During running your main fuel for your muscles and brain is
from carbohydrate – from your body’s muscle glycogen stores and glucose in the
blood and from fat. To keep it simple if your running session is about 45 mins
and an easy pace then you should not need to refuel your muscles during this
session. However if you have a more intense running session scheduled such as a
fartlek, interval training, tempo session, high amount of high intensity hill
reps etc. and your session is 30 – 60 mins duration then it may actually be of
benefit to consume some carbohydrate during the session.
Now you think I am a
real nutter don’t you… First let me explain why? And then how? Then
you can determine if I am nutty or not.
Running that last for approximately 1 hour does not tend to challenge
your muscle glycogen fuel stores so why would consuming carbohydrate possibly
be beneficial to your running performance?
Carbohydrate supplementation immediately before and during
exercise for high intensity running (>75% VO2 max) between about 30 mins to
1 hour has been shown to improve running performance (Rollo et al 2010). A study by Rollo and
colleagues investigated whether mouth rinsing with a CHO-electrolyte (CHO-E)
solution would influence the performance of a 1-h run. Runners consumed a 6.4%
carbohydrate-electrolyte drink immediately prior to their 1hr treadmill run and
thereafter every 15 mins during the run. They reported a 2% improvement in
performance from the CHO-E mouth rinse compared to placebo (dummy test).
Studies suggest that you do not need to ingest the
carbohydrate but just rinsing your mouth with carbohydrate should do the job. Also
if you do ingest the carbohydrate solution there does not appear to be a
disadvantage. So perhaps give it a go! Mouth rinse or ingest a carbohydrate
solution next time during a high intensity shorter duration run and see whether
you notice any effects – suggest you trial it more than once to be able to
interpret better whether you notice any change. Some people get gut upset when
they ingest carbohydrate/food during intense sessions so you may steer more
towards the mouth rinse option. Also
note that the effect is due to the carbohydrate, the electrolytes did not
appear to influence the effect.
The effect is possibly due to a Central Nervous System mediated
action via oral and / or gastrointestinal carbohydrate receptors (e.g.
activation of receptors linked to the brain). Further investigations suggest
the CHO mouth rinse stimulates the supra-spinal message system of the brain and
this relates to motivation and reward.
Rollo I, Cole M, Miller R and Williams C (2010) Influence of
mouth rinsing a carbohydrate solution on 1-h running performance. Med Sci Sports Exerc.42(4):798-804.