Flexibility is a key element in preventing a torn ACL. Sometimes people get an image of floppiness or looseness when they hear the term "flexibility." Quite the contrary, having flexible connective tissue-tendons and ligaments-as well as the muscles themselves allows these structures to operate in their full range of motion without injury and to respond to sudden shocks while maintaining stability.
Flexible muscles, tendons and ligaments allow the power generated by the muscles to move the body more efficiently, and with less chance of injury. Think of a supple sapling in a wind storm, able to bend and move with the power of the storm. Think now of a seemingly strong, stiff oak tree, which is more likely to snap or be uprooted because it cannot bend.
How do you become more flexible? Stretching, of course! Easy, right? Not so fast. The fitness and sports conditioning communities have a running debate about what is the most effective stretching method: static or dynamic.
Static stretches are the stretch and hold routines-several sets of 30 second stretches per muscle group-while dynamic stretches involve engaging the opposing muscle to the one you’re stretching (up to 20 repetitions of 2 second stretches) in order to get the most out of your efforts.
Do yourself a favor and try out both methods to see what works best for you–you may even find that some combination of static and dynamic stretching meets your needs. Two of the classics in the field are Stretching, 20th Anniversary Revised Edition, by Bob and Jean Anderson, which comes from the static approach, and The Whartons’ Stretch Book, by Jim and Phil Wharton, a dynamic or "active isolated stretching" plan.