What Happens When You Run? Breaking Down the Gait Cycle with Biomechanics

Have you ever thought about what your body does when you run? Your legs seem to move automatically, but behind the scenes, your body repeats a precise sequence of movements called the gait cycle. This cycle describes everything from how your foot hits the ground to how you push off and swing forward. It is like your body’s secret formula for running efficiently and keeping balanced.

In this article, we will break down the gait cycle, keeping the biomechanics terms like heel strike and midstance intact, but in an understandable way—even if you are not a scientist.

What is the Gait Cycle?

The gait cycle is the complete sequence your legs go through during each stride of running. It starts when your foot hits the ground (called initial contact) and ends when the same foot comes back down again after swinging through the air. Unlike walking, running has a unique feature: the aerial phase. This is the moment when neither foot is on the ground, and you are essentially flying! This different pattern during running ensures increasing locomotion speed while saving energy. (Cappellini et al. 2006)

The running gait is characterized by two main phases: the stance phase, where one foot is on the ground, and the swing phase, during which the same feet is off the ground (Kapri and Mehta 2021). The toe-off, a crucial element of the gait cycle, marks the transition from the stance phase to the swing phase. Let’s have a look at these two phases!

Stride phases scheme (Kapri and Mehta 2021)

1. Stance Phase: Ground Contact and Push-Off

The stance phase is the part of the gait cycle where your foot is in contact with the ground. All the action occurs at this instant: absorbing shock, stabilizing your body, and pushing you forward. It’s about 40-50% of your running cycle.

Key Sub-Phases of the Stance Phase:

• Initial Contact:

This is how your foot first hits the ground.‍

-Heel strike: The heel touches the ground first, which is common for long-distance runners (Kasmer et al. 2013).

- Midfoot strike: The middle of the foot lands first, offering a balance between cushioning and efficiency.

- Forefoot strike: The ball of the foot makes contact first, often seen in sprinters.

• Midstance:

During midstance, your body weight is fully supported by your stance leg. This phase is all about balance and stability.

Your ankle, knee, and hip are slightly bent, acting like shock absorbers. If your foot rolls inward too much (overpronation) or not enough (oversupination), it can cause imbalances and even injuries over time.

Overpronation and oversupination visualisation (Wenger, 2024)

• Toe-Off (Propulsion):

This is when your foot leaves the ground, propelling you forward. The big toe and the ball of the foot push off the ground, powered by the calf muscles (gastrocnemius and soleus). This phase is critical for speed and efficiency. As noted by Cappellini et al., the propulsive second half of the stance phase relies heavily on elastic energy stored in the muscles and tendons during the initial contact.

In the image below, the left foot is captured in the stance phase of the gait cycle.

2. Swing Phase

The swing phase begins the moment your foot leaves the ground and continues until it touches back down. This phase accounts for 50-60% of your running cycle and is all about repositioning your leg for the next step.

Key Sub-Phases of the Swing Phase:

• Early Swing:

As your foot lifts off the ground, your hip flexors and hamstrings pull your leg forward. The knee bends to create a compact shape, making it easier for your leg to swing.

• Late Swing (Terminal Swing):

Your leg extends forward, preparing for the next landing. The hamstrings work to control this forward motion and prevent you from overstriding (placing your foot too far in front of your center of mass, which can increase injury risk).

In the image below, the runner is captured in the swing phase of their stride.

Why Understanding the Gait Cycle Matters :

Understanding the gait cycle is key to improving running biomechanics, enhancing performance, and reducing the risk of injuries. By analyzing how your body moves during each phase—stance, swing, and the aerial phase—you can identify inefficiencies and tailor your training to your specific needs and goals.

For example, a sprinter may focus on optimizing their propulsion phase to maximize speed, while a long-distance runner might work on improving shock absorption during midstance. Knowing which phase to target allows you to address individual biomechanics, refine your technique, and make adjustments that align with your running style and objectives.

Additionally, understanding the gait cycle helps you spot potential problems that could lead to injuries like shin splints or knee pain. With this knowledge, you can adopt strategies—like strength training, cadence optimization, and drills—to run more efficiently and effectively.

Conclusion: Running Smarter Starts with Understanding

The gait cycle is more than just a sequence of movements—it is the foundation of how we run. By understanding the biomechanics behind each phase, from initial contact to propulsion and swing, you can unlock the potential to run more efficiently, avoid injuries, and tailor your training to your specific goals.

Whether you are a sprinter aiming for explosive power or a long-distance runner seeking endurance and balance, focusing on the nuances of your gait cycle allows you to refine your form and maximize performance. So next time you lace up your running shoes, remember that each step is part of a well-orchestrated system. With the right knowledge and training, you can make every stride count. Happy running!

References

Cappellini, G., Y. P. Ivanenko, R. E. Poppele, and F. Lacquaniti. ‘Motor Patterns in Human Walking and Running’, 2006. https://doi.org/10.1152/jn.00081.2006.

Kasmer, Mark E., Xue-Cheng Liu, Kyle G. Roberts, and Jason M. Valadao. 2013. ‘Foot-Strike Pattern and Performance in a Marathon’. International Journal of Sports Physiology and Performance 8 (3): 286–92. https://doi.org/10.1123/ijspp.8.3.286.

Kapri, Ekata, and Manju Mehta. 2021. ‘Biomechanics of Running: An Overview on Gait Cycle’. ResearchGate. https://doi.org/10.34256/ijpefs2131.

Peter, Wenger. n.d. ‘Understanding Pronation in Running: A Comprehensive Guide: Princeton Sports and Family Medicine, P.C.: Sports Medicine’. Princeton Sports & Family Medecine. Accessed 19 December 2024. https://www.princetonmedicine.com/blog/understanding-pronation-in-running-a-comprehensive-guide.

Prateek, G. V., Pietro Mazzoni, Gammon M. Earhart, and Arye Nehorai. ‘Gait Cycle Validation and Segmentation Using Inertial Sensors’. IEEE Transactions on Bio-Medical Engineering 67, no. 8 (August 2020): 2132–44. https://doi.org/10.1109/TBME.2019.2955423.

Robberechts, Pieter, Rud Derie, Pieter Van den Berghe, Joeri Gerlo, Dirk De Clercq, Veerle Segers, and Jesse Davis. ‘Predicting Gait Events from Tibial Acceleration in Rearfoot Running: A Structured Machine Learning Approach’. Gait & Posture 84 (February 2021): 87–92. https://doi.org/10.1016/j.gaitpost.2020.10.035.

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