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Cardiac Output (Q) is the product of stroke volume (SV) and heart rate (HR), where Q=HR x SV. [1] In essence, then, more work equates to more blood pumped by the heart per minute. As an individual increases fitness levels, the heart is able to pump more blood per stroke, i.e. more cardiac output in fewer heart beats, thereby increasing efficiency. [2]


  1. Brookes, Douglas S. (2004). The Complete Book of Personal Training. Champaign, IL: Human Kinetics, 288. 
  2. Donche, Dan (2008). FF Trainer Certification Guide. USA: Fatal Fitness.