The Claim
Endurance training volume differs substantially between 12-year-old endurance athletes and non-endurance-trained peers, with athletes averaging 7.0 hours per week versus 2.5 hours per week, but this difference does not lead to significantly different rates of change in VO2max, stroke volume, or left ventricular dimensions over 14 months.
What the research says
Supports is higher
Support is ahead, but a single strong opposing study can change this.
These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.
Twelve-year-old endurance athletes train an average of 7.0 hours per week, while non-athletes train 2.5 hours per week, but both groups show similar changes in VO2max, stroke volume, and left ventricular dimensions over 14 months.
See the scientific wording
Endurance training volume differs substantially between 12-year-old endurance athletes and non-endurance-trained peers, with athletes averaging 7.0 hours per week versus 2.5 hours per week, but this difference does not lead to significantly different rates of change in VO2max, stroke volume, or left ventricular dimensions over 14 months.
In young children, the heart grows and strengthens in response to physical activity, but there is a natural limit to how fast it can adapt. Even when children train much more than others, their hearts cannot change faster because they are still growing and their bodies have fixed biological rules for how quickly the heart can get bigger or pump more blood.
What the research says
1 studyEven though the young athletes trained way more than the others, both groups got better at the same rate in heart and lung function over a year and a half — meaning just training more didn’t make them improve faster.
Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.