Endurance Athletes, Hormones, Fueling, str fx's
Posted By: KP
Date: Tuesday, 28 October 2008, at 7:18 a.m.
From discussion on another board: a male athlete asks about shin splints and micro-fractures or stress fractures ==>
Question: "The thing that stood out to me was that while plenty of the runners were showing signs of osteopenia, I was surprised that there was no comment as to whether any of them had INCREASED bone mineral density, which the standard theory of bone remodeling would seem to predict. Such an increase would have been measurable by CT. An omission from the study, or did it just not occur?"
KP: Osteopenia, by definition is a decrease in bone mineralization. That would answer part of your question. Among others, predisposing factors for stress fractures are osteopenia, the Caucasian race, biomechanical disorders and metabolic irregularities (the latter could be called insufficiency fractures). Metabolic disorders can occur is endurance athletes who maintain reduced calories. Lower testosterone has been reported in long distance runners in males and amenorrhea and decreased estrogen in females. So, running can have an ambiguous affect -- stimulating bone on the one hand and secondarily causing bone loss due to hormonal changes in some endurance athletes.
Question: is amenhorrea a metabolic disorder or does 'metabolic disorder' mean something else?
KP: Interesting question. This is not my area of expertise so I invite others to comment. As well, your question doesn't entirely leave out male endurance athletes as guys can negatively influence T-levels on the way to osteopenia and/or hypogonadism. For the women, if we leave out anatomical abnormalities then we could say amenorrhea might result from abnormality in the hypothalamic-pituitary-ovarian axis. Perhaps as a result of nutritional deficiency. This could lead you to say amenorrhea was a symptom of another issue. Metabolism is the process your body uses to make energy from the food you eat. A metabolic disorder occurs when abnormal chemical reactions in your body alter this process. Some female endurance athletes risk athletic amenorrhea. For a long time it was thought that low body fat and exercise related chemicals might alter the relationship of female sex hormones estrogen and progesterone leading to athletic amenorrhea. More recently, evidence shows that there is no difference in body composition or hormone levels in the women with athletic amenorrhea. It has been shown that athletic amenorrhea is directly caused by low energy availability. Some endurance athletes simply do not take in enough calories to cover the expenditure on exercise leaving them short of energy to maintain normal menstrual cycles. Once periods cease a woman might see declining hormones and osteopenia or osteoporosis. This has come to be know as the "female athletic triad" or disordered eating, amenorrhea and osteoporosis. For what it's worth, there is a Dr. Sabine Naessen whose relatively new doctoral thesis is centered around the fact that some eating disorders are the result of metabolic disorders.
This discussion may serve to emphasize the importance of nutrition and proper fueling of endurance athletes when it comes to maximal recovery and maximal health. Performance in endurance sport over the short term may not serve long term health.
Dr. Kevin Purcell, DC
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