The effect of calcium and vitamin D supplementation on bone health of male Jockeys.

OBJECTIVES: Engagement in high volumes of physical activity coupled with energy restriction during periods of musculoskeletal development may compromise bone health. Jockeys limit caloric intakes on a weekly basis often from their mid-to-late teens. The aim of this study was to establish whether calcium and vitamin D supplementation would improve bone turnover markers (BTM) and non-weight bearing bone properties of young male jockeys. DESIGN: A six-month randomised, double-blinded, placebo-controlled trial with two groups of apprentice male jockeys was conducted. METHODS: Participants (age 20.18±3.23years) were supplemented with 800mg of calcium and 400IU of vitamin D (n=8) or a placebo (n=9) daily. Bone properties were assessed at the ultra-distal (4%) and proximal (66%) radius using pQCT at baseline and six months. Vitamin D, P1NP and CTX were assessed. RESULTS: ANCOVA results for blood-borne markers indicated higher vitamin D levels (18.1%, p=0.014, partial η2=0.38) and lower CTX (ng·L-1) (-24.8%, p=0.011, partial η2=0.40) in the supplemented group with no differences observed in P1NP. Analysis of bone variables indicated no between group differences in either trabecular or cortical bone properties at the 4% and 66% sites post-intervention. CONCLUSIONS: This trial is the first to examine the efficacy of calcium and vitamin D supplementation in improving non-weight bearing bone properties in a young male athletic population. Results indicate positive alterations to bone metabolism; however, longer duration or higher dosage appears to be required to detect changes in bone material properties at the radius. Further examination of such interventions in weight-restricted athletes is warranted.

Tibial bone responses to 6-month calcium and vitamin D supplementation in young male jockeys: A randomised controlled trial.

Young male jockeys compromise bone health by engaging in caloric restriction and high volumes of physical activity during periods of musculoskeletal growth and development. The aim of this randomised, double-blinded, placebo-controlled trial was to establish whether calcium and vitamin D supplementation would improve bone properties of young male jockeys. We conducted a 6-month trial with two groups of weight-, height- and age-matched apprentice male jockeys (age=20.2 ± 3.2 yrs). Participants were supplemented with 800 mg of calcium and 400 IU of vitamin D (S, n=8) or a placebo (cellulose) (P, n=9) daily for 6-months. Baseline calcium intake was (669.7 ± 274.3 (S) vs 790.4 ± 423.9 (P) and vitamin D 64.6 ± 19.5 (S) vs 81.2 ± 24.4 (P) with no statistical differences. Peripheral quantitative computed tomography (pQCT) measured ultra-distal (4%) and proximal (66%) tibial bone properties at baseline and 6 months. Blood-borne markers of bone turnover, P1NP and CTX and vitamin D concentration were assessed. After co-varying for height, weight and baseline bone measurements, the supplemented group displayed greater post-intervention bone properties at the 66% proximal site with cortical content (mgmm) 6.6% greater (p<0.001), cortical area (mm(2)) 5.9% larger (p<0.001), cortical density (mgcm(2)) 1.3% greater (p=0.001), and total area (mm(2)) 4% larger (p=0.003). No other between group differences in bone variables were observed. Blood analysis indicated higher vitamin D levels (18.1%, p=0.014) and lower CTx (ng/L) (-24.8%, p=0.011) in the supplemented group with no differences observed in P1NP. This is the first randomised controlled trial to examine the efficacy of calcium and vitamin D supplementation in improving bone properties in a highly vulnerable, young athletic, weight-restricted population. Results using pQCT indicate beneficial effects of supplementation on bone properties in as little as six months. Although the study size is small, this intervention appears promising as a strategy for improving bone health in young athletes in weight-restricted sports.

The Effect of Calcium or Calcium and Vitamin D Supplementation on Bone Mineral Density in Healthy Males: A Systematic Review and Meta-Analysis.

Research examining the preventative effects of calcium and vitamin D supplementation has focused on children and females, leaving the effects on male bone mineral density (BMD) largely unexplored. Thus, the aim of this systematic review and meta-analysis is to examine the efficacy of calcium supplementation, with or without vitamin D for improving BMD in healthy males. Medline, EMBASE, SPORTDiscus, Academic Search Complete, CINHAHL Plus and PubMed databases were searched for studies including healthy males which provided participants calcium supplementation with or without vitamin D and used changes to BMD as the primary outcome measure. Between trial standardized mean differences of percentage change from baseline in BMD of femoral neck, lumbar spine, total body and total hip sites were calculated. Nine studies were included in the systematic review with six references totaling 867 participants contributing to the meta-analysis. Significant pooled effects size (ES) for comparison between supplementation and control groups were found at all sites included in the meta-analysis. The largest effect was found in total body (ES = 0.644; 95% CI = 0.406-0.883; p < .001), followed by total hip (ES = 0.483, 95% CI= 0.255-0.711, p < .001), femoral neck (ES = 0.402, 95% CI = 0.233-0.570, p = .000) and lumbar spine (ES = 0.306, 95% CI = 0.173-0.440,p < .001). Limited evidence appears to support the use of calcium and vitamin D supplementation for improving BMD in older males. There is a need for high quality randomized controlled trials, especially in younger and middle-aged male cohorts and athletic populations to determine whether supplementation provides a preventative benefit.

Exercise performance over the menstrual cycle in temperate and hot, humid conditions.

PURPOSE: This study investigated the effects of the menstrual cycle on prolonged exercise performance both in temperate (20°C, 45% relative humidity) and hot, humid (32°C, 60% relative humidity) conditions. METHODS: For each environmental condition, 12 recreationally active females were tested during the early follicular (day 3-6) and midluteal (day 19-25) phases, verified by measurement of estradiol and progesterone. For all four tests, thermoregulatory, cardiorespiratory, and perceptual responses were measured during 60 min of exercise at 60% of maximal oxygen consumption followed by an incremental test to exhaustion. RESULTS: No differences in exercise performance between menstrual cycle phases were found during temperate conditions (n = 8) despite a higher resting and submaximal exercise core temperature (Tc) in the luteal phase. In hot, humid conditions (n = 8), however, prolonged exercise performance, as exercise time to fatigue, was significantly reduced during the luteal phase. This finding was not only accompanied by higher resting and submaximal exercise Tc but also a higher rate of increase in Tc during the luteal phase. Furthermore, submaximal exercise HR, minute ventilation, and RPE measures were higher during the luteal phase in hot, humid conditions. No significant differences were found over the menstrual cycle in heat loss responses (partitional calorimetry, sweat rate, upper arm sweat composition) and Tc at exhaustion. CONCLUSION: In temperate conditions, no changes in prolonged exercise performance were found over the menstrual cycle, whereas in hot, humid conditions, performance was decreased during the luteal phase. The combination of both exercise and heat stress with the elevated luteal phase Tc at the onset of exercise resulted in physiological and perceptual changes and a greater thermosensitivity, which may explain the decrease in performance.