RESEARCH: Studies reviewed this week: 08 February 2021 to 14 February 2021

HYDRATION: Incidence of Hyponatremia During a Continuous 246-km Ultramarathon Running Race

I've shared a few articles on hydration in the past (fluid loss impact on vagal autonomic function; dehydration does not impact performance). Clearly the impacts of hydration status are nuanced and need to be carefully considered. That's why it's interesting to have a study that looks into "the incidence of exercise-associated hyponatremia (EAH) in a 246-km continuous ultra-marathon".

The authors studie 63 athletes over two years at the Spartathlon event finding that:

  • Of the 63 finishers recruited, nine began the race with values indicative of mild hyponatremia.
  • Seven runners were classified as hyponatremic at the 93-km checkpoint, three of whom had sodium levels of severe hyponatremia.
  • After the race, 41 total finishers (65%) developed either mild (n = 27, 43%) or severe hyponatremia (n = 14, 22%).
The incidence of EAH of 52 and 65%, when excluding or including these individuals with pre-race hyponatremia, was the highest reported in current literature.

PRACTICAL TAKEAWAY - there is a significant chance of hyponatremia in events that are long, hot, and physically demanding. The authors point out that "athletes should always remain cognizant of their competitive habits and understand how these habits affect their sodium levels. Accordingly, ultra-endurance athletes should recognize and respond appropriately to the symptoms of EAH".

NUTRITION: Metabolic and performance effects of raisins versus sports gel as pre-exercise feedings in cyclists

Potatoes have shown to be "effective race nutrition and provide equivalent CHO compared to commercial gels and drinks". In this study the authors set out "to examine potential differences in metabolism and cycling performance after consumption of moderate glycemic raisins vs. a high glycemic commercial sports gel". The authors found that:

Performance was not different between the raisin (189.5 +/- 69.9 kJ) and gel (188.0 +/- 64.8 kJ) trials.
Overall, minor differences in metabolism and no difference in performance were detected between the trials.

PRACTICAL TAKEAWAY - raisins may be a cost effective and natural option for CHO during training and racing.

PHYSIOLOGY: Physiological Indicators of Trail Running Performance

I find it interesting to learn about the physiological characteristics of top performers as it can be useful to understand what characteristics to train. I've shared some studies that look into this in the past (here, here, and here). In this review the authors set out to " provide a systematic overview of physiological parameters used to determine the training status of a trail runner and how well these parameters correlate with real-world trail running performance".

The findings were that:

  • Trail running performance most commonly correlated (mean [SD]) with maximal aerobic capacity (71%; r = −.50 [.32]), lactate threshold (57%; r = −.48 [.28]), velocity at maximal aerobic capacity (43%; r = −.68 [.08]), running economy (43%; r = −.31 [.22]), body fat percentage (43%; r = .55 [.21]), and age (43%; r = .52 [.14])
  • Regression analyses in 2 studies were based on a single variable predicting 48% to 60% of performance variation, whereas 5 studies included multiple variable regression analyses predicting 48% to 99% of performance variation.
  • The classic endurance model shows a weaker association with performance in trail running than in road running.

PRACTICAL TAKEAWAY - training for trail racing should aim to optimise the characteristics of running that we already know and that are well-known from road running. However, consideration does need to be made for the specifics of trail running which are not captured by the classic endurance training model.

COVID: COVID-19 vaccination in athletes: ready, set, go…

Here's a useful article looking at the implications of taking the COVID vaccines for athletes. A few key points include:

It might also be appropriate to consider a temporary reduction in training load in the first 48–72 h post vaccine injection, particularly after the second dose.
Clinicians will thus need to be cognizant of athlete-specific factors, such as planning vaccination in the context of peak training or the tapering period before major competition, and discussions will likely involve shared decision making with athletes, coaches, and administrators.

PRACTICAL TAKEAWAY - understanding the benefits and potential side-affects of vaccines is important if or when planning to take them.

NUTRITION: Can taste be ergogenic?

One of the issues that ultramarathon runners have with their in-race nutrition is taste fatigue later in the race. It can be a risky prospect planning to eat all the same flavour, consistency, or texture of foods during a race. This is study titled "can taste be ergogenic?" seemed like it could be an interesting look into that (while also potentially addressing some ideas like menthol in hot environments).

In this article the authors "outline the ergogenic potential of substances that impart bitter, sweet, hot and cold tastes administered prior to and during exercise performance and whether the ergogenic benefits of taste are attributable to the placebo effect". A few interesting points include:

Carbohydrate mouth rinsing seemingly improves endurance performance, along with a potentially ergogenic effect of oral exposure to both bitter tastants and caffeine although subsequent ingestion of bitter mouth rinses is likely required to enhance performance.
Efficacy is not limited to taste, but extends to the stimulation of targeted receptors in the oral cavity and throughout the digestive tract, relaying signals pertaining to energy availability and temperature to appropriate neural centres.

PRACTICAL TAKEAWAY - make sure that you consider the taste aspect in addition to other attributes of sports nutrition products when planning your race nutrition plan.

NUTRITION: Carbohydrate restriction following strenuous glycogen-depleting exercise does not potentiate the acute molecular response associated with mitochondrial biogenesis in human skeletal muscle

I shared this study on twitter and perhaps tried to draw too many implications from it resulting in some good discussion in the twitter thread. I think it is a very useful and insightful study so I want to be fair and represent the authors intentions effectively here.

The authors set out to determine "whether post-exercise CHO restriction following strenuous exercise combining continuous cycling exercise (CCE) and sprint interval exercise could affect the gene expression related to mitochondrial biogenesis and oxidative metabolism in human skeletal muscle". The findings were as follows:

Compared to pre-exercise, strenuous cycling led to a severe muscle glycogen depletion (> 90%) and induced a large increase in PGC1A and PDK4 mRNA levels (~ 20-fold and ~ 10-fold, respectively) during the acute recovery period in both trials.
CHO restriction during the 3-h post-exercise period blunted muscle glycogen resynthesis but did not increase the mRNA levels of genes associated with muscle adaptation to endurance exercise, as compared with abundant post-exercise CHO consumption.
CHO restriction after a glycogen-depleting and metabolically-demanding cycling session is not effective for increasing the acute mRNA levels of genes involved in mitochondrial biogenesis and oxidative metabolism in human skeletal muscle.

PRACTICAL TAKEAWAY - for the time being, I would suggest a useful takeaway is that not eating after a hard training session does not show any benefit at the 3hr mark after training. [there may be benefit at 8hrs, and there may be benefit to using a specific strategy like train-low; these both need to be considered in more detail.]

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