Dean Benton and Martin Bingisser

A systems approach to calf complex injuries

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At beginning of this year we penned our thoughts on the hamstring injury phenomena and illustrated how a reductionist approach to reducing hamstring injuries just doesn’t work. A complex problem can’t be solved by something as simple as getting stronger; it demands a more holistic interpretation. Below we turn our attention to a similar injury trend: injuries to the calf complex.

Dissecting injury trends

The Australian Football League (AFL) is perhaps the most professional league in the world when  it comes to documenting injuries. Every year they share that information publicly, and hamstring injuries are consistently the leading soft tissue injury. But close behind are injuries to the calf complex, and the numbers are increasing. Similar upward trends have been seen in other fields sports as well. Interestingly the incidence of hamstring and calf injuries in the athletics world is comparatively low – particularly in the sprint and jump events.

When it comes to the increasing challenge of calf injuries, a reductionist approach, like with the hamstring, is still quite widespread: many practitioners point the finger at weak muscles causing the problem. The solution: make the calf stronger and it will no longer break. Rather than fixing the problem this has just created a paradox: we focus more and more on calf strength in our training, but injury rates appear to be nevertheless increasing in many sports.

The role of the calf complex

Let’s start with a short review of anatomy. Like the hamstring, we often refer to the calf as one muscle, when in fact it is a connected muscular system consisting of the gastrocnemius, soleus, and plantaris muscles, with attached tendons and connective tissue. We mention this not because there will be an exam, but because it shows the connectedness and complexity of the anatomy involved. Focusing on one muscle overlooks the rest of the system and how it interacts.

It’s also important to understand the function. The role of the calf in the running cycle is as a ‘brace’ – not a ‘pump.’ In good sprinting technique, the foot plantar flexes early in the stance phase, so that there is no, or very little dorsiflexion of the ankle at speed when the athlete is in contact with the ground. This means that the serial elastic components are loaded and unloaded, while the contractile elements of the muscles contract isometrically at their optimum length.1 Or quite simply put, the calf complex helps ensure good ankle stiffness and prevent “collapse” of the ankle towards the running surface.

Furthermore, good runners can be observed as having good timing of ankle plantar flexion immediately before foot contact. Conversely, forces associated with mistiming and/or misplacement of the foot, that are either excessive or poorly absorbed, can lead to calf and achilles injuries.2 In other words, poor mechanics and poor ankle stiffness requires an athlete to push off the ground at speed, rather than bounce off it.

Without doubt the calf complex must tolerate significant forces when sprinting. Research by both Komi et al and Dorn drew similar conclusions that calf and achilles tendon in series experiences tensile forces up to 12 times body weight at speed.3 4 So, without a doubt, strength is important. However, so is timing and coordination. High tension in the ankle and foot joints is specifically important during the contact phase for maximal elastic loading of the achilles tendon. This loading may be determined by the timing of the planter flexors in generating force, rather than the force itself.5

A systems approach would look at the calf complex in the context of running, related timing and coordination as well as strength. If we accept that muscles set up forces, but it is the serial elastic components that store energy and convey forces into the ground at high-speed, then this will dictate criteria for our performance enhancement and injury prevention programming.

Training specificity and focusing on function

We now understand how the calf complex is built and functions. The next step is how to train it. Specificity is a foundational principle of training. It is assumed that in high level sports, more specific training will transfer better from training to the game. Concepts like Dynamic Correspondence try to define specificity in more detail6, but the key concept is whether or not the function of the training exercise and the function of the training goal are aligned. This means that we aren’t just defining specificity as focusing on the same muscles, but also on training similar coordinative demands as well. Specific training requires muscles to perform in a similar context as they will be required to in the sport.

Let’s take an example from calf training. As we described above the primary function of the calf complex is bracing. While exercises like loaded calf raises train similar muscles, they are doing so in a completely different context and therefore can be considered less specific. The forces and loads seen in sprinting also can’t be matched in the weight room; calf raises feature moderate loads for long duration rather than high peak loads for short durations. More specificity can be found in locomotive exercises such as advanced running drills, plyometrics, sled pull, and loaded stairs.

Locomotive exercises not only allow the muscles to be trained in the right context, but they allow athletes to train and improve the coordinative/skill elements at the same time. The nature and timing of foot contact is critical to performance and injury prevention. We sometimes see extremes in different populations. Sprint athletes can be too early with plantar flexion immediately before contact and distance athletes too late. Both of these extremes can result in collapse at the ankle at speed. These peculiarities of different sports need to be taken into account, even if the underlying principles remain the same. For example, plyometrics that are unilateral and multidirectional in nature should be considered for field sport athletes. Mainly as field sport acceleration is often multidirectional in nature with very high medio-lateral force demands on the foot and ankle system.

This is not to say there is no place for non-locomotive calf complex strength training exercises. One application could be for an athlete returning from injury who is not able to tolerate exercises that are explosive in nature. However, aside from not meeting the principles of specificity, non-locomotive calf strength training exercises do not even come close to replicating the magnitude of forces that must be tolerated whilst sprinting. 7

By taking a principled approached to training the calf complex, we also must apply the principle of overload. This can be done appropriately with bounding and hopping exercises. Mero’s classic research paper highlights the vertical forces associated with speed bounding, distance bounding and hopping, which are 1.2 times, 3 times and 3.8 times greater than sprinting respectively. 8 Proper progressions, as outlined by John Pryor in his HMMR Classroom lesson on bounding, take into account risk factors to help athletes get the benefits of bounding without the possible negative outcomes.

Specificity and testing

The same principles of specificity are also relevant when it comes to testing. Understandably professionals involved in preparing running-based athletes are inclined to want to test strength qualities – specifically calf strength. However, we shouldn’t forget that we need to measure what is important, rather than making something important simply because we can measure it. Our assessment of strength must also adhere to Verkhoshansky’s criteria. Seated calf raises on a force platform may well assess intramuscular coordination, but is completely devoid of intermuscular coordination and many other essential criteria in sport performance.

One of the easiest and simplest means of identifying ankle stiffness is with the use of the ‘slo-mo’ video function on an iPhone when sprinting. Of course, it could be argued this is purely subjective. However, advancements in artificial intelligence software now permits kinematic assessment with an iPhone. As such, ankle stiffness is now easily quantifiable.

Final thoughts

Training exercises that prepare the calf complex and feet to be stable and strong are clearly essential for mastering high-intensity sprinting. Often there is a perception that plyometrics cause injury; conversely, they can prevent injuries.9 It could be suggested that the fear that plyometrics can cause injury may well result in many field sport athletes being undertrained in terms preparing them for field sport sprinting demands. Consideration should also be given to considering what we think to be preventative may just as well be the ‘cause’ – not the ‘cure’ for injury.

References

  1. Bosch, F & IJzerman, J. (2015). Running mechanics in injury prevention and performance. In D. Joyce & D. Lewindon (Eds), Sports Injury Prevention and Rehabilitation (pp. 106-120). Routledge.
  2. Bosch, F & IJzerman, J. (2015). Running mechanics in injury prevention and performance. In D. Joyce & D. Lewindon (Eds), Sports Injury Prevention and Rehabilitation (pp. 106-120). Routledge.
  3. Komi, P. V., Fukashiro, S., & Järvinen, M. (1992). Biomechanical loading of Achilles tendon during normal locomotion. Clinics in sports medicine, 11(3), 521-531.
  4. Dorn, T. W., Schache, A. G., & Pandy, M. G. (2012). Muscular strategy shift in human running: dependence of running speed on hip and ankle muscle performance. Journal of Experimental Biology, 215(11), 1944-1956.
  5. Bosch, F & IJzerman, J. (2015). Running mechanics in injury prevention and performance. In D. Joyce & D. Lewindon (Eds), Sports Injury Prevention and Rehabilitation (pp. 106-120). Routledge.
  6. Verkhoshansky, Y. (2009). Supertraining [Paperback]. First Edition. Verkhoshansky.
  7. Lai, A., Purdam, C., & Smith, R. (2016). Calf muscle strain injuries. Implications for rehabilitation and prognosis. Unpublished manuscript.
  8. Mero, A., & Komi, P. V. (1994). EMG, force, and power analysis of sprint-specific strength exercises. Journal of Applied Biomechanics, 10(1), 1-13.
  9. Radcliffe, J., & Farentinos, R. (2015). High-Powered Plyometrics, 2E. Human kinetics.