The influence of diet and nutrition on bone metabolism in endurance athletes

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Townsend, R., 2016. The influence of diet and nutrition on bone metabolism in endurance athletes. PhD, Nottingham Trent University.

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Abstract

Both accelerated and suppressed bone remodelling can lead to the development of a stress fracture injury. A stress fracture injury can threaten an athlete’s performance by causing months of missed training time if a stress fracture is sustained during a crucial phase of the season. This thesis presents a series of studies that investigated bone metabolism in endurance athletes and potential ways to improve bone health and reduce the risk of stress fracture injury.
Triathletes are endurance athletes that anecdotally have a high incidence of stress fracture injury, but there is limited research into bone health in these athletes. Therefore, the first two studies in this thesis investigated bone metabolism in a group of elite British triathletes during off-season and pre-competition training. The results showed that elite triathletes had elevated bone turnover at both phases of the season, although this was highest during off-season training. The high bone turnover may be related to large training volumes, low energy intakes and high dermal calcium losses in the sweat.
Given the potential contribution of high dermal calcium losses to the disruption of calcium homeostasis and the different rates of losses in different types of training sessions, the timing of calcium ingestion around training sessions may be more important than total calcium intakes throughout the day. As such, the third study in this thesis investigated the mechanism and timeframe of Parathyroid hormone (PTH) and calcium regulation during exercise and recovery. The results showed that PTH secretion was controlled by a combination of changes in ionised calcium (Ca2+) and phosphate (PO4) and that the mechanism might be different during exercise and recovery. Taken together these results advocate the use of pre-exercise calcium supplementation, which may prevent the disruption of calcium homeostasis and attenuate the PTH and bone resorption response to intense exercise, although further research is required before this can be implemented in elite triathletes.
The large training volumes performed by elite triathletes, meant that daily energy expenditures and energy requirements were high, although consuming almost 6,000 kcal.d-1 was difficult when three or four training sessions were regularly performed each day. Therefore, a practical nutritional intervention was needed to help triathletes ingest some of the required nutrients. The fourth study in this thesis investigated the effect of a post-exercise carbohydrate and protein (CHO+PRO) recovery solution on the bone metabolism response to an intense running bout. The results showed that consuming a CHO+PRO recovery solution immediately after exercise created a more positive bone turnover balance in the acute recovery period from exercise, by suppressing bone resorption and increasing bone formation. Further research is required to explore the long-term effects of post-exercise suppression of bone resorption.
This thesis had direct impact on elite British triathletes, by influencing athlete behaviour and nutritional practices in the daily training environment. The research has also influenced British Triathlon coaches and sports science and medicine staff by increasing the importance placed on bone health and by providing information that will allow training and nutritional practices to be improved or altered to promote a more anabolic environment for bone.

Item Type:	Thesis
Creators:	Townsend, R.
Date:	December 2016
Rights:	This work is the intellectual property of the author. You may copy up to 5% of this work for private study, or personal, non-commercial research. Any re-use of the information contained within this document should be fully referenced, quoting the author, title, university, degree level and pagination. Queries or requests for any other use, or if more substantial copy is required, should be directed to the owner of the Intellectual Property Rights.
Divisions:	Schools > School of Science and Technology
Record created by:	Linda Sullivan
Date Added:	07 Jul 2017 11:33
Last Modified:	07 Jul 2017 11:33
URI:	https://irep.ntu.ac.uk/id/eprint/31215