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What do heart rate monitors do, and do you need one?
By Seiji Ishii
Heart rate monitors are ubiquitous for almost anyone training for nearly anything. Yes, they measure heart rate, but what does this mean, and what do you do with this information? And do you need one?
The intensity of Exercise and Fuel Sources
Training efforts are programmed and described by three parameters: intensity, duration, and frequency. Intensity is the most important, and a lot of effort, technology, and study is aimed at determining the best way to test and monitor it.
Athletes and coaches manipulate aerobic training to improve fat utilization, as it is in almost unlimited supply, and it’s the most efficient way for the body to produce energy. Even skinny chumps like Keefer have enough fat stores to drive almost indefinite movement. The more intensity an athlete can fuel with predominantly fat, the better, as muscular fatigue starts when the body switches to carbohydrates as the primary energy source.
So, knowing when the body switches from using mostly fat to using mostly carbohydrates is essential. To bet better at burning fat requires, well, burning fat, so training at or under this breakpoint is a primary goal of aerobic exercise. And that’s where heart rate monitors enter the picture; heart rate can be an estimation of what the body is using for fuel – but it’s just that, an estimation and not a direct measurement.
How the body reacts to fuel sources
When exercise intensity is low, it’s easy to carry on a conversation, and breathing is possible through the nose. At these levels of output, half of the energy or more comes from fat. When the intensity rises to the point where speaking in full sentences or breathing through the nose is not possible, the breakpoint is called the First Ventilatory Threshold (VT1) or Aerobic Threshold (AeT). It corresponds to a blood lactate level of 1mMol/L above baseline (or at 2mMol/L), indicating that byproducts of carbohydrate metabolism are accumulating.
As the exercise intensity increases, the body relies on more carbohydrates, and the associated blood lactate levels rise. But incredibly, the slow-twitch muscles of the body can aerobically utilize it for fuel. This ability to use lactate as fuel is why pure aerobic fitness is the base; it cleans up the “trash” produced by higher output. The more aerobically fit you are, the better you perform at higher intensities as you can remove lactate at a quicker rate.
As the intensity of exercise continues to increase, the ability to use lactate for fuel gets overrun by the rate of accumulation. This rise in blood lactate triggers deeper breathing as the body attempts to blow off excess CO2 produced by the higher rate of carbohydrate metabolization. This breathing breakpoint is evident and is the Second Ventilatory Threshold (VT2) or Anaerobic Threshold (AnT). After this deep breathing starts, the clock starts ticking, and the athlete is operating on borrowed time. Slowing down is an inevitability.
OK, so do I need a heart rate monitor?
If your primary goal is to improve aerobic capacity, and it should be for the first 8-12 weeks of training at the very least, then no, a heart rate monitor isn’t necessary. You could just pay attention and stay at or below VT1. And remember, breathing is a direct reflection of what is going on inside the body, not an estimation. So in a way, monitoring breathing can be more accurate than a heart rate monitor.
But – you have to pay attention. And – you don’t have an easily downloadable form of data. It’s a personal choice; can and will you pay attention to your breathing (which to me seems just as easy as looking at a heart rate monitor), and do you want or need that kind of data?
Other zones of training exist outside of VT1 and VT2, and they are useful tools to enhance training further. There is also a relationship between ventilatory thresholds and heart rate that is informative. I will delve into these subjects in the future here on Keefer Inc. But for the majority of aerobic training, the only “zone” that matters exists below VT1.
The Bottom Line
Most of your off the bike, aerobic training should be focused on raising the ceiling of your aerobic capacity and should at or below VT1. Remember that the mechanisms driving this low-intensity work also play a pivotal role in how well you do at higher intensities. And to know during training when you are approaching the threshold of aerobic capacity can simply be done by monitoring breathing. So a heart rate monitor is not an absolute necessity.
But heart rate monitors can provide data that can be helpful, and they can help determine other factors when combined with ventilatory threshold monitoring.
So, don’t let the lack of a monitor stop you from working on the essential part of aerobic training, and tune in for future installments where I will discuss testing to determine what heart rate corresponds to VT1 and more.
