RESEARCH: studies reviewed this week - 17 August 2020 to 23 August 2020

NUTRITION: Carbohydrate availability and exercise training adaptation: too much of a good thing?

Planning and periodising sports nutrition is important and can have a big impact on performance. It is important to "fuel for the work required", however, some studies "have demonstrated that deliberately training in conditions of reduced CHO availability can promote training-induced adaptations of human skeletal muscle". This is the source of the idea of train-low, race high.

The authors of this study investigated the reasons for the potentially augmented response suggesting that these come from:

Enhanced activation of key cell signalling kinases (e.g. AMPK, p38MAPK), transcription factors (e.g. p53, PPARδ) and transcriptional co-activators (e.g. PGC-1α), such that a co-ordinated up-regulation of both the nuclear and mitochondrial genomes occurs.

They recommend an approach that uses other nutrition interventions to optimise this type of training:

Consuming additional caffeine, protein, and practising CHO mouth-rinsing before and/or during training may help to rescue the reduced training intensities that typically occur when 'training low', in addition to preventing protein breakdown and maintaining optimal immune function.

PRACTICAL TAKE AWAY - training low occasionally can have benefits. Use the authors guidelines to ensure that these sessions are completed optimally.

NUTRITION: Ketone Diester Ingestion Impairs Time-Trial Performance in Professional Cyclists

This study is excellent because it tested the effects of ketones (along with a standardised CHO breakfast) on the performance of elite cyclists. This effectively answers the question that many viewers of cycling or athletes who can't get ketone esters to test themselves want answered: do ketones actual improve performance? The test protocol was as follows:

  • Cyclists consumed a standardized meal [2 g/kg body mass (BM) carbohydrate (CHO)] the evening prior to a trial day and a CHO breakfast (2 g/kg BM CHO) with 200 mg caffeine on the morning of a trial day.
  • Cyclists were randomized to consume either the ketone diester (2 × 250 mg/kg) or a placebo drink, followed immediately by 200 mL diet cola, given ~ 30 min before and immediately prior to commencing a 20 min incremental warm-up.
  • Cyclists completed a ~31 km laboratory-based TT on a cycling ergometer programmed to simulate the 2017 World Road Cycling Championships course.

The results found that:

Pre-exercise ingestion of the diester resulted in a 2 ± 1% impairment in TT performance that was associated with gut discomfort and higher perception of effort.

Ketone ingestion induces hyperketonemia in elite professional cyclists when in a carbohydrate fed state, and impairs performance of a cycling TT lasting ~50 min.

PRACTICAL TAKE AWAY - ketones have not been shown to improve performance yet.

EQUIPMENT: Altered Running Economy Directly Translates to Altered Distance-Running Performance

This study set out to test whether or not laboratory and model results of adding weight to shoes would impact performance in a time trial. The study tried two additional weights, 100g and 300g, and estimated an increase in running time of 1% and 3% respectively. The results showed that:

On the basis of a linear fit of all the data, 3000-m time increased 0.78% per added 100g per shoe.

Adding shoe mass predictably degrades running economy and slows 3000-m time-trial performance proportionally.

PRACTICAL TAKE AWAY - while shoe weight is important, I expected the results to be more significant. 100g is a lot of weight difference for a shoe and often 20-40g heavier shoes can provide substantially more comfort and cushioning. When choosing race shoes choose the lightest appropriate shoe, but don't sacrifice significant comfort or cushion for weight.

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