Elsevier

Journal of Biomechanics

Volume 61, 16 August 2017, Pages 263-268
Journal of Biomechanics

Short communication
The use of a single inertial sensor to estimate 3-dimensional ground reaction force during accelerative running tasks

https://doi.org/10.1016/j.jbiomech.2017.07.035Get rights and content

Abstract

The purpose of this investigation was to determine the feasibility of using a single inertial measurement unit (IMU) placed on the sacrum to estimate 3-dimensional ground reaction force (F) during linear acceleration and change of direction tasks. Force plate measurements of F and estimates from the proposed IMU method were collected while subjects (n = 15) performed a standing sprint start (SS) and a 45° change of direction task (COD). Error in the IMU estimate of step-averaged component and resultant F was quantified by comparison to estimates from the force plate using Bland-Altman 95% limits of agreement (LOA), root mean square error (RMSE), Pearson’s product-moment correlation coefficient (r), and the effect size (ES) of the differences between the two systems. RMSE of the IMU estimate of step-average F ranged from 37.70 N to 77.05 N with ES between 0.04 and 0.47 for SS while for COD, RMSE was between 54.19 N to 182.92 N with ES between 0.08 and 1.69. Correlation coefficients between the IMU and force plate measurements were significant (p  0.05) for all values (r = 0.53 to 0.95) except the medio-lateral component of step-average F. The average angular error in the IMU estimate of the orientation of step-average F was ≤10° for all tasks. The results of this study suggest the proposed IMU method may be used to estimate sagittal plane components and magnitude of step-average F during a linear standing sprint start as well as the vertical component and magnitude of step-average F during a 45° change of direction task.

Introduction

The ground reaction force vector (F) is often used to evaluate human movement in various contexts. Recent studies have shown that the magnitude (Fres) and direction of F can be used to assess performance in both sprint acceleration and change of direction tasks (Dos’Santos et al., 2017, Rabita et al., 2015). Force plates are traditionally used for measuring F. However, their use in the field is limited by their cost and because they confine movement to a small area thus providing only a brief snapshot of the motion being analyzed. These shortcomings may be overcome by using wearable accelerometers which have been used to estimate F during ambulatory movements (Cerrito et al., 2015, Wundersitz et al., 2013). In this context, a single sensor is placed close to the body’s center of mass (COM) and used to measure translational acceleration at this point, thus enabling estimation of F via Newton’s 2nd Law (with knowledge of subject mass) (Cerrito et al., 2015, Wundersitz et al., 2013). However, the orientation of the sensor in the inertial world frame must be known to determine the 3-dimensional components of F using the accelerometer-measured acceleration vector (Gullstrand et al., 2009, Wundersitz et al., 2013). Combining the accelerometer with an angular rate gyroscope to form an inertial measurement unit (IMU) enables the estimation of the 3-dimensional orientation of body segments and thus the means to express sensor referenced vectors in an inertial reference frame (Sabatini, 2011). While some have estimated F using multiple IMUs – one attached at each body segment – and an inverse dynamics approach (Logar and Munih, 2015), the feasibility of using a single, sacrum-worn IMU to estimate F is unknown.

Thus, the purpose of this study was to quantify the error in the estimation of F using a single, sacrum-worn IMU during a linear sprint start and a 45° change of direction task. The criterion validity of the proposed method was determined by comparing the IMU estimates to measurements made by a force plate.

Section snippets

Materials and methods

Fifteen subjects (12 male, 3 female, age: 23.20 ± 2.11 yrs, height: 1.78 ± 0.09 m, mass: 75.46 ± 12.56 kg) gave written consent to participate in this study which was approved by the Appalachian State University Institutional Review Board. An IMU (Yost Data Logger 3-Space Sensor, YEI Technology, Portsmouth, OH) was attached to the sacrum at the midpoint between the posterior superior iliac spinae (Gard et al., 2004, Gullstrand et al., 2009) of each subject using an elastic strap and double-sided tape (

Results

A one to one comparison of the estimates between the two systems for both the SS and COD tasks are shown in Fig. 3. The results from the Bland-Altman analysis are shown in Table 1 and Fig. 4. IMU estimates of F¯ during SS were significantly correlated with FP estimates except for F¯y (r = −0.35). RMSE values were ≤77.05 N and effect size was 0.04, 0.47, 0.23, and 0.19 for Fx, Fy, Fz and Fres respectively. IMU estimates of F¯ during COD were all significantly correlated with FP estimates except for

Discussion

The results from this study suggest that the proposed IMU method may provide valid estimates of F¯z, F¯res, and the orientation of F¯ during both sprint start and change of direction tasks as well as F¯x for the sprint start task. The validity of these variables is suggested by statistically significant correlations (r = 0.84–0.94) with FP measures and RMSE between 37.70 N and 77.05 N. The results from the Bland-Altman analysis suggest estimation error in 95% of future measurements for these

Acknowledgements

This project was partially funded by the Appalachian State University Office of Student Research.

Conflict of Interest Statement

There are no conflicts of interest.

References (18)

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Study conducted at Appalachian State University, Boone, North Carolina, U.S.A.

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