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- Alex Hutchinson (@sweatscience)
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Training on “empty” — i.e. with low carbohydrate stores — is one of the hot topics in sports nutrition these days. (I’ve posted on it a few times, for example here and here.) Louise Burke of the Australian Institute of Sport has a good summary of the current thinking in the ACSM’s Sports Medicine Bulletin.
Traditionally, athletes have approached their daily workouts to train as hard as possible, using strategies that promote good performance, just as they would in a race or match. In many sports, these strategies involve fueling up with carbohydrates before, during and between workouts to sustain the capacity to produce power. Recently, however, scientists have proposed an alternative approach…
I won’t bother trying to summarize the whole thing, because Burke is already compressing a lot of information into a small space — if you’re interested in the topic, it’s worth a read. A couple of minor points to highlight, though:
While some publicity surrounding this study suggests otherwise, the outcomes from [training low] weren’t achieved by following a low carbohydrate diet.
This is about having low carb stores for a short period of time, for instance by depleting carbs with a prior workout, not being in a chronically low-carb state. And a very interesting point:
It makes sense that sessions completed at lower intensity or at the beginning of a training cycle are best suited for, or perhaps least disadvantaged by, [train low] strategies. Conversely, quality sessions done at higher intensities or in the transition to peaking for competition might best be undertaken with better fuel support.
In other words, nutrition should be periodized. What you eat — and how you think about the relationship between your food and your performance — should be different in base phase than it is come competition time.
Burke keeps mentioning “muscle chemistry” – I’m not sure exactly what that means. Could you elucidate?
Also, the first study she links seems to have the confounding factor of recovery time – the “training low” leg gets a full rest day between workouts, while the “training high” leg never gets any rest. So I’m not sure that study is about glycogen stores at all!
I’m so glad to see some attention paid to this issue. Too often, athletes (and even weekend warriors) fall into the habit of thinking one way is the only way. But as with so many training issues, changing things up based on circumstance is often the best for our bodies and programs. Thanks for a great, concise look at the issue.
I run everyday before going to work and need to have at least a banana in my stomach before going out the door.
@Jessica, @Dog: thanks for the comments!
@BethSkw: I totally agree about the problems of interpreting a comparison between training every day and training twice a day (with a very short recovery) every second day. Seems like there would be a lot of different things going on besides glycogen. It’s very challenging to actually isolate the variables we’re interested in, because you can’t just empty glycogen from muscles without using them, and that’s precisely the variable you don’t want to change…
As for “muscle chemistry,” there are some straightforward factors (like the amount of glycogen the muscle can store) and some more complicated stuff that’s getting a little out of my depth. For example, Burke writes:
“Other studies have found that exercising while fasted (a pre-breakfast workout completed on water) was better at changing the chemistry of the muscle than training while consuming carbohydrate.”
The study she’s talking about (which I blogged about here) found that a group that trained for four weeks without breakfast boosted the amount of glycogen that their muscles could store by 55%, while the control group that ate breakfast only boosted glycogen storage by 3%. The study also looked at “citrate synthase (CS) and 3-hydroxy-CoA dehydrogenase (HAD)” activity in the vastus lateralis muscle. These markers relate to the oxidative capacity of the muscle and its choice of fuel (fat vs. carb).
Again, this is a little out of my depth! But basically, she’s saying that studies have found changes at the cellular level that we might reasonable expect would have some sort of impact on performance — but that hasn’t yet translated to any actual performance boost.
My students just wrote their final on Tuesday, and this ACSM article was a part of their exam!
I think a few of the underlying messages are that ‘it depends’: athletes need to work with someone to monitor all those variables (Although I am biased because I’m the one working with athletes!) and that sports nutrition is actually significantly more exercise physiology than most realize…
I look forward to reading your book Alex!
Interesting, similar effect to the intermittent fasting approach seen in some bodybuilding circles? Some bodybuilders claim strength and lean results using this approach. I was intrigued by this approach as a geezer soccer player who at 48 is more worried about strength loss(burst speed) while running both on the pitch and when I run 5k and 10k races. N=1, I have great results with morning runs in a fasted state. I also seem to do much better on race days when I show up fasting.
Alex, looking forward to the book.
I have an N=1 story also. I’ve been training on empty for several years now. I have done 3hr runs on empty, with no intake during either. I put it to the test by racing on empty, an ultra-marathon, 40mile mountain trail, which I won. So at least for me, it works !
There are huge adaptation mechanisms going on that have not been properly looked at yet. ITMG, PPAR, IL-6.. to name just some. Already there have been some adaptation studies – http://www.ncbi.nlm.nih.gov/pubmed/21051570
The current studies have not looked at the time dependence aspect of it.. i.e. what does training this way for 2yrs do versus 4 weeks ?? Also, nutrition is huge.. Insulin Sensitivity, Fat Adaptation, Nutrient Partitioning, Upregulated Lypolysis Enzymes, etc… diet affects these. Again, have they looked at individuals with diets that improve all these pathways and therefore enhance the training on empty strategy ??
lots to still find out Alex, we need to talk !
Thanks for the nice comments, guys. Noa, your students are obviously going to be pretty darn up-to-date! That’s awesome.
Russell and Barry, I guess we can combine your experiences and call it n=2. It’s surprising to me: in all the discussion I’ve heard of training on empty, the assumption has been that the end result is that you race more effectively WHILE FUELLED. Of course, avoiding potential gastrointestinal problems might be one benefit of racing on empty; but from a fuelling perspective it’s certainly an unorthodox approach.