How to Identify Male Cyclists at Risk of RED-S?

Relative energy deficiency in sport (RED-S) is a clinical model that describes the potential adverse health and performance consequences of low energy availability (LEA) in male and female athletes. Identification of athletes at risk of LEA can potentially prevent these adverse clinical outcomes.

Athletes at risk of RED-S are those involved in sports where low body weight confers a performance or aesthetic advantage. In the case of competitive road cycling, being light  weight results in favourable power to weight ratio to overcome gravity when cycling uphill. How can male cyclists at risk of LEA be effectively identified in a practical manner?

Energy availability (EA) is defined as the residual energy available from dietary intake, once energy expenditure from exercise training has been subtracted. This available energy is expressed as KCal/Kg fat free mass (FFM). A value of 45 KCal/Kg FFM is roughly equivalent to basal metabolic rate, in other words the energy required to sustain health. In order to quantify EA, accurate measurements of energy intake and expenditure, and FFM assessed from dual X ray absorptiometry (DXA), need to be undertaken. However this is not practical or feasible to undertake all these measurements outside the research setting. Furthermore, methodology for assessing energy intake and expenditure is laborious and fraught with inaccuracies and subjectivity in the case of diet diaries for “free living athletes“. Even if a value is calculated for EA, this is only valid for the time of measurement and does not give any insights into the temporal aspect of EA. Furthermore, an absolute EA threshold has not been established, below which clinical symptoms or performance effects of RED-S occur.

Self reported questionnaires have been shown to be surrogates of low EA in female athletes. However there are no such sport specific questionnaires, or any questionnaires for male athletes. Endocrine and metabolic markers have been proposed as quantitative surrogate measures of EA and shown to be linked to the RED-S clinical outcome of stress fractures in runners. In female athletes the clinical sign of regular menstruation demonstrates a functioning H-P ovarian axis, not suppressed by LEA. What about male athletes? Although hypothalamic suppression of the reproductive axis due to LEA can result in low testosterone, high training loads, in presence of adequate EA, can lead to the same negative effect on testosterone concentration.

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Male cyclists present a further level of complexity in assessing EA status. In contrast to runners, stress fracture will not be an early clinical warning sign of impaired bone health resulting from low EA. Furthermore cyclists are already at risk of poor bone health due to the non weight bearing nature of the sport. Nevertheless, traumatic fracture from bike falls is the main type of injury in cycling, with vertebral fracture requiring the longest time off the bike. Chris Boardman, a serial Olympic medal winner in cycling, retired in his early 30s with osteoporosis. In other words, in road cycling, the combined effect of the lack of osteogenic stimulus and LEA can produce clinically significant adverse effects on bone health.

What practical clinical tools are most effective at identifying competitive male cyclists at risk of the health and performance consequences of LEA outlined in the RED-S model? This was the question our recent study addressed. The lumbar spine is a skeletal site known to be most impacted by nutrition and endocrine factors and DXA is recognised as the “gold standard” of quantifying age matched Z score for bone mineral density (BMD) in the risk stratification of RED-S. What is the clinical measure indicative of this established and clinically significant sign of RED-S on lumbar spine BMD? Would it be testosterone concentration, as suggested in the study of runners? Another blood marker? Cycle training load? Off bike exercise, as suggested in some previous studies? Clinical assessment by interview?

Using a decision tree approach, the factor most indicative of impaired age matched (Z score) lumbar spine BMD was sport specific clinical assessment of EA. This assessment took the form of a newly developed sports specific energy availability questionnaire and interview (SEAQ-I). Reinforcing the concept that the most important skill in clinical medical practice is taking a detailed history. Questionnaire alone can lead to athletes giving “correct” answers on nutrition and training load. Clinical interview gave details on the temporal aspects of EA in the context of cycle training schedule: whether riders where experiencing acute intermittent LEA, as with multiple weekly fasted rides, or chronic sustained LEA with prolonged periods of suppressed body weight. Additionally the SEAQ-I provided insights on attitudes to training and nutrition practices.

Cyclists identified as having LEA from SEAQ-I, had significantly lower lumbar spine BMD than those riders assessed as having adequate EA. Furthermore, the lowest lumbar spine BMD was found amongst LEA cyclists who had not practised any load bearing sport prior to focusing on cycling. This finding is of particular concern, as if cycling from adolescence is not integrated with weight bearing exercise and adequate nutrition when peak bone mass (PBM) is being accumulated, then this risks impaired bone health moving into adulthood.

Further extension of the decision tree analysis demonstrated that in those cyclists with adequate EA assessed from SEAQ-I, vitamin D concentration was the factor indicative of lumbar spine BMD. Vitamin D is emerging as an important consideration for athletes, for bone health, muscle strength and immune function. Furthermore synergistic interactions with other steroid hormones, such as testosterone could be significant.

What about the effects of EA on cycling performance? For athletes, athletic performance is the top priority. In competitive road cycling the “gold standard” performance measure is functional threshold power (FTP) Watts/Kg, produced over 60 minutes. In the current study, 60 minute FTP Watts/Kg had a significant relationship to training load. However cyclists in chronic LEA were under performing, in other words not able to produce the power anticipated for a given training load. These chronic LEA cyclists also had significantly lower testosterone concentration. Periodised carbohydrate intake for low intensity sessions is a strategy for increasing training stimulus. However if this acute intermittent LEA is superimposed on a background of chronic LEA, then this can be counter productive in producing beneficial training adaptations. Increasing training load improves performance, but this training is only effective if fuelling is tailored accordingly.

Male athletes can be at risk of developing the health and performance consequences of LEA as described in the RED-S clinical model. The recent study of competitive male road cyclists shows that a sport specific questionnaire, combined with clinical interview (SEAQ-I) is an effective and practical method of identifying athletes at risk of LEA. The temporal dimension of LEA was correlated to quantifiable health and performance consequences of RED-S.

References 

Low energy availability assessed by a sport-specific questionnaire and clinical interview indicative of bone health, endocrine profile and cycling performance in competitive male cyclists  Keay, Francis, Hind, BMJ Open in Sport and Exercise Medicine 2018

2018 UPDATE: Relative Energy Deficiency in Sport (RED-S) Keay, BJSM 2018

Fuelling for Cycling Performance Science4Performance

Pitfalls of Conducting and Interpreting Estimates of Energy Availability in Free-Living Athletes International Journal of Sport Nutrition and Exercise Metabolism 2018

IOC consensus statement on relative energy deficiency in sport (RED-S): 2018 update BJSM 2018

The LEAF questionnaire: a screening tool for the identification of female athletes at risk for the female athlete triad BJSM 2013

Low Energy Availability Is Difficult to Assess but Outcomes Have Large Impact on Bone Injury Rates in Elite Distance Athletes International Journal of Sport Nutrition and Exercise Metabolism 2018

Treating exercise-associated low testosterone and its related symptoms The Physician and Sports Medicine 2018

Male Cyclists: bones, body composition, nutrition, performance Keay, BJSM 2018

Cyclists: Make No Bones About It Keay, BJSM 2018

Male Athletes: the Bare Bones of Cyclists

Cyclists: How to Support Bone Health?

Synergistic interactions of steroid hormones Keay BJSM 2018

Fuel for the Work Required: A Theoretical Framework for Carbohydrate Periodization and the Glycogen Threshold Hypothesis Sports Medicine 2018

 

Cyclists: How to Support Bone Health?

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Supporting Bone Health

The wonderfully named “hip hop” study was conducted to investigate whether hopping would improve the strength of the hip bone in older males. You may be wondering how this is relevant to male cyclists in their twenties. Yet, in a recent pilot study, some male cyclists were found to have areas of the skeleton that were below average bone mineral mineral (BMD) for an 85 year old man. This finding of low BMD in cyclists was confirmed in a recent BBC programme where Dr Karen Hind at Leeds Beckett University presented the differences in BMD across sports. Keen-eyed cyclists amongst you will have recognised Ed Clancy from JLT Condor representing cyclists, though these findings will be relevant to all levels of competitive cyclists.

So maybe research with the same aims as the “hip hop” study is exactly what needs to be conducted amongst male cyclists to investigate practical and effective ways of supporting bone health and ultimately preventing injury and optimising performance. This is aim of forthcoming research in collaboration with Dr Hind.

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Microscopic structure of bone

In common with other sports, cycling is an excellent form of exercise, driving positive adaptations throughout the body, such as improved cardiovascular fitness, body composition, muscular strength and endurance together with beneficial psychological effects. However, unlike many other forms of exercise, cycling does not encourage beneficial adaptations to the full skeletal system. This is due to a lack of mechanical osteogenic (bone building) stimuli provided in cycling, particularly at the lumbar spine. In competitive road cycling, low body mass confers a performance advantage, so restrictive or inconsistent nutrition can lead to relative energy deficiency in sport (RED-S). The consequent Endocrine system dysfunction can compound the negative effects on bone health of a non-load-bearing sport.

In a study of masters cyclists, decreases in BMD at all sites were more marked than in sedentary individuals. Some cyclists went from being osteopenic to osteoporotic; a rare case where exercise has a negative impact on a system in the body. Does this matter? Like all athletes, cyclists are more concerned with current athletic performance than warnings about future issues, such as osteoporosis and fracture. Yet, out of athletes across all sports, cyclists should perhaps be the most concerned. In the case of runners, suboptimal bone heath and associated RED-S may well present as a stress fracture. In the case of cyclists by the nature of non-load bearing exercise, they can push for longer with suboptimal bone and nutritional status. The full extent of any bone health issues may only come to light as result of a bike crash. Looking at the time off from injury in elite cyclists, the majority are due to fracture, with vertebral fractures often requiring long duration of recovery compared to other sites.

Maybe maintenance of BMD for adult cyclists would be realistic goal. How can this be achieved?

Multidirectional, dynamic loading patterns have been shown to produce the most positive skeletal responses. This is seen in the different site specific effects of sports, where changes of direction or plane of movement provide maximal mechanical osteogenic stimulus. Jumping and hopping have been shown to be good for bone health in premenopausal women, where brief high impact exercises were found to be beneficial for the bone mineral density (BMD) of the femoral neck of the hip.

What about targeting the lumbar spine, which is the site most at risk in cyclists? In young children, a few mechanical loading cycles of two-footed jumping from a small step improved BMD at lumbar spine compared with those that did not perform this jumping exercise. However bone is at its most responsive in childhood and skeletal loading has a more long term effect on both microarchitecture and BMD than when performed as an adult. Nevertheless, even in adulthood bone is still a dynamic tissue, able to adapt to loading stresses. Resistance training seems to be the most effective way of providing mechanical osteogenic stimulus to the lumbar spine with an additional indirect osteogenic effect of muscle pulling on bone. For example rowers have site-specific increases in BMD at the lumbar spine. In a recent study, resistance training was found to improve BMD in male distance runners with similar levels of testosterone and bone markers. This concurs with recent pilot study of cyclists, where those performing current resistance training or with recent history of participating in other sports, such as rugby or rowing, fared better in terms of BMD. In other words, the improvement in BMD mediated via mechanical rather than Endocrine effects.

Nevertheless, any form of skeletal-loading exercise will not produce the expected beneficial osteogenic effect, if performed in suboptimal nutritional status. Sufficient quantity and quality of nutrition are required to prevent RED-S. Specific nutritional factors, such as vitamin D, calcium and polyphenols, are recognised to be important in bone health. Boron is also described as decreasing bone resorption by stabilising and extending the half-life of vitamin D and improving sex steroid availability. Whilst high intake of caffeine, which can accumulate if athletes take on board caffeine gels, has a negative impact on BMD. Optimal nutritional status will in turn support the Endocrine system to mediate advantageous adaptations to exercise exercise, including bone health.

How can cyclists optimise bone health and performance on the bike with consistent and targeted skeletal-loading exercise and nutritional strategies? Watch this space! A study is planned to investigate practical and effective strategies to achieve this. No on bike hip hop dance required.

In meantime there will be more discussion on “Health, Hormones and Human Performance” at the BASEM conference 22 March. All welcome, including athletes and coaches, alongside healthcare professional working with athletes.

References

Male Athletes: the Bare Bones of Cyclists

Cyclists: Make No Bones About It BJSM 2018

Which type of exercise gives you the strongest bones? BBC

Studies

Male Cyclists: Bones, Body composition, Nutrition, Performance BJSM 2018

Longitudinal Changes in Bone Mineral Density in Male Master Cyclists and Nonathletes The Journal of Strength & Conditioning Research 2011

A meta-analysis of brief high-impact exercises for enhancing bone health in premenopausal women  Osteoporosis International 2012

Jumping Improves Hip and Lumbar Spine Bone Mass in Prepubescent Children: A Randomized Controlled Trial JBMR 2001

Review Exercise and Sports Science Australia (ESSA) position statement on exercise prescription for the prevention and management of osteoporosis Journal of Science and Medicine in Sport 2016

Resistance training is associated with higher bone mineral density among young adult male distance runners independent of physiological factors The Journal of Strength & Conditioning Research 2018

Relative Energy Deficiency in Sports (RED-S) Practical considerations for endurance athletes

Nothing Boring About Boron Integrated Medicine 2015

Cumulative Endocrine Dysfunction in Relative Energy Deficiency in Sport (RED-S) BJSM 2018