Heart Rate Variability (HRV) is a fantastic tool that I've just recently implemented into my training regiment. Everyday, at the same time, I measure my HRV... it takes only 3-5 minutes... and assists you in deciphering whether you can go hard that day or you should take it easy. You'll also be able to decipher if you've recovered after rest days. It's extremely simple, you use a bluetooth monitor with an app... and voila... in 3-5 mins. you got your reading.

Many of us go by feel when we're training; this tool helps by quantifying data and validating how you're feeling.

Stay healthy and maximize your training.