The calf muscles are arguably the most important muscles for runners and pretty much everyone who stands on two feet. In this blog post, we will focus on the importance of the calf muscles for runners.
When I say calf muscles, I'm referring to the muscles at the back of the lower leg. The two largest muscles in this region are the gastrocnemius and soleus. These two muscles combine in the lower part of the leg to form the Achilles tendon. Applying more stress to the lower leg than the calves can tolerate exposes runners to multiple injuries, including but not limited to Achilles tendinopathy, calf strains and medial tibial stress syndrome, better known as shin splints.
When the foot contacts the ground, the calf muscles and Achilles tendon absorb and store energy. During the propulsive phase of the gait cycle, the calf muscles and Achilles tendon release the stored energy and propel us forward. During this storage and release cycle, the calf muscles can be exposed to forces as high as 12.5 times our body weight (Komi et al., 1992). Of the calf muscles, the soleus produces significantly more force. A more recent study by Dorn et al. (2012) demonstrated that when running at 6.96 m/s (approximately 25 km/h), the gastrocnemius produced around 3.23 times bodyweight of force and the soleus produced around 8.71 times bodyweight of force. Interestingly, Komi et al. (1992) suggested that running at around 14.4 km/h (4 min 10 sec per km pace) exposes the Achilles tendon to forces equal to 8.3 times bodyweight.
To further put the importance of the calf muscles into perspective, Dorn et al. (2012) demonstrated that at running speeds below 7 m/s or 25.2 km/h, the gastrocnemius and soleus contributed most significantly to stride length. In addition, compared to muscles such as the hamstring, gluteus maximus and rectus femoris, the soleus produced the greatest peak force by a considerable margin. At running speeds above 7m/s or 25km/h, only then is the soleus outdone by the hamstrings and iliopsoas for peak force production. At these speeds, the work of the calf muscles actually reduces as there is less ground contact time.
According to a Runner's World article written by Jane McGuire in 2019, the average pace for male and female marathon runners is 6.43 min/km (9.3 km/h) and 7.46 min/km (8 km/h), respectively.
So what do these numbers tell us? While most runners spend more time focusing on the bigger muscle groups, such as the glutes, we should be paying a lot more attention to strengthening our calves. Interestingly, if people do strengthen their calves, they tend to complete calf raises with their knees extended. This is better than nothing, but it targets the gastrocnemius more than the soleus. To target the soleus, which is clearly the more important calf muscle for runners, you need to complete calf raises with your knees flexed. Heavy seated calf raises are the best way to work on your soleus strength.
If you want to work on your calf strength but don't know where to start, book an appointment with one of our experienced podiatrists. Doing so may help you to avoid an injury or even achieve a PB!
Author: Andrew Apolloni