In this episode of the Athletes Compass podcast, hosts Paul Laursen, Marjaana Rakai, and Paul Warloski explore how the heart functions as a major limiter of VO2 max and endurance performance. They break down the components of cardiac output, discuss genetic ceilings and the effects of aging on heart rate, and offer practical training strategies to maximize cardiac function. Drawing on scientific literature and real-world athlete examples, the team gives actionable advice for improving VO2 max—even for everyday athletes.

Key Takeaways:

• The heart, especially cardiac output, is often the primary limiter of VO2 max.
• VO2 max = cardiac output (stroke volume × heart rate). Both factors matter.
• Aging reduces max heart rate—roughly 1 beat per year—which can lower VO2 max.
• Genetics play a role, but consistent, individualized training has a big impact.
• High training volume improves efficiency and threshold; HIIT boosts VO2 max ceiling.
• Training zones differ across sports due to body position and demands (e.g., swimming vs. running).
• Individual variability in heart rate response and adaptation is normal.
• Accurate zone setting requires solid data: races, FTP tests, 5K runs, etc.

• Paul Warloski - Endurance, Strength Training, Yoga
• Marjaana Rakai - Tired Mom Runs - Where fitness meets motherhood.