The Calf Complex
Triceps surae complex (TSC) injuries continue to be a mainstay in many sports. In English rugby union TSC injuries were the 2nd most common injury causing the 2nd most amount of time loss. Furthermore rates in AFL have shown to be on a slight improvement
The specificity of TSC injuries has been an evolving area in the recent years. In a retrospective study performed by Waterworth et al. demonstrated that the soleus was the most injured muscle in the triceps surae complex (TSC).
The anatomy of the TSC especially the soleus, is complex and variable. However what is known is that the soleus makes up the majority of the cross-sectional of the TSC and largest physiological cross-sectional area out of any lower limb muscle, hence one of the strongest muscles in the body.
Recent research from O’Neill has shown those without Achilles tendinopathy were able to demonstrate 2 x bodyweight (BW) peak plantar flexion torque compared to 1.2 x BW in those with Achilles tendon pain even in the asymptomatic contralateral leg. Seeing as the TSC functionally cannot be disconnected from the Achilles tendon, these strength measures give an insight in the minimum requirement for risk mitigation of calf and Achilles tendon injury. The author notes in unpublished data in Olympic level athletes that 3.5 x BW for females and 4 x BW for males is a minimum requirement for adequate plantar flexion torque.
The suggested capacity is supported by the seminal paper by Dorn et al. who demonstrated the key role of the soleus in locomotion. Another study showed its performance impact on change of direction performance.
In other demands the soleus plays an integral piece of the puzzle in not just Achilles tendinopathy, triceps surae injuries but also has a potential protective role in ACL injuries.
In conclusion, the soleus has the capability to produces a high levels of force and has a high level of resistance to fatigue. It plays a significant role in performance and injury prevention however it is not the only plantar flexor of the ankle and knee extensor of the knee. It must be considered in combination with other additional muscles that act across both these joints in order to rehab appropriately.