Dr Dan Plews and Ed Maunder
Scientists have investigated many different strategies that may up-regulate adaptations to endurance training. One thing that the majority of these strategies have in common – e.g. training with low-glycogen availability, under heat stress, or at altitude – is that they make training harder. With low-glycogen availability you have less carbohydrate energy available and may well feel flat; under heat stress the powers and paces you achieve at the various intensity thresholds decrease as you get hotter, and at altitude, it is more difficult to get the necessary oxygen to the working muscles due to the thin air. Therefore, any greater adaptive pay off comes at some cost
One strategy that may not come at this “makes it harder” cost that has seen some attention in the exercise physiology literature is bicarbonate supplementation during training. Many of you may be familiar with bicarbonate in an acute performance context; as an acid-base buffer, bicarbonate is often taken by middle-distance athletes to increase buffering capacity and therefore combat the acidic effects of very high-intensity exercise. However, in the present context, we are talking about the use of bicarbonate supplementation to drive mitochondrial adaptations to training. After all, having a great buffering capacity doesn’t necessarily provide a huge performance advantage in the context of long-distance triathlon. However, given the high-intensity performance-enhancing effects of bicarbonate supplementation, this strategy may therefore actually make those gnarly workouts feel a little easier (as long as your gastrointestinal system can tolerate it!).
This field was initiated with a study showing training with bicarbonate supplementation increased the power output at lactate threshold, and high-intensity time-to-exhaustion, to a greater extent than placebo in relatively untrained people (2). These results were supported by a study in rats, in which mitochondrial respiratory activity increased to a greater extent following training in the bicarbonate vs. placebo group (1), as well as an acute study of untrained humans showing PGC-1α mRNA expression was elevated to a greater extent three-hours following a 10 x 1-min fixed workload interval training session with bicarbonate vs. placebo supplementation, again in untrained participants (4). Those who have done our online course LDT102 will be familiar with PGC-1α, which scientists consider the “master regulator” of mitochondrial training adaptation – therefore expressing greater PGC-1α mRNA in response to training is widely viewed as a positive effect.
Notwithstanding the obvious critique points here – that the studies above were done in either rats or untrained volunteers, and therefore may not be representative of effects in long-distance triathletes – this line of research is more compelling than most due to a 2015 study identifying a possible physiological mechanism behind this effect (3). Rather than supplementing with acid-buffering bicarbonate, in this study acid – that is, hydrogen ions (H+) – were supplemented alongside an acute interval training session, generating the reverse-effect (greater rather than blunted acidity). Muscle biopsies taken before, after, and 2-h after the training sessions demonstrated that PGC-1α mRNA expression was blunted by the acid supplementation, as was the mRNA expression of mitochondrial enzyme citrate synthase. Thus, this study supports that – independent of other factors – high levels of acidity in the muscle may inhibit the mitochondrial adaptive process.
This raises the question – should we all, therefore, avoid high-intensity workouts that generate an acidic environment in the muscle where we seek adaptation? Categorically, no. Many great things are going on in the muscle as a result of high-intensity, highly-acidic exercise that contributes positively to mitochondrial training adaptations, and we know that high-intensity exercise is a great stimulus for mitochondrial adaptation to training. These studies simply show that acidity per se, independent of everything else, does not seem to be helpful for the mitochondrial adaptive process. This is what makes bicarbonate – which makes high-intensity training easier – a possibly adaptation-enhancing supplement.
That is also not to say that going harder is always better. These studies were generally done using fixed-workload protocols; that is, the participants were instructed to push the same power with bicarbonate and placebo. Indeed, we view training adaptations as very specific to the intensities achieved during training; meaning that an 8 x 4-min interval session designed to develop your threshold – and therefore elicit the physiological disturbances seen at threshold - is better done at 98-100% of your threshold power rather than 102-105% of threshold power.
Whilst this is a very promising line of research, we will await further great studies of the effects of bicarbonate supplementation during endurance training in trained endurance athletes before we make firm recommendations here! If however you feel like a bit of self-experimentation and fancied having a go at this strategy to see what it feels like, you could try ingesting 0.2 grams of sodium bicarbonate per kilogram of body mass (therefore 13 grams for a 65-kg athlete) 90 and 60 min prior to an interval training session with high-intensity repetitions lasting three minutes or less. As many middle-distance runners will attest, you may find this rough on the stomach; so bear this mind if you do give it a go!
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