Countermeasure Development for Lumbopelvic Deconditioning in Space

Physical inactivity and lumbopelvic deconditioning have been linked to increased incidence of non-specific low back pain (LBP) and spinal injury in those who are exposed to microgravity (e.g. astronauts and individuals on long-duration bed rest) and in the general population. Astronauts have an increased risk of experiencing moderate to severe LBP during microgravity exposure and herniated intervertebral discs within 1 year following spaceflight. Atrophy and reduced motor control of the lumbar multifidus (LM) and transversus abdominis (TrA) muscles resulting from periods of deconditioning are linked to non-specific LBP and spinal injury risk in both post-flight astronauts and general populations. However, voluntary recruitment of these two key muscles is difficult and presents a rehabilitation challenge. This chapter reviews the concept of spinal stability as it relates to microgravity, discusses how existing exercise countermeasures used in space do not successfully maintain lumbopelvic muscle size, and introduces the functional readaptive exercise device (FRED) that shows potential to activate the LM and TrA muscles automatically and in a tonic fashion, which has relevance to rehabilitation of both astronaut and terrestrial populations

The immediate effects of exercise using the Functional Re-adaptive Exercise Device on lumbopelvic kinematics in people with and without low back pain

Background - Dysfunction of the lumbar multifidus (LM) and transversus abdominis (TrA) muscles is associated with low back pain (LBP). The Functional Re-adaptive Exercise Device (FRED) has shown potential as a non-specific LBP intervention by automatically recruiting LM and TrA. Loss or lordosis and altered lumbopelvic positioning has also been linked to LBP and is often trained within LM and TrA interventions. The effect that FRED exercise has on lumbopelvic positioning and lumbar lordosis is unknown. Objectives - To assess the effect of FRED exercise on lumbopelvic kinematics and alignment to establish whether FRED exercise promotes a favourable lumbopelvic posture for training LM and TrA. Design - Within and between-group comparison study. Method - One hundred and thirty participants, 74 experiencing LBP, had lumbopelvic kinematic data measured during over-ground walking and FRED exercise. Magnitude-based inferences were used to compare walking with FRED exercise within participants and between the asymptomatic and LBP groups, to establish the effects of FRED exercise on lumbopelvic kinematics, compared to walking, in each group. Results - FRED exercise promotes an immediate change in anterior pelvic tilt by 8.7° compared to walking in the no-LBP and LBP groups. Sagittal-plane spinal extension increased during FRED exercise at all spinal levels by 0.9° in the no-LBP group, and by 1.2° in the LBP group. Conclusions - FRED exercise promotes a lumbopelvic position more conducive to LM and TrA training than walking in both asymptomatic people and those with LBP

Movement amplitude on the Functional Re-adaptive Exercise Device: deep spinal muscle activity and movement control

Purpose: Lumbar multifidus (LM) and transversus abdominis (TrA) show altered motor control, and LM is atrophied, in people with low-back pain (LBP). The Functional Re-adaptive Exercise Device (FRED) involves cyclical lower-limb movement against minimal resistance in an upright posture. It has been shown to recruit LM and TrA automatically, and may have potential as an intervention for non-specific LBP. However, no studies have yet investigated the effects of changes in FRED movement amplitude on the activity of these muscles. This study aimed to assess the effects of different FRED movement amplitudes on LM and TrA muscle thickness and movement variability, in order to inform an evidence-based exercise prescription. Methods: Lumbar multifidus and TrA thickness of eight healthy male volunteers was examined using ultrasound imaging during FRED exercise, normalised to rest at four different movement amplitudes. Movement variability was also measured. Magnitude-based inferences were used to compare each amplitude. Results: Exercise at all amplitudes recruited LM and TrA more than rest, with thickness increases of approximately 5 mm and 1 mm, respectively. Larger amplitudes also caused increased TrA thickness, LM and TrA muscle thickness variability and movement variability. The data suggest that all amplitudes are useful for recruiting LM and TrA. Conclusions: A progressive training protocol should start in the smallest amplitude, increasing the setting once participants can maintain a consistent movement speed, in order to continue to challenge the motor control system

Trunk muscle activation during movement with a new exercise device for lumbo‐pelvic reconditioning

Gravitational unloading leads to adaptations of the human body, including the spine and its adjacent structures, making it more vulnerable to injury and pain. The Functional Re‐adaptive Exercise Device (FRED) has been developed to activate the deep spinal muscles, lumbar multifidus (LM) and transversus abdominis (TrA), that provide inter‐segmental control and spinal protection. The FRED provides an unstable base of support and combines weight bearing in up‐right posture with side alternating, elliptical leg movements, without any resistance to movement. The present study investigated the activation of LM, TrA, obliquus externus (OE), obliquus internus (OI), abdominis, and erector spinae (ES) during FRED exercise using intramuscular fine‐wire and surface EMG. Nine healthy male volunteers (27 ± 5 years) have been recruited for the study. FRED exercise was compared with treadmill walking. It was confirmed that LM and TrA were continually active during FRED exercise. Compared with walking, FRED exercise resulted in similar mean activation of LM and TrA, less activation of OE, OI, ES, and greater variability of lumbo‐pelvic muscle activation patterns between individual FRED/gait cycles. These data suggest that FRED continuously engages LM and TrA, and therefore, has the potential as a stationary exercise device to train these muscles

Hypogravity reduces trunk admittance and lumbar muscle activation in response to external perturbations

Reduced paraspinal muscle size and flattening of spinal curvatures have been documented after spaceflight. Assessment of trunk adaptations to hypogravity can contribute to develop specific countermeasures. In this study, parabolic flights were used to investigate spinal curvature and muscle responses to hypogravity. Data from five trials at 0.25g, 0.50g and 0.75g were recorded from six participants, positioned in a kneeling-seated position. During the first two trials, participants maintained a normal, upright posture. In the last three trials, small-amplitude perturbations were delivered in the anterior direction at the T10 level. Spinal curvature was estimated using motion capture cameras. Trunk displacement and contact force between the actuator and participant were recorded. Muscle activity responses were collected using intramuscular electromyography (iEMG) of the deep and superficial lumbar multifidus, iliocostalis lumborum, longissimus thoracis, quadratus lumborum, transversus abdominis, obliquus internus and obliquus externus muscles. The root mean square iEMG and the average spinal angles were calculated. Trunk admittance and muscle responses to perturbations were calculated as closed-loop frequency response functions. Compared with 0.75g, 0.25g resulted in: lower activation of the longissimus thoracis (P=0.002); lower responses of the superficial multifidus at low frequencies (P=0.043); lower responses of the superficial multifidus (P=0.029) and iliocostalis lumborum (P=0.043); lower trunk admittance (P=0.037) at intermediate frequencies; and stronger responses of the transversus abdominis at higher frequencies (p=0.032). These findings indicate that exposure to hypogravity reduces trunk admittance, partially compensated by weaker stabilizing contributions of the paraspinal muscles and coinciding with an apparent increase of the deep abdominal muscle activity

Systematic review of the technical and physiological constraints of the Orion Multi-Purpose Crew Vehicle that affect the capability of astronauts to exercise effectively during spaceflight

Background The constraints of the Orion Multi-Purpose Crew Vehicle present challenges to the use of current exercise countermeasures necessary to prevent severe deconditioning of physiological systems during microgravity exposure beyond Low Earth Orbit. The purpose of this qualitative systematic review was to determine the technical constraints of the Orion Multi-Purpose Crew Vehicle which may hinder astronauts’ capabilities to effectively exercise during long distance spaceflight. Methods Databases were searched from the start of their records to December 2018. Included documents were quality assessed with the AMSRG quality scoring tool and Thematic Analysis was used to analyse the included documents to assess technical constraints of the Orion Multi-Purpose Crew Vehicle. Results 19 studies were included in the final review. All identified constraints, other than data transmission limitations, were found to ultimately be a result of the volume and upload mass constraints of the Orion Multi-Purpose Crew Vehicle. There was a lack of detailed studies and lack of consistency in specifying spacecraft in the literature that limit the conclusions of this review. Conclusion Space agencies are advised to ensure that information on relevant spacecraft constraints is readily available to researchers. This information should be made accessible in an official published document as opposed to disparate and grey literature, and include quantitative information rather than qualitative summaries

Effects of a six-week exercise intervention on function, pain and lumbar multifidus muscle cross-sectional area in chronic low back pain: A proof-of-concept study

Introduction Exercise with the Functional Re-adaptive Exercise Device (FRED) has previously been shown to activate the lumbar multifidus (LM) and transversus abdominis (TrA) muscles in non-symptomatic volunteers. This study aimed to determine the effects of a six-week FRED exercise intervention on pain intensity, patient-reported function and LM cross sectional area (CSA) in people with chronic non-specific low back pain (LBP). Methods Thirteen participants undertook six weeks of FRED exercise for up to 15 min, three times per week. At six weeks pre-, immediately pre-, immediately post-, and six and 15 weeks post-intervention, participants completed the Numeric Pain Rating Scale, Patient-Specific Functional Scale, and ultrasound imaging was used to assess the size of the LM muscles at L5 level. Changes in outcomes were assessed using effect size, confidence intervals and minimum clinically important difference (MCID). Results There was no improvement in pain intensity following the intervention. Patient-reported function improved by at least twice the MCID for all follow-up assessments compared to immediately pre-intervention (d = 4.20–6.58). Lumbar multifidus CSA showed a large effect size increase from immediately pre-intervention to immediately post-intervention (d = 0.8–1.1); this was maintained at six weeks post-intervention (not measured at 15 weeks post-intervention). Conclusion Six weeks of FRED exercise improved physical function in all 13 participants with chronic non-specific LBP who took part in this study and most participants' lumbar multifidus muscle CSA. On this basis, it may be an effective intervention for people with chronic LBP and should now be tested in a randomised controlled trial

Intermittent short-arm centrifugation is a partially effective countermeasure against upright balance deterioration following 60-day head-down tilt bed rest

This study investigated whether artificial gravity (AG), induced by short-radius centrifugation, mitigated deterioration in standing balance and anticipatory postural adjustments (APAs) of trunk muscles following 60-day head-down tilt bed rest. Twenty-four participants were allocated to one of three groups: control group (N=8); 30 minutes continuous AG daily (N=8); intermittent 6x5 minutes AG daily (N=8). Before and immediately after bed rest, standing balance was assessed in four conditions: eyes open and closed on both stable and foam surfaces. Measures including sway path, root-mean-square, and peak sway velocity, sway area, sway frequency power, and sway density curve were extracted from the centre of pressure displacement. APAs were assessed during rapid arm movements using intramuscular or surface electromyography electrodes of the rectus abdominis, obliquus externus and internus abdominis, transversus abdominis, erector spinae at L1, L2, L3, and L4 vertebral levels, and deep lumbar multifidus muscles. The relative latency between the EMG onset of the deltoid and each of the trunk muscles was calculated. All three groups had poorer balance performance in most of the parameters (all P<0.05) and delayed APAs of the trunk muscles following bed rest (all P<0.05). Sway path and sway velocity were deteriorated, and sway frequency power was less in those who received intermittent AG than in the control group (all P<0.05), particularly in conditions with reduced proprioceptive feedback. These data highlight the potential of intermittent AG to mitigate deterioration of some aspects of postural control induced by gravitational unloading, but no protective effects on trunk muscle responses were observed

Effect of time on biomechanics during exercise on the functional re-adaptive exercise device

Mechanistic studies of the Functional Re-adaptive Exercise Device (FRED) have shown it automatically recruits Lumbar Multifidus (LM) and Transversus Abdominis (TrA) – two deep-spinal muscles that are atrophied and show altered motor control in low back pain (LBP). No studies have investigated the time required to familiarise to FRED exercise, which is required to inform future FRED based clinical trial protocols. This study therefore determined the effect of time, during FRED exercise, on biomechanical outcome measures, to establish the familiarisation period, and assess for loss of technique throughout a ten minute trial. A cohort comparison study of 148 participants, 70 experiencing low back pain, had lumbopelvic kinematics, exercise frequency and movement variability measured during a 10 minute trial. Magnitude-based inference was used to assess for familiarisation, using plots of variation over time with familiarised reference ranges. The no pain group took 170 seconds, and the back pain group took 150 seconds, to familiarise. A familiarisation period of at least 170 seconds (2.8 minutes) is recommended. This justifies, and provides a familiarisation time for use of the FRED as a motor control intervention