Bodyweight Supported Treadmill Training: Current Evidence (Part 1)

PART 1

This information was previously presented to staff at a rehabilitation hospital in New Jersey. It has since been adapted for the purpose of this blog. It is not comprehensive of all literature. The articles chosen for this post were included based on level of evidence and availability. All articles were originally found on the Physiotherapy Evidence Database (PEDro) and had ratings on the PEDro scale of >/= 5/10. Some articles were chosen from Google Scholar from the first two pages of “highly cited” papers on BWSTT. The purpose of this was to recreate the most common forms of literature searches by clinicians and provide articles which were open access so that they could review the papers used after the presentation if interested. Articles were excluded if they used robotics as a primary outcome, if BWSTT was not a harness based system (e.g. Alter G treadmill), or if the average patient age was outside of a range deemed appropriate to the inpatient rehab facility (< 45).

A breakdown of the articles chosen:

Articles

Introduction

Bodyweight supported treadmill training (BWSTT) is used fairly frequently in both inpatient and outpatient neurological based settings. It was originally based on the hypothesis of the central pattern generator (CPG) after application to persons with spinal cord injury (SCI) achieved significant results. Some refer to this as the crossed extension reflex, but they are separate entities. The aim of the central pattern generator is to create a reciprocal pattern of flexion and extension under primary control at the level of the spinal cord. This reflex is NOT under conscious control, and is an automatic and repetitive movement.

CPG
Poorly drawn image depicting the Central Pattern Generator by myself

Recent literature has proposed different mechanisms behind the purpose of BWSTT. This leans towards improvements in motor control and grading movement to allow adaptations to progressive loading strategies. During BWSTT, the cortical areas are activated for inter-limb coordination including: the supplementary motor area, premotor cortex, and sensorimotor cortex. This indicates that there is a certain level of supraspinal control required, casting further doubt on the CPG hypothesis (1). It also gives a certain level of insight into why we have improvements in pathological conditions other than SCI, which will be appreciated in Parts 2, 3, and 4.

Supraspinal
Cortical areas activated during stepping

 

If motor control is the basis of improvements in gait with BWSTT, the question arises as to how this may occur. According to Kleim and Jones, there are 10 major principles of neuroplasticity, which are intimately related to motor control (2). These include:

  1. Use it or lose it
  2. Use it and improve it
  3. Specificity
  4. Repetition Matters
  5. Intensity Matters
  6. Time Matters
  7. Salience Matters
  8. Age Matters
  9. Transference
  10. Interference

It can be argued that BWSTT when applied correctly will meet all 10 of these principles. This is dependent on level of the patient and ability to meet repetition, time, and intensity requirements and the importance they place on the task after proper education by their therapist.

 

Why Use BWSTT?

Some benefits include BWSTT being a relatively low risk, functional task with the ability to control many variables at once. It can be used for pre-gait training or gait training with reduced physical burden on the therapist. There is objective grading of load with values such as speed, distance, and time calculated accurately via the machine they are placed on. There is also safe, but higher loading of the cardiovascular system, which may not be achieved with other activities based on level of function. Finally, therapists can optimize their tactile and verbal cues due to improved independence and safety inside a harness system.

 

What To Aim For

Gait kinematics studied on healthy controls (I know, not perfect when basing it on pathological populations) report that gait changes dramatically at < 1.5 mph. Also, bodyweight unloading begins to deviate from “normal” gait kinematics at 75% bodyweight support including altered knee and ankle joint trajectories and leg muscle EMG pattern changes (3). Therefore, it is best to aim for above 1.5 mph and at < 75% bodyweight unloading. If this is not achievable initially, continue to progress each session to faster speeds and then begin unloading once > 1.5 mph is achieved.

mocap1
Image Credit: Leeds Beckett University – Animation and Visual Effects Team

To Facilitate or Not to Facilitate

There have been some published protocols on proper hand placements for BWSTT facilitation (4). These are thought to facilitate optimal sensory input into the brain, allowing for improved feedback and better movement patterns. However, facilitation has not been shown to be more beneficial than robotic assistance (1). Anecdotally, many will report that with chronic neurological insult, hand placements may provide more efficient training sessions than robotic assist due to time of setup and breaks between sets.

 

This concludes Part 1 of a 4 Part series on BWSTT. Part 1 provided a general introduction, background, purpose, and methods of best practice for implementation. Part 2 will include current evidence for BWSTT in patients post-cerebrovascular accident.

 

Thank you for reading,

-Jared Burch, PT, DPT

 


References:

  1. Yagura, H., Hatakenaka, M., & Miyai, I. (2006). Does Therapeutic Facilitation Add to Locomotor Outcome of Body Weight− Supported Treadmill Training in Nonambulatory Patients With Stroke? A Randomized Controlled Trial. Archives of physical medicine and rehabilitation87(4), 529-535.
  2. Kleim, J. A., & Jones, T. A. (2008). Principles of experience-dependent neural plasticity: implications for rehabilitation after brain damage. Journal of speech, language, and hearing research, 51(1), S225-S239.
  3. Van Hedel, H. J. A., Tomatis, L., & Müller, R. (2006). Modulation of leg muscle activity and gait kinematics by walking speed and bodyweight unloading. Gait & posture24(1), 35-45.
  4. Behrman, A and Harkema, S. (2002). Locomotor Training After Human Spinal Cord Injury: A series of Case Studies. Physical Therapy. 7.

 

 

 

Featured Imaged Credit: I, Science Magazine

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