Triathlons are becoming hugely popular today as they use three different disciplines: swimming, cycling and running. Triathlons are one of the healthiest forms of exercise as they promote the use of all muscle groups and the swimming and cycling part are low impact and thus easy on the joints. There are various distances used which start with a sprint (750m swim, 20k cycle, 5k run), olympic (1.5k swim, 40k cycle, 10k run), half ironman (2.2k swim, 90k cycle, 22k run) and ironman (3.9k swim, 180k cycle, 44k run). Ironman is one of the toughest sporting challenges known to man. Sinus bradycardia is common amongst triathletes and is nothing to worry about. Mary Ellen got an ECG done in 2015 and it showed up a heart rate of 42 bpm which is much lower than the average 60-100 bpm but is a sign of fitness. There is a theory out there that the less your heart beats, the more time you have in life.