Article Information

Miloslav Kubícek^1*, Tomáš Brozek²

¹Director of Military rehabilitation center in Slapy, Slapy nad Vltavou, Czech Republic

²Department of Psychology, Faculty of Arts, Prague, Charles University, Czech Republic and Military rehabilitation center in Slapy, Slapy nad Vltavou, Czech Republic, Czech Republic

^*Corresponding Author: Tomáš Brozek, Department of Psychology, Faculty of Arts, Prague, Charles University, Czech Republic

Received: 01 October 2023; Accepted: 09 October 2023; Published: 27 October 2023

Citation: Kubíček M, Brožek T. The Relationship between Antigravity Treadmill Therapy Settings and Gait Cycle Parameters. Journal of Orthopedics and Sports Medicine. 5 (2023): 406-415.

Abstract

Keywords

Antigravity treadmill; Symmetry index; Body-weight unloading; Overground gait; Post-surgery recovery

Article Details

1. Introduction

Gait retraining is an integral part of the rehabilitation program of patients with musculoskeletal or neurological impairment. In addition to conventional and overground walking rehabilitation, Body-Weight Supported Treadmill Therapy (BWSTT) is gaining more and more popularity [1]. Walking with partially unloaded body-weight has proven to be a suitable therapy for post-stroke survivors [2-6], patients suffering from Parkinson's disease [7,8], spinal cord injury [9,10] or children with cerebral palsy [11,12] as well as conditions post musculoskeletal injury or surgery [13-16]. Despite the fact that the benefits of this modern approach have been proven across various indications, there is an on-going discussion regarding the influence of weight support on the gait alteration during walking.

Multiple experiments were conducted on health participants in order to evaluate this influence and modify the gait retraining protocol for patients with impairment [17]. Fischer and Wolf [1] conducted a study on ten healthy subjects. They monitored the effect of a suspension vest allowing weight support on multiple spatiotemporal kinematic and kinetic measures. While a positive effect on the reduction of joint loads was discovered, no effect on gait curvature patterns was demonstrated [1]. A similar suspension system was the subject of research by Barela et al. [17] Unlike its predecessor, however, she demonstrated a significant impact of body-weight support (BWS) on spatiotemporal gait parameters. Van Hedel et al. [18] and Threlkeld et al. [19] also partly agree with this conclusion. They confirmed the influence of the suspension vest on the gait cycle parameters, but only for certain settings - for speeds less than 2.5 km/h and weight unloading greater than 50%. Blaszczyk et al. [20] did not monitor the effect of weight unloading, but monitored the effect of excessive loading on spatiotemporal gait measures. By comparing the measurements of obese and lean subjects, it was shown that some walking parameters are indeed influenced by one's own weight. The subject of Lee and Hidler's [21] research was not the effect of the load, but the effect of the walking surface. They concluded that there are differences between overground and treadmill walking, but the overall patterns are preserved.

The relationship between BWSTT settings and gait parameters, or their symmetry indexes, is important to know not only for comparison with overground walking, but also from the point of view of suitability for recovery evaluation. If gait parameters or their symmetry indexes are recorded during the BWSTT, it is desirable to know if these are suitable for monitoring the gait restoration process or if they are influenced by the therapy settings and thus should not be related to the recovery process. Hassid et al. [22] have observed improved symmetry of single limb stance time during BWSTT in otherwise asymmetrically stepping hemiparetic patients induced by appropriate setting of speed and BWS level. Unfortunately, this is the only research on the effect of BWSTT setting on gait symmetry.

The reason for conducting this research is the absence of evidence tracking the effect of body-weight supported treadmills on the principle of lower-body positive pressure. Weight unloading works without the need for a suspension vest, but with the help of an air-tight chamber surrounding the lower half of the body. The higher the pressure is created in the chamber, the more the weight load is reduced. It is assumed that the difference in the principle of operation is so significant that it is not possible to anticipate the same conclusions and thus deserves separate research. The primary aim of this study is to statistically evaluate and compare the effect of BWS with the effect of speed on basic spatiotemporal gait parameters (cadence, stance time, step length, step time, stride length, swing time) in patients recovering after lower-limb surgery. As a secondary outcome measure, relationship between BWSTT settings and symmetry indexes of respective gait parameters was determined and differences in respective gait parameters between affected and unaffected limb were compared.

2. Materials and Methods

The Body-Weight Supported Treadmill Therapy (BWSTT) was provided to patients recovering from lower limb surgery as part of a routine rehabilitation protocol between January and June 2023 at multiple rehabilitation centers. Patients were fully informed about the course of treatment and agreed with the participation. Pregnant and those suffering from severe cardiovascular diseases, epilepsy, bronchial asthma or angina pectoris, severe disc herniation, acute, unstable fractures or conditions where increased abdominal pressure is contraindicated were excluded. Therapy records, automatically stored in the devices, were retrospectively exported and analyzed. As part of the study, no personal or other patient data were processed.

The study data was collected and processed in accordance with the 1975 Declaration of Helsinki ethical guidelines adopted by the General Assembly of the World Medical Association (1997-2000) and by the Convention on Human Rights and Biomedicine of the Council of Europe (1997) [23].

Body-weight supported treadmill (BTL Industries, Ltd.) with embedded load cell (H8C) measuring and storing the gait parameters recorded throughout each session was used. The device works on the principle of lower-body positive pressure, which means that the patient performs exercises with the lower half of the body in an air-tight chamber surrounding the treadmill. The patient is integrated into this chamber, represented by an inflatable bag, using special shorts that enable zipping into the bag [24,25]. Before each session, the device is calibrated to the patient's weight and adjusted according to the patient's movement abilities. Speed, Inclination and BWS level are adapted to the recovery phase and gradually increased to prepare the patient for full load.

Data processing, filtration and analysis was performed using a custom-written script (MatLab R2010b, Mathworks, Inc., Narick, MA, USA). For the purpose of evaluating the relationship between BWS level and gait parameters, only records were used, during which zero inclination and a constant speed of 2 km/h were set. Similarly, the impact of speed settings on gait parameters was evaluated from exercises with set zero inclination and a constant BWS of 50%. A symmetry index was calculated for the gait parameters, which were recorded for each limb separately (stance time, step length, step time and swing time), based on the following equation:

Where P represents the respective gait parameter.

The significance and strength of the relationship was calculated using the Pearson correlation coefficient. The absolute value of the magnitude of the correlation coefficient defined the strength of the relationship [26]:

1. 9 - 1.0 very high correlation
2. 7 - 0.9 high correlation
3. 5 - 0.7 moderate correlation
4. 3 - 0.5 low correlation
5. < 0.3 little if any correlation

A level of p < 0.05 was considered statistically significant. Since the Shapiro-Wilk test showed a significant departure from normality, the data were presented as median (interquartile range).

3. Results

Of the total number of 1032 records, 405 met the conditions for analysis (Figure 1).

Figure 1: Diagram showing the process of data sorting and analysis.

Collected data is summarized for individual gait parameters across different ranges of BWS levels and speed settings in Table 1 and Table 2, respectively.

Table 1: Characteristics of the monitored gait parameters across the respective range of BWS levels at a constant speed of 2 km/h. Data are represented as median (interquartile range).

While in Table 1 it is rather difficult to find any pattern defining the development of gait parameters for individual ranges of BWS levels, in Table 2 an increasing (step length) or decreasing (cadence) tendency can be observed for some gait parameters.

Table 2: Characteristics of the monitored gait parameters across the respective range of speed settings at a constant BWS level of 50%. Data are represented as median (interquartile range).

This was confirmed by statistical analysis using the Pearson correlation coefficient (Table 3) which showed a statistically significant correlation between speed settings and all gait parameters except swing time of unaffected limb. The strength of the relationship between gait parameters and speed setting was evaluated as little too low. The impact of the speed setting on the calculated symmetry indices of all relevant gait parameters (stance time, step length, step time and swing time) was evaluated as statistically insignificant. The correlation between the BWS level setting and any of the gait parameters did not reach statistical significance. Likewise, the relationship between BWS settings and symmetry indices of all relevant gait parameters was insignificant.

Table 3: Evaluation of statistical significance and strength of relationship between BWSTT settings (BWS and speed) and gait cycle parameters and their symmetry indexes. A level of p < 0.05 was considered statistically significant.

The statistical significance of the relationship between the gait parameters and the speed setting can also be seen from the graphs in Figure 2. A comparison of the steepness of the trendlines shows that the value of the gait parameters is more significantly influenced by the speed setting than the body-weight support.

Figure 2: Graphs showing the dependence of measured gait parameters and their calculated symmetry indexes (SI) on BWS and speed settings as scatter plots interspersed with trendlines. The steepness of the trendlines determines the strength of the relationship between the parameter displayed on the x-axis and the therapy setting on the y-axis.

The differences in the individual gait parameters of the affected and unaffected limb can be seen in Tables 1 and 2. Stance time and step length parameters are lower, while step time and swing time are higher in the operated than in the healthy limb.

4. Discussion

This study retrospectively analyzed therapy records from multiple sites and demonstrated a significant effect of speed on gait parameters during the BWSTT, the impact of BWS was considered insignificant on all gait parameters. The effect of speed on the gait cycle in overground walking of healthy subjects was previously analyzed by Fukuchi et al. [27]. Impact was evaluated as significant across all monitored parameters in a positive direction for cadence, step length and stride length and in a negative direction for stance time, which is in accordance with the present trial. This conclusion leads to the assumption that the effect of speed is expected in both overground and BWSTT training and thus from the point of view of the walking cycle, during BWSTT therapy, patients undergo walking training in similar conditions as in regular overground practice. No negative effect of BWS was observed and, on the contrary, several benefits arise from the principle of BWSTT compared to overground rehabilitation. During exercise, patients are weight-supported, so they do not overload the joints and other parts of the locomotor system with their entire weight, which enables the involvement of the limb in the early recovery phase after injury or surgery.

Comparison with the conclusions of the existing clinical evidence investigating the influence of the BWSTT setting on gait patterns is not completely unambiguous. Firstly, the studies that investigated the effect of BWSTT used a device working on the principle of a suspension system, and secondly, these studies differ slightly in their conclusions. While Fischer and Wolf did not confirm the effect of BWS on gait curvature, Barela et al. [17], van Hedel et al. [18] and Threlkeld et al. [19] found a significant impact on spatiotemporal gait parameters [1]. In addition, it can be assumed that the principle of the suspension vest will influence walking parameters in a completely different way than in the case of lower-body positive pressure.

Another aim of this research was to find out if the BWSTT setting affects one of the main indicators of walking symmetry - the symmetry index. This indicator was calculated for the gait parameters stance time, step length, step time and swing time, which enable separate monitoring for each limb. The results of the Pearson correlation coefficient analysis showed that there is no significant relationship between the symmetry index of any gait parameter and the BWSTT (speed, BWS) setting. Such finding brings a promising aspect in monitoring the progress of gait symmetry restoration during BWSTT. Since the impact of any monitored therapy setting on this indicator was not proven, the symmetry index recorded directly during the BWSTT can be used to evaluate the improvement of asymmetry in patients recovering after lower limb impairment.

Comparison of data for the affected and unaffected limb showed that the injured lower limb recorded a shorter stance time and step length and a longer step time and swing time. This trend is consistent with the evidence on patients recovering from total hip arthroplasty and tibial fracture [28,29].

Some limitations of this research must be acknowledged. Since the data were analyzed retrospectively from therapies performed as part of the rehabilitation routine, records with settings typical for the recovery of post-operative conditions of the musculoskeletal system were dominantly represented - speed settings in the range of 0.5 - 4 km/h and BWS 40 - 70%. For this reason, a small amount of data outside the therapeutic range was analyzed. For the sake of simplifying the research, only records with zero inclination were analyzed and therefore the impact of inclination on gait parameters and symmetry indices cannot be evaluated.

Despite these shortcomings, this is unique research of BWSTT working on the lower-body positive pressure principle and the first study investigating the dependence of BWSTT settings and the gait symmetry parameter. Further research should continue to investigate the influence of inclination on the gait cycle and its symmetry.

5. Conclusion

The present study concluded that body-weight supported treadmill walking is, in terms of gait parameters, comparable to regular overground walking. In addition, the unweighting element enables performing the same movement with a lower load on the lower extremities and thus might be more suitable for gait recovery after surgery or injury of the locomotor system. Symmetry index was evaluated as a suitable tool for monitoring the process of gait symmetry restoration during therapy on a body-weight supported treadmill.

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