effort: use of physical or mental energy; hard work; "he got an A for effort"; "they managed only with great exertion"
Exertion is a concept describing the use of physical or perceived energy. It normally connotates a strenuous or costly effort related to physical, muscular, philosophical actions and work.
Exercise above that required for a relaxed swim in calm water. The main causes of exertion during a dive are current or extra equipment (such as for photography or specialty diving).
"The sense of exertion is not speedy, aggressive or heavy handed; rather your are relaxed and energized. You are constantly inquisitive, but your awareness is also disciplined, so you accomplish every activity without difficulty, and you inspire those around you to do the same." (pg 165)
(noun) -- action; something physical that is tiring ch. 10
Effort, work. Some people have asthma symptoms after a time of strong exertion such as running very fast.