Despite how good exercise makes us feel, we have to remember that it is a stress on the body. Our bodies can't distinguish between exercise stress and other stress. If you train with heart rate and pay attention to your data, you will notice changes in your resting heart rate over a point in time. This can be due to increased cardiovascular fitness (your heart rate becomes lower) impending sickness (your resting heart rate is higher than normal) or dehydration (resting HR will also be higher than normal). Many things can affect your heart rate.
Your heart is controlled by your autonomic nervous system (ANS), which is the involuntary part of your nervous system. This system breaks into two more branches, called the sympathetic and parasympathetic branches. When you're under stress, the sympathetic part of your ANS is active. It puts all systems on alert. The other branch, the parasympathetic branch, is the relaxed part that just goes about it's business when you're in a relaxed state. When your heart rate increases, that means the sympathetic branch is more active. Your heart rate beats in a more regular rhythm when you're stressed. That also means that your HRV (time between heart beats) decreases. (source)
When you're more relaxed, your heart rate decreases and beats only to meet the body's requirements. If you've ever taken your heart rate manually, I'm sure you've noticed that your heart rate doesn't always beat like a metronome. In this state, your HRV increases. Meaning that the time between beats increases. Because of these differences, HRV is a great indicator of the balance between the activity of the 2 branches of the autonomic nervous system and therefore it's an indirect measurement of stress. Higher HRV means lower stress. Lower HRV means higher stress (source)
Heart rate offers athletes as to how their body is responding to the stress of exercise as well as any other stressors they have in their life. Garmin and Polar have factored this into their watch technology with their versions of recovery advisors. They measure the stress put on your heart through your effort and give you an estimated time to full recovery. I say estimated because everyone is different. Some people recover faster than others. Also, what you do post activity will greatly affect your ability to recovery. If you don't eat and rehydrate immediately after a workout, that will delay your recovery. If you don't sleep well, that will also affect your recovery. There are several external factors that can affect how well you recover.
How do you know when you're fully recovered? That's the tough part for a lot of athletes. These days with all the technology available to track our fitness, there really is no excuse not to track your recovery. The latest Garmin (735xt) has an HRV recovery feature in it. And you can download various apps that will also track your recovery by monitoring heart rate variability.
For the last year I have been using HRV4Training. It is an app that I downloaded on my phone. I think it was $13. I chose this one because it didn't require a heart rate strap. The last thing I wanted to do was to sleep with my heart rate strap on. No thank you. Instead, this app takes a reading from your fingertip. According to the creators, this is just as accurate as using your heart rate strap because "current generation phones can be used to detect changes in blood volume during a cardiac cycle by illuminating the skin and measuring changes in light absorption using the camera" (source).
HOW FREAKING COOL IS THAT?!?!??!?!
How it works:
When I get up in the morning, I go and get my phone (I don't keep it in the bedroom) then go back and lie down. I fully relax and let my heart rate come back down before I take the measurement. The measurement takes 1 minute and it's quite bright since the uses light in addition to the camera. The app can link to Strava and Training Peaks so it can collect your workout data for analysis. Once the measurement is done, you answer a series of questions based on your training, how you feel, how your training was, if you're sore, if you drank any alcohol the night before etc. Based on your answers and your HRV, it will tell you if you're good to go, if you should limit intensity or take a rest day.
The app also allows you to track your CTL and ATL (fitness and fatigue). It gives you a V02 max estimate. You can analyze correlations between various things like sleep and heart rate. You can analyze HRV trends to see if you're adapting to your training. There is SO much information and data in this app. If you're a data junkie, then you'll love this app.
|Current bike fitness over the last 2 months. As you can see I've had a few hard bike workouts in there.|
|This is based on my last 2 months of riding. Some de-conditioning happening + going a bit too hard on my last two rides means that I have to be careful with my effort over the next little while.|
|Even though I'm in the moderate category for injury, my training is still considered well polarized.|
Training this way has definitely made me pay more attention to recovery and patterns that start to emerge when I don't necessarily take the best care of myself. The older I get, the more important tracking recovery becomes.
How to you track your recovery? By feel? By resting heart rate? Or not at all?