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May 13, 2009
Avoid Knee Injuries by Doing Less Stretching

ACL (anterior cruciate ligament) injuries are a hot topic these days, from orthopedic surgery centers to the sidelines at high school soccer games. The ACL is one of the four major ligaments of your knee joint, and unfortunately is often injured by athletes during sudden dislocation, torsion or hyperextension of the knee joint.

To make matters worse for females, Randy Dick, the senior assistant director of health and safety for the NCAA says that females are 3-3x more likely than males to injure their ACL. Some statistics have females as much as eight times as likely to injure their ACL as male counterparts. The medical field is rife with studies about ACL injuries and rehabilitation, and what some research shows may surprise you. Some females need to get “stiffer” joints in order to prevent this and other injuries.

What is Flexibility

To understand why you may need to get stiffer joints, you’ll have to first understand flexibility a little better. Joint range of motion is controlled by the active and passive structures that act on that joint, i.e. the muscles (active), and ligaments, tendons, cartilage and bone (passive).

There are two types of flexibility, active and passive. Active flexibility exists in the belly of muscles, allowing an athlete to go through a full active range of motion (think about a deep and safe squat). Passive flexibility (think about bending down and touching your toes) involves the passive structures (tendons and ligaments) that merely transmit the forces that the muscles produce.

Active flexibility is good for athletes, but too much passive flexibility can actually be harmful.

Stiffness is Good

To understand why too much passive flexibility is bad, we’ll have to understand one more big word: musculotendinous stiffness. This refers to the elastic characteristics of the muscles and tendons that control a given joint. Researchers from the Neuromuscular Research Lab at The University of North Carolina compared hamstring (a major muscle responsible for limiting ACL loading) characteristics in males and females. The study showed that males had much greater musculotendinous stiffness. In effect, their hamstring muscles and tendons were stiffer and quicker, better at responding to dynamic knee loads.

The researchers believe that females’ lack of stiffness places greater strain on their ACL, and can have a profound effect when strain is applied frequently, as in many sports. In another study from The Center for Health, Exercise and Sports Medicine at the University of Melbourne researchers examined patients recovering from ACL reconstruction. The subjects further along in the rehabilitation process (who performed better in knee stability tests) all had significantly more musculotendinous stiffness in the musculature of the operated limb.

Your muscles and tendons are like a series of rubber bands. You don’t want your rubber bands to be too loose, they will be slow to respond to quick changes in direction or speed, and put dangerous amounts of stress on ligaments and other soft-tissues. A study from Southern Cross University in New South Whales, Australia, showed that a musculotendinous unit on the stiff end of the elasticity spectrum was able to contract much more forcefully than a loose unit. Stiffer muscles and tendons operate at a more efficient length, produce force more quickly, and are especially good at creating force in the initial stages of movement (called rate of force development). If you think of your body as a car, rate of force development would be your first gear. You want your car to have a big first gear and accelerate quickly. And in the case of a lot of ACL injuries, you want your muscles to contract very quickly in order to protect against ligament damage.

Getting Stiffer…

So, what’s the easiest way to get stiffer? At SPARTA, athletes do aggressive plyometrics under the supervision of experienced coaches, but if you want to do something on your own, Sprint. Sprinting forces your body into forceful, fast ground contacts that build strong, responsive tendons, in a full, safe range of motion.

May 13, 2009
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7 thoughts on “Avoid Knee Injuries by Doing Less Stretching”

  1. Great article, but I have a few questions. Your title implies that stretching would be contraindicated for those looking to have healthy knees. I agree that we are not looking to stretch the passive structures, thus destabilizing the joints. But, what about the over active/tight and under active/weak myofascial structures that lead to arthrokinematic dysfunction? For example, what about an over active and tight TFL/IT, biceps femoris (short head), adductor complex, and lateral gastroc? If these structures are short and over active, it can lead to excessive knee valgus, thus increasing the likelihood of an ACL injury. When an athlete laterally plants to move in the opposite direction, these structures will lead to the athlete’s foot externally rotating, while the hip and knee complex internally rotating, increasing the rotational forces on the knee, thus increasing the risk for the ACL.

    In light of this, would you not agree that there are certain areas that should be stretched in order to allow optimal biomechanics, keeping the myofascial tissues in their proper length and tension, thus allowing for optimal force reduction and production?

    I can understand what your saying in light of the research you stated. I would agree that we are not to excessively stretch the passive structures, but the active structures are a different story. These structures can alter
    arthorkinematics and either increase or decrease risk factors.

    I would be interested in hearing your thoughts on this.

    Phil, glad things are going well for you. Your place looks great and we’d love to see you and the wife if your in So Cal.

  2. Interesting comment. Of a more general nature, I would imagine Sparta advocates dynamic warmups for most athletes. While exercise prescriptions need to be individualized, do you advocate static stretching at all for the average Sparta client? And if so, when is this done (i.e., after activity)?

    John Weatherly

  3. Great comments. We actually do all our flexibility work through strength exercises (i.e. we squat to full depth, overhead press to lockout, etc.). In a decade of coaching thousands of athletes, I have never had major flexibility issues with athletes, it just took a few workouts longer for some individuals to attain full range of motion. The biggest key for me was never being complacent with a shorter range of motion and letting the athlete know it!

    Such an approach to promoting flexibility through active range of motion has allowed us to quickly eliminate and maintain all flexibility. After this ROM is attained, the only need is myofascial release, applied every day for 10-20 minutes before the workout.

    We don’t do static stretching ever. Our dynamic warm-up are games of tag or movement mechanics based (sprint or jumping drills for dorsiflexion, lateral ground contacts, etc.).


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