Suchergebnisse

Military training increases tibial density and size, but it is unknown if men and women adapt similarly to the same arduous training. Seventy-seven men and 57 women not using hormonal contraceptives completed this study. Tibial volumetric bone mineral density (vBMD) and geometry were measured by peripheral quantitative computed tomography (4%, 14%, 38%, and 66% sites) at the start (week 1) and end (week 14) of British Army basic training. Training increased trabecular vBMD (4% site in men; 4% and 14% sites in women), cortical vBMD (38% site), total area (14% and 38% sites), trabecular area (14% site), cortical area and thickness (14%, 38%, and 66% sites), periosteal perimeter (14%, 38%, and 66% sites), and all indices of estimated strength (14%, 38%, and 66% sites); and, decreased endosteal perimeter (66% site) in men and women (all p ≤ 0.045). The increase in trabecular vBMD (4% and 14% sites) was greater in women and the increases in cortical area and strength (38% site) were greater in men (sex × time interactions, all p ≤ 0.047). P1NP increased and βCTX and sclerostin decreased during training in men and women, consistent with adaptive bone formation. PTH decreased in men but increased in women. Arduous weight-bearing activity increased the density and size of the tibia after 14 weeks. Women experienced similar tibial adaptations as men, however, a greater increase in trabecular vBMD in women compared with men could be due to higher loading at this skeletal site in women, whereas the small increase in cortical area could be due to inhibitory effects of oestradiol.

Purpose: Short periods of basic military training increase the density and size of the tibia, but the adaptive response of bone microarchitecture, a key component of bone strength, is not fully understood. Methods: Tibial volumetric bone mineral density (vBMD), geometry, microarchitecture and mechanical properties were measured using high-resolution peripheral quantitative computed tomography in 43 male British Army infantry recruits (mean ± SD, age 21 ± 3 years, height 1.76 ± 0.06 m, body mass 76.5 ± 9.4 kg). Bilateral scans were performed at the distal tibia at the start (week 1) and end (week 13) of basic military training. Concurrent measures were obtained for whole-body areal bone mineral density (aBMD) using DXA, and markers of bone metabolism (βCTX, P1NP, PTH, total 25(OH)D and ACa) from venous blood. Results: Training increased areal BMD for total body (1.4%) and arms (5.2%) (P ≤ 0.031), but not legs and trunk (P ≥ 0.094). Training increased trabecular (1.3 to 1.9%) and cortical vBMD (0.6 to 0.9%), trabecular volume (1.3 to 1.9%), cortical thickness (3.2 to 5.2%) and cortical area (2.6 to 2.8%), and reduced trabecular area (−0.4 to −0.5%) in both legs (P < 0.001). No changes in trabecular number, thickness and separation, cortical porosity, stiffness or failure load were observed (P ≥ 0.188). βCTX decreased (−0.11 μg∙l-1, P < 0.001) and total 25(OH)D increased (9.4 nmol∙l-1, P = 0.029), but no differences in P1NP, PTH or ACa were observed between timepoints (P ≥ 0.233). Conclusion: A short period of basic military training increased density and altered geometry of the distal tibia in male military recruits. The osteogenic effects of basic military training are likely due to an increase in unaccustomed, dynamic and high-impact loading.

ACKNOWLEDGMENTS We gratefully acknowledge all participants, the assistance of Karen Secombes for sample collection, Megan Forrester for advising on cytokine and flow cytometry analyses, and Rebecca Barr for packaging and blinding the supplement capsules. Vit D3 supplements were donated by Pure Encapsulations (Sudbury, MA). FUNDING Pathways to a healthy lifestyle studentship, RANK prize funding (WM), University of Aberdeen Development fund (HM), NHS endowments EA0702 (AO), Rural and Environment Science and Analytical Services Division of the Scottish government (RESAS) (FT). This research was funded in whole, or in part, by the Wellcome Trust [Grant number 094847/Z/10/Z]. For the purpose of open access, the author has applied a CC BY public copyright license to any Author Accepted Manuscript version arising from this submission. ; Peer reviewed ; Publisher PDF

Purpose. To determine vitamin D metabolites and vitamin D receptor (VDR) single-nucleotide polymorphisms (SNPs) relationships with physical performance. Methods. In 1205 men and 322 women (94.8% white Caucasian, 22.0 ± 2.8 years) commencing military training, we measured: serum vitamin D metabolites (25-hydroxyvitamin D (25(OH)D) and 24,25-dihydroxyvitamin D (24,25(OH)2D) by high-performance liquid chromatography tandem mass spectrophotometry, and 1,25-dihydroxyvitamin D (1,25(OH)2D) by immunoassay); VDR SNPs (rs2228570, rs4516035, and rs7139166 by polymerase chain reaction genotyping); and endurance performance by 2.4 km run, muscle strength by maximal dynamic lift, and muscle power by maximal vertical jump. Results. Serum 25(OH)D was negatively associated with 2.4 km run time and positively associated with muscle power (β = –12.0 and 90.1), 1,25(OH)2D was positively associated with run time and negatively associated with strength and muscle power (β = 5.6, –1.06, and –38.4), and 24,25(OH)2D was negatively associated with run time (β = –8.9; P < 0.01), after controlling for age, sex, smoking, alcohol, physical activity, time outdoors, season, and BMI. Vitamin D metabolites (25(OH)D, 1,25(OH)2D, and 24,25(OH)2D) together explained variances of 5.0% in run time, 0.7% in strength, and 0.9% in muscle power (ΔF P < 0.001). All performance measures were superior with low 1,25(OH)2D:24,25(OH)2D ratio (P < 0.05). VDR SNPs were not associated with physical performance (ΔF P ≥ 0.306). Conclusion. Vitamin D metabolites accounted for a small portion of variance in physical performance. Associations between vitamin D metabolites and run time were the most consistent. VDR SNPs explained no variance in performance. Greater conversion of 25(OH)D to 24,25(OH)2D, relative to 1,25(OH)2D (i.e., low 1,25(OH)2D:24,25(OH)2D ratio), was favourable for performance, indicating 24,25(OH)2D may have a role in optimising physical performance.

Purpose: To determine the relationship between vitamin D status and exercise performance in a large, prospective cohort study of young men and women across seasons (Study-1). Then, in a randomized, placebo-controlled trial, to investigate the effects on exercise performance of achieving vitamin D sufficiency (serum 25(OH)D ≥ 50 nmol·L-1) by a unique comparison of safe, simulated-sunlight and oral vitamin D3 supplementation in wintertime (Study-2). Methods: In Study-1, we determined 25(OH)D relationship with exercise performance in 967 military recruits. In Study-2, 137 men received either placebo, simulated-sunlight (1.3x standard erythemal dose in T-shirt and shorts, three-times-per-week for 4-weeks and then once-per-week for 8-weeks) or oral vitamin D3 (1,000 IU[BULLET OPERATOR]day-1 for 4-weeks and then 400 IU[BULLET OPERATOR]day-1 for 8-weeks). We measured serum 25(OH)D by LC-MS/MS and endurance, strength and power by 1.5-mile run, maximum-dynamic-lift and vertical jump, respectively. Results: In Study-1, only 9% of men and 36% of women were vitamin D sufficient during wintertime. After controlling for body composition, smoking and season, 25(OH)D was positively associated with endurance performance (P ≤ 0.01, [INCREMENT]R2 = 0.03–0.06, small f2 effect sizes): 1.5-mile run time was ~half-a-second faster for every 1 nmol·L-1 increase in 25(OH)D. No significant effects on strength or power emerged (P > 0.05). In Study-2, safe simulated-sunlight and oral vitamin D3 supplementation were similarly effective in achieving vitamin D sufficiency in almost all (97%); however, this did not improve exercise performance (P > 0.05). Conclusion: Vitamin D status was associated with endurance performance but not strength or power in a prospective cohort study. Achieving vitamin D sufficiency via safe, simulated summer sunlight or oral vitamin D3 supplementation did not improve exercise performance in a randomized-controlled trial.

Purpose This study aimed to determine the relationship between vitamin D status and upper respiratory tract infection (URTI) of physically active men and women across seasons (study 1) and then to investigate the effects on URTI and mucosal immunity of achieving vitamin D sufficiency (25(OH)D ?50 nmol·L-1) by a unique comparison of safe, simulated sunlight or oral D3 supplementation in winter (study 2). Methods In study 1, 1644 military recruits were observed across basic military training. In study 2, a randomized controlled trial, 250 men undertaking military training received placebo, simulated sunlight (1.3× standard erythemal dose, three times per week for 4 wk and then once per week for 8 wk), or oral vitamin D3 (1000 IU·d-1 for 4 wk and then 400 IU·d-1 for 8 wk). URTI was diagnosed by a physician (study 1) and by using the Jackson common cold questionnaire (study 2). Serum 25(OH)D, salivary secretory immunoglobulin A (SIgA), and cathelicidin were assessed by liquid chromatography-mass spectrometry LC-MS/MS and enzyme-linked immunosorbent assay. Results In study 1, only 21% of recruits were vitamin D sufficient during winter. Vitamin D-sufficient recruits were 40% less likely to suffer URTI than recruits with 25(OH)D 0.05). Supplementation did not affect salivary secretory immunoglobulin A or cathelicidin. Conclusion Vitamin D sufficiency reduced the URTI burden during military training.

PURPOSE: This study aimed to determine the relationship between vitamin D status and upper respiratory tract infection (URTI) of physically active men and women across seasons (study 1) and then to investigate the effects on URTI and mucosal immunity of achieving vitamin D sufficiency (25(OH)D ≥50 nmol·L(−1)) by a unique comparison of safe, simulated sunlight or oral D(3) supplementation in winter (study 2). METHODS: In study 1, 1644 military recruits were observed across basic military training. In study 2, a randomized controlled trial, 250 men undertaking military training received placebo, simulated sunlight (1.3× standard erythemal dose, three times per week for 4 wk and then once per week for 8 wk), or oral vitamin D(3) (1000 IU·d(−1) for 4 wk and then 400 IU·d(−1) for 8 wk). URTI was diagnosed by a physician (study 1) and by using the Jackson common cold questionnaire (study 2). Serum 25(OH)D, salivary secretory immunoglobulin A (SIgA), and cathelicidin were assessed by liquid chromatography–mass spectrometry LC-MS/MS and enzyme-linked immunosorbent assay. RESULTS: In study 1, only 21% of recruits were vitamin D sufficient during winter. Vitamin D–sufficient recruits were 40% less likely to suffer URTI than recruits with 25(OH)D 0.05). Supplementation did not affect salivary secretory immunoglobulin A or cathelicidin. CONCLUSION: Vitamin D sufficiency reduced the URTI burden during military training.