What if I told you that there was a single muscle that, when strengthened, can help you run more efficiently, decrease back pain, and even have a positive impact your metabolism? Would you still believe me if I told you that this muscle only makes up about 1% of your body weight? This blog will put the spotlight on this muscle, and its name is the soleus.
When we talk about the calf musculature, many people think of the large calf muscle called the gastrocnemius. This is the main calf muscle that forms the teardrop shape on the back of your leg when you see someone with very defined calves. There is an additional calf muscle that lies under the gastroc, and this muscle is the soleus. Despite making up only about 1% of your body weight and being a relatively small muscle, the soleus has a major impact. The soleus is primarily activated when doing a calf raise with your knee bent. This is why you commonly see both a standing calf raise machine and a seated calf raise machine at your gym. While the soleus will still be activated to some extent when doing a standing calf raise, you can really isolate it by doing a seated calf raise with your knee bent.
The soleus plays a major role in everyday life. It is an endurance muscle that is constantly working throughout the day. Whether you’re walking, driving your car, or even reaching overhead, the soleus is working. Roughly 88% of the soleus mass is made up of type 1 fibers which are also known as your “slow twitch fibers”. This means that this muscle is built for endurance so it can keep you moving all day long. Because of how active this muscle is, there are many benefits to target this muscle during your strength training routine. There is plenty of research out there on the importance of the soleus and in this blog, I wanted to highlight a few of the more recent studies that I have come across and share with you the biggest takeaways.
For those of you who are runners, strengthening the soleus muscle can help you become a more efficient runner. One study in 2021 looked at the effect of the soleus on running efficiency. For 14 weeks the participants engaged in a training routine that targeted the soleus and were then re-examined to determine the impact on running efficiency. This study found that the most efficient runners had high plantar flexor muscle strength (plantar flexion is pointing your toe downwards which engages your calves, ex: heel raise). The soleus generates most of the energy used to accelerate the body while running and strengthening this muscle helped reduce the metabolic energy cost of running.1 Another study from 2016 found that using rigid shoe insoles significantly increased soleus activation and force output. This helped produce more metabolic power and lead to more efficient running mechanics. So the main takeaways from these two articles are that strengthening your soleus can improve your running efficiency and if you want to increase soleus activation, you can choose a shoe with a stiffer insole. This is not to stay that a stiffer insole is the best shoe for running, but if you want to train your soleus more you can use this a stiffer insole to help increase the activation of this muscle and potentially improve your running.2
One of the most interesting studies I have read recently looked at the effect of soleus activation on metabolism and glucose regulation. In this study they had subjects do “soleus push-ups” (seated calf raise) while sitting throughout the day. The volume of soleus pushups was very high (about 4 ½ hours total work per day) but the results were fascinating. They found that after doing this simple exercise, the subjects had 52% LESS increase in blood glucose and 60% LESS hyperinsulinemia (reduced insulin levels) which lasted up to 2 hours. After you eat a meal, your blood glucose will go up depending on what you consume. Your insulin then also raises to match the spike in blood glucose following a meal. These results showed that you can increase the clearance of glucose from your blood stream after working the soleus. Now, I don’t know about you, but I am definitely not doing 4 ½ hours of soleus push ups each day. However, the main takeaway from these findings is that you can certainly have long lasting benefits on your metabolism and blood glucose after working your soleus. This can help you maximize the time when you are stuck sitting for a prolonged period. So, the next time you are stuck on a plane, sitting at your desk for hours or going on a road trip, you can do seated calf raises periodically and know that this can have some positive effects.3
I hope this blog helps you realize the benefits of working the soleus and gave you some key takeaways from the research. If this interested you, follow us @streamlineperformancept on Instagram as every Wednesday I record a story in which I provide key takeaways from some research articles I have read. Click on the videos below for some other ideas of how you can start strength training your soleus during your next workout!
References: (click on title for link to article)
1) Bohm S, Mersmann F, Santuz A, Arampatzis A. Enthalpy efficiency of the soleus muscle contributes to improvements in running economy. Proc Biol Sci. 2021 Jan 27;288(1943):20202784. doi: 10.1098/rspb.2020.2784. Epub 2021 Jan 27. PMID: 33499791; PMCID: PMC7893283.
2) Takahashi, K. Z. et al. Adding Stiffness to the Foot Modulates Soleus Force-Velocity Behaviour during Human Walking. Sci. Rep. 6, 29870; doi: 10.1038/srep29870 (2016).
3) Hamilton, M. T., Hamilton, D.G, Zderic, T.W. A potent physiological method to magnify and sustain soleus oxidative metabolism improves glucose and lipid regulation. iScience. 2022 Aug 4. DOI:https://doi.org/10.1016/j.isci.2022.104869