Influence of body weight unloading on human gait characteristics: a systematic review

Abstract

Background: Body weight support (BWS) systems have shown promise as rehabilitation tools for neurologically impaired individuals. This paper reviews the experiment-based research on BWS systems with the aim: (1) To investigate the influence of body weight unloading (BWU) on gait characteristics; (2) To study whether the effects of BWS differ between treadmill and overground walking and (3) To investigate if modulated BWU influences gait characteristics less than unmodulated BWU.

Method: A systematic literature search was conducted in the following search engines: Pubmed, Scopus, Web of Science and Google Scholar. Statistical analysis was used to quantify the effects of BWU on gait parameters.

Results: 54 studies of experiments with healthy and neurologically impaired individuals walking in a BWS system were included and 32 of these were used for the statistical analysis. Literature was classified using three distinctions: (1) treadmill or overground walking; (2) the type of subjects and (3) the nature of unloading force. Only 27% studies were based on neurologically impaired subjects; a low number considering that they are the primary user group for BWS systems. The studies included BWU from 5% to 100% and the 30% and 50% BWU conditions were the most widely studied. The number of participants varied from 1 to 28, with an average of 12. It was seen that due to the increase in BWU level, joint moments, muscle activity, energy cost of walking and ground reaction forces (GRF) showed higher reduction compared to gait spatio-temporal and joint kinematic parameters. The influence of BWU on kinematic and spatio-temporal gait parameters appeared to be limited up to 30% unloading. 5 gait characteristics presented different behavior in response to BWU for overground and treadmill walking. Remaining 21 gait characteristics showed similar behavior but different magnitude of change for overground and treadmill walking. Modulated unloading force generally led to less difference from the 0% condition than unmodulated unloading.

Conclusion: This review has shown that BWU influences all gait characteristics, albeit with important differences between the kinematic, spatio-temporal and kinetic characteristics. BWU showed stronger influence on the kinetic characteristics of gait than on the spatio-temporal parameters and the kinematic characteristics. It was ascertained that treadmill and overground walking can alter the effects of BWU in a different manner. Our results indicate that task-specific gait training is likely to be achievable at a BWU level of 30% and below.

Keywords: Body weight support; Gait characteristics; Rehabilitation.

Fig. 1

Flowchart for classification of studies into six categories which are indicated in colour. Similar colour scheme is followed in Figs. 3, 4, 5, and 6 in the results section

Fig. 2

Summary of BWS studies where O:Overground, M:Modulated, T:Treadmill, UM:Unmodulated. Plot A shows the number of studies per category. Only 27% of these studies are based on subjects with neuromuscular disorders i.e the NI group. Plot B shows the number of studies for each level of BWU. The most investigated BWU level is 50%, followed by 30%, 40% and 20% respectively. NI represents the category of subjects with neuromuscular impairment

Fig. 3

Influence of body weight unloading on gait spatio-temporal parameters where a. Stride length, b. Cadence, c. Walking speed, d. Total stance phase, e. Initial double limb support (DLS) phase, and f. Single limb support (SLS) phase. Vertical bars represent the normalized mean values, error bars depict standard deviation between studies and dashed lines illustrate the result of linear regression for each category. Absence of error bar at a BWU level indicates that the data was available from only one study

Fig. 4

Influence of body weight unloading on joint kinematics and joint kinetics where a. Hip joint angle range of motion (ROM), b. Knee joint angle ROM, c. Ankle joint angle ROM, d. Ankle propulsive impulse, e. Hip extension moment, f. Hip flexion moment, g. Knee extension moment, h. Knee extension moment, and i. Anke plantarflexion moment. Extension and flexion moments are represented by positive and negative signs to imply opposite directions. Vertical bars represent the normalized mean values, error bars depict standard deviation between studies and dashed lines illustrate the result of linear regression for each category. Absence of error bar at a BWU level indicates that the data was available from only one study

Fig. 5

Influence of body weight unloading on ground reaction forces (GRF) and metabolic parameters where a. Anteroposterior GRF negative (deceleration) peak, b. Anteroposterior GRF positive (acceleration) peak, c. Vertical GRF peak I, d. Vertical GRF peak II, e. Energy cost of walking, and f. Heart rate. Vertical bars represent the normalized mean values, error bars depict standard deviation between studies and dashed lines illustrate the result of linear regression for each category. Absence of error bar at a BWU level indicates that the data was available from only one study

Fig. 6

Influence of body weight unloading on mean muscle activity over gait cycle where a. Medial gastrocnemius (MG), b. Lateral gastrocnemius (LG), c. Rectus femoris (RF), d. Biceps femoris (BF) long head and e. Tibialis anterior (TA). Vertical bars represent the normalized mean values, error bars depict standard deviation between studies and dashed lines illustrate the result of linear regression for each category. Absence of error bar at a BWU level indicates that the data was available from only one study