Here are what I think are the 3 biggest mistakes an S&C coach can make.
1. Slow steady state cardio training for athletes competing in speed/power based events. This one drives me insane and I have to say it usually gets spouted to me by old school coaches that are stuck in the 80's or sport sceintists that bang on about research having never coached in their lives. WAKEY WAKEY.......YOU ARE SO FAR BEHIND THE CURVE ITS NOT EVEN FUNNY. How do I know its wrong - because I used to do it and it didn't work. I still see this all the time and the best answer they can give is that's how we have always trained....wrong answer!! If I hear another coach tell me they are developing an aerobic base I will scream!!! There are so many reasons I won't go into them now...trust me if you are still doing this (and you know who you are) then stop. I can feel an e-book coming on 101 reasons why steady state cardio sucks!
2. Taking the principle of specificity and flogging it until its dead. Seriously I've watched a coach working with a swimmer using a metranome so that the swimmer can lift at the same tempo as his stroke rate and......guess what....each set lasts as long as one race. Why don't you just go and swim!! Strength work is about transfer of training effect.....not specificity.....if the strength drill is too close to the actual sports technique research shows you will actually reduce the sporting performance. Our job as coaches is to make the most out of the athlete that we are working with - we need to give the coach the strongest, fastest most powerful athlete possible. If we deliver that then the coach can go to town on the technical and tactical work.
3. Thinking that there are 'bad' exercises. Don't be fooled into thinking that full squats are bad or bench pressing is the devils exercise. There's no such thing as a bad exercise, just crappy programming. I've worked with some pretty extreme sports and the nature of the sport means the body has to do some things that strictly speaking it's not designed to do. it's not that a particular exercise is bad, it's more to do that the coach or athlete has not thought about proper progressions or whether the exercise is suitable for that individual. We must not do straight leg sit ups....its bad for your back.....what if your sport is gymnastics and requires that type of movement?