In the latest edition of “Mick talks with…” I sit down with Brady Green to discuss all things calf injury and rehabilitation.
For those of you who don’t know Brady, he's a PhD Candidate at the La Trobe University Sport and Exercise Medicine Research Centre and Physiotherapist at the Essendon Football Club. Brady has published works on calf and hamstring muscle strain injuries and has extensive experience in managing these injuries at a clinical level.
I learned plenty from this chat, and I'm sure you will too. This is Part 1, in a 2-part interview.
Mick: Hi Brady, and thanks for sitting down to chat today. Let’s cover some basics first - what is the “calf”, and why is it so important for sports performance?
Brady: As clinicians when we think of the “calf” we typically think about the soleus and the gastrocnemius muscles. There are of course other muscles of the lower leg, but because they are the two largest contributors to function, and they are also the muscles that are most commonly injured, we tend to focus on the soleus and gastrocnemius. But while the soleus and gastrocnemius are the two main muscles that make up the “calf”, they are very different from one another.
The soleus is a very complex muscle that lies deep to the gastrocnemius. It’s a really important muscle for athletic performance, which is something that we probably haven’t recognised fully in the past. Some of the earliest thinking about soleus was that it was essentially just a postural muscle, mostly populated by slow twitch muscle fibers, and that it didn't contribute a great degree to power-based, more explosive athletic tasks. How wrong this was! When we run, when we cut, when we jump, the soleus is doing a large amount of work, and studies do show this. The soleus has a large physiological cross sectional area, demonstrating the important role it plays in generating force.
And then of course we have the gastrocnemius. It is the more proximal and superficial of the two muscles. It is split into the medial and lateral gastrocnemius, and is a biarticular muscle. It has a high population of fast twitch fibers, and contributes greatly during explosive muscle actions. Studies often show it to kick-in even more significantly at later time-points, or closer to terminal propulsion, compared to the more consistent action of soleus. Given that gastrocnemius is quite an explosive muscle, it can be more fatigable as well. But to answer the second part of your question more directly: the “calf” complex is one of the key links contributing to how well we perform athletic tasks; running, accelerating, decelerating, jumping, cutting, and so on. Injuries to the calf can therefore cause us headaches clinically.
Mick: That’s really interesting to hear. I remember being taught at physiotherapy school that soleus is merely a postural muscle, and it wasn’t as injured as much as the gastrocnemius, and it certainly wasn’t given much credit for its power production. It was almost like you could neglect the soleus in preference of the bigger, supposedly more powerful gastrocnemius. But that’s not the case is it?
Brady: A large factor with that is probably what was accepted as clinical dogma at the time. In reality there wasn't really much data available about calf strain injuries, let alone their function in activities like running, and for these reasons the ability to diagnose soleus injuries perhaps wasn't what it is now. For example, while imaging only makes up one part of the equation, a lot of the early studies utilized ultrasound to diagnose the location of calf strain injuries. However we know now that ultrasound is an ineffective means to detect soleus involvement. Unsurprisingly in those earlier studies the rates of soleus injuries were often low, which probably directed our attention and expectations of the structure involved. If we want to get any sort of diagnostic quality with imaging for soleus, MRI is the gold standard for determining the anatomical location of injury. So I’m not convinced we were as well equipped to be detecting and thinking about soleus injuries. We know now that they are far more prevalent than early studies reported. This is really evident in the AFL data that we've looked at as part of my PhD. The prevalence of soleus involvement as the primary muscle injured is about 85% of all calf strain presentations, which is a huge proportion!
But another important thing to add is that while MRI can be helpful, it is only one part of the clinical puzzle and not the sole determinant for making a diagnosis or for determining the course of what happens after a diagnosis is made. There are many occasions that the clinical information gained “on the table” or in the medical room is clear enough to guide the subsequent management and decision-making regarding prognosis. What we find clinically, and how this evolves over time, is by far the best information to guide what we do.
Mick: It's certainly an understated injury, and this question extends on what you just mentioned. Clinically, I see a lot of calf strains in the thirty to forty year old male, playing tennis or going for a run. What is the research showing us about incidence and prevalence in this age group? Is this just a clinical bias that I'm seeing, or is it pretty standard around the world?
Brady: Unfortunately, probably. We published a systematic review of risk factors for calf strain injuries in the British Journal of Sports Medicine. From this study we know there is strong evidence that increased chronological age is a risk factor for future calf strain injury. So as you get older, it’s likely you are at a greater risk of suffering a calf strain. The other main risk factor was having a history of a previous calf strain. So once you have had one calf strain, there’s strong evidence that you’re at greater risk of having a calf strain again in the future.
Now, I also think that clinically, we sometimes look at “older age” and write it off as a mundane finding in terms of injury risk. But we need to drill a bit deeper into the underpinnings of what happens as we age, which probably gives us good information about why they're tearing their calf. We know that the calf muscles are some of the quickest to atrophy as we get older or with the removal of a loading stimulus. So therefore if we're losing cross sectional area of a muscle, then we are also losing some of the force generating qualities as well. We also know that as we get older, we lose length in our fascicles in the calf too. So if we're losing fascicle length, to some degree we're probably losing force generation at high speeds and at longer muscle-tendon unit lengths. Another age-related change is that we lose the stiffness property of the calf muscle-tendon unit, which is needed for optimal action of the stretch-shortening cycle during activities like running.
So suddenly these older men that you are seeing in the clinic, yes they are older, but they are probably in a perfect situation to sustain a muscle injury, and it is quite unsurprising that they are “popping” their calf when they suddenly accelerate, jump, serve in tennis, and so on. But we also need to remember that each of the mal-adaptations I mentioned are modifiable, which gives us some of the key areas to target with exercise interventions for injury prevention or risk reduction strategies in older athletes.