The best swimmers among female Ironman triathletes complete the swimming portion of the event in 50 minutes to an hour. At the World Championship, the cutoff time for all competitors is two hours, 20 minutes. Any participant who fails to complete the 2.2-mile swim within that time is eliminated from the competition.
There are two sources of this essential vitamin, including vitamin K1, or phylloquinone which is primarily found in green leafy vegetables and vitamin K2 or menaquinone which is synthesized by certain intestinal bacteria.
Bacteria in the colon (large intestine) can also convert K 1 into vitamin K 2. In addition, bacteria typically lengthen the isoprenoid side chain of vitamin K 2 to produce a range of vitamin K 2 forms, most notably the MK-7 to MK-11 homologues of vitamin K 2.