Biology:Key determinants of gait

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Gait is a form of animal locomotion requiring the alternating action of the lower limbs, which results in the translation of the center of mass (COM) in space in a way that elicits the smallest energy expenditure. A normal gait pattern depends on a range of biomechanical features, controlled by the nervous system for increased energy conservation and balance.[1] These biomechanical features of normal gait have been defined as key determinants of gait. It is therefore necessary for the refined neurological control and integration of these gait features for accuracy and precision with less energy expenditure. As a result, any abnormality of the neuromusculoskeletal system may lead to abnormality in gait and increased energy expenditure.

Overview

The six determinants of gait have been long-lasting theories of gait that have been extensively studied biomechanically. These six kinematics or determinants of gait were established by Saunders et al. [1] in 1953.[2] Due to the extensive studies in these determinants, they have gone through various refinements over the past five decade, which have led to either authentication, acceptance or disputation of each of the six determinants of gait. The six determinants of gait have been predominantly embraced as a fact for half a decade since its proposition,[3] and have made appearances in various literature,[4][5][6][7] but without extensive testing. Albeit, recent studies have depicted that, the first three determinants might actually contribute marginally or far less to reducing the vertical displacement of the center of mass (COM).

These determinants of gait are known to ensure economical locomotion,[8] by the reduction in vertical center of mass (COM) excursion leading to reduction in metabolic energy. It is therefore suggested that the precise control of these determinants, also referred to as kinematic features of gait [9] leads to increased energy conservation. These kinematic features of gait are integrated or coordinated in order to ensure a circular arc trajectory of the COM, as theory proposed as the 'compass gait (straight knee)'.[10] The theory underlying the determinants run contrary to that of the 'inverted pendulum' theory with a static stance leg acting as a pendulum that prescribes an arc.[11][12] The six determinants of gaits and their effects on COM displacement and energy conservation are described below in chronological order;

Six determinants of gait

Pelvic rotation

This kinematic feature of gait operates under the theory of compass gait model.[13] In this model, the pelvis rotates side to side during normal gait. In effect, it aids in the progression of the contralateral side through reduced hip flexion and extension. Its effect on the reduction of metabolic energy and the increased energy conservation is through the reduction of vertical COM displacement. This notion of reduction of metabolic cost may be disputed by a study done by Gard and Childress (1997),[14] who stated that there may be minimal effect of pelvic rotation on vertical COM displacement. Furthermore, other studies have found pelvic rotation to have little effect on the smoothing of COM trajectory.[15] Actually pelvic rotations has been shown to accounted about 12% reduction in the total COM vertical displacement.[16]

Pelvic tilt/Obliquity

Normal gait results in tilting of the swing phase side, in relation to the control by the stance side hip abductors. As a consequence, there is the neutralization of raising of COM during the transition from hip flexion to extension. Its effect on the reduction of metabolic energy and the increased energy conservation is via the reduction of vertical COM trajectory or peak form compass gait model. Pelvic obliquity's effects on reduction of vertical displacement of COM has been examined and been shown to only reduce vertical displacement of COM by at most, only 2–4 mm.[17]

Knee flexion at stance phase

The knee usually supports the body weight in flexed position during walking. The knee is usually fully extended at heel strike and then begins to flex (average magnitude of 15 degrees) when foot is completely flat on the ground. The effects of the stance-phase knee flexion is to lower the apex of vertical trajectory of the COM via shortening of the leg resulting in some energy conservation.[18] But recent studies testing this third determinant of gait have reported varied results. It was found out that stance-phase knee flexion did not contribute to the reduction in vertical trajectory of COM.[19] Furthermore, Gard and Childress (1997) indicated that maximum COM is reached at mid-stance when knee is slightly flexed, depicting minor reduction of the maximum height of the COM by a few millimeters.[20]

Foot and ankle motions

Saunders et al. showed relationship between angular displacement and motions of foot, ankle and knee.[21] This results in two intersecting arcs of rotation at the foot during stance phase at heel contact and heel rise. At heel contact the COM reaches its lowest point of downward displacement when the foot is dorsiflexed and the knee joint fully extended in order for the extremity to be at its maximum length. The ankle rockers at heel strike and mid-stance leads to decrease COM displacement through the shortening of the leg. Studies by Kerrigan et al. (2001) and Gard & Childress (1997) have showed the major role played by heel rise in reducing the COM vertical displacement.[22][23]

Knee motion

The motion of the knee are related to those of the ankle and foot motions and results in the reduction of COM vertical displacement. Therefore, an immobile knee or ankle could lead to increases in COM displacement and energy cost.

Lateral pelvic displacement

In this key gait feature, the displacement of the COM is realized by the lateral shift of the pelvis or by relative adduction of the hip. Correction of disproportionate lateral displacement of the pelvis is mediated by the effect of tibiofemoral angle, and relative adduction of the hip, which results in reduction in vertical COM displacement [24] [Saunders et al., 1953].

It is clear that these kinematic features play a critical role in ensuring efficiency in normal gait. But there may be the need for further extensive testing or validation of each of the key determinants of gait.

References

  1. ↑ Kuo, A. D., & Donelan, J. M. (2010). Dynamic principles of gait and their clinical implications. Physical therapy, 90(2), 157
  2. ↑ Saunders, J., Inman, V., & Eberhart, H. (1953). The major determinants in normal and pathological gait. American Journal of Bone and Joint Surgery, 35, 543–558.
  3. ↑ Gard, S. A., & Childress, D. S. (2001). What determines the vertical displacement of the body during normal walking?. JPO: Journal of Prosthetics and Orthotics, 13(3), 64-67.
  4. ↑ McMahon, T. A. (1984). Muscles, reflexes, and locomotion. Princeton, NJ: Princeton University Press
  5. ↑ Perry, J. (1992). Gait analysis: Normal and pathological function. Thorofare, NJ: Slack, Inc.
  6. ↑ Rose, J., & Gamble, J. (Eds.). (1994). Human walking (2nd ed.). Baltimore, MD: Williams & Wilkins.
  7. ↑ Whittle, M. W. (1996). Gait analysis: An introduction (2nd ed.). Oxford, UK: Butterworth-Heinemann.
  8. ↑ Kuo, A. D., & Donelan, J. M. (2010). Dynamic principles of gait and their clinical implications. Physical therapy, 90(2), 157
  9. ↑ Inman, V. T., Ralston, H. J., & Todd, F. (1981). Human walking. Williams & Wilkins.
  10. ↑ Cavagna, G., Saibene, F., & Margaria, R. (1963). External work in walking. Journal of Applied Physiology, 18, 1–9. Cavagna, G. A., & Margaria, R. (1966). Mechanics of walking. Journal of Applied Physiology, 21, 271–278
  11. ↑ Cavagna, G., Saibene, F., & Margaria, R. (1963). External work in walking. Journal of Applied Physiology, 18, 1–9. Cavagna, G. A., & Margaria, R. (1966). Mechanics of walking. Journal of Applied Physiology, 21, 271–278
  12. ↑ Kuo, A. D. (2007). The six determinants of gait and the inverted pendulum analogy: A dynamic walking perspective. Human movement science, 26(4), 617-656.
  13. ↑ Della Croce, U., Riley, P. O., Lelas, J. L., & Kerrigan, D. C. (2001). A refined view of the determinants of gait. Gait & posture, 14(2), 79-84.
  14. ↑ Gard, S. A., & Childress, D. S. (1997). The effect of pelvic list on the vertical displacement of the trunk during normal walking. Gait & Posture, 5(3), 233-238
  15. ↑ Kuo, A. D., & Donelan, J. M. (2010). Dynamic principles of gait and their clinical implications. Physical therapy, 90(2), 157
  16. ↑ Della Croce, U., Riley, P. O., Lelas, J. L., & Kerrigan, D. C. (2001). A refined view of the determinants of gait. Gait & posture, 14(2), 79-84.
  17. ↑ Gard, S. A., & Childress, D. S. (1997). The effect of pelvic list on the vertical displacement of the trunk during normal walking. Gait & Posture, 5(3), 233-238
  18. ↑ Saunders, J., Inman, V., & Eberhart, H. (1953). The major determinants in normal and pathological gait. American Journal of Bone and Joint Surgery, 35, 543–558
  19. ↑ Kuo, A. D., & Donelan, J. M. (2010). Dynamic principles of gait and their clinical implications. Physical therapy, 90(2), 157.
  20. ↑ Gard, S. A., & Childress, D. S. (1997). The effect of pelvic list on the vertical displacement of the trunk during normal walking. Gait & Posture, 5(3), 233-238.
  21. ↑ Saunders, J., Inman, V., & Eberhart, H. (1953). The major determinants in normal and pathological gait. American Journal of Bone and Joint Surgery, 35, 543–558.
  22. ↑ 11. Kerrigan, D. C., Della Croce, U., Marciello, M., & Riley, P. O. (2000). A refined view of the determinants of gait: significance of heel rise. Archives of Physical Medicine and Rehabilitation, 81(8), 1077-1080.
  23. ↑ Gard, S. A., & Childress, D. S. (1997). The effect of pelvic list on the vertical displacement of the trunk during normal walking. Gait & Posture, 5(3), 233-238
  24. ↑ Saunders, J., Inman, V., & Eberhart, H. (1953). The major determinants in normal and pathological gait. American Journal of Bone and Joint Surgery, 35, 543–558.




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