Training tips from the first man to ever swim the length of the Amazon River. 1) In 2007, aged 52, Slovenian Martin Strel became the first man to swim the length of the Amazon. See www.amazonswim.com 2) “Swimming for 12 hours a day, I’d burn 10,000-12,000 calories (42,000-50,000 kilojoules). Food was really important. I’d eat…