<pulserate> indicates the pulse rate of the diver during the dive, given in beats per seconds (SI units are used!) as a real number.
The pulse rate is considered to be constant until a next <pulserate> statement alters it.
(see also <waypoint>)
<!-- 60/min = 1/s --> <pulserate>1.0</pulserate>
<!-- 45/min --> <pulserate>0.75</pulserate>