Many of my ultra friends have started experimenting with low heart rate training. The technique is based on the idea that we can train our body to run faster while remaining in an aerobic zone (burning fat versus carbs as a primary fuel). Many people have had success with the method. I’ve played around with the idea, but found the long, slow running to be too boring. It took the fun out of running.
For years, I’ve used a different technique that accomplishes a similar task. I purposely fast about 12-24 hours before some of my long runs, then do not eat during the run. This forces glycogen depletion very early in the run- my body burns it’s available stockpile of carbs. At first, the crash is severe. It’s what marathoners like to call “the wall.” My average pace decreases dramatically and I feel terrible. After a few such runs, the crash becomes a lot less severe and I’m able to maintain a much faster post-crash pace. Furthermore, the subjective feeling evolves from “horrible” to “eh, this isn’t too bad.” In essence, I’m training my body to deal with glycogen depletion and utilize fat as a primary fuel source.
With low heart rate training, the goal is to increase your aerobic pace to decrease finish times. This works well if you remain under that aerobic threshold, or the point where your body is using mostly fat as fuel, for the entire race. Personally I don’t like to have that limitation. I like the freedom of adjusting my pace based on how I feel, the terrain, available food, competition… whatever.
Low heart rate training teaches your body to utilize fat as a fuel, which allows you to run faster while using more fat and less glycogen. Regularly training on an empty stomach does something similar. Check out these articles:
Piece of evidence #1: http://www.marathonguide.com/training/articles/MandBFuelOnFat.cfm
Piece of evidence #2: http://www.ncbi.nlm.nih.gov/pubmed/20452283
The Elite Question
People sometimes ask how elite ultrarunners run races while consuming very little food. Here’s an example. At Bighorn a few weeks ago, Damian Stoy, the 50 mile overall winner, ran the race on three gels. That’s roughly 300 calories. He would have burned between 5000-6000 calories for the entire race. Assuming he started with about 2000 calories worth of glycogen (stored in muscles and the liver), he would have had at least a 2700 calorie deficit over the course of the race. Most of that 2700 calories had to come from fat.
How is it he could have maintained a winning pace (9:22) over rugged terrain with lots of climbing while fighting a glycogen deficit? he had to rely on fat as fuel. But he clearly wasn’t running below his aerobic threshold (he was breathing hard when he passed me).
I would hypothesize he does what most fast runners tend to do- eat very little before and during training runs.
What Would I Recommend?
Low heart rate training is an invaluable tool… for building a good endurance base. The low intensity dramatically decreases recovery time and limits the occurrence of injuries. I highly recommend new runners use the method to build an endurance base regardless of your goal distances.
Once you build that base, however, low heart rate training is of little value. The slow pace will limit your speed. Doing speedwork like fartlek runs, tempo runs, and interval training will help make you faster. If you’re planning to run anything over a half marathon, adding foodless training will continue to develop your ability to use fat as fuel. This will limit the negative effects of the “wall” that cripples so many runners.
Let’s look at a typical marathoner. Most marathon training plans top out at around 20-22 mile long runs. If a marathoner eats before a long run of that distance, it’s unlikely they will experience glycogen depletion during training. When running the actual race, they cross that line of glycogen depletion during those last few miles. Since it’s something their body rarely if ever experiences, it hits hard. Really, really hard.
They could eliminate this problem using a few methods:
1. Run the entire race below their aerobic threshold so they burn mostly fat. This would be the strategy recommended by the low heart rate crowd. The problem- you’re forced to stay below that threshold or you’ll hit ‘the wall.”
2. Eat enough to cover the deficit. In the case of a marathon, consuming 300-800 calories before or during the race will be enough to supply enough calories to cover that deficit. Personally I like this strategy, but it will fail if you can’t eat.
3. Train to run despite the wall. By training regularly on an empty stomach and purposely hitting the wall, you’ll limit the negative effects of glycogen depletion.
The best-case scenario would be to utilize all three. Build an endurance base using low heart rate training, During the race, eat if you can. If you can’t, your foodless training will guarantee performance won’t be impeded by a glycogen crash.
The Actual Training
I try to use this method at least twice per week. It’s pretty easy- just run long enough to deplete your glycogen stores. The longer you fast before your run, the earlier you’ll crash. If I eat immediately before a run, I’ll usually hit the wall around mile 18-20. If I fast for 12 hours, it usually hits around 13-15. If I fast for 24 hours, I may hit the wall within the first 5-8 miles. Your results will vary. Once you hit the crash, continue running for a few miles. I aim for about four to five miles.
The first few times are going to be awful. Your pace will decrease dramatically. You’ll feel drained. Stuff will hurt. You’ll probably feel depressed. Don’t worry- all of these symptoms will ease after a few training sessions. Eventually the “crash” barely registers. Furthermore, each subsequent crash experienced in the same run is lessened. In an ultra, this is important because most people decide to drop from races while in the middle of an especially bad low point. Make the low points more tolerable and your finish rate increases.
This method also teaches you to predict when glycogen depletion is about to occur. You’ll learn the subtle, often-missed early signs. In a race, these signs can be used as a cue to eat something, thus preventing the crash before it becomes worse.
I like to do these training sessions a few months before my goal race. Four or five sessions seems to produce good results. Eight to ten sessions seems to maximize the effect.
Training on an empty stomach can be an invaluable tool to your training if you plan to run longer races. It’s not difficult (though mildly unpleasant in the beginning). The potential benefits can be huge as it frees you from the shackles of maintaining an aerobic-zone pace and regular food consumption. Personally this method has been instrumental in my own training for 100 mile races.
What do you think? Do any of you do this now? Will you add it to your training regimen?