Quote Originally Posted by Cassandra_Cain View Post
Good example....didn't get a good night of sleep? your HR will be higher than normal even if you keep the workload the same. riding high at altitude? your HR will be lower and so will the stroke volume, lowering your VO2 max - thus your performance. not drinking enough water or are dehydrated? yeap, HR gets affected. Worrying? uh-huh, more HR fluctuation.

In each of these cases, if you went strictly by HR, you'd end up altering your riding without needing to.
When riding at altitude or dehydrated your expectations of your performance should be altered.

V.