M. Saini et al., THE VERTICAL DISPLACEMENT OF THE CENTER-OF-MASS DURING WALKING - A COMPARISON OF 4 MEASUREMENT METHODS, Journal of biomechanical engineering, 120(1), 1998, pp. 133-139
Measuring the vertical displacement of the center of mass (COM) of the
the body during walking may provide useful information about the ener
gy required to walk. Four methods of varying complexity to estimate th
e vertical displacement of the COM were compared in 25 able-bodied, fe
male subjects. The first method, the sacral marker method, utilized an
external marker oil the sacrum as representative of the COM of the bo
dy. The second method, the reconstructed pelvis method which also util
ized a marker over the sacrum, theoretically controlled for pelvic til
t motion. The third method, the segmental analysis method, involved me
asuring motion of the trunk and limb segments. The fourth method, the
forceplate method, involved estimating the COM displacement from groun
d reaction force measurements. A two-tailed paired t-test within an AN
OVA showed no statistically significant difference between the sacral
marker and the reconstructed pelvis methods (p = 0.839). There was als
o no statistically significant difference between the sacral marker an
d the segmental analysis method (p = 0.119) or between the reconstruct
ed pelvis and the segmental analysis method (p = 0.174). It follows th
at the first method which is the most simple, cart provide essentially
the same estimate of the vertical displacement of the COM as the more
complicated second and third measures. The forceplate method produced
data with a lower range and a different distribution than the other t
hree methods. There was a statistically significant difference between
the forceplate method and the other methods (p < 0.01 for each of the
three comparisons). The forceplate method provides information that i
s statistically significantly different from the results of the kinema
tic methods. The magnitude of the difference is large enough to be phy
siologically significant and further studies to define the sources of
the differences and the relative validity of the two approaches are wa
rranted.