speed, and body size (height, weight, leg length). ⢠Multivariate PCA and canonical ... Stride Length: Releasing the Constraint of Obstetric Selection. Anat. Rec.
Kinematic effects of body size differences during walking Maria C. Fox1, Katherine K. Whitcome2, and John D. Polk1 University of Illinois at Urbana-Champaign, Department of Anthropology, 2California Northstate University, College of Health Sciences
Introduction
Methods
• Interspecific scaling relationships suggest that larger individuals should be relatively weaker and experience kinematic and kinetic constraints compared to smaller animals 1-3
• VICON 3D motion capture data collected for 34 adult subjects (16 males, 18 females) • 3x10s trials of quiet stance, slow walking (1.25m/s), and fast walking (1.75m/s)
• Larger animals use extended postures to reduce muscular effort and smaller animals use flexed postures because they experience fewer mechanical constraints 4-5
• Calculated segment angles in MATLAB at mid-stance and heel strike; averaged across trials for each subject
• Whether these principles explain instraspecific variation in posture and performance (in humans in particular) is unclear 6-8
• Univariate correlations and linear regressions examined relationships between kinematic variables and sex, speed, and body size (height, weight, leg length)
• This research examined 34 adults to determine if angular kinematics differ with height and other measures of body size at two walking speeds
• Multivariate PCA and canonical correlations evaluated relationships between and among size and kinematic variables
Results Relative Stride Length vs. Height
Thigh Angle During Gait HeelStrike
MidStance
Relative Stride Frequency vs. Height
r = -0.42
r = -0.21
r = 0.52
2.2 0.14
F
r = -0.24
r = 0.48
M
120
Sex F
r = -0.28
M
2.2
180
190
Height (cm)
160
170
180
Sex
0.08
F
r = -0.94
0.16
M
0.14
0.12 0.10
1.6 170
0.10
1.8
100 160
0.12
Fast
2.0
Fast
Fast
110
1.6
Relative Stride Frequency
Sex
Relative Stride Length
100
1.8
Slow
Slow
110
Slow
2.0
Mean Thigh Angle (º)
r = -0.92
0.16
120
190
160
170
180
0.08
190
Height (cm)
160
170
180
Height (cm)
190
Figure 2. Relative stride length (left), calculated by stride length / limb length and relative stride frequency (right) calculated by stride frequency / limb length during slow and fast walking.
Figure 1. Mean thigh angle during heel strike (left) and mid-stance (right) during slow and fast walking. Higher angles indicate greater flexion.
PCA of Gait Data at Heel Strike
3
PCA of Gait Data at Mid−Stance
2
Sex F
1
0
M
Leg length Height Weight
Height 160 170
−1
180
Thigh Angle
190
−2
Shank Angle Foot Angle
Component 2 (23.0% of variance)
3
Component 2 (30.0% of variance)
1
Thigh Angle
2
Sex F
1
M
Height
0
160 170 180
−1
Foot Angle
Height Leg length Weight
−2
190
Shank Angle
−3 −2
0
Component 1 (46.2% of variance)
2
Figure 3. Principal components analysis of body size and kinematic variables (segment angles) at heel strike. Labeled arrows indicate size and direction of PCA loadings.
−4
−2
0
Component 1 (61.4% of variance)
2
4
Figure 4. Principal components analysis of body size and kinematic variables (segment angles) at mid-stance. Labeled arrows indicate size and direction of PCA loadings.
Discussion & Conclusions
References
• At heel strike, shorter individuals had greater thigh flexion, but at mid-stance the pattern reversed (Fig. 1); an analysis of body weight revealed the same results
1. McMahon, T. A. (1973). Size and Shape in Biology: Elastic criteria impose limits on biological proportions, and consequently on metabolic rates. Science, 179(4079), 1201–1204. 2. McMahon, T. A. (1975). Using body size to understand the structural design of animals: quadrupedal locomotion. Journal of Applied Physiology, 39(4), 619– 627. 3. Biewener, A. A. (2005). Biomechanical consequences of scaling. Journal of Experimental Biology, 208(9), 1665–1676. 4. Alexander, R. M., & Jayes, A. S. (1983). A dynamic similarity hypothesis for the gaits of quadrupedal mammals. Journal of Zoology (London), 201, 135–152. 5. Biewener, A. A. (1989). Scaling body support in mammals: limb posture and muscle mechanics. Science, 245(4913), 45–48. 6. Hora, M., Soumar, L., Pontzer, H., & Sládek, V. (2017). Body size and lower limb posture during walking in humans. PLOS ONE, 12(2), e0172112. 7. Hora, M., Sládek, V., Soumar, L., Stráníková, K., & Michálek, T. (2012). Influence of body mass and lower limb length on knee flexion angle during walking in humans. Folia Zoologica, 61(3–4), 330–339. 8. Gruss, L. T. (2007). Limb length and locomotor biomechanics in the genus Homo: An experimental study. American Journal of Physical Anthropology, 134(1), 106–116. 9. Whitcome KK, Miller EE, Burns JL. 2017. Pelvic Rotation Effect on Human Stride Length: Releasing the Constraint of Obstetric Selection. Anat. Rec. 300:752–763.
• Results at mid-stance contradict interspecific scaling expectations of decreased flexion in taller individuals during weight support • Shorter individuals had greater relative stride lengths (p < 0.0131) and relative stride frequencies at both speeds (p < 0.0001) (Fig. 2), which may relate to greater thigh flexion at heel strike or increased pelvic rotation in females 9 • Most variation in PCA Comp. 1 at heel strike and mid-stance is explained by sex and body size; Comp. 2 primarily explains variation in kinematic variables (Figs. 3-4) • PCA and canonical correlations show inverse relationships between kinematic and body size variables: at heel strike, smaller individuals have greater thigh flexion (Fig. 3, Comp. 1); at mid-stance, greater thigh flexion is accompanied by less distal limb flexion (Fig. 4, Comp. 1) • This initial analysis confirms that kinematics differ in humans of varying sizes and likely have effects on locomotor performance and behavior, although intraspecific human scaling may not follow predictions based on broad interspecific studies 3-5 • Future research will examine both kinematic and kinetic effects of body size differences in a large sample using absolute and relative speeds for both walking and running
IMAGE (to right): re-drawn from https://s-media-cache-ak0.pinimg.com/ originals/88/33/64/883364f2f6c073fd4f42ffb02bb3faeb.jpg
Acknowledgments Funding provided by the University of Cincinnati Charles Phelps Taft Research Center. Thanks to Kelsey Jelenc and Zac Bronner for assistance with data collection and processing.
