It could be a "fatigue factor" issue but even more critical, the problem with training at heart rates (H/R) that are too high (and doing so for long periods)....is that this DE-trains your metabolism. Stick with me, here.
Fat (as a fuel-source) is VERY complex. That's why it was STORED in the first place. It requires oxygen (as much as 10-20x more) to be metabolized (used), compared to more simple fuels. The MOST simple fuel is a monosaccharide. Mono means one saccharide means sugar. Now, this monosaccharide requires one oxygen "unit" in order to be used. On the other hand, FAT can require up to 20 "units" of oxygen..
Now here's the problem. You can store up to about 90 minutes of the fuel-derivative (called glycogen) of those saccharides. This means storage of carbohydrates, both mono & poly...simple & complex. After 90 minutes or so............YOU BONK! another words exercise-induced hypoglycemia. And to further complicate this, these calories cannot be replaced at the same rate that you will use them. TRUST me here. You'll burn up to 700+ calories/hour, yet your liver will only process/absorb about 250-300/hour. So where does the rest of your fuel come from? You got it.......................FAT.
Using FAT is preferable because you get 9 calories per gram rather than 4 calories per that same 'gram-size' held in carbs. Twice the fuel per unit of measure!!! Plus, since it's stored, you carry a lot more calories, enough for 24 consecutive marathons!!! (And I've been to Shoney's buffets where I swore that someone was carrying enough for a coast-to-coast trip.) This is not so much an issue when the race-event is sub-90 minutes. But if you TRAIN above your Maximum Aerobic Function (MAF) zones, and rely exclusively on sugar as a fuel source, you very well may have:
-made your heart (as a pump/muscle) stronger
-increased your cardio-pulmonary ability to remove/process blood-lactate (lactic acid)
-applied more force to the propelling parts (muscles)
However, if this comes at the expense of delivering fuel efficiently for the entire 120+ minute event, you may be fast through 90 minutes, but a lot of good that does if the event is long enough that even the best Olympians finish it in 1:45
In other words, Jeff Gordon's racecar is A LOT faster than my car. But give him a quarter-tank of gas and I'll take him in a 300 mile race every time.
We even test one's fuel-economy (because that's essentially what we're talking about) in the lab. We call it substrate utilization. In English, this means "fuel-usage ratios." This test is a measure of the ratio of fats-to-carbs you're using to propel yourself at given heart rates. It's ideal to use a higher percentage of fat at higher heart rates.....OR.......use a higher percentage of FAT at lower heart rates, yet be knocking down good PACE at lower heart rates.
The best triathletes, cyclist, and runners in the world all have the ability to optimize fat-usage at near race pace intensity. Lance is about as good at 120 miles as he is at 20 miles. So how does he train for this and what is the "training secret" of the world's best elite endurance athletes? Well, these guys use a "staged" approach for their training. We call this "periodization."
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Stage 1 - optimize your fat-using ability by training aerobically (w/
oxygen) Stage 2 - develop your speed (your "output"....i.e.: pace-per-mile, watts-produced, strokes-per-25 yards, etc...) at aerobic levels. We call this your 'maximum aerobic function' and we test it in "MAF-assessments" Stage 3 - only when your aerobic efficiency has reached a plateau do we insert increased intensity work.......intervals, tempo, repetitions, etc. The work we DO insert must be specific to the event targeted. (I've seen coaches prescribe "bike-sprints" to triathletes of 30-90 seconds?!?!?!. Odd, because at the end of a bike leg, I'm wanting to LOWER my heart rate to set up the run, not sprint to the dismount line entering T2) Stage 4 - Know when to get off the intensity and when to sharpen, taper, and rest for an optimal race. |
Stages 1 and 2 are what make the foundation. This type of training makes up 85-95% of every training minute you spend. (In fact, we recommend that all of our athletes read about how, in the 1950's, Arthur Lydiard coached Peter Snell using 100+mile weeks and Peter Snell was a 800 meter runner!! And we recommend reading the book "Training For Endurance" by Dr. Phil Maffetone.)
Stage 3 is "science"..........the fast stuff. The hard work..........no pain no gain and the exciting stuff that everyone brags about to their buddies. This is type of training that fills the pages of Triathlete magazine. But STILL, at the end of the day only represents 5-15% of the total mix and only at the right time.
Stage 4 is where a good coach comes in handy. "Tapering" is more art than science and involves a lot of trial and error. Some athletes never tap into their final 5% of race potential.
So to answer your question, training at higher heart rates is ok, but only after developing your aerobic base. Higher heart rate training should be done only at strategic points in your training and for specified durations. This is probably more than you wanted to know, but I get the impression that you're looking at workouts (the trees) and you need to see the entire development of your ability (the forest).
For more information on the TRImyCoach.com training programs, you can visit our website at www.TRImyCoach.com
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