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  • Writer's pictureJo Clubb

Calf Muscle Complex: Anatomy, Function & Testing

Updated: May 29

Understanding calf strength testing is crucial for enhancing athletic performance. In this post, we explore the anatomy and function of the calf group, along with effective methods for measuring muscle strength.

In sports science, we spend a considerable amount of time and energy focusing on the hamstring muscle groups and the hip and groin areas. In fact, we've already discussed testing both of these regions in our athlete testing series in collaboration with VALD.

However, are we overlooking a crucial muscle group? The calf complex is critical for producing and transmitting forces through the lower limbs, impacting the entire body. So let's delve into the significant contribution of the calf complex to vertical and horizontal force and explore how we can measure and track strength in this muscle group.

Anatomy of the Calf Complex

The calf complex plays a vital role in running, sprinting, jumping, and changing direction. The calf complex consists of the posterior compartment of the lower limb, which is divided into the deep and superficial compartments.

The deep posterior compartment includes the flexor hallucis longus, tibialis posterior, flexor digitorum longus, and popliteus muscles.

The superficial compartment consists of the gastrocnemius, soleus, and plantaris. The gastrocnemius and the soleus are collectively referred to as the triceps surae. These muscles are responsible for plantar flexing the foot and, in the case of the gastrocnemius, also knee flexion.

Given its role in transmitting these critical forces, it's essential to consider how we can measure and track strength in this muscle group.

Significance of the Calf Muscles in Athletic Performance

Studies highlight the crucial role of the calf muscles in athletic performance. For instance, research by Tim Dorn and his colleagues at the University of Melbourne shows that the soleus contributes significantly to vertical ground force across various running speeds. The soleus, gastrocnemius, and vastus muscle groups collectively provide approximately 75% of the total vertical force impulse needed to accelerate the body upward, with the soleus alone contributing as much as 50%.

Similarly, a study by Hamner and Delp demonstrated that the soleus is the largest contributor to upward mass centre acceleration at various speeds, contributing up to 77% of total vertical acceleration at five meters per second. These findings underscore the importance of the calf complex in running and the necessity of incorporating calf strength testing into our athlete assessment protocols. For more detail on these studies, watch the video below taken from the Global Performance Insights YouTube channel:

Methods for Measuring Calf Strength

There are several options for measuring calf strength, each with its advantages and limitations. We will explore three different methods using tools available from VALD Performance. For demonstrations of the following tests, watch the video above:

  1. Handheld Dynamometer:

  • The handheld dynamometer, such as VALD's DynaMo, allows for portable strength testing. The participant lies in a supine straight-leg position and pushes against the pad of the dynamometer for three to four seconds. While handheld dynamometers are accessible and portable, they require careful attention to inter- and intra-tester reliability.

  1. Fixed Frame Dynamometer:

  • The ForceFrame is a fixed frame dynamometer that can assess ankle plantar flexion strength in either a supine or seated position. The contribution of the gastrocnemius and soleus varies depending on the knee position. Testing in both bent and straight-leg positions can provide a comprehensive assessment of the calf muscles.

  1. Force Plate:

  • Force plates, such as ForceDecks, offer a precise method for measuring calf strength. Testing can be done in a seated position with a custom rig or a weighted barbell. This method provides outputs similar to other isometric tests, including absolute force, relative force (body weight), and left-right asymmetries.

Key Considerations for Calf Strength Testing

  • Isometric Testing:

  • Isometric tests are particularly relevant for the calf muscles, which work quasi-isometrically during running. This makes isometric testing and training especially beneficial for capturing and enhancing calf muscle strength. But make sure your athletes are not cheating through joint movement!

  • Rate of Force Development (RFD):

  • To measure RFD, instruct athletes to contract as hard and as fast as possible. However, the reliability of RFD measurements can be an issue, so consider whether this data is necessary for your assessments.

  • Relative Force:

  • Measuring force relative to body weight provides valuable insights. For example, data from the Irish rugby national men's team shows an average force relative to body weight of around 1.5, with a target of 2 for optimal performance. More on that in the video above.


The calf muscle group is critical for so many movement demands in sports yet, these muscles can often get overlooked in favour of the hamstring and hip and groin groups. We have the ability to assess their strength via numerous means nowadays. We are no longer just relying on counting calf raises!

Whether using handheld dynamometers, fixed frame dynamometers, or force plates, each method provides valuable insights into calf muscle function. Given the significant role of the calf complex in running and other dynamic movements, regular testing and tracking of calf strength are essential for athlete performance and injury prevention.

Frequently Asked Questions (FAQs) on Calf Testing

What muscles make up the calf complex?

The deep posterior compartment includes the flexor hallucis longus, tibialis posterior, flexor digitorum longus, and popliteus muscles. The superficial compartment consists of the gastrocnemius, soleus, and plantaris. The gastrocnemius and soleus together are referred to as the triceps surae.

What are the common methods for testing calf strength?

Historically we have relied upon calf raise testing, either through an endurance-based test counting until failure, or load based using calf raise machines. Now, common methods include using a handheld dynamometer, a fixed frame dynamometer like VALD's ForceFrame, and force plates.

How does the knee position affect calf strength testing?

The contribution of the gastrocnemius and soleus varies with knee position. A bent knee position primarily engages the soleus, while a straight leg position engages the gastrocnemius more. This is important for both testing and training the calf muscles.

What is the significance of isometric testing for calf muscles?

Isometric testing is highly relevant for calf muscles, which work quasi-isometrically during running. It provides a reliable assessment of muscle strength and function, while also being safe and minimally-fatiguing.


This article is support by VALD Performance. For more information, about their technology, visit their website.

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Stay tuned for more insights on strength testing in our series sponsored by VALD Performance. Subscribe to our blog to stay updated!

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