Muscles are a must for walking, but you may not realize just how complex and intricate their motions can be. Check out the variety of muscles and their movements that make the gait cycle possible.
Taking a step would not be possible without the extensive lineup of muscles that help ensure you can effectively move forward. During the gait cycle, the muscles of your lower extremities have a big job to do. But they’re prepared to do it, with each lower extremity operated by 50 muscles that pick up the work.1
Each muscle has a distinctly different task or series of tasks. No two muscles have identical actions, and each muscle is active to some degree during every gait cycle.1 Muscles in your hip, leg, ankle and foot activate the elements of gait needed for motion as well as stabilization and deceleration.2
Multiple Movements from a Single Muscle
Many of the muscles perform multiple movements to achieve their specific actions. They may move eccentrically, concentrically or isometrically. Their actions may work across one or more joints, or a distal or proximal portion of a joint.1
The tibialis posterior muscle of your lower leg is a prime example. Prior to mid stance phase, the muscle moves eccentrically to control the lowering of your foot’s arch. After mid stance, that same muscle moves concentrically as it lifts the arch and helps externally rotate the tibia. The muscle then continues its concentric action as it assists with the ankle motion required for toe off.1
Action before the Action
Before your body even takes a step, your central nervous system incorporates what is called the gait-initiation motor control program wherein a subtle series of postural adjustments shift the center of pressure (COP) as needed to the appropriate leg.3 The COP first heads towards the foot that is about to become the swing leg, then back to the leg that is readying for stance. All this is happening before any noticeable movement of your center of mass takes place.
The act of walking actually starts with the relaxation of the calf muscles that comprise the gastrocnemius-soleus muscle group.2 This action allows your body to incline forward, ahead of the center of gravity. As your body weight shifts forward, your supporting foot is tasked with bearing that weight, as outlined in our gait post on foot and ankle stability.
Major muscular activity doesn’t begin until the last 10 percent of the swing phase and ends in the first 10 percent of the stance phase, the two gait phases outlined in our gait cycle overview post. Although the gait cycle is often associated with moving forward, the muscular movement in the swing phase is meant to slow us down, not propel us into motion.2
Bursts of Activation
Nearly all muscles in your lower extremities go through one or two brief bursts of electrical activity during a gait cycle, with each burst generally lasting 100 to 400 msec. This muscular activation happens over and over with each stride.1A general overview of muscles that contribute to gait give you a broad picture of just how involved each step can be.
- Trunk: Two essential muscles include the erector spinae and rectus abdominis, which activate on the left and right side of the body activate simultaneously.
- Hip: Area muscles that come into play include hip extensors, flexors, abductors, adductors and rotators.
- Knee: Knee extensors and flexors are the two area muscle groups most active during walking.
- Ankle and foot: Several area muscles play an essential role, including the extensor digitorus, extensor hallucis longus, fibularis longus and brevis, ankle plantar flexors and intrinsic muscles of the foot.
As with any component of the gait cycle, your muscle activity is intricate, complex and only one small part of a larger whole that makes walking possible.
REFERENCES:
- Newmann D. Kinesiology of the Musculoskeletal System. 2nd ed. St. Louis, MO: Mosby Elsevier; 2009.
- Cailliet R. Foot and Ankle Pain. 3rd ed. Philadelphia: F.A. Davis Company; 1997.
- Michaud TC. Human Locomotion: The Conservative Management of Gait-Related Disorders. Newton, MA: Newton Biomechanics; 2001.