School of Allied Health Sciences, Griffith University, Nathan Campus, Brisbane, 4111 QLD, Australia.
Praxis für Physiotherapie und Osteopathische Techniken, Kaiserstrasse 34, 53721 Siegburg, Germany; KBR GmbH, Albin- Koebis Strasse 4, Cologne 51147, Germany.
Spine J. 2021 Mar;21(3):477-491. doi: 10.1016/j.spinee.2020.09.006. Epub 2020 Sep 20.
One of the primary changes in the neuromuscular system in response to microgravity is skeletal muscle atrophy, which occurs especially in muscles that maintain posture while being upright on Earth. Reduced size of paraspinal and abdominal muscles has been documented after spaceflight. Exercises are undertaken on the International Space Station (ISS) during and following space flight to remediate these effects. Understanding the adaptations which occur in trunk muscles in response to microgravity could inform the development of specific countermeasures, which may have applications for people with conditions on Earth such as low back pain (LBP).
The aim of this study was to examine the changes in muscle size and function of the lumbar multifidus (MF) and anterolateral abdominal muscles (1) in response to exposure to 6 months of microgravity on the ISS and (2) in response to a 15-day reconditioning program on Earth.
Prospective longitudinal series.
Data were collected from five astronauts who undertook seven long-duration missions on the ISS.
For the MF muscle, measures included cross-sectional area (CSA) and linear measures to assess voluntary isometric contractions at vertebral levels L2 to L5. For the abdominal muscles, the thickness of the transversus abdominis (TrA), obliquus internus abdominis (IO) and obliquus externus abdominis (EO) muscles at rest and on contraction were measured.
Ultrasound imaging of trunk muscles was conducted at four timepoints (preflight, postflight, mid-reconditioning, and post reconditioning). Data were analyzed using multilevel linear models to estimate the change in muscle parameters of interest across three time periods.
Beta-coefficients (estimates of the expected change in the measure across the specified time period, adjusted for the baseline measurement) indicated that the CSA of the MF muscles decreased significantly at all lumbar vertebral levels (except L2) in response to exposure to microgravity (L3=12.6%; L4=6.1%, L5=10.3%; p<.001), and CSAs at L3-L5 vertebral levels increased in the reconditioning period (p<.001). The thickness of the TrA decreased by 34.1% (p<.017), IO decreased by 15.4% (p=.04), and the combination of anterolateral abdominal muscles decreased by 16.2% (p<.001) between pre- and postflight assessment and increased (TrA<0.008; combined p=.035) during the postreconditioning period. Results showed decreased contraction of the MF muscles at the L2 (from 12.8% to 3.4%; p=.007) and L3 (from 12.2% to 5%; p=.032) vertebral levels following exposure to microgravity which increased (L2, p=.046) after the postreconditioning period. Comparison with preflight measures indicated that there were no residual changes in muscle size and function after the postreconditioning period, apart from CSA of MF at L2, which remained 15.3% larger than preflight values (p<.001).
In-flight exercise countermeasures mitigated, but did not completely prevent, changes in the size and function of the lumbar MF and anterolateral abdominal muscles. Many of the observed changes in size and control of the MF and abdominal muscles that occurred in response to prolonged exposure to microgravity paralleled those seen in people with LBP or exposed to prolonged bed rest on Earth. Daily individualized postflight reconditioning, which included both motor control training and weight-bearing exercises with an emphasis on retraining strength and endurance to re-establish normal postural alignment with respect to gravity, restored the decreased size and control of the MF (at the L3-L5 vertebral levels) and anterolateral abdominal muscles. Drawing parallels between changes which occur to the neuromuscular system in microgravity and which exercises best recover muscle size and function could help health professionals tailor improved interventions for terrestrial populations. Results suggested that the principles underpinning the exercises developed for astronauts following prolonged exposure to microgravity (emphasizing strength and endurance training to re-establish normal postural alignment and distribution of load with respect to gravity) can also be applied for people with chronic LBP, as the MF and anterolateral abdominal muscles were affected in similar ways in both populations. The results may also inform the development of new astronaut countermeasures targeting the MF and abdominal muscles.
在对微重力的神经肌肉系统的主要变化之一是骨骼肌萎缩，这尤其发生在地球直立时维持姿势的肌肉中。太空飞行后已经记录到脊柱旁和腹部肌肉的减少。在国际空间站（ISS）上进行锻炼，以减轻这些影响。了解微重力下躯干肌肉的适应情况可以为特定的对策提供信息，这些对策可能对地球上有腰痛（LBP）等疾病的人有应用。
本研究的目的是检查在 ISS 上暴露 6 个月微重力以及在地球进行 15 天再适应计划后，腰椎多裂肌（MF）和前外侧腹肌（1）的肌肉大小和功能的变化。
前瞻性纵向系列。
数据来自五名在 ISS 上进行了七次长期任务的宇航员。
对于 MF 肌肉，测量包括横截面积（CSA）和线性测量，以评估 L2 至 L5 椎体水平的自愿等长收缩。对于腹部肌肉，测量横突腹（TrA）、内斜腹肌（IO）和外斜腹肌（EO）肌肉在休息和收缩时的厚度。
在四个时间点（飞行前、飞行后、中期再适应和后期再适应）进行了躯干肌肉的超声成像。使用多水平线性模型分析数据，以估计在三个时间段内感兴趣的肌肉参数的变化。
β系数（在指定时间段内测量的预期变化估计值，根据基线测量值进行调整）表明，MF 肌肉的 CSA 在所有腰椎水平（L2 除外）都显著减少，对微重力的暴露（L3=12.6%；L4=6.1%，L5=10.3%；p<.001），L3-L5 椎体水平的 CSA 在再适应期间增加（p<.001）。TrA 的厚度减少了 34.1%（p<.017），IO 减少了 15.4%（p=.04），前外侧腹肌减少了 16.2%（p<.001），在飞行前和飞行后评估之间，在再适应后增加（TrA<0.008；组合 p=.035）。结果表明，MF 肌肉在 L2（从 12.8%到 3.4%；p=.007）和 L3（从 12.2%到 5%；p=.032）椎体水平的收缩减少，在再适应后增加（L2，p=.046）。与飞行前的测量值相比，再适应后除 L2 的 MF 肌肉 CSA 仍比飞行前大 15.3%（p<.001）外，肌肉大小和功能没有残留变化。
飞行中锻炼的对策减轻了，但并没有完全防止腰椎 MF 和前外侧腹肌的大小和功能的变化。在长时间暴露于微重力后观察到的 MF 和腹部肌肉大小和控制的许多变化与腰痛或在地球上长时间卧床休息的人相似。每日个体化的飞行后再适应，包括运动控制训练和承重锻炼，重点是重新训练力量和耐力，以重新建立与重力有关的正常姿势排列，恢复 MF（在 L3-L5 椎体水平）和前外侧腹肌的减小和控制。将微重力对神经肌肉系统的变化与最佳恢复肌肉大小和功能的运动进行对比，可以帮助健康专业人员为地面人群量身定制改进的干预措施。结果表明，为长期暴露于微重力的宇航员制定的锻炼原则（强调力量和耐力训练，以重新建立与重力有关的正常姿势排列和负荷分布）也可应用于慢性腰痛患者，因为 MF 和前外侧腹肌在这两种人群中受到相似的影响。结果还可能为针对 MF 和腹部肌肉的新宇航员对策的发展提供信息。
