Why is Bale so susceptible to calf injuries?

The medical report from Real Madrid indicated that he would be out of action for two to three weeks.  Once again this has been diagnosed a soleus muscle injury; but this time the injury is to the right leg.  Gareth's been troubled by injuries to the soleus on and off for the past twelve months; and these appear to be recurrent in nature.  The question nearly everyone asks is: "What makes this particular muscle so susceptible to repeated injury?"

Anatomically the calf group is made up of three muscles, often referred to as the ‘Triceps Surae', and comprises of the gastrocnemius, soleus, and plantaris muscles.  Together, these blend to form the Achilles tendon.  The most commonly injured of the three muscles is the gastrocnemius, which is the superficial bulky muscle that gives the calf it's characteristic shape.  The soleus muscle lies deeper and lower than the gastrocnemius, originating behind it's lower fibres.  The third muscle that comprises the trio is known as the plantaris muscle, and this is a deeper muscle running along the posterior aspect of the tibia.  Academics agree that the plantaris muscle is rarely involved in calf injuries (Armfield et al, 2006).

The soleus muscle is an important muscle for ankle strength.  It has a predominance of slow twitch fibres thus biasing it's function towards power, and the soleus also acts as a postural muscle.  It therefore has an influence on lower limb biomechanics and gait.  Consequently if any dysfunction occurs in the ankle or foot, the potential exists for the soleus to be affected; which may present as a recurrent injury depending on the underlying cause.

The present injury will be Gareth Bale's third soleus strain this season.  Since arriving at Real Madrid, he's not had to look far to find injury problems.  Gareth has suffered with soleus issues in previous seasons in addition to hip and abdominal injuries.  Calf strains are common in football as we know and with the lower limb accounting for 87% of injuries sustained (Ekstrand et al, 2011) then it's hardly surprising that these will arise time and again.  The key factor, however, between recovering from strains of the superficial gastrocnemius muscle and the deeper soleus lies in establishing the true extent of the injury.

Soleus muscle strains or tears are more difficult to assess than gastrocnemius injuries and a full MRI scan is required to provide the most accurate images of the damaged tissue (Balius et al, 2014).  The disadvantage with MRI scanning though is that the scans are performed with the muscle at rest.   Ultrasound scanning, which is the preferred modality for injuries that are more superficial, can be adapted to provide a dynamic, moving image of an injured muscle which can be viewed in real time.  But due to the depth of the soleus muscle, there are areas where dynamic ultrasound is simply unable to provide an accurate enough image to allow clear visualisation of the tissue damage sustained.

Therefore, in recovering a soleus muscle injury, it may well be that the true extent of the tissue damage cannot be wholly defined.  Bryan Dixon (2009) reported that injuries to the soleus muscle can often be underestimated due to the generally sub-acute nature of their clinical presentation.  In football, this usually shows as the injured player reporting some gradually increasing discomfort over a period of ranging from a few days to several weeks as opposed to an obvious strain resulting from one single, specific incident.  The player will report that the calf "feels tight" and that the discomfort is "always there".  As the soleus muscle is a deeper, power-based muscle which has an influence on a player's gait, any underlying weakness or incomplete healing may not be evident until higher-level activities are resumed, thereby leading to localised discomfort and the likelihood that the process of repeated injury is already well under way.  Thus, the classic presentation of a soleus muscle injury is one of pain and stiffness with gradually worsening symptoms over time.

Pedret et al (2015) found that injuries to different areas of the soleus muscle responded to treatment at different rates.  It is thought that injuries occurring in the central tendon of the soleus muscle where it blends with the Achilles tendon have a longer recovery time than injuries to the medial or lateral aspects of the muscle.  We know that the body doesn't repair injured tissues with a like-for-like substance and that the healing process in muscular tears / strains is through the laying down of scar tissue.  This inevitably affects flexibility and strength to some degree, likely leading to biomechanical imbalances as a result.

Recurrent or repeated injuries are often the product of such muscular imbalances and if one leg is taking the strain slightly more than the other or in a slightly different way, then any structure which has been injured will be susceptible to further injury if it hasn't healed correctly before returning to play.  An earlier study by Koulouris et al (2007) suggested that deep strains of the soleus muscle could potentially lead to associated strains of the gastrocnemius muscle; likely as a result of an imbalance in biomechanical loads on the calf and lower limb complex as a whole.

In Gareth's case he's reported to have felt fit enough to return to activity on previous occasions with this injury, but clearly something's not quite right.  There are a couple of likely options.  This might be a biomechanical issue directly related to the way he runs, or whether his foot posture is affecting his calf muscles to the extent that he's overloading his lower calf when running, for example.  If this is the case then no amount of rest will help in the long term; since the incorrect loading will gradually return as he increases his activity and the same symptoms are likely to recur once again.  However, current available evidence would suggest that the soleus muscle also requires longer healing time than other muscles in the calf; due to it's deep-seated location and involvement in lower-limb posture.  If it's simply a case of coming back too early before complete healing has had the chance to take place, then the same thing applies.

The most important aspect of the whole rehab process for Real Madrid's medical team is going to be to determine why this particular injury keeps recurring.  Once they've identified the underlying cause, the subsequent aim will then be how to address this in order to help prevent Gareth from having similar recurrences in future.

References:

Armfield DR, Kim DH, Towers JD, Bradley JP, Robertson DD (2006). Sports-related muscle injury in the lower extremity.  Clinics in Sports Medicine. Vol. 25; 803 - 842.

Balius R, Rodas G, Pedret C, Capdevila L, Alomar X, Bong DA (2014). Soleus muscle injury: sensitivity of ultrasound patterns. Skeletal Radiology. Vol. 43; 805 - 812.

Bryan Dixon J (2009).  Gastrocnemius v Soleus strain:  how to differentiate and deal with calf muscle injuries.  Current Reviews in Musculoskeletal Medicine. Vol. 2 (2): 74 - 77.

Ekstrand J, Hagglund M, Walden M (2011).  Injury incidence and injury patterns in professional football -   the UEFA injury study.  British Journal of Sports Medicine. Vol 45 (7); 553 - 558.

Koulouris G, Ting AY, Jhamb A, Connell D, Kavanagh EC.  Magnetic resonance imaging findings of injuries to the calf muscle complex.  Skeletal Radiology. Vol. 36 (10); 921 - 927.

Pedret C, Rodas G, Balius R, Capdevila L, Bossy M, Vernooij WM, Alomar X (2015).  Return to play after soleus muscle injuries.  Orthopaedic Journal of Sports Medicine. Vol. 3 (7).  Published online 2015 Jul 22; doi: 10.1177/2325967115595802