While walking may seem as simple as putting one foot in front of the other, your body’s working hard during each and every step. An overview of the gait cycle makes that evident. Check it out!
A lot can happen in a single second, which is how long it takes you to complete a full gait cycle. The gait cycle starts when your foot initially hits the ground and ends when that same foot hits the ground for the next step. The average person may go through 5,000 gait cycles per day without giving them a second thought, but your body is working hard to ensure you remain balanced, stable and moving forward with each and every step.1
Going through the Motions
Each gait cycle consists of two distinct phases: the stance phase and the swing phase.1,2
Stance phase: This closed-chain motion lasts about 0.6 seconds and occurs when your foot is making contact with the ground. The stance phase consists of the heel strike, full forefoot load, heel lift and toe off. It can be subdivided into three periods: contact, midstance and propulsive.
The contact phase occurs when your foot first touches and then makes full contact with the ground. Midstance occurs when your body’s center of mass is essentially vaulting over the foot on the ground. The propulsive phase begins when your heel and then toes completely lift off the ground.
Swing phase: This open-chain motion lasts about 0.4 seconds and occurs when your leg is swinging through the air preparing for the next impact.
ILLUSTRATION HERE: Michaud p. 87 OR Neumann p. 636
Stance Phase Efficiency
Swing phase motions are part of your body’s neurological makeup from birth, while efficient movements during the stance phase must be learned.3,4 And it’s not something you pick up overnight. It can take up to 10 years for children to finally move through the stance phase with the same level of metabolic efficiency as adults. A series of five movements contribute to the efficiency of your gait, and they are:
- Pelvic rotation
- Pelvic tilt
- Knee flexion and extension
- Interactions between the hip, knee and ankle
- Lateral pelvic displacement, or the horizontal shift of your pelvis or abduction of your hips
Each of these five factors has a specific impact on energy expenditure, with the overall goal of moving your “center of mass through space along a path requiring the least expenditure of energy.”5 To do so, you must adjust the joint positions in your pelvis and legs so your center of mass has what is called a flattened pathway.
Flattened Pathway Explained
A flattened pathway refers to the relatively flat line of motion your center of mass takes as you complete a gait cycle, something your body habitually does after years of practice. You can contrast the flattened path with a choppy one, or by trying to walk forward while locking your knees and hips in place. Notice how your center of mass is forced to jerk up and down to accommodate the immobility of your joints.
You can also waste energy with a pathway that is overly flattened by excessively bending your knees and hip joints. Your center of mass may follow a flattened path, but you’re also using 50 percent more oxygen while moving forward with the exaggerated flexion of your knee and hip joints.6
This same exaggerated flexing of the extremities is what keeps the movement of small mammals much more inefficient than larger mammals. A mouse uses 20 times more energy than a pony during the gait cycle, thanks to the constant, exaggerating flexing of the extremities that take place with a rodent’s every step.7
Understanding the phases of the gait cycle is only a small step toward understanding everything your body does while taking a step. Stay tuned for more.
REFERENCES:
- Michaud TC. Human Locomotion: The Conservative Management of Gait-Related Disorders. Newton, MA: Newton Biomechanics; 2001.
- Newmann D. Kinesiology of the Musculoskeletal System. 2nd St. Louis, MO: Mosby Elsevier; 2009.
- Elfman H, Manter J. The evolution of the human foot, with especial reference to the joint. J Anat. 1936;70:56-67.
- Scott E. Personal communication referenced in: Inman VT, Ralston HJ, Todd F. Human Walking. Baltimore: Williams & Wilkins, 1981.
- Saunders JB, Inman VT, Eberhart HT. The major determinants in normal and pathological gait. J Bone Joint Surg. 1953;5813:153.
- McMahon T, Valiant G, Frerick E. Groucho running. J Appl Physiol. 1987;62:2326-2337.
- Taylor C. Relating mechanics and energetics during exercise. Adv Vet Sci Comp Med. 1994;38A:181-215.