Monitoring natural human gait in real-life environments is essential in many applications, including quantification of disease progression, monitoring the effects of treatment, and monitoring alteration of performance biomarkers in professional sports. Nevertheless, developing reliable and practical techniques and technologies necessary for continuous real-life monitoring of gait is still an open challenge. A systematic review of English-language articles from scientific databases including Scopus, ScienceDirect, Pubmed, IEEE Xplore, EBSCO and MEDLINE were carried out to analyse the ‘accuracy’ and ‘practicality’ of the current techniques and technologies for quantitative measurement of the tri-axial walking ground reactions outside the laboratory environment, and to highlight their strengths and shortcomings. In total, 679 relevant abstracts were identified, 54 full-text papers were included in the paper and the quantitative results of 17 papers were used for meta-analysis and comparison. Three classes of methods were reviewed: (1) methods based on measured kinematic data; (2) methods based on measured plantar pressure; and (3) methods based on direct measurement of ground reactions. It was found that all three classes of methods have competitive accuracy levels with methods based on direct measurement of the ground reactions showing highest accuracy while being least practical for long-term real-life measurement. On the other hand, methods that estimate ground reactions using measured body kinematics show highest practicality of the three classes of methods reviewed. Among the most prominent technical and technological challenges are: (1) reducing the size and price of tri-axial load-cells; (2) improving the accuracy of orientation measurement using IMUs; (3) minimizing the number and optimizing the location of required IMUs for kinematic measurement; (4) increasing the durability of pressure insole sensors, and (5) enhancing the robustness and versatility of the ground reactions estimation methods to include pathological gaits and natural variability of gait in real-life physical environment.

Interaction of walking people with vibrating structures is known to be an important yet challenging phenomenon to simulate. Despite of its considerable effects on the structural response, no properly formulated and experimentally verified model currently exists to simulate this interaction in the vertical direction. This work uses a single-degree-of-freedom mass-spring-damper model of a walking human to simulate its interaction with a vibrating structure. Extensive frequency response function measurements were performed on a test structure that was occupied by more than a hundred test subjects walking in various group sizes and at different times in 23 tests. The identified modal properties of the occupied structure were used in three different identification procedures to estimate the parameters of the walking human model. A discrete model of human-structure system was used to simulate interaction of each walking person with the structure. The analysis identified the range of 2.75-3.00 Hz for the natural frequency and 27.5%-30% for the damping ratio of the model of a walking human, having constant mass of 70 kg. The extent of the experimental data and the measurement details, diversity of loading scenarios and consistency of the results of the different identification procedures, provided high level of confidence on the suggested parameters for the single-degree-of-freedom walking human model

Monitoring natural human gait in real-life environments is essential in many applications, including quantification of disease progression, monitoring the effects of treatment, and monitoring alteration of performance biomarkers in professional sports. Walking ground reaction forces are among the key parameters necessary for gait analysis. However, these parameters are commonly measured using force plates or instrumented treadmills which are expensive and bulky and can only be used in a controlled laboratory environment. Despite the importance of real-life gait measurement, developing reliable and practical techniques and technologies necessary for continuous real-life monitoring of gait is still an open challenge, mainly due to the lack of a practical and cost-effective wearable technology for ground reaction force measurement. This paper presents a methodology to estimate the total walking ground reaction force GRFvt in the vertical direction using data from a single inertial measurement unit. Correlation analysis of the vertical acceleration of different body segments with GRFvt indicated that the 7th cervical vertebrae is one of the best locations for the sensor. The proposed method improves the accuracy of the state-of-the-art GRFvt estimation by 25%, by utilising the time-varying ratio of the vertical acceleration of the human body centre of mass and measured C7 vertical acceleration. Results of this study showed that the proposed method estimated consistently the GRFvt in both indoor and urban outdoor environment, with a 4-8% peak-to-peak normalised root mean square error.

Realistic simulation of the dynamic effects of walking pedestrians on structures is still a considerable challenge. This is mainly due to the inter- and intrasubject variability of humans and their bodies and difficult-to-predict loading scenarios, including multipedestrian walking traffic and unknown human-structure interaction (HSI) mechanisms. Over the past three decades, several attempts have been made to simulate walking HSI in the lateral direction. However, research into the mechanisms of this interaction in the vertical direction, despite its higher likelihood and critical importance, is fragmented and incoherent. It is, therefore, difficult to apply and codify. This paper critically reviews the efforts to date to simulate walking HSI in the vertical direction and highlights the key areas that need further investigation.

Monitoring natural human gait in real-life environment is essential in many applications including the quantification of disease progression, and monitoring the effects of treatment and alteration of performance biomarkers in professional sports. Nevertheless, reliable and practical techniques and technologies necessary for continuous real-life monitoring of gait is still not available. This paper explores in detail the correlations between the acceleration of different body segments and walking ground reaction forces GRF(t) in three dimensions and proposes three sensory systems, with one, two, and three inertial measurement units (IMUs), to estimate GRF(t) in the vertical (V), medial-lateral (ML), and anterior-posterior (AP) directions. The nonlinear autoregressive moving average model with exogenous inputs (NARMAX) non-linear system identification method was utilized to identify the optimal location for IMUs on the body for each system. A simple linear model was then proposed to estimate GRF(t) based on the correlation of segmental accelerations with each other. It was found that, for the three-IMU system, the proposed model estimated GRF(t) with average peak-to-peak normalized root mean square error (NRMSE) of 7%, 16%, and 18% in V, AP, and ML directions, respectively. With a simple subject-specific training at the beginning, these errors were reduced to 7%, 13%, and 13% in V, AP, and ML directions, respectively. These results were found favorably comparable with the results of the benchmark NARMAX model, with subject-specific training, with 0% (V), 4% (AP), and 1% (ML) NRMSE difference.