People Who Have Done a Lot of Endurance Training Can

Multiple Choice

People who have done a lot of endurance training can have a resting heart rate of 50 beats per minute compared to the normal resting heart rate of 70 -80 beats per minute. This decreased heart rate in trained individuals is the partly result of

A) endorphins released from the brain which have an inhibitory effect on heart rate.
B) sympathetic activity becoming more active and parasympathetic activity becoming less active at rest.
C) decreases in both sympathetic and parasympathetic activity.
D) increases in both sympathetic and parasympathetic activity.
E) parasympathetic activity becoming more active and sympathetic activity becoming less active at rest.