The Study
A race against time: timing constraints of cardiac filling and athletic performance.
This study compared two groups of people—athletes and non-athletes—and saw that their hearts work differently during exercise. It doesn't prove that training made their hearts this way, just that the hearts of athletes look different. Think of it like noticing that basketball players are taller than non-players—it doesn't mean basketball made them tall, just that tall people often play basketball.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
Athletes' hearts have more time to fill with blood at rest, and during hard exercise, they squeeze blood out faster to keep up with demand.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 576 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1This means athletes can deliver more oxygen to muscles during intense activity, giving them a major performance edge without needing a faster heartbeat.
- 2At rest: athletes' hearts take 30% longer to fill and 15% longer to pump.
- 3During hard exercise: athletes pump 31% more blood per second through the heart and move 20% more total blood per minute than non-athletes.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
American journal of physiology. Heart and circulatory physiology
Year
2026
Authors
Luke W. Spencer, M. Flannery, K. Janssens, Y. Bekhuis, L. Wright, Erin J. Howden, T. Van Puyvelde, D. Prior, Amy M. Mitchell, S. Rowe, Stephen J. Foulkes, André La Gerche
Related Content
Claims (10)
Endurance athletes have longer heart filling and pumping phases at rest than sedentary people, leading to more blood pumped per heartbeat and higher overall heart output during physical activity.
Endurance athletes have a larger volume of blood pumped by the heart per beat during exercise than non-athletes, even though both groups increase their heart output by a similar percentage from rest. This difference is due to a higher baseline capacity to fill the heart with blood, not stronger heart contractions.
During intense exercise, endurance athletes have a shorter time between heart contractions and relaxations compared to sedentary people, allowing more time for the heart to fill with blood even under maximum stress.
During high-intensity exercise, trained endurance athletes have 31% higher blood flow rates through the heart's main artery per square meter of body surface area than untrained individuals, leading to higher volumes of blood pumped per heartbeat and per minute at the same relative effort level.
Endurance athletes pump more blood per minute during intense exercise than sedentary people, mainly because their hearts push out more blood with each beat, not because their hearts beat faster, when both groups exercise at the same relative intensity.
During exercise, trained endurance athletes have a greater volume of blood pumped per heartbeat than untrained individuals, even when the heart has less time to fill with blood between beats.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.