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

Optimal health: for all athletes! Part 4 Mechanisms

As described in previous blogs, the female athlete triad (disordered eating, amenorrhoea, low bone mineral density) is part of Relative Energy Deficiency in sports (RED-S). RED-S has multi-system effects and can affect both female and male athletes together with young athletes. The fundamental issue is a mismatch of energy availability and energy expenditure through exercise training. As described in previous blogs this situation leads to a range of adverse effects on both health and sports performance. I have tried to unravel the mechanisms involved. Please note the diagram below is simplified view: I have only included selected major neuroendocrine control systems.

REDs

Low energy availability is an example of a metabolic stressor. Other sources of stress in an athlete will be training load and possibly inadequate sleep. These physiological and psychological stressors input into the neuroendocrine system via the hypothalamus. Low plasma glucose concentrations stimulates release of glucagon and suppression of the antagonist hormone insulin from the pancreas. This causes mobilisation of glycogen stores and fat deposits. Feedback of this metabolic situation to the hypothalamus, in the short term is via low blood glucose and insulin levels and in longer term via low levels of leptin from reduced fat reserves.

A critical body weight and threshold body fat percentage was proposed as a requirement for menarche and subsequent regular menstruation by Rose Frisch in 1984. To explain the mechanism behind this observation, a peptide hormone leptin is secreted by adipose tissue which acts on the hypothalamus. Leptin is one of the hormones responsible for enabling the episodic, pulsatile release of gonadotrophin releasing hormone (GnRH) which is key in the onset of puberty, menarche in girls and subsequent menstrual cycles. In my 3 year longitudinal study of 87 pre and post-pubertal girls, those in the Ballet stream had lowest body fat and leptin levels associated with delayed menarche and low bone mineral density (BMD) compared to musical theatre and control girls. Other elements of body composition also play a part as athletes tend to have higher lean mass to fat mass ratio than non-active population and energy intake of 45 KCal/Kg lean mass is thought to be required for regular menstruation.

Suppression of GnRH pulsatility, results in low secretion rates of pituitary trophic factors LH and FSH which are responsible for regulation of sex steroid production by the gonads. In the case of females this manifests as menstrual disruption with associated anovulation resulting in low levels of oestradiol. In males this suppression of the hypothamlamic-pituitary-gonadal axis results in low testosterone production. In males testosterone is aromatised to oestradiol which acts on bone to stimulate bone mineralisation. Low energy availability is an independent factor of impaired bone health due to decreased insulin like growth factor 1 (IGF-1) concentrations. Low body weight was found to be an independent predictor of BMD in my study of 57 retired pre-menopausal professional dancers. Hence low BMD is seen in both male and female athletes with RED-S. Low age matched BMD in athletes is of concern as this increases risk of stress fracture.  In long term suboptimal BMD is irrecoverable even if normal function of hypothamlamic-pituitary-gonadal function is restored, as demonstrated in my study of retired professional dancers. In young athletes RED-S could result in suboptimal peak bone mass (PBM) and associated impaired bone microstructure. Not an ideal situation if RED-S continues into adulthood.

Another consequence of metabolic, physiological and psychological stressor input to the hypothalamus is suppression of the secretion of thyroid hormones, including the tissue conversion of T4 to the more active T3. Athletes may display a variation of “non-thyroidal illness/sick euthyroid” where both TSH and T4 and T3 are in low normal range. Thyroid hormone receptors are expressed in virtually all tissues which explains the extensive effects of suboptimal levels of T4 and T3 in RED-S including on physiology and metabolism.

In contrast, a neuroendocrine control axis that is activated in RED-S is the hypothalamic-pituitary-adrenal axis. In this axis, stressors increase the amplitude of the pulsatile secretion of CRH, which in turn increases the release of ACTH and consequently cortisol secretion from the adrenal cortex. Elevated cortisol suppresses immunity and increases risk of infection. Long term cortisol elevation also impairs the other hormone axes: growth hormone, thyroid and reproductive. In other words the stress response in RED-S amplifies the suppression of key hormones both directly and indirectly via endocrine network interactions.

The original female athlete triad is part of RED-S which can involve male and female athletes of all ages. There are a range of interacting endocrine systems responsible for the multi-system effects seen in RED-S. These effects can impact on current and future health and sports performance.

For further discussion on Endocrine and Metabolic aspects of SEM come to the BASEM annual conference 22/3/18: Health, Hormones and Human Performance

References

Teaching module on RED-S for BASEM as CPD for Sports Physicians

Optimal health: including female athletes! Part 1 Bones Dr N. Keay, British Journal of Sport Medicine

Optimal health: including male athletes! Part 2 Relative Energy Deficiency in sports Dr N.Keay, British Journal of Sport Medicine 4/4/17

Optimal health: especially young athletes! Part 3 Consequences of Relative Energy Deficiency in sports Dr N. Keay, British Association of Sport and Exercise Medicine

Keay N, Fogelman I, Blake G. Effects of dance training on development,endocrine status and bone mineral density in young girls. Current Research in Osteoporosis and bone mineral measurement 103, June 1998.

Jenkins P, Taylor L, Keay N. Decreased serum leptin levels in females dancers are affected by menstrual status. Annual Meeting of the Endocrine Society. June 1998.

Keay N, Dancing through adolescence. Editorial, British Journal of Sports Medicine, vol 32 no 3 196-7, September 1998.

Keay N, Effects of dance training on development, endocrine status and bone mineral density in young girls, Journal of Endocrinology, November 1997, vol 155, OC15.

Relative Energy Deficiency in sport (REDs) Lecture by Professor Jorum Sundgot-Borgen, IOC working group on female athlete triad and IOC working group on body composition, health and performance. BAEM Spring Conference 2015.

Mountjoy M, Sundgot-Borgen J, Burke L, Carter S, Constantini N, Lebrun C, Meyer N, Sherman R, Steffen K, Budgett R, Ljungqvist A. The IOC consensus statement: beyond the Female Athlete Triad-Relative Energy Deficiency in Sport (RED-S).Br J Sports Med. 2014 Apr;48(7):491-7.

“Subclinical hypothydroidism in athletes”. Lecture by Dr Kristeien Boelaert at BASEM Spring Conference 2014 on the Fatigued Athlete

From population based norms to personalised medicine: Health, Fitness, Sports Performance Dr N. Keay, British Journal of Sport Medicine

Factors Impacting Bone Development

Optimal body mass index (BMI) coupled with favourable body composition of lean mass and visceral fat is associated with accrual of bone mineral density (BMD) and peak bone mass (PBM) which is vital for setting up BMD within normal ranges for adult life.

New research demonstrates that high BMI exerts a negative effect on the accumulation of BMD and bone architecture in young people. This is something of a surprise. Elevated BMI in young people is known to have a deleterious effect on cardio-metabolic health. However, to date the thinking has been that raised BMI would at least mean that weight bearing exercise would be “weighted” and hence favour accumulation of BMD. Rather it is reported that elevated BMI with increased visceral fat results in impaired bone architecture and BMD. Coupled with decreased lean mass, this means less muscle to exert force on the skeleton to promote BMD accumulation. This distorted body composition impairs attainment of PBM.screen-shot-2016-12-01-at-08-29-56

In my research, deficiency of BMD was found to be irreversible later in adult life, despite normalising body weight, shown for those at the other end of the spectrum of BMI. Those with relative energy deficiency in sports (REDs), formally known as the female athlete triad, demonstrated suboptimal BMD correlated with previous duration of low weight, amenorrhea and delayed onset of menarche, many years on despite return to optimal body weight and normal menstrual status.

Adverse body composition with increased deposition of visceral fat is seen in patients with growth hormone (GH) deficiency, for example post pituitary surgery. Interestingly in these young people with high levels of visceral fat, low levels of GH were recorded. The proposed mechanism of suppression of GH secretion in overweight young people has been discussed. Interestingly high levels of leptin are found in overweight youngsters, compared to low levels found my studies of low weight young dancers with menstrual disturbance. In other words, there appears to be feedback between body weight, body composition and the endocrine system. The other disadvantage of high levels of adipose tissue is that fat soluble vitamin D is “fat locked” and unable to support bone mineral accumulation.

Optimal BMI and body composition are factors associated with accrual of BMD and PBM which is vital for setting up BMD within normal ranges for adult life. In those young people with high BMI and disrupted body composition, dietary measures are needed to reduce body weight. Combined with exercise, including resistance and cardiovascular weight bearing forms, to improve body composition and thus bone architecture and BMD accrual.

For further discussion on Endocrine and Metabolic aspects of SEM come to the BASEM annual conference 22/3/18: Health, Hormones and Human Performance

References

Optimal health: including female athletes! Part 1 Bones Dr N. Keay, British Journal Sport Medicine

Optimal Health: Especially Young Athletes! Part 3 – Consequences of Relative Energy Deficiency in Sports Dr N. Keay, British Association Sport and Exercise Medicine

Science Daily

EurekaAlert

Paediatric Reports

Health and Fitness in young people

Recent reports reveal that children in Britain are amongst the least active in the world. At the other end of the spectrum there have been a cluster of articles outlining the pitfalls of early specialisation in a single sport.

Regarding the reports of lack of physical activity amongst young people in Britain, this is of concern not only for their current physical and cognitive ability, but has repercussions for health in adult life. Research demonstrates that young people with low cardiovascular fitness have an increased risk of developing cardiovascular disease in adult life. Conversely, the beneficial effects of weight bearing exercise in prepubescent girls has been shown to enhance bone mineral density accumulation, which will have beneficial impact on peak bone mass. However, as I found in my longitudinal studies, the level of exercise has to be in conjunction with an appropriate, well-balanced diet to avoid relative energy deficiency deficiency in sport (RED-S), which can compromise bone mineral density accumulation.m-running

At the other end of the scale, early specialisation in a single sport does not necessarily guarantee long term success. Rather, this can increase the risk of overuse injury in developing bodies, which in turn has long term consequences. Ensuring that all elements of fitness are considered may be an injury prevention strategy. I agree that injury prevention can be viewed as part of optimising sports performance, especially in young athletes for both the present and in the long term.

Sleep is a vital element in optimising health and fitness, especially in young people who may be tempted to look at mobiles or screens of other mobile devices which delays falling asleep by decreasing melatonin production. Sleep promotes mental freshness and physical elements such as boosting immunity and endogenous release of growth hormone. As Macbeth put it, sleep is the “chief nourisher in life’s great feast”.

A balanced approach to health and fitness should be promoted, with young people encouraged to take part in a range of sporting activities.

For further discussion on Endocrine and Metabolic aspects of SEM come to the BASEM annual conference 22/3/18: Health, Hormones and Human Performance

References

Young athletes’ optimal health: Part 3 Consequences of Relative Energy Deficiency in sports Dr N. Keay, British Association Sport and Exercise Medicine, 13/4/17

Sleep for health and sports performance Dr N. Keay, British Journal Sport Medicine, 7/2/17

Optimising health, fitness and sports performance for young people Dr N. Keay, British Journal Sport Medicine

Telegraph article

Active Healthy Kids global alliance

Poor cardiovascular fitness in young people risk for developing cardiovascular disease 

Sports Specialization in Young Athletes

IOC consensus statement on youth athletic development British Journal Sport Medicine