SPLMNTL CALCIUM TO OFFSET BONE MINERAL DENSITY LOSS IN COMPETITIVE MALE CYCLISTS

SPLMNTL 钙可抵消男性自行车运动员的骨矿物质密度损失

• 批准号: 7377864
• 负责人: DAN BARRY
• 金额: $ 2.23万
• 依托单位: UNIVERSITY OF COLORADO DENVER
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-04-01 至 2007-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7377864
• 关键词: SPLMNTL; CALCIUM; OFFSET; BONE; MINERAL

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Rationale Although it is generally true that exercise is beneficial for bone health,1 under certain conditions exercise can be associated with loss of bone mineral density (BMD). In this pilot study, we will evaluate the impact of calcium (Ca) loss through sweating on bone density. One study of calcium loss and bone density in athletes4 found that male college basketball players had significant decreases in total BMD over the course of a season. When the same athletes were given supplemental Ca in the form of a Ca-fortified sports drink the following competitive season, there was an increase in BMD rather than a loss. To further explore the potential role of calcium loss through sweat, we have chosen to conduct the study in competitive road cyclists. Their high training volume (10-15 h/wk or more) is expected to generate a large sweat Ca loss. Also, the training/competitive season for road cycling is relatively long (Jan to Sept), which is suitable for determining the effects on bone metabolism. Another reason we chose to study road cyclists is because they appear to be at increased risk for low BMD.6-12 We will examine the loss of calcium through sweat in this pilot study as one potential mechanism of loss of BMD. However, strenuous exercise has also been found to disrupt sex and stress hormone levels in humans.13-16 Strenuous exercise may also result in systemic inflammation.17-19 These alterations may also effect bone metabolism. Aims and Hypotheses: The primary goal of this Pilot Study is to evaluate in a prospective, controlled fashion a potential mechanism by which vigorous, prolonged exercise (both in terms of length of an exercise bout and duration of the training/competitive season) may promote bone loss. Our hypotheses are as follows: H1: Dermal Ca loss as a result of prolonged, vigorous exercise training is a significant determinant of bone loss in competitive road cyclists over a season of training and competition. H2: Increasing Ca intake to higher than currently recommended levels (2000 mg/d) will attenuate the loss of bone in competitive road cyclists over a season of training and competition. Methods: To address these hypotheses, we will study 20 competitive cyclists over a season of training and competition. Participants will be men aged 18-35 yr who have been racing for 2 or more seasons and train 10 or more hours/week. They will have baseline calcium intakes at or below the recommended daily allowance of 1000mg/day. They will be randomized to take placebo or supplemental calcium to 1800-2000mg/day or maintain their usual intake of 1000-1200mg/day. Participants will perform a 2 hour simulated training ride on a stationary trainer at baseline, mid-season, and after the season ends. BMD will be measured at these visits, and estimates of their sweat calcium loss will be determined by measuring sweat calcium concentrations and determining sweat loss (estimated from change in body weight corrected for water consumption and urine production). Analysis: Our primary outcome measure is BMD in the placebo non-supplemented vs. the calcium supplemented group. We will attempt to control for confounders such as changes in sex and stress hormones, inflammatory makers, and change in body weight through the season.

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。尽管运动对骨骼健康有益是普遍事实，但在某些情况下，运动可能与骨密度（BMD）的损失有关。在这项初步研究中，我们将评估通过出汗丢失钙（Ca）对骨密度的影响。一项关于运动员钙流失和骨密度的研究发现，大学篮球男运动员在一个赛季的过程中，总骨密度显著下降。当同样的运动员在接下来的比赛季节以加钙运动饮料的形式补充钙时，骨密度增加而不是减少。为了进一步探讨汗液中钙流失的潜在作用，我们选择在竞技公路自行车运动员中进行研究。他们的高训练量（10-15小时/周或更多）预计会产生大量的汗液钙损失。此外，公路自行车的训练/比赛季节相对较长（1月至9月），适合测定对骨代谢的影响。我们选择研究公路自行车运动员的另一个原因是，他们似乎有更高的低骨密度风险。6-12在这项初步研究中，我们将通过汗液来检查钙的损失，作为骨密度损失的一种潜在机制。然而，剧烈运动也被发现会破坏人类的性和应激激素水平。剧烈运动也可能导致全身炎症。这些改变也可能影响骨代谢。目的和假设：本初步研究的主要目的是以一种前瞻性的、可控的方式评估剧烈的、长时间的运动（一次运动的长度和训练/比赛季节的持续时间）可能促进骨质流失的潜在机制。我们的假设如下：H1：长时间剧烈运动训练导致的真皮钙流失是竞技公路自行车运动员在一个赛季的训练和比赛中骨质流失的重要决定因素。H2：在一个赛季的训练和比赛中，将钙摄入量增加到高于目前推荐水平（2000毫克/天）将减轻竞技公路自行车运动员的骨质流失。方法：为了解决这些假设，我们将研究20名竞技自行车运动员在一个赛季的训练和比赛。参与者将是年龄在18-35岁之间的男性，他们已经参加了2个赛季或以上的比赛，每周训练10小时或以上。他们的基线钙摄入量等于或低于每日推荐摄入量1000毫克/天。他们将被随机分配服用安慰剂或补钙1800-2000mg/天，或维持他们通常的摄入量1000-1200mg/天。参与者将在基线、赛季中期和赛季结束后在固定训练机上进行2小时的模拟训练。在这些访问中测量骨密度，并通过测量汗液钙浓度和汗液损失来估计他们的汗液钙损失（根据体重变化估计，校正了水消耗和尿产生）。分析：我们的主要结局指标是未补充安慰剂组和补钙组的骨密度。我们将尝试控制混杂因素，如性和应激激素的变化、炎症因子和整个季节体重的变化。