Lumbopelvic Muscle Changes Following Long-Duration Spaceflight.

Kyle P Mcnamara,Katelyn A Greene,Leon Lenchik,Ashley A Weaver,Austin M Moore

doi:10.3389/fphys.2019.00627

Abstract

Long-duration spaceflight has been shown to negatively affect the lumbopelvic muscles of crewmembers. Through analysis of computed tomography scans of crewmembers on 4- to 6-month missions equipped with the interim resistive exercise device, the structural deterioration of the psoas, quadratus lumborum, and paraspinal muscles was assessed. Computed tomography scans of 16 crewmembers were collected before and after long-duration spaceflight. The volume and attenuation of lumbar musculature at the L2 vertebral level were measured. Percent changes in the lumbopelvic muscle volume and attenuation (indicative of myosteatosis, or intermuscular fat infiltration) following spaceflight were calculated. Due to historical studies demonstrating only decreases in the muscles assessed, a one-sample t test was performed to determine if these decreases persist in more recent flight conditions. Crewmembers on interim resistive exercise device-equipped missions experienced an average 9.5% (2.0% SE) decrease in volume and 6.0% (1.5% SE) decrease in attenuation in the quadratus lumborum muscles and an average 5.3% (1.0% SE) decrease in volume and 5.3% (1.6% SE) decrease in attenuation in the paraspinal muscles. Crewmembers experienced no significant changes in psoas muscle volume or attenuation. No significant changes in intermuscular adipose tissue volume or attenuation were found in any muscles. Long-duration spaceflight was associated with preservation of psoas muscle volume and attenuation and significant decreases in quadratus lumborum and paraspinal muscle volume and attenuation.

Highlights

Significant skeletal muscle atrophy has been observed in crewmembers of long-duration spaceflights and persists for months following spaceflight, in the legs and back (LeBlanc et al, 2000; Ploutz-Snyder et al, 2015; Chang et al, 2016)
The psoas, quadratus lumborum, and paraspinal muscle volumes were grouped into a single mask to quantify the total change in lumbopelvic muscle volume (Table 1)
Fourteen of the 16 (88%) crewmembers showed a decrease in total lumbopelvic muscle volume following spaceflight, ranging from 2.4 to 10.5%

Summary

Introduction

Significant skeletal muscle atrophy has been observed in crewmembers of long-duration spaceflights and persists for months following spaceflight, in the legs and back (LeBlanc et al, 2000; Ploutz-Snyder et al, 2015; Chang et al, 2016). Long-duration bed rest studies have been used as corollary for spaceflight studies of muscle degradation as they are both associated with increased muscle soreness, decreased muscle performance, and decreased postural stability (Nicogossian et al, 1994; LeBlanc et al, 2000; Cao et al, 2005; Muir et al, 2011; Macias et al, 2017). These studies may not adequately capture the full degree of lumbopelvic muscle degradation that occurs with long-duration spaceflight (LeBlanc et al, 1992). During spaceflight, even with the use of advanced exercise equipment, microgravity causes an absence of anticipatory loads, disrupting the feedforward mechanism that normally activates the lumbopelvic muscles (Winnard et al, 2017)

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