Justifying A Clinical Trial of the Functional Readaptive Exercise Device for Lumbopelvic Motor Control Rehabilitation after Spaceflight

Introduction
Astronauts have 68% increased incidence of back pain (Sayson and Hargens 2008) and 4.3 times higher risk of herniated disc than controls (Johnston et al. 2010). Atrophy of lumbar multifidus (LM) and transversus abdominis (TrA) and difficulty controlling spinal mechanics is commonly found in post flight astronauts (Hides et al. 2011; Buckey 2006). Exercise using the Functional Readaptive Exercise Device (FRED) shows strong potential to recruit the LM and TrA muscles automatically (Debuse et al. 2013) which could benefit current post spaceflight rehabilitation. The mechanistic effects of exercise on the FRED were investigated to inform decisions regarding a future clinical trial.
Methods
A series of mechanistic studies investigated the acute effects of the FRED and designed a training protocol. Mechanistic magnitude based inference statistics were used to investigate muscle recruitment and kinematic studies. Muscle recruitment was investigated in a small sample using ultrasound. Lumbopelvic kinematics were investigated across four studies that included 308 participants in total and recruited groups with low back pain.
Results
The following effects were found during FRED exercise. The LM and TrA muscles were recruited more than at rest and increasing the movement amplitude causes a greater variability of muscle activity (effect size ≥ 0.2). Lumbar lordosis is automatically increased compared to walking in groups with and without low back pain (effect size ≥ 0.2). First time users with and without low back pain required 170 seconds to familiarise to the exercise. Visual feedback was required for users to achieve and maintain a desired target speed and use of the handles caused a trunk flexion and reduced challenge to the exercise movement (effect size ≥ 0.2).
Discussion
The mechanistic studies justify a clinical trial as exercise on the FRED appears to automatically cause LM and TrA muscle recruitment, and increased lumbar lordosis, which is likely to benefit post flight rehabilitation. It is recommended that a training protocol for a clinical trial include a 170 second minimal familiarisation period, use live visual feedback on performance linked to target speed and should not use the handles during exercise.