A personalized method for estimating centre of mass location of the whole body based on differentiation of tissues of a multi-divided trunk
Introduction
The location of the centre of mass of the whole body can be determined using direct methods, i.e. by a reaction board method, or using indirect methods. The latter usually involve the application of generalized data based on several investigations of the mass and location of the centre of mass of the body parts (Miller and Nelson, 1973).
The relative value (to the height) of the location of the centre of mass for healthy, young, adult people lies usually between 54% and 58% with respect to the soles of the feet (Bober, 1965). It is closer to the head in males and closer to the feet in females (Croskey et al., 1922).
Unfortunately, some biomechanists (e.g. Grimshaw et al., 2006) overlook technical problems associated with determination of the location of the centre of mass. They use for example the trunk as a one segment only. With this approach, especially when the trunk is curved, the location of the centre of mass would be of poor value.
Harless (1860), Dempster (1955), Clauser et al. (1969), Liu and Wickstrom (1973) performed physical segmentation of cadavers. Among above approaches that of Clauser et al. is of a high value since they gave regression equations which enable obtaining of individualized inertial quantities of investigated subjects.
Another approach to localization of the whole body centre of mass is by obtaining volume of body parts through: (a) anthropological linear measurements using special instrumentation, (b) photogrammetry, (c) water immersion, and (d) 3D scanning. Then a volume is multiplied by mean density of body parts or body layers (Hanavan, 1964, Jensen, 1978, Yeadon, 1990). Here, usually a uniform density was assumed for obtaining inertial values.
Hatze (1980) presented mathematical model of the human body in order to acquire volume and inertial quantities. However, some authors (e.g. Vaughan et al., 1999, Robertson, 2013) point out that this approach suffers from the disadvantage that too many variables (242) need to be measured.
Radiation techniques were used by few researchers. The group of Zatsiorsky and Seluyanov, 1979, Zatsiorsky et al., 1981 and Zatsiorsky and Seluyanov (1983)) used gamma scanning. They presented several regression equations for determining the mass of the body parts as well as the centre of mass locations from the whole body mass and height as well as from specific anthropometric measurements.
de Leva (1996) presented modified approach to Zatsiorsky׳s method, i.e. instead of anthropological landmarks he gave locations of centre of mass with respect to joint axes.
Several authors used image techniques. Computerized tomography (Erdmann, 1995, Erdmann, 1997, Pearsall et al., 1996), nuclear magnetic resonance or magnetic resonance imaging (Martin et al., 1989, Bauer et al., 2007), dual energy X-ray absorptiometry (DEXA) imaging (Durkin and Dowling, 2003, Wicke et al., 2007, Lee et al., 2009) were used to obtain inertial segment parameters.
Section snippets
Division of a trunk
Many researchers studying inertial data of the human body treated the trunk as a one segment (e.g. Harless, 1860, Clauser et al., 1969) although this part constitutes about half of the body mass.
Several other researchers used an approach of dividing the human trunk with planes perpendicular to the longitudinal trunk׳s axis, e.g. Hanavan (1964), Zatsiorsky and Seluyanov (1983), Jensen (1978), Yeadon (1990). Only Dempster (1955) and Erdmann, 1995, Erdmann, 1997 presented models of a trunk divided
The concept of the investigations
The aims of the investigations were: (1) to examine the accuracy of the combining of Clauser׳s and Erdmann׳s methods for locating the whole body centre of mass, and (2) to give the possibility of establishing location of the centre of mass for asymmetrical body position and individuals of varying morphology.
It was hypothesized that Clauser׳s and Erdmann׳s approaches for obtaining personalized inertial body data could be used to determine the location of the whole body centre of mass with
Subjects
Thirty young, fit males were included in the study. All were involved in recreational sport training as students of physical education major (none of them participated in sport in a professional way). They were aged 21–40 years (mean 24.13, S.D. 3.81), with a height of 171–190 cm (179.15, 6.42 cm) and mass of 63.3–91.5 kg (73.97, 7.03 kg).
Investigations were non-invasive. An informed consent has been obtained from all participants. All subjects agreed to participate in investigations comprising
Mass of body parts and of the whole body
The mass of the whole body measured individually on a scale (direct method) equalled in mean value M.dir=73.79 kg (SD=7.15 kg). The mass of the whole body obtained by summing up the masses of all body parts calculated using Clauser׳s and Erdmann׳s methods was almost the same, M.indir=73.75 kg (SD=7.90 kg).
Location of the whole body centre of mass
In absolute values the mean position of the whole body centre of mass with respect to the soles obtained using the direct method (D.dir) was 98.82 cm (S.D.=4.12 cm), with a range of 91.4 to 108.7 cm.
Mass of the whole body obtained by the authors
The fact that the mass of the whole body obtained using the two methods (direct and indirect based on personalized values of mass of body parts) was almost identical was rather accidental. The mass of the whole body differs during the day. At a given point it depends on a filled or empty stomach, intestine and bladder. Nevertheless, Pearson׳s correlation coefficient between the whole body mass obtained using a scale and the whole body mass obtained using Clauser׳s and Erdmann׳s (indirect)
Conclusions
For accurate location of the whole body centre of mass a personalized approach is needed. In this case Clauser׳s and Erdmann׳s methods give a high accuracy for determining the mass and for locating the centres of mass of body parts. This gives high accuracy of determining the location of the centre of mass of the whole body. This approach was successfully verified.
Using Clauser׳s and Erdmann׳s methods one can obtain an accurate location of the centre of mass in several situations such as: (a)
Conflict of interest statement
There is no conflict of interest regarding the study and preparation of the manuscript.
Acknowledgement
There were no study sponsors involved in the research leading to this manuscript.
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Comparison of body segment models for female high jumpers utilising DXA images
2022, Journal of BiomechanicsCitation Excerpt :By dividing the trunk into more subportions and using Erdmann’s method (Erdmann, 1997) the authors concluded that an accurate location of the centre of mass can be obtained in situations e.g., for raised shoulders, for an arched body (high jumper as an example) and for people of different gender. According to Erdmann and Kowalczyk (2015,2020) raising of shoulders will involve about 20% of the whole trunk mass and therefore, arched trunk and shifting of a shoulder give the reason to divide the trunk into more parts. They recommended analysing the trunk between hip joints up to the border of the trunk and neck, despite position of the arm joints.
Basic inertial quantities including multi-segment trunk of fit, young males obtained based on personalized data
2020, Journal of BiomechanicsCitation Excerpt :All equations were presented in the work of Erdmann and Kowalczyk (2015). The procedure for obtaining the mass of body parts and position of the centre of mass of the trunk is presented in more detail in the works of Erdmann (1997) and of Erdmann and Kowalczyk (2015). In this method, at first the density of 50 trunk tissues was obtained (Erdmann and Gos, 1990).
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2019, Journal of BiomechanicsCitation Excerpt :By comparison, the results of this study are intended to be used to predict BSPs for individuals. Compared to the method explained by Erdmann and Kowalczyk (2015), this method consists of fewer torso measurements to predict the torso BSPs, whereas as Erdmann and Kowalczyk divided the torso into several functional segments, accomplishing their goal of providing a more detailed tissue distribution description. When comparing these results to those of Hatze (1980), these final models and predictive abilities are again far simpler, both mathematically and in practice for data collection and parameter prediction.
Body segment parameters for rigid body modelling in biomechanical analyses
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