The ‘train low, race high’ theory seems to turn conventional wisdom on its head.

It suggests that, although low muscle glycogen is known to blunt performance on the day of a race, when it comes to training, some glycogen depletion might actually help boost endurance.

Scientists believe that this is because low-carbohydrate training (ie training performed when stores of muscle glycogen are low) can help switch on certain genes in the muscle, which enable a greater proportion of energy to be derived from fat stores.

This in turn has two potential benefits: firstly, it helps endurance athletes such as cyclists achieve lower levels of body fat, increasing power-to-weight ratio. Secondly, by increasing fat-burning capacity, muscle glycogen can be conserved during long races/sportives, thereby prolonging endurance.

Unfortunately, since even a small drop in muscle glycogen can make your muscles feel heavy, leaden and tired (especially at higher workloads), low-glycogen training is not particularly pleasant or enjoyable and may result in the abandonment of your cycling session – not good at all for increased fat-burning! But now new research published by Australian scientists suggests that there could be a way round this.

The science

In their study, researchers investigated whether a low dose of caffeine taken one hour before training could help to at least partially overcome the fatigue and drop in power commonly observed when low-glycogen training is attempted.

Twelve well-trained triathletes performed four sessions of high-intensity cycling intervals (8 x 5-minute bouts at each triathlete’s maximum self-selected intensity) under four different conditions:

- Normal levels of muscle glycogen, a no-caffeine (placebo) pill beforehand.

- Low levels of muscle glycogen, a no-caffeine (placebo) pill beforehand.

- Normal levels of muscle glycogen, plus 3mg per kilo of body weight caffeine beforehand.

- Low levels of muscle glycogen, plus 3mg per kilo of body weight caffeine beforehand.

High-intensity intervals were used in this study because intense training is very challenging when muscle glycogen is low, and any benefits from caffeine would have to be significant to observe an improvement.

In a nutshell

The results showed that both pre-exercise muscle glycogen levels and whether or not the subjects used caffeine beforehand affected performance.

When no caffeine was used, starting the trial with low muscle glycogen reduced power output by around eight per cent compared to starting with normal levels of glycogen. When caffeine was used in the normal muscle glycogen trial, average power output was boosted by 2.8 per cent.

In the low muscle glycogen trial, performance was boosted by 3.5 per cent (ie, was only 4.5 per cent down compared to the normal glycogen, no-caffeine trial).

So what?

The key take-home message is that caffeine can enhance power output regardless of your initial level of muscle glycogen – good for those who want to perform some low-glycogen training.

Granted, it wasn’t able to fully overcome the negative effects of starting a session with low muscle glycogen, but remember, these trials used high-intensity intervals, which would have been very negatively affected by low glycogen.

For less-severe sessions of low-glycogen training, a little bit of caffeine could put some zing into your legs and help you through.

Just a word of caution: low-glycogen training is stressful for the body. Novices should not use it and even experienced cyclists should only use it sparingly (once, or at the very most, twice per week).