Running Injuries and Kinetic Chain Disruptions

– Derek M. Hansen –

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.

Hamstrings

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:

Very high muscle tone above or below the site of the injury. Many people claim that tight hamstrings lead to strains in this muscle group. I’ve found that the muscles above or below the hamstring muscles have as much to do (if not more so) with the hamstring injury as the hamstring itself. Muscle strains in the lower part of the hamstring are almost always associated with extremely tight calf muscles. Additionally, strains in the upper to middle portion of the hamstring are almost always associated with tightness and dysfunction in the glutes and hip flexors.

Fatigue is present. Rarely do you see an athlete pull a hamstring on the first play of a game or in the first heat of a race. Hamstring pulls are common at the end of the first half, towards the end of the game or a few rounds into a 100m competition. Assuming that the athlete has had a good warm-up, being fresh and energetic is a good means of avoiding injury. However, when an athlete is fatigued, Kinetic Chain Disruptions manifest themselves as muscle strains in compensating segments. A tight calf can lead to an over-strain of the hamstring on full extension during a sprint stride. Triple-extension on a powerful movement must include all of the required muscle groups to fire effectively. If you are tired and tight, one of those segments will be exposed to greater risk.

Cold environmental conditions. Cold temperatures will exacerbate tightness in hyper-tonic (tight) muscle and magnify risk in situations of Kinetic Chain Disruptions. Reduced blood flow and, hence, reduced muscle temperature will not only tight up calves and glutes, but also render the hamstrings more susceptible to injury.

Poor running technique. All things being equal, the athlete with less efficient sprint mechanics will be more susceptible to injury of the hamstring. Poor leverage in the lower limbs due to over-striding combined with Kinetic Chain Disruptions can be a recipe for disaster, placing even more stress on the hamstring. The athlete with better technique will be in a position to better distribute forces and minimize risk of a hamstring pull even if Kinetic Chain disruptions are present.

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.

Knee soreness. Most knee soreness that I encounter in athletes is associated with tight glutes (maximus and medius – leading to iliotibial tract tightness) and/or a tight vastus lateralis muscle. As a result, the vastus medialis muscle often is inhibited and does not fire effectively enough to stabilize the patella. The result is pain throughout the knee, but most commonly in the patellar tendon (jumper’s knee). It is often diagnosed as tendonitis or tendonopathy, although I don’t believe that there is actual inflammation or degeneration in the tendon for the majority of cases. How do I know? I’ve had athletes work on static stretching of the glutes for a few sessions and the pain disappeared almost immediately following the stretching session. The pain relief has also lasted for many days after the stretching session, but ultimately does return if the stretching protocols are not maintained and the soft-tissue structures tighten up again.

Shin splints. I had one football athlete complain of sore shins and tibialis anterior cramping. A conventional calf massage helped to alleviate the shin-splint pain, but the tibialis anterior remained locked up. When queried about what lead up to the shin pain, he stated that it started hurting after an explosive cut (change of direction) on a receiving route. I found that his vastus lateralis was incredibly tight and not firing properly during eccentric movements. I deduced that his quadriceps were not working effectively to slow him down and much of the force was shifted to the lower leg, thus leading to the tibialis cramping. When we loosened up the lateral quadriceps, his tibialis cramping ceased.

Foot pain. A good deal of foot pain – both on the top and bottom of the foot – is related to high muscle tone or tightness in the calf muscles. Reduced calf involvement in a running stride will inevitable lead to greater stresses on the foot, particularly at impact and full extension.

Low back pain. Tightness and dysfunction in the gluteal muscles can contribute significantly to lower back pain. If the hip extensors are not working properly during high velocity, repetitive lower-limb movements, the lower back will take up much of the stress through unnecessary flexion and rotation. Tight gluteal muscles will often lock up the sacro-iliac joint and reduce the ability of the hips to rotate freely.

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:

Regular massage sessions. Anyone who runs fast needs to get their glutes, hamstrings, calves and quads loosened up on a regular basis. If you consistently get a massage from the same therapist, they can also give you on-going feedback on the status of your individual muscle groups, identifying problem areas that need additional work. Most athletes do not have the self-awareness to determine where these problem areas exist and need a second opinion on matters. A skilled therapist can safely bring down muscle tone, increase circulation and restore function to overused muscles.

On-going light static stretching. For those who cannot afford to regularly pay for a massage, targeted static stretching can also help to bring down muscle tone in overworked muscle groups. When performed at relatively low tension, and long duration, muscles will slowly release and relax. Just read the recent research on static stretching and muscle strength. Numerous research studies have shown that pre-exercise static stretching will result in reduce strength and power performance. As muscle tone is reduced, the ability of the muscle to reach maximal tension is significantly reduced. This is why someone who has inhaled 10 tequila shooters rarely wins the Olympic 100 meter race.

Shifting to softer training surfaces. Training on hard surfaces can quickly result in hyper-tonic muscle in the calves and hips. Shifting to softer surfaces for a portion of your training can provide the break that your muscles need without having to cut your training volume or intensity. Natural grass is best, as it can provide a good combination of shock absorption and surface stability. Artificial turf surfaces are softer than pavement and rubberized track surfaces, but still can be more rigid than natural grass.

Contrast hydro-therapy. Hot-cold contrast therapy either through saunas, showers, hot-tubs and cold tubs can be useful in flushing out the muscles of waste products and encouraging the central nervous system to recover and bring down muscle tone. Common recommendations for durations include three to four sets of three minutes on hot to one minute for cold. Always end on cold to minimize the incidence of an inflammatory response at the completion of the session.

Evaluation of footwear suitability. Shoes that are either too hard or too soft can exacerbate muscle tightness and coordination. Soft shoes that may initially appear to be providing useful cushioning and comfort may actually not provide enough elasticity and stability. If the shoe soles are too soft, the force of strides on ground contact will actually over-compress the sole and result in a hard impact. The same goes for a shoe that is too hard and rigid. If the shoe upper is too light and unsupportive, the foot can slide around inside the shoe resulting in tightening of the foot arch and calves – kind of like wearing flip-flops while sprinting. The Nike Free model of running shoes was a good example of this phenomenon. I had some football athletes using these shoes for sprint workouts and they were actually sliding around inside these shoes. The Nike Free shoes were literally disintegrating on every sprint repetition. And, athletes were complaining of shin splints, foot pain and turf toe.

Examination of running mechanics. Always monitor the technical execution of your athletes to ensure that movement efficiency is maximized and risk of injury is minimized. As fatigue can always rear its ugly head, time must be taken to evaluate biomechanics. In some cases, longer rest periods must be inserted into the workout to ensure that an athlete can execute the required movements at maximum intensity. Video analysis should be performed periodically and compared against previous evaluations. Coaches cannot always pick up errors on the spot and can conduct comparisons of technique over time. Corrections can then be implemented next workout.

Short-term reduction of training volume. In all cases of significantly high tone in key muscle groups, it is a good idea to modify the training volume to ensure that risk of injury is reduced. Even very small reductions in training volume – when done in coordination with some of the aforementioned tips provided in this article – will yield significant results. I’ve seen a reduction in training volume for as little as three to five days result in significant improvements in muscle tone and performance. Remember that no training program is written in stone, with iterative modifications required throughout the training weeks, months and years to yield the best results.

Recommendations

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.

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