Time of Day Does Matter in Training, Science Says So…

If you have read any of my past TriLab blog postings, you’ll know that I have a penchant for very early morning workouts. I’ve been known to hit the bike trainer for intense intervals at 4:30am with little in my stomach and my contact lenses still settling into place. I often swim/bike/run at crazy early hours and have always looked at this as a good thing, it doesn’t disrupt my family or work time and I feel energized through the day from my early morning exercise endorphin dump.

So “What’s the problem?” you may ask. Well, it all began during a recent blood lactate test on the bike with Coach Gareth. For an easy understanding of blood lactate testing you can check my earlier blog postings but very quickly…lactate accumulates in the blood and is used as an energy source by the body. As effort increases lactate reaches a point where the body cannot use it effectively and it accumulates as a waste or by-product. This accumulation of lactate is an indicator & predictor for performance.

We discovered something interesting from my recent blood samples. Over the past couple of months, my heart rate at a specific power output has decreased significantly. This means that my body isn’t working as hard to maintain the same speed. It’s an indicator that I have developed more general fitness which is a good thing. On the other hand, my lactate levels at those same power levels have remained largely the same, which shows that my physiology has not adapted quite as quickly to burning fats over carbs. There are several reasons for this but one of them could be that I’m not getting the maximum from my quality sessions when they are performed in the wee hours.

In the early morning hours, I’m not properly fueled to burn fats as I’ve just come out of 7-8 hours of fasting. My body temperature is very low to start. As a result, I end up pushing higher power wattage to get my heart rate into the ‘proper zone’ for the prescribed workout. My body is not at all warmed up when I start and muscles are not firing properly and efficiently. I am also less focused, as I’m still kind of groggy for the beginning of the workout. All of this could be leading me to less effective workouts when I’m supposed to be doing true quality sessions. High intensity intervals on the bike, in the pool or on the run are very specific, somewhat risky and should be treated with great care.

Research shows that people who can burn primarily fats during exercise are more efficient (go faster for longer), than people who burn a higher percentage of carbs. We all burn both fats & carbs, but we have a finite amount of carbs and an infinite amount of fats to burn, to we want to train our bodies to burn primarily fats. Maximizing each training session is essential in training the body to make the shift.

As a result of this last test, I’m shifting all of my quality workouts to the afternoons and only doing easy aerobic intensity workouts in the early morning during the week. Something like an easy aerobic spin/run is much more appropriate for the early morning than lung-busting Vo2 Max efforts. In my case, the harder stuff is better when saved for the more human hours. This is just my personal experience, but it is all fairly backed up by science and will hopefully continue to lead to more improvements across the 3 disciplines.

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