Pelvic Rotation Effect on Human Stride Length: Releasing the Constraint of Obstetric Selection

Abstract

As human walking speed increases, pelvic step accounts for a greater percentage of total step length and is associated with an increase in amplitude of pelvic rotation. As a result, for any given speed individuals of varied pelvic width and leg length should differ in locomotor kinematics and energetic cost. Yet despite absolutely shorter legs and wider pelves relative to leg length in females, mass-specific cost of transport in walking does not differ by sex. Focusing on stride length as the major component of gait economy, we perform a quantitative analysis of temporal, spatial and rotational gait parameters using kinematic measurements obtained from 30 healthy adults walking at two comfortable speeds. We predicted that a larger component of stride length would derive from pelvic rotation in females and that a stride length model incorporating pelvic and limb kinematics would be a better predictor than a simple limb-based model. We found that pelvic rotation was greater in females at both speeds but reached significance only at the faster speed. A larger component of female stride length derived from pelvic rotation and the female hip translated farther than the male hip, but only when walking faster. The Model LIMB and PELVIS was a better predictor of stride length than the limb only model and accurately predicted female stride length but not male stride length. Females exploit the breadth of their obstetric pelvis to obtain longer strides relative to leg length and perform at comfortable travel speeds with greater excursion angles than males.

Evolution of the human pelvis and obstructed labor: new explanations of an old obstetrical dilemma

“…Warrener and colleagues 33,34 showed that females and males do not differ in efficiency in either walking or running on a treadmill ( Figure 5). The kinematic study of Whitcome et al 35 showed that during walking at higher speed, females translate more of the pelvic rotation into strides than males, which leads to similar efficiency of locomotion despite wider hips. Thus, instead of decreasing efficiency, a wide pelvis contributes to stride length and, particularly in individuals with shorter legs, may even be beneficial for walking.…”

Anatomy, Development, and Function of the Human Pelvis

“…To start the issue, Cara Lewis (Boston University) and colleagues provide a broad overview of basic pelvic anatomy and function in living humans. Lewis (, this issue) presents evidence that there are significant differences in pelvic function between males and females—a finding that is supported in detail by other scholars (Gruss et al, , this issue; Wall‐Scheffler and Myers, , this issue; Whitcome et al , this issue) later in the issue. Finally, Lewis (, this issue) discusses the etiology of over and under coverage of the acetabulum and the resulting complications—femoroacetabular impingement, which causes pain and limits hip mobility—in the context of hip evolution and pelvic dimorphism, suggesting that the higher prevalence in females than in males may be a result of the evolutionary challenge of bipedalism and obstetrical adequacy in human females.…”

“…This suggests that a narrow pelvis is not in any way necessary for bipedal locomotion. On the contrary, the papers by Wall‐Scheffler and Myers (, this issue), Gruss et al (, this issue), and Whitcome et al (, this issue) confirm that our adaptation to bipedalism makes use of our pelvic breadth in increasing our stride length, a point made earlier for australopiths by Rak (). All humans today and in the past have a relatively broad pelvic girdle compared to apes and evolutionary changes that have taken place within human evolution have been primarily in the anterior–posterior dimension of the pelvis rather than the transverse one.…”

“…However, up until this point, this hypothesis has not been formally tested. Three studies published in this issue address this very question (Gruss et al, , this issue; Wall‐Scheffler and Myers, , this issue; Whitcome et al, , this issue) and are stunning in how concordant the results are. Gruss (Radford University) and colleagues present their findings (Gruss et al, , this issue) as a formal test of Rak's hypothesis.…”

“…Katherine Whitcome's (California Northstate University) study concurs. She and her colleagues (Whitcome et al, , this issue) studied the kinematics of gait in 30 individuals and found that women have a larger component of pelvic rotation contributing to stride length than men, especially at faster walking speeds. These data are consistent with her earlier findings (Whitcome et al, ) that women have more oblique zygapophyses in their lumbar vertebrae and are consequently capable of more lumbopelvic rotation than men.…”