text: Grainger, 40, was involved in many different sports before taking up rowing.
  And she credits the enduring influence of her karate instructor and school art teacher, Mr Davis, for her success.
  "Everything he taught me about sport and about myself, stays with me to this day," she told BBC Radio Scotland.
  "I went from white belt to black belt and I was the first student he had who went from the white belt to black belt in the school.
  "The day after I got my black belt I went to see him and I had a thank you card and a bottle of wine from my parents just to say thank you for getting me there.
  "He presented me with the first ever black belt he had ever won, and gave it to me as my black belt. It was just incredible.
  "It's the one thing, you know if your house was on fire, that I would go to get.
  "Obviously the family photos and memories, but I would go to get my black belt.
  Find out how to get into martial arts in our special guide.
  "It was such a kind gift to give, and obviously meant so much to him and it meant far more to me because of that."
  Grainger says the "discipline" of karate appealed to her.
  "I was at Bearsden Academy [near Glasgow] and I loved sport at that age but I wasn't really a member of any club and I didn't do anything special," she explained.
  "I remember my mum and dad saying 'you need to do more'. I went along to see what it was like and to keep them happy.
  "I fell in love with the sport, the discipline, the competitive side and the training and I did it for the six years I was at Bearsden Academy.
  "He [Mr Davis] was a very high level black belt at the time - I got involved and absolutely loved it.
  "He was a complete inspiration, he really believed in me.
  "He showed me how much fun sport can be and the confidence you get from it, the enjoyment and I learned so much about myself."
  Grainger took a two-year break from rowing after winning Olympic gold at London 2012, following silver medals at Sydney, Athens and Beijing.
  But after a selection ordeal where her place was only confirmed six weeks beforehand, she won double sculls silver with Victoria Thornley in Rio.
  "We have absolutely amazing experts behind the scenes in strength and conditioning, training and coaching," she added.
  "They reassured me from when I started again knowing that I could still be in fantastic physical shape and my strength and fitness wouldn't be the limiting factor come racing.
  "It was hard and it was sore - we put everything on the line to get in amongst the medals.
  "We were racing against the odds as much as we were the opposition as we hadn't really shown the form all season to get on to the Olympic podium.
  "So we committed very, very early to the race physically, and countered every challenge that came at us from the opposition.
  "We were in a leading position until right before the end.
  "When you have got the Polish team that went on to win gold, attacking and coming through us, we were trying everything physically to counter them.
  "You just know you have run out of options physically - we left everything that we had out on the lake."
target: Five-time Olympic medallist Katherine Grainger has revealed how her grounding in karate at school has had a profound influence on her rowing career.