the body is supported by an external system (Bench Press or Leg Press Machine).
If you’re not already engaging in a dynamic warm-up before training, you need to start! Each sport requires specific movements, and many times the dynamic warm-up will include drills that prepare the body for those moves and for the sport. If you’ve been performing the same dynamic warm-up routine all season, the off-season is a great time to try new movements and drills and to focus on areas that need work.
Strength Training: Bands, balls and bodyweight
You don’t always have to head to the weight room for a great resistance-training workout. Bands, balls, bodyweight and other exercise gear add variety to any workout while forcing you to adjust to the new way the load (weight or resistance) stresses your body.
For an active recovery week, pick a different piece of equipment each day and use it in your workout:
Monday: Medicine Ball
Watch video of Indianapolis Colts QB Peyton Manning performing med ball core work to improve strength
Tuesday: Bands
Watch video of Pro Bowl receiver Terrell Owens discussing the benefits of resistance band training
Wednesday: Stability Ball
Watch video of Phoenix Suns PG Steve Nash using stability ball training to improve strength and power
Thursday: Bodyweight
Watch video of NFL All-Pro DE Dwight Freeney using his bodyweight to improve upper-body explosion and power
Friday: Suspension Training
Watch video of Oklahoma City Thunder G/F Kevin Durant using TRX Suspension Training to boost upper-body strength 
Adjust the exercises, the load and the volume, but have fun. You could see great improvement. You might even become sore in ways you’ve never experienced.
For a complete guide to alternative training methods, including exercises and equipment, go to Alternative Training Methods.
Speed and Agility: 
To get fast and quick, you must run fast and move at quick speeds. But, sports aren’t always played in a straight line or from one cone to the next. Add variety to your routine by playing games (check out the sections about sport-specific cross training below) and getting involved with other sports during the summer. You’ll maintain “fast feet” and still change up your activity.
Football Athletes: Hop in a pick-up game of soccer or touch game of rugby
•    Improves agility and conditioning
•    Enhances movement skills and teamwork
Related link: More cross training activities and games for football
Soccer Athletes: Organize a flag football game
•    Enhances ability to move around another player and body position
•    Improves speed work and interval-type conditioning
•    Develops agility and quickness
Related link: More cross training activities and games for soccer
Basketball Athletes: Play sand volleyball
•    Enhances jumping ability
•    Improves leg strength
•    Practices getting into a low athletic position, which transfers over to defense on the court
•    Develops lateral movement, by working to lift the feet through the hips
Related link: More cross training activities and games for basketball
Volleyball Athletes: Join a 3-on-3 basketball team
•    Builds explosive reaction time
•    Develops jumping power
•    Improves lateral moves
Related link: More cross training activities and games for volleyball
Baseball Athletes: Organize a dodgeball game to test your throwing form without a baseball
•    Improves throwing skills from a variety of positions
•    Builds shoulder strength and functional mobility by throwing a larger ball
•    Teaches you to move and react to the action around you
Related link: More cross training activities and games for baseball