Athletic Fatigue: Part 2

A degree of athletic fatigue following a training session, as described in part 1, is required to set in motion mechanisms to drive beneficial adaptations to exercise. At what point does this process of functional over-reaching tip into non-functional over-reaching denoted by failure to improve sports performance? Or further still along the spectrum and time scale, the chronic situation of overtraining and decrease in performance? Is this a matter of time scale, or degree, or both?

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Integrated Periodisation of Training Load, Nutrition and Recovery keeps an individual on the green plateau, avoiding descent into the red zone, due to an excess or deficiency

Determining the tipping point between these fatigue situations is important for health and performance. A first step is always to exclude underlying organic disease states, be these of Endocrine, systemic inflammatory or infective aetiologies. Thereafter the crucial step is to assess whether the periodisation of training, nutrition and recovery are integrated over a training block and in the longer term over a training season.

What about the application of Endocrine markers to monitor training load? Although the recent studies described below are more applicable to research scenarios, they give some interesting insights into the interactive networks effects of the Endocrine system and the multifactorial nature of fatigue amongst individual athletes.

In the short term, during a 2 day rowing competition, increases in wakening salivary cortisol were noted followed by return towards baseline in subsequent 2 day recovery. Despite individual variability with salivary cortisol measurement, this does at least offer a noninvasive way to adjust training loads around competition time for elite athletes.

Over an 11 day stimulated training camp and recovery during the sport specific preparatory phase of the training season, blood metabolic and Endocrine markers were measured. In the case of an endurance based training camp in cyclists, a significant increase in urea (due to protein breakdown associated with high energy demand training) and decrease in insulin-like growth factor 1 (IGF1) from baseline were noted. Whereas for the strength-based athletes for ball sports, an increase in creatine kinase (CK) was seen, as a result of muscle damage. This study demonstrates how different markers of fatigue are specific to sport discipline and mode of training. Large inter-individual variability existed between the degree of change in markers and degree of fatigue.

In the longer term, for the case of overtraining syndrome potential Endocrine markers have been reviewed. Whilst basal levels of most measured hormones remained stable, a blunted submaximal exercise response of growth hormone (GH), prolactin and ACTH could be indicative of developing overtraining syndrome. Whilst this review is interesting, dynamic testing is not a practical approach and these findings are not specific to over training. Rather this blunted dynamic exercise response would indicate relative suppression of the neuroendocrine hypothalamic-pituitary axis which could potentially involve other stressors such as inadequate sleep or poor nutrition. Although basal levels may lie “within the normal range”, if both pituitary derived stimulating hormone and end endocrine gland hormone concentrations fall in the lower end of the normal ranges (eg low end of range TSH and T4) this is consistent with mild hypothalamic suppression observed over the range of training and fatigue conditions (functional/non-functional and overtraining) and/or Relative Energy Deficiency in Sports (RED-S).

Although the studies above are of research interest, non invasive monitoring, specific to an athlete is more practical for monitoring the effects of training. Several useful easily measurable metrics can give clues: resting heart rate, heart rate variability, power output. Tools on Strava and Training Peaks provide practical insights in monitoring training effectiveness via these metrics. A range of mobile apps makes it ever easier to augment a personal training log to include these training metrics, along with feel, sleep and nutrition. Such a log provides feedback on health and fitness for the individual athlete, in order to personalise training plans. Certainly adding the results from any standard basal blood tests will also help add to the picture, along the lines of building a longitudinal personal biological passport. After all, “normal ranges” are based on the general population, of which top level athletes may represent a subgroup. The more personalised the metics recorded over a long time scale, the more sensitive and useful the process to guide improvement in sport performance.

Context is key when considering athletic fatigue: temporal considerations and individual variation. Certainly the interactive network effects of the Endocrine system are important in determining the degree of adaptation to exercise and therefore sports performance. However the Endocrine system acts in conjunction with many other systems (metabolic, immune and inflammatory), in determining the effectiveness of training in improving sports performance. So it is not surprising that one metric or marker in isolation is not predictive of fatigue status in individual athletes.

For more discussion on Health, Hormones and Human Performance come to the British Association of Sport and Exercise Medicine annual conference

Presentations

References

Athletic Fatigue: Part 1

Endocrine system: balance and interplay in response to exercise training

Temporal considerations in Endocrine/Metabolic interactions Part 1

Fatigue, sport performance and hormones..more on the endocrine system Dr N Keay, British Journal of Sports Medicine 2017

Sport Performance and RED-S, insights from recent Annual Sport and Exercise Medicine and Innovations in Sport and Exercise Nutrition Conferences Dr N Keay, British Journal of Sports Medicine 2017

Capturing effort and recovery: reactive and recuperative cortisol responses to competition in well-trained rowers British Journal of Sports Medicine

Blood-Borne Markers of Fatigue in Competitive Athletes – Results from Simulated Training Camps Plos One

Hormonal aspects of overtraining syndrome: a systematic review BMC Sports Science, Medicine and Rehabilitation 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

Strava Fitness and Freshness Science4Performance 2017

From population based norms to personalised medicine: Health, Fitness, Sports Performance Dr N Keay, British Journal of Sports Medicine 2017

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

What has your gut microbiome ever done for you?

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Our body acts as a host to vast array of micro-organisms. Often, we are only aware of these micro-organisms causing unwanted infection: for example when a cut on the skin becomes infected, or we suffer with a bout of infective gastro-intestinal upset. Actually, this perception of the micro-organisms, living both on and inside, only causing unwanted infections is very biased. The microbiome (all the micro-organisms, their genetic material and metabolites produced) plays a vital role in keeping us healthy.

Recent research demonstrates that elite level cyclists host distinct clusters of microbiome communities when compared to controls which contribute to more effective metabolic pathways.

The gut microbiota consist of the range of micro-organisms living in our gut, mainly the colon. Recent research reveals that the diversity and functions of the gut microbiota have far reaching impact on health. For example, there is an important interaction between these micro-organisms and mitochondria, which are the organelles in cells responsible for producing energy. This cross talk is of particular consideration for athletes who seek to optimise energy production for training and competition. The gut microbiota also interact with the immune system and central nervous system function, including behaviour. There is evidence that the gut microbiota even influences brain development.

Microbiome Mitochondria Feedback

On the other side of the coin, any disruption in the beneficial types of gut microbiota have been linked to chronic disease states including obesity, metabolic syndrome and mental health issues. What causes imbalances in gut microbiota to produce such problems? A possible aetiology is a poorly balanced diet, or the side effect of medication which does not support the growth and function of beneficial bacteria. Rather an overgrowth of potentially harmful bacteria is favoured: dysbiosis. In athletes there is a condition know as “leaky gut” which can result from endurance training. In this scenario, blood is diverted away from the gut during exercise to the exercising muscles. After stopping exercise, blood flow is restored to the gut resulting in a mild reperfusion injury. This results in a slightly “leaky gut” so that unwanted bacteria in the gut are able to pass into the body and provoke an inflammatory response. Equally this situation can also mean desirable nutrients in the gut as less well absorbed. Although a degree of inflammatory response supports desirable adaptations to exercise, clearly an over-response will be counter productive to improving sports performance.

The gut microbiota have been reported to regulate immune function. Athletes in heavy training can experience suppressed functional immunity so any strategies to support the gut microbiota will potentially be beneficial in preventing infection.

What can you do to support a beneficial gut microbiota to support health and sport performance?

  • Try to include at least one fermented food source in your diet every day to boost your probiotic bacteria. Try sourdough bread, yogurt, kefir (similar to yogurt), sauerkraut, kimchi (Korean fermented vegetables), tempeh and miso (fermented soya products) and kombucha (fermented teas). These products can be found in health food shops and are becoming more widely available in some supermarkets and lunch places.
  • Regularly eat pre-biotic foods like garlic, onion, leeks, chickpeas, beans and lentils. These provide fuel for your probiotic bacteria, enabling them to proliferate.
  • Have adequate fibre in your diet from a wide variety of plant foods: eg wholegrains, legumes, vegetables, fruits, nuts, seeds. Dietary fibre is fermented by your probiotic bacteria to produce short chain fatty acids (SCFAs) which play a key role in keeping your gut healthy.
  • Consume foods and drinks rich in polyphenols: eg berries, green tea, coffee, black tea, red wine, dark chocolate, apples. Polyphenols, found in many plant foods, have been shown to help increase probiotic bacteria in the gut.
  • Take a good quality, multi-species probiotic supplement during winter, heavy training blocks and when travelling abroad, especially for races. To find out more about the potential benefits of probiotic supplementation for athletes, see this blog by nutritional therapist Jo Scott-Dalgleish: http://www.endurancesportsnutritionist.co.uk/blog/probiotics-guide-endurance-athlete/

To find out more about the interaction between Health, Hormones and Human Performance come to the British Association of Sport and Exercise Medicine annual conference

References

Community characteristics of the gut microbiomes of competitive cyclists Microbiome August 2017

Ubiquitous Microbiome: impact on health, sport performance and disease

Endocrine system: balance and interplay in response to exercise training

Inflammation: Why and How Much? Dr N. Keay, British Association of Sport and Exercise Medicine 2017

Athletic Fatigue: Part 1

Interpreting athletic fatigue is not easy. Consideration has to be given to context and time scale. What are the markers and metrics that can help identify where an athlete lies in the optimal balance between training, recovery and nutrition which support beneficial adaptations to exercise whilst avoiding the pitfalls of fatigue and maladaptation? This blog will discuss the mechanisms of athletic fatigue in the short term.

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Proposed causes of fatigue dependent on duration and intensity of training session

In the short term, during an endurance training session or race, the temporal sequence of athletic fatigue depends on duration and intensity. It is proposed that below lactate threshold (LT1), a central mechanism governs: increasing central motor drive is required to maintain skeletal muscular power output until neuromuscular fatigue cannot be overcome. From lactate threshold (LT1) to lactate turn point (LT2), a combination of central and peripheral factors (such as glycogen depletion) are thought to underpin fatigue. During high intensity efforts, above LT2 (which correspond to efforts at critical power), accumulation of peripheral metabolites and inability to restore homeostasis predominate in causing fatigue and ultimately inability to continue, leading to “task failure”. Of course there is a continuum and interaction of the mechanisms determining this power-duration relationship. As glycogen stores deplete this impacts muscle contractility by impairing release of calcium from the sarcoplasmic reticulum in skeletal muscle. Accumulation of metabolites could stimulate inhibitory afferent feedback to central motor drive for muscle contraction, combined with decrease in blood glucose impacting central nervous system (CNS) function.

Even if you are a keen athlete, it may not be possible to perform a lactate tolerance or VO2 max test under lab conditions. However a range of metrics, such as heart rate and power output, can be readily collected using personalised monitoring devices and then analysed. These metrics are related to physiological markers. For example heart rate and power output are surrogate markers of plasma lactate concentration and thus can be used to determine training zones.

A training session needs to provoke a degree of training stress, reflected by some short term fatigue, to set in motion adaptations to exercise. At a cellular level this includes oxidative stress and exerkines released by exercising tissues, backed up by Endocrine responses that continue to take effect after completing training during recovery and sleep. Repeated bouts of exercise training, followed by adequate recovery, result in a stepwise increase in fitness. Adequate periodised nutrition to match variations in demand from training also need to be factored in to prevent the Endocrine system dysfunction seen in Relative Energy Deficiency in Sports (RED-S), which impairs Endocrine response to training and sports performance. Integrated periodisation of training/recovery/nutrition is essential to support beneficial multi-system adaptations to exercise on a day to day time scale, over successive training blocks and encompassing the whole training and competition season. Psychological aspects cannot be underestimated. At what point does motivation become obsession?

In Part 2 the causes of athletic fatigue over a longer time scale will be discussed, from training blocks to encompassing whole season.

For more discussion on Health, Hormones and Human Performance come to the British Association of Sport and Exercise Medicine annual conference

Presentations

References

Endocrine system: balance and interplay in response to exercise training

Power–duration relationship: Physiology, fatigue, and the limits of human performance European Journal of Sport Science 2016

Strava Ride Statistics Science4Performance 2017

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

Relative Energy Deficiency in Sports (RED-S) Practical Considerations for Endurance Athletes

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

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

Addiction to Exercise – what distinguishes a healthy level of commitment from exercise addiction? Dr N Keay, British Journal of Sports Medicine 2017