Skylar wants to improve her fitness level for a chance to be on the rowing team. She has been rowing 2−3 times per week at 9 m. p.h. at her local gym for 30 minutes, with her heart rate increasing to between 155−170 beats per minute. She is using the frequency principle to improve her fitness level when she increases her: a) days rowing to 4−5 per week
b) heart rate to 165−180 beats per minute
c) rowing speed to 11−12 m. p.h.
d) time rowing to 40−45 minutes per session