Spinal Health during Unloading and Reloading Associated with Spaceflight

Green, David A.; Scott, Jonathan

doi:10.3389/fphys.2017.01126

Cited by 32 publications

(35 citation statements)

References 66 publications

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“…Longer periods of severe muscle disuse, as in bedrest, result in changes that are consistent with the significant decrease in mitochondrial content measured in spaceflight [ 17 , 18 , 19 , 20 , 21 ]. The decrease in aerobic capacity significantly affects most of the postural muscles [ 51 ], including the soleus and spinal muscles [ 52 , 53 , 54 ], as opposed to fast muscles such as the deltoid, which shows minimal effects of hypoactivity at the mitochondrial level [ 55 ]. These mitochondrial impairments enhance the muscle atrophy process, leading to muscle deconditioning [ 56 ].…”

Section: Discussionmentioning

confidence: 99%

Early Deconditioning of Human Skeletal Muscles and the Effects of a Thigh Cuff Countermeasure

Fovet

Guilhot

Stevens

et al. 2021

IJMS

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Muscle deconditioning is a major consequence of a wide range of conditions from spaceflight to a sedentary lifestyle, and occurs as a result of muscle inactivity, leading to a rapid decrease in muscle strength, mass, and oxidative capacity. The early changes that appear in the first days of inactivity must be studied to determine effective methods for the prevention of muscle deconditioning. To evaluate the mechanisms of muscle early changes and the vascular effect of a thigh cuff, a five-day dry immersion (DI) experiment was conducted by the French Space Agency at the MEDES Space Clinic (Rangueil, Toulouse). Eighteen healthy males were recruited and divided into a control group and a thigh cuff group, who wore a thigh cuff at 30 mmHg. All participants underwent five days of DI. Prior to and at the end of the DI, the lower limb maximal strength was measured and muscle biopsies were collected from the vastus lateralis muscle. Five days of DI resulted in muscle deconditioning in both groups. The maximal voluntary isometric contraction of knee extension decreased significantly. The muscle fiber cross-sectional area decreased significantly by 21.8%, and the protein balance seems to be impaired, as shown by the reduced activation of the mTOR pathway. Measurements of skinned muscle fibers supported these results and potential changes in oxidative capacity were highlighted by a decrease in PGC1-α levels. The use of the thigh cuff did not prevent muscle deconditioning or impact muscle function. These results suggest that the major effects of muscle deconditioning occur during the first few days of inactivity, and countermeasures against muscle deconditioning should target this time period. These results are also relevant for the understanding of muscle weakness induced by muscle diseases, aging, and patients in intensive care.

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Section: Discussionmentioning

confidence: 99%

Early Deconditioning of Human Skeletal Muscles and the Effects of a Thigh Cuff Countermeasure

Fovet

Guilhot

Stevens

et al. 2021

IJMS

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“…Aging and muscle-wasting diseases have shown a relationship between muscle strength and fat infiltration of muscle (Jones et al, 1983; Liu et al, 1993; Ryan and Nicklas, 1999; Goodpaster et al, 2001; Visser et al, 2002). Investigations into the fat content of neck muscles as well as curvature and intervertebral disc changes may help explain the persistence of herniated nucleus pulposus risk despite preserved muscle size (Johnston et al, 2010; Bailey et al, 2018; Green and Scott, 2018). While MFI was included in this analysis, none of the changes with spaceflight were found to be significant.…”

Section: Discussionmentioning

confidence: 99%

“…The immediate risk of disc herniation upon return from mission is even higher; astronauts are 35.9 times more likely to experience a herniation during the first year post-flight (Johnston et al, 2010). Recent studies have found an association between spinal muscle atrophy and decreased lumbar lordosis that can lead to disc herniation (Bailey et al, 2018; Green and Scott, 2018).…”

Section: Introductionmentioning

confidence: 99%

Neck Muscle Changes Following Long-Duration Spaceflight

et al. 2019

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The effects of long-duration spaceflight on crewmember neck musculature have not been adequately studied. The purpose of this study was to evaluate the changes in the neck musculature on pre-flight and post-flight magnetic resonance imaging (MRI) examinations of six crewmembers on 4- to 6-month missions equipped with the advanced resistive exercise device (aRED). The MRI images were resliced to remove variations in spinal curvature, the cross-sectional area (CSA), and muscle fat infiltration (MFI) of neck musculature at the C1-C2, C4-C5, C7-T1, and T1-T2 intervertebral disc levels were measured bilaterally. Percent changes in the neck muscle CSA and fatty infiltration following spaceflight were calculated, and mixed models were used to assess significance of these changes. Crewmembers on missions equipped with the aRED experienced an average 25.1% increase in CSA for the trapezius muscle at C6-C7, an average 11.5% increase in CSA for the semispinalis capitis muscle at C4-C5, an average 9.0% increase in CSA for the sternocleidomastoid muscle at C4-C5, and an average 23.1% increase in CSA for the rhomboid minor at T1-T2. There were no significant changes in the CSA of the levator scapulae, splenius capitis, rectus capitis posterior major, scalenus anterior, scalenus posterior, scalenus medius, longissimus capitis, or obliquus capitis inferior muscles at the locations measured. None of the muscles analyzed experienced statistically significant changes in fatty infiltration with spaceflight. Our study indicates that long-duration spaceflight conditions are associated with preservation of CSA in most neck muscles and significant increases in the CSAs of the trapezius, semispinalis capitis, sternocleidomastoid, and rhomboid minor muscles. This may indicate that cervical muscles are not subjected to the same degradative effects microgravity imparts on the majority of muscles.

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“…Exposure to microgravity during spaceflight provokes rapid adaptation in lumbar spine morphology (for review, see (24)). Increased spinal length, loss of lumbar lordosis, vertebral osteopenia, and atrophy of the lumbar multifidus (LM) at L4 and L5 vertebral levels have been observed following space missions (4,11,30).…”

Section: Introductionmentioning

confidence: 99%

Lumbar muscle atrophy and increased relative intramuscular lipid concentration are not mitigated by daily artificial gravity after 60-day head-down tilt bed rest

Martino

Hides

Elliott

et al. 2021

Journal of Applied Physiology

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Exposure to axial unloading induces adaptations in paraspinal muscles, as shown after spaceflights. This study investigated whether daily exposure to artificial gravity (AG) mitigated lumbar spine flattening and muscle atrophy associated with 60-day head-down tilt (HDT) bed rest (Earth-based space analogue). Twenty-four healthy individuals participated in the study: Eight received 30 minutes continuous AG; eight received 6x5 minutes AG, interspersed with rest periods; eight received no AG exposure (control group). Magnetic Resonance Imaging (MRI) of the lumbopelvic region was conducted at baseline (BDC) and at day 59 of HDT (HDT59). T1-weighted images were used to assess morphology of the lumbar spine (spinal length, intervertebral disc angles, disc area) and volumes of the lumbar multifidus (LM), lumbar erector spinae (LES), quadratus lumborum (QL), and psoas major (PM) muscles from L1/L2 to L5/S1 vertebral levels. A chemical shift-based 2‐point lipid/water Dixon sequence was used to evaluate muscle composition. Results showed that: spinal length and disc area increased (P<0.05); intervertebral disc angles (P<0.05) and muscle volumes of LM, LES, and QL reduced (P<0.01); and fat/water ratio for the LM and LES muscles increased (P<0.01) after HDT59 in all groups. Neither of the AG protocols mitigated the lumbar spinal deconditioning induced by HDT bed rest. The increase in lipid/water ratio in LM and LES muscles indicates an increased relative intramuscular lipid concentration. Altered muscle composition in atrophied muscles may impair lumbar spine function after body unloading, which could increase injury risk to vulnerable soft tissues. This relationship needs further investigation.

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Spinal Health during Unloading and Reloading Associated with Spaceflight

Cited by 32 publications

References 66 publications

Early Deconditioning of Human Skeletal Muscles and the Effects of a Thigh Cuff Countermeasure

Early Deconditioning of Human Skeletal Muscles and the Effects of a Thigh Cuff Countermeasure

Neck Muscle Changes Following Long-Duration Spaceflight

Lumbar muscle atrophy and increased relative intramuscular lipid concentration are not mitigated by daily artificial gravity after 60-day head-down tilt bed rest

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