Butkus never did one power clean his entire playing career or life for that matter. Now a days, I think it's against the law if you don't do a power clean or flip a truck tire in a sports drink or shoe commercial. These exercises may look impressive but what are they really doing?
The mainstay for most football strength and conditioning programs, power cleans are thought to build more explosive power and training the "fast twitch" muscles. First off, fast and slow twitch muscles are a extremely complicated subject, football and strength coaches oversimplified this process for decades and understand nothing about it. A personal trainer or coach that tells you that an exercise is training the "fast twitch" muscles has no idea how the body actually works and you should run, and run away fast!
During a power clean, how do you get the weight started? Is it a smooth slow contraction where the muscles do all the work with no momentum? Or is it a sudden violent jerk? We all know it's a sudden jerk. After you've jerked the weight hard enough to get it started, you're muscles are really doing no work until the weight travels high enough until you can rotate under it and catch the weight. All the while exposing your joints, muscles, bones tendons, ligaments to an insane amount of force. Bottom line: In a power clean you are throwing the weight, you have to, otherwise you wouldn't be able complete the movement. When you throw weights, there's a high chance of injury.
Do power cleans relate to football?
Power cleans are a closed skill set, meaning that the environment is the same with the same movement pattern each time. Football requires and open skill set, meaning the environment is always changing and you have to be flexible with how you respond each time. Power cleans have no relationship or transfer to anything done in football or any sport for that matter. If your sport is doing power cleans or cross fit, then do you need to do power cleans, just find a good orthopedist.
What exercises should you do to increase explosiveness and power for football?
No exercise can reproduce the countless number of explosive moves you do while playing football. Whatever cards you were dealt genetically will be improved by building strength in the safest and most productive manner. In general, train all the major muscle groups by doing the basics and using the most sophisticated equipment possible. If barbells are all you got then do the following exercises along with neck training, Squats, Deadlifts, Standing Presses, Pull Ups, Bench Press, Bicep curls, and Dips will literally do wonders if done right. There are many variations but this is a great place to start. With good equipment you'll have better options.
What form should I use while lifting weights?
One of the best way to lift weights is negative accentuated training. This means you smoothly lift the weight in a slow controlled manner and lower the weight even slower. For example take 2 seconds to lift and 4 seconds to lower. Depending on the exercise, a pause should occur in the isometric position.
Workout to prevent injuries and increase performance. You'll get more than enough explosive work during a full season of practice, pre season games, regular season games, playoffs, and hopefully Super Bowl. Play fast and practice fast, take care of your body. Set yourself up to be just as strong at the end of the season. After all your body is an investment, if you don't take care of it you can't play.