Why Worry About Heart Rate and LT Anyway?
The good news about LT, and associated heart rate, is that it turns out LT is very "trainable". Lactate threshold typically occurs at 55 to 65 percent of VO2 max in healthy, untrained people. In highly-trained endurance athletes, lactate threshold is often greater than 80 percent of VO2 max.
In other words, you can train your body to process lactate at higher percentages of VO2 max, which means increased levels of speed before the onset of discomfort forces an end to the effort. In short, you can go faster for a given distance.
Studies have shown lactate threshold to be a reliable predictor for endurance race performance. VO2 max is not nearly as reliable. So, if you have been tested for VO2 max and your numbers weren't stellar, do not panic.
Can Heart Rate Determine the Maximum Fat Burning Zone?
The study by Carey verified what other researchers have found in past studies and that is, similar to LT, there is not a single "jump off the page" heart rate value that is your maximum fat-burning number. This value can be determined by laboratory tests, but few people want to go through frequent laboratory tests to keep tabs on that maximum fat burning number.
Though there is considerable difference between individuals if you are doing your workouts aerobically (between roughly 60- and 80-percent of maximum heart rate), more than likely you are doing good things for your heart and your hiney.
The research indicates that heart rate remains a valid tool for estimating the body's response to exercise and LT. Heart rate training zones can be used to design training plans for improved performance and to assess progress.
For triathletes, though you can estimate your LT in cycling from a test in running (or vice versa), it is best to confirm the values by testing in both sports or collecting data during workouts. This data can include rating of perceived exertion for similar workouts in both sports. Also consider your personal sport history when estimating your training zones.
I could not find any current studies validating the use of age-based heart rate training zones. Perhaps they exist, but I could not find one.
Your heart rate training values and LT heart rate should be based on your history and physiology. You can do very simple field tests to get started. As you gain fitness and experience, obtain the best field estimate of LT heart rate by using a combination of graphical test results, rating of perceived exertion, breathing rate and how long you can continue tolerating increases in pace before voluntarily stopping. LT is usually near the end of your pace-increase tolerance. Continue to refine your estimated LT values as you gain more experience.Search for a cycling event
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Carey DG. Quantifying differences in the "fat burning" zone and the aerobic zone: implications for training. J Strength Cond Res. 2009 Oct;23(7):2090-5.
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