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MELBOURNE, AUSTRALIA - JANUARY 11: Andy Murray of Great Britain puts on a heart rate monitor during a practice session ahead of the 2016 Australian Open at Melbourne Park on January 11, 2016 in Melbourne, Australia. (Photo by Michael Dodge/Getty Images)

MELBOURNE, AUSTRALIA - JANUARY 11:  Andy Murray of Great Britain puts on a heart rate monitor during a practice session ahead of the 2016 Australian Open at Melbourne Park on January 11, 2016 in Melbourne, Australia.  (Photo by Michael Dodge/Getty Images)