Something I made reference to in my first post that I want to expand on a bit further is the concept of heart rate based training, sometimes referred to as heart rate training or heart rate interval training, although the last is slightly misleading because not all heart rate training is interval based. Put simply, heart rate based training is exactly what it sounds like: using your heart rate to control your training. People have been doing some flavor of heart rate based training for many years, but recently there has been a resurgence, because of cheap and popular wearable tech that can tell you your heart rate easily and quickly (and sometimes even accurately!). Sometimes people get a bit too hung up on the "heart rate" part. A better word for what we're doing might be "biofeedback training", because really it isn't the heart rate, it's the feedback loop based on concrete, observable biological behavior of the human body. Why is this important? Well, because the human brain is a really bad observer of our own biological processes. Yes, of course, we know when we're exercising, and we know when we are sweating or breathing hard. But that information is really inaccurate. Early forms of this kind of training used something called RPE, which is still popular with some trainers, and particularly in settings where monitoring equipment isn't available. RPE is just an acronym for Rated Perceived Exertion, which is a fancy way of saying "try to observe how hard you're working". Athletes assign themselves a number from 1 to 10. What does 1 mean? Well, that's left intentionally a bit vague because every body is different. 8 or 9 should be "short of breath". That kind of thing. Some people use the "sentence word syllable" method, where how hard you are working is measured by how much of an answer you can give if somebody asks you a question. All of these methods are trying to get at a core concept: detecting how hard your body is working, so that we can use that information to design a workout that meets certain needs. For example, if you want to build cardio capacity, intervals of certain lengths that push you into the "red zone" for certain amounts of time can do this. But to really get this kind of training right, the data should be accurate, and scales like RPE can only take us so far. What we want to know is how hard the body is working, and one of the best ways to tell that is to use heart rate. Heart rate is, of course, individual to some extent. Your age, gender, fitness level and genetic factors can tweak what's considered a "high heart rate". But this rate is fairly stable from day to day (although it can change slightly as you get in better shape), which makes it easy to measure your personal "resting" and "working really hard" heart rate, and then use those numbers to control your intervals. This is what Cycology and other studios like it do; they measure your rate (either by just guessing based on your age and gender, or by actually putting you through some tests) and use that to create "heart rate bands", such as green for 60-70% of max, or red for 90-100% of (safe) max heart rate. Then they design workouts around asking you to work hard enough (typically by adjusting resistance on the bike) to "hit the orange zone" or "stay in the green". That way, each person can get the individual workout that fits their body best. To do this, of course, we need heart rate monitoring equipment, some wireless tech and a bit of snazzy setup; but in the last few years, this has become accessible and popular enough that you can ask folks to wear these heart rate monitors (or, like me, bring their own) and they will do it.
There are two main types of heart rate monitor and I've used both. The first, and most accurate, is worn around the chest and detects electrical impulses from the heart. They have been around forever, and they can be very accurate when worn correctly. Problem is, they often aren't worn correctly, and for some people (like me) they just feel really uncomfortable. So, the second kind which is growing in popularity is wrist-mounted sensors. These have many advantages; they are small, easy to use and comfy. And the best ones, when worn correctly, are fairly accurate. But they have a tendency to "drop out". They rely on comparing the color of your skin as blood flows past (yes! really!) , and sometimes they just sorta don't catch up for a bit. Even at the best of times, they have some lag, because the software has built in error correction which uses consecutive measurements to try to soften the data. So, for now, if you want the best, you gotta stick with the chest.
I find heart rate based training enormously useful for myself. Often, I will think I am "working harder", but a quick glance at my wrist will tell me I'm just fooling myself. And usually, when I use this data to do a deeper self-check, I realize that I was just engaging in wishful thinking. The heart rate monitor "keeps me honest". if you will, and that is often the difference between a great workout and a mediocre one.