If you could measure only one thing on your body every day, heart rate variability would win hands down.
Heart rate variability, or HRV, refers to the amount of time that elapses between heart beats. In general, a higher HRV (i.e., more time between beats) is better, because it indicates less stress on the body.
This information is invaluable for athletes. If you measure your HRV and it's high, you're ready to kick butt during a tough workout. If it's low, you should take it easy and focus on recovery.
For more in-depth information on HRV, check out this article.
You cannot track your HRV like your heart rate. You need some type of technology to detect the minor differences in time between beats.
The ithlete Finger Sensor does just that.
The sensor that slips over your finger detects your heartbeat using infrared light, similar to how a pulse monitor works at a doctor's office. The sensor connects to your smartphone with a headphone jack and feeds the data into the ithlete app.
Once you launch the app, the finger sensor calibrates and shows your heart rate information. All you need to do is sit still and start the test. Follow the breathing instructions displayed on your phone screen, and after one minute you will have your HRV.
This data is tracked on a day-to-day basis to establish your baseline, so the software can determine if your individual HRV is high or low. Not everyone is the same.
I found this data to be incredibly powerful. After a good night's sleep, my HRV tended to be quite high. But after hard day of training and a late night, it was significantly lower. This allowed me to make informed decisions about the intensity and volume of my next workout.
Although the test lasts only a minute, the sensor sometimes takes a few minutes to calibrate. On a few occasions, I couldn't get it to work at all. But they appeared to be isolated instances.
Overall, the ithlete Finger Sensor is proving to be an invaluable tool in my training toolbox. You can purchase the ithlete Finger Sensor at myithlete.com for $69.99.