The Human Heart and Its Cardiac Cycle

by Len Kravitz, PhD and Colin Carriker, MS on Jan 14, 2014

The cardiac cycle describes three phases of a single heartbeat:

  • Phase 1 (diastolic). Ventricular filling occurs during the diastolic phase. Blood moves passively (70%) (as the tricuspid and mitral valves open) and by atrial contraction (30%) from the atria into the right and left ventricles.
  • Phase 2 (systolic). For a brief instant, the heart closes all of its valves and begins to create a forceful contraction (called an isovolumetric contraction). This is followed immediately by systolic ejection of blood through the aorta and pulmonary semilunar valves into the systemic (entire body except lungs) and pulmonary (lungs) arteries.
  • Phase 3. For only a brief moment, the heart closes all valves and goes into relaxation (called isovolumetric relaxation). It then repeats the cardiac cycle beginning at Phase 1.

To view the full article which ran in the February 2013 issue of IDEA Fitness Journal click here.

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About the Authors

Len Kravitz, PhD

Len Kravitz, PhD IDEA Author/Presenter

Len Kravitz, PhD, is the program coordinator of exercise science and a researcher at the University of New Mexico in Albuquerque, where he recently won the Outstanding Teacher of the Year award. Len was also honored as the 2006 Fitness Educator of the Year by the American Council on Exercise.

Colin Carriker, MS

Colin Carriker, MS IDEA Author/Presenter