@CharleneMarie72 wrote:
I appreciate your response and tips. So from what I am understanding, I used up my readily available carbohydrates for the first 4 miles (which would equal 350 calories of just digested breakfast, F, 29, 130lbs- burn about 75-80 per mile) and then my body started metabolizing fat for energy which resulted in the drop in HR.
I'm also understanding from your reply that I need to "train" my body to metabolize fat if I am planning on distance runs. Basically what I am doing is hard-core speed work and not allowing my body to practice using fat stores.
You say I can see how this would happen by running a 10K in an hour. Would my HR drop based on the food that I just ate? Also, why was my heart working for hard and my perceived exertion was maybe a 7 with the exception of two steep hills climbs.
Interestingly, I ran 2.5 the day before and never once got out of cardio. The run was awful and I attributed it to bad fueling the day before and over dressing for the temperature. Maybe it's because my body doesn't know how to perform in cardio (or just isn't fit to).
Thank you again for your time in responding to my post. I really appreciate your insight and time
Oh no, nothing that extreme at all.
When you start out the first 30 min may be say 80% carbs at your high intensity and slowly lower to 70% carbs say. The ratios total depend on fitness, and how well trained that fat burning engine is for how fast they change.
You wouldn't use up available carbs that fast at all, even if you were using 100% of them.
And it's not what you ate (though that does come in to play), it's what is already in the muscles, where the majority of carb stores are.
The fitness level also determines how many of those carbs are taken out of the blood stream supplied by the liver first, which is smaller amount available, or taken out of the muscles, much bigger amount available. That takes a bit of time. HR won't show that part, but it's a part of fitness level.
So the ultimate foul up for endurance cardio is never train the lower aerobic system, always going hard. So the ratio takes longer to switch to better fat usage, the carbs used at first are from the limited liver amount, and that has negative of when blood sugar runs low, your brain gets tired, that's the first set-in of fatigue, usually 60-90 min depending on fitness and how hard you went out.
That's what you need mid-race fueling for, replacing blood sugar your brain wants. You could never eat enough to help the muscle with their level of burning.
And once those muscle stores run out - "the wall" is hit. With little to no carbs to burn and only fat, your pace is going to slow way down, and mental ability is shot with low blood sugar. Muscle breakdown will occur to try to provide some carbs as converted, though it's been happening anyway after 60-90 minutes to a small degree.
But if you train the fat burning system, you switch to fat burning faster, you can run faster while using a higher % of it, putting off the wall until hopefully the end of the race so you never feel it, and blood sugar is spared too.
This usually won't matter in a 10K if you've done enough even high in training. You'll have enough carb stores usually to go hard.
The problem is in training, because now you better eat enough, and enough carbs, if you want a decent workout the next day or day after. There's a reason why several days of recovery are recommend after a race, it's hard on the body.
The food you just ate has little bearing on selection of energy choices. You already got fat floating around available, muscles have some so no need for release from fat stores which doesn't happen right after meal, and actually studies have shown when cardio is intense enough, the normal ratio is used despite having just eaten.
Many people if they make every workout in 2 weeks a max of recovery HR zone, which your zones may call that fat burning per the recent fad name, they notice they have started to speed up already, despite keep HR low. After 4 weeks total, may even reach old pace, with lower HR. Then you just keep getting faster.
You can improve the fat burning side of the aerobic zone much easier and more than you can improve the carb burning anaerobic line. There is little room for improvement there handling lactic acid better, which is about the only improvement available.
And the fat burning side helps the carb burning side too - but not vice versa.
The difference in HR and perceived effort was likely that running outside feels easier, compared to a treadmill. Studies have shown when runners attempted to do the same pace on the treadmill as they felt comfortable doing on the track, it was actually slower with lower HR, it just felt the same.
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