– Derek M. Hansen – October 28, 2008 –
Working with track and field sprinters and athletes in speed-dependent sports such as football and soccer has made me very aware of the prevalence of hamstring strains and other debilitating soft-tissue injuries. The recovery period for these types of injuries can vary from weeks to months, depending on the severity of the problem. There is also a high probability that many of these injuries will re-occur and become chronic. Understanding how to better manage, rehabilitate and prevent such injuries requires a greater knowledge of the root causes, as well as associated treatment strategies.
Articulating the Problem
Our extremities have evolved in such a way to allow us to perform complex tasks, absorb impacts and generate significant amounts of force. The articulations or “joints” of our extremities assist in force production and absorption through use of angular momentum. The combination of various muscles, levers and joints can allow us to kick a ball, throw a punch, run fast or jump high.
In the case of sprinting, our muscles flex and extend the joints at extremely high velocities. A complex kinetic chain of movement is engaged allowing elite sprinters to attain relatively high speeds by their fifth stride of a 100m sprint (approximately 8.2 meters per second). This complex chain includes extensors of the hip, knee and ankle that are all involved in the ultimate force producing event – the sprint stride. At ground contact – the point of force production in an acceleration stride – the muscles of the hip, hamstring, quadriceps, calves and feet must be highly coordinated to ensure that the stride safely and efficiently produces the required force. Some muscles contract and relax in a coordinated sequence, seemingly in a wave-like pattern. Others are required to co-contract (agonist and antagonist) in order to ensure adequate joint stiffness for support. If at any point in the chain the leg muscles are not functioning properly and unable to contribute their share of the required force in the time required, the forces can be shifted to another segment in the chain. This compensational shift can lead to an overload and overuse of specific muscles, tendons and ligaments, enhancing the risk of injury.
When improper function occurs in one or several muscles in the lower extremities of an athlete running at high speeds, I refer to this as a “Kinetic Chain Disruption.” One must think of an extending sprint stride as a leather bullwhip (A bullwhip’s length, flexibility, and tapered design allows it to be thrown in such a way that, toward the end of the throw, part of the whip exceeds the speed of sound, thereby creating a small sonic boom, or loud crack.) If a particular segment of the whip was weakened or made more rigid (i.e. dried out) than the rest of the whip, it would not only adversely affect the velocity, but also the long-term integrity of the whip. Therefore, leather whips must be properly “dressed” and greased to keep them supple and strong for high velocity cracking.
This same principle applies to limbs that are required to operate at high velocities and forces. If any part of the kinetic chain is weakened or too rigid – through adversely high muscle tone – other areas in the chain are at risk for over-compensating and over-loading. In many sports, a muscle strain may not occur for some time after the initial kinetic chain disruption has developed. Because sports such as football and soccer involve a good deal of sub-maximal sprinting efforts, the problem can stay hidden until one extreme sprint effort is required. Athletes will often admit that they were “pushing” or “reaching” to catch another athlete or the ball right before they pulled a muscle.
Hamstring strains are common in speed dependent sports that require a lot of speed changes, including stop-and-go activities that involve a great deal of hard re-accelerations, particularly in mid-stride. I’ve seen pulled hamstrings in everything from football, soccer, basketball, tennis, field hockey, lacrosse, rugby, baseball, bobsleigh and even, yes, ultimate frisbee. In a majority of the problems I’ve encountered, there were some commonalities that lead to the hamstring injury. Most of the injuries included one or a combination of the following factors:
Other Kinetic Chain Disruptions
While hamstrings strains are one of the most common injuries associated with Kinetic Chain Disruptions, there are many other afflictions that involve breaks in the chain of movement. Provided below are common injury areas and associated root causes.
Solutions – Rehabilitation and Prevention
As you can deduce from the examples listed above, a good number of Kinetic Chain Disruptions are caused by tight muscles (kinetic chain segments). These tight muscles often occur due to overuse, heavy impacts or direct trauma in the case of contact sports. Management of these issues must be done on a regular basis. Provided below are a list of active management techniques that can be employed if Kinetic Chain Disruptions are detected:
Comprehensive evaluations of the status of an athlete must be performed on an ongoing basis to ensure that all of the muscles required for locomotion are in good working order. Talking to the athlete may not always yield useful information about what ails them. Regular massage therapy can not only be useful for relaxing contractile tissues, but can also be used to gauge muscle tone throughout key kinetic chains. Once awareness is increased, proper measures can be implemented to rectify Kinetic Chain Disruptions and restore proper muscle firing patterns. The probability of significant soft-tissue injury can be prevented through regular maintenance and recognition of common disruptions. It can be likened to putting out fires before the house burns down.