Treadmills are for fat people at the YMCA.
I would have to agree. As a PT and as an ATC, I see coaches "speed train" athletes on a treadmill. It usually requires the athlete to hold on to the rails, stand on the non-moving edges as the treadmill is accellerated to a speed of 6-10 MPH, then the athlete jumps on and starts running immediately 6-10 MPH (or literally falls and gets nasty abrasions. Don't laugh, happens more then you'd think) I believe this is possibly one of the most injurious thing done to lower extremity muscles, tendons and joints.
Think about it-the body is "stationary" and the "ground" is moving. This is unnatural.
The stress and strain placed on the ankle and lower extremity is almost exactly the opposite as it is in "real life". In real life, the ground doesn't agressively "yank" your ankle backwards as your shin bone continues to move forward. This sprinting motion on the treadmill is damaging to the lower extremity, especially when the athlete already has a history of lower extremity and ankle problems. I do NOT endorse these activities and only wish I could make my coaches drop them.
I believe this one activity (sprinting like this on the treadmill) is one of the more potentially harmful activity we have our athletes perform.