Morning Resting Heart Rate (MRHR), when tracked regularly, is an easy method for monitoring fatigue levels, understanding how well you’re adapting to workouts, and can help prevent long-term overtraining.
I like to keep an eye on my resting morning heart rate trends over time, and especially in the two or three days after a hard sessions. If it’s significantly elevated from its normal average (7 or more beats per minute), that’s a sign for me, that I haven't fully recovered from the workout or maybe the daily stressors of . . .