Hypertrophy in the cervical muscles and thoracic discs in bed rest?

Abstract

The impact of prolonged bed rest on the cervical and upper thoracic spine is unknown. In the 2nd Berlin BedRest Study (BBR2-2), 24 male subjects underwent 60-day bed rest and performed either no exercise, resistive exercise, or resistive exercise with whole body vibration. Subjects were followed for 2 yr after bed rest. On axial cervical magnetic resonance images from the skull to T3, the volumes of the semispinalis capitis, splenius capitis, spinalis cervicis, longus capitis, longus colli, levator scapulae, sternocleidomastoid, middle and posterior scalenes, and anterior scalenes were measured. Disc height, anteroposterior width, and volume were measured from C2/3 to T6/7 on sagittal images. The volume of all muscles, with the exception of semispinalis capitis, increased during bed rest (P Ͻ 0.025). There were no significant differences between the groups for changes in the muscles. Increased upper and midthoracic spine disc height and volume (P Ͻ 0.001) was seen during bed rest, and disc height increases persisted at least 6 mo after bed rest. Increases in thoracic disc height were greater (P ϭ 0.003) in the resistive vibration exercise group than in control. On radiological review, two subjects showed new injuries to the mid-lower thoracic spine. One of these subjects reported a midthoracic pain incident during maximal strength testing before bed rest and the other after countermeasure exercise on day 3 of bed rest. We conclude that bed rest is associated with increased disc size in the thoracic region and increases in muscle volume at the neck. The exercise device needs to be modified to ensure that load is distributed in a more physiological fashion. morphology; uncovertebral joint; magnetic resonance imaging; spaceflight; microgravity PROLONGED BED REST is a methodology used by space agencies to simulate the deleterious effects of spaceflight on the human body (28) and hence also to trial various types of countermeasures against the detriments that occur in spaceflight. Very little data is available on the effect of bed rest or spaceflight on the cervical spine and its musculature. This is understandable, as the effect of bed rest and spaceflight on the musculoskeletal system is most prominent in the lower half of the body (11), and hence research typically focuses on this area of the body.The 2nd Berlin BedRest Study (BBR2-2) was a 60-day head-down tilt (HDT) bed rest study in which the primary focus was on the impact of exercise countermeasures on bone loss (4). When we initiated the study, we felt it important to also gain a deeper understanding of body regions not typically examined in such bed rest studies, such as the cervical spine. Furthermore, from an ethical point of view, we considered it important to better understand what kinds of changes subjects undergo in such studies. In this vein, it was appropriate to investigate body regions such as the cervical and upper thoracic spine. Also, we were aware of anecdotal reports of headache during HDT bed rest, but to our knowledge, these have never been...

Pain and Vertebral Dysfunction in Dry Immersion: A Model of Microgravity Simulation Different from Bed Rest Studies

“…For example, for meals the subjects used cervical muscles or a hand in order to keep the head in an easier position to ingest foods (Figure 9). This observation is in agreement with the results showed by Belavý et al (2013) [38] that during HDBR there is a hypertrophy of the cervical muscles. With respect to the thoracic location of VD in T4-T5 and T8-T9 (personal data), it is possible that the upward shift in body mass with the head-down position contributed to increased force required during respiration resulting in strain in the thoracic region.…”

Serum sclerostin and DKK1 in relation to exercise against bone loss in experimental bed rest

“…It has been well established that bed rest does not represent disuse for all body regions. For example, increases in muscle size occur at the neck [35] and in the psoas muscle [36], a powerful flexor of the lumbar spine. Likely, these muscles are used more in bed rest when subjects change position.…”

Intervertebral Disc Swelling Demonstrated by 3D and Water Content Magnetic Resonance Analyses after a 3-Day Dry Immersion Simulating Microgravity

“…We used a 3D MRI analysis of IVD compared to classical measurements (Hurxthal, 1968; Belavý et al, 2013). As Belavy described in 2013 (Belavý et al, 2013) on analysis of the cervical region, the following method was used to reduce measurement error due to the small size of the cervical discs (C2/3 and C7/T1): (1) each parameter was measured twice in all images, and (2) if the average value for a given parameter from all images at a given IVD varied by more than 3%, then the operator repeated the measurements until agreement was within the 3% threshold.…”