Strength and Conditioning
Become strong. To generate a vast amount of pace, you must broaden your shoulders, and build muscle on your arms and legs. Use dumbbells for your arms, bench press to broaden your shoulders, and leg exercise to keep your legs strong.
Improve your conditioning. Fast bowlers tend to bowl immense pace for many overs. This requires stamina. Be sure to run long distances so you can handle bowling a lot of overs, and get faster on your sprints, so you can maintain a quick run-up.
Build speed. Before you focus on line and length, you must work on speed. You do not need to reach the fastest you can bowl, but gradually improve speed until you feel comfortable with the pace you bowl at.
