Temporal considerations in Endocrine/Metabolic interactions Part 1


It is not a simple question of what, but when we eat, sleep and exercise.

The Endocrine system displays temporal variation in release of hormones. Integrating external lifestyle factors with this internal, intrinsic temporal dimension is crucial for supporting metabolic and Endocrine health.

Amplitude and frequency of hormonal secretion display a variety of temporal patterns:

  • Diurnal variation, synchronised with external light/dark. Orchestrated by a specific area of the hypothalamus, the neuroendocrine gatekeeper.
  • Circadian rhythm, roughly 24-25 hours which can vary with season according to duration of release of melatonin from the pineal gland.
  • Infradian rhythms longer than a day, for example lunar month seen in patterns of hypothalamic-pituitary-ovarian axis hormone release during the menstrual cycle.
  • Further changes in these temporal release and feedback patterns occur over a longer timescale during the lifespan.

Hormones influence gene expression and hence protein synthesis over varying timescales outlined above. The control system for hormone release is based on interactive feedback loops. The hypothalamus is the neuroendocrine gatekeeper, which integrates external inputs and internal feedback.  The net result is to maintain intrinsic biological clocks, whilst orchestrating adaptations to internal perturbations stimulated by external factors such as sleep pattern, nutrition and exercise.

Circadian alignment refers to consistent temporal patterns of sleep, nutrition and physical activity. Circadian misalignment affects sleep-architecture and subsequently disturbs the interaction of metabolic and Endocrine health. This includes gut-peptides, glucose-insulin interaction, substrate oxidation, leptin & ghrelin concentrations and hypothalamic-pituitary-adrenal/gonadal-axes. The main stimuli for growth hormone release are sleep and exercise. Growth hormone is essential for supporting favourable body composition. These integrated patterns of environmental factors may have a more pronounced effect on those with a genetic predisposition or during crucial stages of lifespan. For example curtailed sleep during puberty can impact epigenetic factors such as telomere length and thus may predispose to metabolic disruption in later life. Regarding activity levels, there are strong relationships between time spent looking at screens and markers, such as insulin resistance, for risk of developing type 2 diabetes mellitus in children aged 9 to 10 years.

In addition to adverse metabolic effects set in motion by circadian misalignment, bone turnover has also shown to be impacted. Circadian disruption in young men resulted in uncoupling of bone turnover, with decreased formation and unchanged bone resorption as shown by monitoring bone markers. In other words a net negative effect on bone health, which was most pronounced in younger adult males compared with their older counterparts. These examples underline the importance of taking into account changes in endogenous temporal patterns during the lifespan and hence differing responses to external lifestyle changes.

For male and female athletes, integrated periodised training, nutrition and recovery has to be carefully planned over training seasons to support optimal adaptations in Endocrine and metabolic networks to improve performance. Training plans that do not balance these all these elements can result in underperformance, potentially relative energy deficiency in sport and consequences for health in both short and long term.

Part 2 will consider the longer term consequences and interactions of these temporal patterns of lifestyle factors, including seasonal training patterns in male and female athletes, on the intrinsic biochronometry controlling the Endocrine and metabolic networks during lifespan.

For further discussion on Health, Hormones and Human Performance, come to the BASEM annual conference


Sports Endocrinology – what does it have to do with performance? Dr N.Keay, British Journal of Sports Medicine 2017

One road to Rome: Metabolic Syndrome, Athletes, Exercise Dr N. Keay

Metabolic and Endocrine System Networks Dr N. Keay

Endocrine system: balance and interplay in response to exercise training Dr N.Keay

Sleep for health and sports performance Dr N.Keay, British Journal of Sports Medicine 2017

Factors Impacting Bone Development Dr N. Keay

Sleep, circadian rhythm and body weight: parallel developments Proc Nutr Soc

Sleep Duration and Telomere Length in Children Journal of Paediatrics 2017

Screen time is associated with adiposity and insulin resistance in children Archives of Disease in Childhood

Circadian disruption may lead to bone loss in healthy men Endocrine today 2017

Successful Ageing Dr N. Keay, British Association of Sport and Exercise Medicine 2017

Clusters of Athletes – A follow on from RED-S blog series to put forward impact of RED-S on athlete underperformance Dr N. Keay, British Association of Sport and Exercise Medicine 2017

Optimal Health: For All Athletes! Part 4 – Mechanisms Dr N. Keay, British Association of Sport and Exercise Medicine 2017





Balance of Recovery and Adaptation for Sport Performance

There has been much recent discussion about the optimal balance of recovery strategies to enable effective return to training, and adaptive processes which occur as the result of training to improve sporting performance.


I have been reading the scientific reports to try and gain an understanding of this balance between recovery and adaptation. However, my investigations were put into context after attending two fascinating meetings last week where insightful talks were given by Dr Hannah Macleod Olympic gold medallist and presentations at the King’s Sport and Exercise Medicine Conference.

The scientific principle behind exercise training, of any sort, is that improvement in exercise performance follows from the cycle of overload exercise, followed by recovery phase during which adaptive changes occur in musculoskeletal, cardiovascular, metabolic and neurological systems to improve exercise performance capacity. If sufficient recovery is not taken before next training session, then rather than a progressive stepwise upward improvement in performance capacity, a downward progression occurs. In order to avoid this overreaching and overtraining scenario, rather to improve performance, training cycle as described by Dr Macleod often consists of 3 weeks “on”, followed by “rest” week together with well structured napping.

Theoretically, if the amount of recovery needed could be shortened, then more training could be done and thus potentially more adaptive advantages gained. However, by shortening recovery time with various strategies, this might actually curtail and reduce the very adaptive changes being sought. Considering recovery and adaptive responses of skeletal muscle to exercise, there are recent apparently contradictory reports on the benefits of ice baths. To ice bath or not to? Certainly for muscle injury RICE (rest, ice, compression, elevation) regime is well established. Does the same apply for skeletal muscle recovery and adaptation post exercise? The most recent study on 9 non-elite athletic males revealed that post resistance exercise there was no difference in the inflammatory markers or cellular stress markers in skeletal muscle whether recovery was either active or with cold water immersion. Nevertheless a previous study 2015 by the same group had reported attenuated gains in muscle mass and strength with cold water immersion recovery during 3 months of resistance training in 24 non-elite athletic males. The main issue seems to be that it all depends on the part of the long term training cycle and the type of sport in which the athlete is involved. For example, during pre-season training, where long term adaptations are being sought, then an ice bath might potentially attenuate adaptive responses gained from strength training. On the other hand, in the acute clinical setting, post match in a multi-day competition, an ice bath may be of benefit during the course of this competition period. Certainly Dr Macleod described having a compressive ice system on the team bus post match during the Olympics in Rio where 8 matches were played over 14 days. So recovery, especially from any impact injuries, was far more important than considerations of longer term performance in resistance training post Olympics. Not to mention the psychological beneficial effect to athletes with reduced perception of fatigue and muscle soreness and feeling in control of all factors possible.

Finally I would also suggest that just as there is variation between individuals in the positive adaptive responses to exercise, probably genetically determined, there may also be individual variation in the extent and benefits of recovery strategies. For example, in a clinical setting, an over-response of the inflammatory pathways can actually cause harm, such as in autoimmune disease. Another point is that I have restricted this blog to discuss cellular responses of skeletal muscle to resistance exercise and competition. Clearly there are other mechanisms involved in exercise training adaptations such as the neuroendocrine system, together with other types of exercise training and other recovery strategies.

In conclusion, just as training is periodised, it would appear that recovery strategies should also be periodised in conjunction with the phase of the training /competition cycle and type of sport. Apart from the scientific rational, the psychological aspects for athletes also has to be considered.

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


“Science in Elite Sport” talk by Dr Hannah Macleod at University of Roehampton 6/12/16

“Assessing the field of play” King’s Sport and Exercise Medicine Conference, Guy’s Hospital 5/12/16

Inflammation: why and how much? Dr N. Keay, British Association of Sport and exercise Medicine 2017

Endocrine system: balance and interplay in response to exercise training

Rapid recovery versus long term adaptation

Cold water therapy and bad journalism

Do post-work out ice bath help with recovery of sore muscles?

The Use of Cryotherapy in Sports Injuries

The effects of cold water immersion and active recovery on inflammation and cell stress responses in human skeletal muscle after resistance exercise

Post-exercise cold water immersion attenuates acute anabolic signalling and long-term adaptations in muscle to strength training