Written by Trent Brown
In most gait texts, articles, or journals we study the various phases of gait such as initial contact, loading response, mid stance, etc. It is generally regarded that 60% of gait is spent in stance phase while 40% is spent in swing phase. As clinicians, it is difficult to determine what to emphasize with gait or mobility training for our clients when so many factors are involved.
Do I focus on lower extremity strengthening, pelvic mobility, core stability, sensation, proprioception, or one of the other myriad of possibilities?
I've focused on the “determinants of gait”. In other words, what determines how successful a client can be with gait, ambulation, or functional mobility? Regardless of a clients’ strength or level of function we must determine whether or not they have the necessary skills to be successful.
Most of our clients have been walking since 10-13 months of age, but typically this natural pattern becomes dysfunctional as we age, leading to falls, excessive energy expenditure, and pain.
The determinants of gait are often classified into 5 features with an overall goal to reduce the amount of movement of the center of gravity outside of the base of support.
1) Lateral Pelvic Tilt in the Frontal Plane
2) Knee Flexion at Mid-stance
3) Knee, Ankle, Foot Interactions
4) Pelvic Rotation in the Transverse Plane
5) Physiological Valgus of the Knee
I have developed a different way of viewing these five determinants. I have added “sit-stand” and “reciprocal arm swing” determinants while removing the “physiological valgus of the knee” determinant. I directly address six determinants or factors that will help you analyze how successful our clients will be with pre-gait, gait, ambulation, and functional mobility.
This is completely new and may be disregarded as a determinant of gait, but I consider this as an absolute determinant.
When can gait begin if a sit-stand doesn’t occur?
Often we spend weeks or months working with a client to get them to complete a sit-stand with increased independence or safety. Like the mobility aspects of gait, our goal is to keep the clients’ COG over the BOS to reduce the work load and effort required to complete a sit-stand.
This must happen prior to initiating locomotion.
Anterior pelvic tilt is required to approximately 10 to 15 degrees to initiate and complete a sit–stand. Likewise, a posterior pelvic tilt during the hip hinge or straightening phase of sit-stand must equally occur to bring the pelvis back to a neutral position.
We must ensure our clients have the appropriate amount of anterior and posterior pelvic tilt to complete this phase. During the rest of the gait cycle approximately 4-5 degrees of pelvic tilt (from neutral) is required for normal ambulation.
Lateral Pelvic Tilt in the Frontal Plane
This controlled “pelvic drop” to the ipsilateral swinging limb occurs when the COG reaches its apex due to the height reached during single leg stance. The Gluteus Medius and large hip abductors provide stabilization via eccentric contraction to allow control of the pelvic drop. Ultimately, the goal of lateral pelvic tilt is to reduce the vertical movement of the COG or bounce during gait. This in turn leads to increased safety and a reduction in energy expenditure.
Knee Flexion at Mid-stance
This determinant works in conjunction with the lateral pelvic tilt in reducing vertical displacement of the COG. At the point when a client reaches “flat foot” until mid-stance, the knee eccentrically loads and slightly flexes due to the weight of the body. This acts as a cushion or buffer between our COG and the ground to avoid a pendulum or bouncing affect.
Knee, Ankle, and Foot Interactions
This rhythmical interaction occurs during the load response (beginning of stance) and pre-swing (end of stance) to alter the length of the limb. This interaction increases the length of the limbs to reduce the amount of drop of the COG toward the floor. While one lower extremity initiates heel strike on a dorsi-flexed ankle, the opposite limb delays the toe-off with a plantar-flexed ankle. This occurs during the lowest vertical point of our COG and the greatest acceleration phase of gait.
Pelvic Rotation in the Transverse Plane
Pelvic rotation is a combination of the advancement of the limb during swing phase with the progression of the opposite limb during stance phase.
When the left limb swings forward, the left side of the pelvis also moves forward rotating the
pelvis to the right (from neutral).
During stance-phase of the left limb (right limb swinging forward) the pelvis rotates to the left.
Reciprocal Arm Swing
The reciprocal arm swing occurs during all phases of gait and directly correlates with step length. The opposite upper limb rhythmically swings in conjunction with the opposing lower limb during each phase. Not only does this pattern increase force production and step length, but balance.
As the majority of the lower body weight swings forward, the opposite upper limb swings forward to reduce the amount of energy expended by the core musculature for stability and acts as an anatomical counterweight reducing energy expenditure and COG displacement.