Effects of a Prolonged Submersion on Bone Strength and Metabolism in Young Healthy Submariners

Abstract

Submariners taking part in prolonged missions are exposed to environmental factors that may adversely affect bone health. Among these, relatively high levels of CO(2), lack of sunlight exposure affecting vitamin D metabolism, limited physical activity, and altered dietary habits. The aims of this study were to examine the effect of a prolonged submersion (30 days) on changes in bone strength using quantitative bone speed of sound and in markers of bone metabolism that include bone turnover (BAP, PINP, TRAP5b, and CTx) and endocrine regulators (serum calcium, PTH, and 25[OH]D) in a group of 32 young healthy male submariners. The prolonged submersion led to increases in body weight and BMI and to a decrease in fitness level. There was a significant decrease in bone strength following the submersion. Speed of sound exhibited continued decline at 4 weeks after return to shore and returned to baseline levels at the 6-month follow-up. There was a significant increase in circulating calcium level. PTH and 25(OH)D levels decreased significantly. Significant decreases were observed in both TRAP5b and CTx levels, markers of bone resorption, as well as in N-terminal propeptide of type I collagen (PINP), a bone formation marker. Prolonged submersion led to a significant decrease in bone strength, accompanied by an overall decrease in bone metabolism. Bone strength was regained only 6 months after return to shore. Prevention and/or rehabilitation programs should be developed following periods of relative disuse even for young submariners. The effects of repeated prolonged submersions on bone health are yet to be determined.

Progressive Adaptation in Physical Activity and Neuromuscular Performance during 520d Confinement

“…Confinement studies have to date examined psychosocial [1], biomedical [2], skilled motor [2], [3] and immune system [4] variables. Aside from the most common case of prolonged confinement, imprisonment, individuals are also confined as part of over-wintering in isolated regions of the Earth [5], military operations [3], [6] and ground based spaceflight operation simulation [1].…”

Hypercortisolism as a Potential Concern for Submariners

“…Additionally, Schlichting et al ( 77 ) also reported a decrease in 25-(OH) vitamin D levels over a 2-mo deployment. Moreover, a recent study of Israeli submariners found that a 30-d submersion led to decreased bone density and 25-(OH) levels, but it also led to decreased circulating parathyroid hormone levels and bone remodeling markers, along with increased circulating calcium levels ( 44 ). Taken together, these data suggest that deployments of ; 2 mo result in bone resorption, but deployments of 1 mo may only result in reduced bone metabolism.…”

Bone marrow changes related to disuse

“…These studies demonstrated that bone change starts with the non-weighted bearing period and can be detected 4–6 weeks after the immobilization period (the entity is different according to individual parameters). In a study carried out using a cohort of patients with ankle fractures the peak of the bone loss was around 4 months; the timing for the peak has been discussed in the literature [2; 3; 5; 7; 11; 18], ranging between 4 to 10 weeks. The original bone mass will not be achieved for many years and the architecture of the bone will never been restored, resulting in weaker bone than normal [25] that is easier to break [26].…”

“…Altogether, 20 subregions were identified and graded as shown in Table 2 for the following morphological criteria as seen on fluid sensitive fat-saturated images: (i) bone marrow signal abnormality (none, subtle—10% of subregion, mild—10–40% of subregion, moderate—> 40% of subregion or severe-> 75% of subregion); (ii) signal intensity relative to hyaline cartilage (hypointense, isointense, hyperintense); (iii) morphology of signal alteration (no present, dotted, linear, patchy or confluent); (iv) presence or absence of hypervascularity [2, 9, 16], qualitatively defined as increased serpiginous linear vascular structures in the periphery of the bone [2, 9]; (v) presence of alteration on T1-weighted images recorded as present or absent. Fig.…”