For journal club we looked at the following paper:
I was lucky enough to ask one of the authors, Craig Sale, some questions about his research. Craig is a Reader in Applied Physiology at Nottingham Trent University and one of his research areas of interest is bone health and metabolism.Thanks to those of you who tweeted your questions. I hope you find this interesting and it gives you a better insight into Craig’s research.
Q: Why did you decide to carry out this research?
A: To answer a possible question over the influences on the bone metabolic response to exercise that had arisen from two previous studies from our group. Two obvious potential influences were exercise duration and intensity and we wanted to examine the latter here.
Q: How did you recruit the participants?
A: Primarily through posters, email and word of mouth.
Q: Why did you choose the study design of three 8-day experimental conditions, separated by a minimum of 1 week?
A: Some of the bone markers are sensitive to exercise and feeding, so for this reason we wanted a control period prior to the exercise trial itself, hence the 3 d lead in period. In order to get the most relevant information on the bone metabolic response to exercise, the days following the exercise are most critical. In this study we chose to examine a 4 d follow-up period for this reason, which was based upon our previous study. You need at least a 1 week separation between trials as bone markers can remain elevated over this period.
Q: How did you randomise the participants into the experimental conditions?
A: There were 6 possible combinations of 3 conditions so the first 6 subjects were randomly assigned to one of the 6 combinations then the 6 combinations were ‘re-set’ and the last 4 subjects were assigned on this basis.
Q: How did you ensure that the participants adhered to the diet that you prescribed?
A: This study was conducted with free-living participants and so it is hard to directly confirm adherence to the dietary control. However, subjects verbally confirmed their adherence to the dietary control on each occasion.
Q: Your findings showed that daily calcium intake of the participants exceeded the recommended daily intake of 700mg a day and there was large variation in calcium intake, do you think this could have affected your results?
A: The habitual dietary intake of the subjects was variable, but this was reduced somewhat by the dietary control imposed during the experimental trials. Some variability would have remained but the effects of this on the bone metabolic responses to exercise is not likely to be large in this within subjects design.
Q: What populations do you intend your findings to be beneficial for?
A: These findings, particularly when combined with the evidence from other well-controlled exercise studies, would be of benefit for any athletic individual.
Q: How much, in your opinion, are the changes in bone turnover due to mechanical muscle tension placed on the bone?
A: As far as a specific quantification is concerned, this is obviously impossible to answer directly. However, it is clear that muscle contractions, occurring concomitant with the direct impact loading of the bone, produced during exercise can generate further osteogenic loading. As such, the effects of muscle contraction in this sense are likely to contribute significantly to changes in bone with exercise and particularly training.
Q: What would you like people to take away from your research and how do you hope to develop your findings?
A: That there is only a small and transient influence of intensity on the bone metabolic response to one hour of exercise. Most likely, from this and subsequent studies from our group, the effect of exercise duration on bone is more critical. This makes sense from a mechanical loading perspective and it would be of interest to examine the influence of changes in “mechanical” intensity rather than cardiovascular exercise intensity. We now have several studies continuing on the effects of exercise and diet/nutrition on bone metabolism as well as studies examining the influence of exercise training on bone structure and geometry.
Thank you to Craig for taking the time to answer the questions about his research and sharing his knowledge.