Abstract
To address a variety of questions pertaining to the interactions between physical activity, musculoskeletal loading and musculoskeletal health/injury/adaptation, simple methods are needed to quantify, outside a laboratory setting, the forces acting on the human body during daily activities. The purpose of this study was to develop a statistically based model to estimate peak vertical ground reaction force (pVGRF) during youth gait. 20 girls (10.9±0.9 years) and 15 boys (12.5±0.6 years) wore a Biotrainer AM over their right hip. Six walking and six running trials were completed after a standard warm-up. Average AM intensity (g) and pVGRF (N) during stance were determined. Repeated measures mixed effects regression models to estimate pVGRF from Biotrainer activity monitor acceleration in youth (girls 10–12, boys 12–14 years) while walking and running were developed. Log transformed pVGRF had a statistically significant relationship with activity monitor acceleration, centered mass, sex (girl), type of locomotion (run), and locomotion type-acceleration interaction controlling for subject as a random effect. A generalized regression model without subject specific random effects was also developed. The average absolute differences between the actual and predicted pVGRF were 5.2% (1.6% standard deviation) and 9% (4.2% standard deviation) using the mixed and generalized models, respectively. The results of this study support the use of estimating pVGRF from hip acceleration using a mixed model regression equation.
Highlights
For many studies, quantifying the forces acting on and within the body during daily living is of great interest
AM acceleration increased with increasing speed and peak vertical ground reaction force (pVGRF) increased with increasing AM acceleration. pVGRF (N) differed (p,0.05) between boys and girls during both walking and running trials
The distribution of residuals was initially noted to be nonGaussian, so natural log transformation of pVGRF was used as the outcome in all regression models
Summary
For many studies, quantifying the forces acting on and within the body during daily living is of great interest This allows further understanding of the relationships between loading of musculoskeletal structures and structure development, injury, and adaptation (e.g. bone development and physical activity correlates [1], post surgical weight bearing asymmetry [2]). To facilitate such studies, simple methods are needed that can be employed outside a laboratory setting to quantify various forces acting on and within the human body during daily activities. While previous reports of the link between pVGRF and injury have been mixed [14], assessment of the pVGRF along with the frequency of its occurrence would provide a ‘snapshot’ of a subject’s pVGRF loading profile over a period of time, possibly providing more insight into the interaction between musculoskeletal structural/material changes and loading, as well as overuse injury development
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