Confused by VO2 max? Our guide puts the metric into perspective.

Catherine O’Hara’s death from a pulmonary embolism has drawn attention to this serious condition in which a blood clot lodges in the lungs. Dr. Leana Wen explains.

New research on heart rate variability suggests that composure isn’t a personality trait. It’s a physiological skill the nervous system can train—one that may determine who thrives when the stakes are ...