To stop getting out of breath and to improve in endurance swimming, you must limit leg effort and rely primarily on the pulling strength of the arms.

noli's read

Sports science fully validates this effort management advice. In freestyle swimming, biomechanical analyses published in the journal *Frontiers in Physiology* show that the arms are responsible for 85 to 90% of overall propulsion. Conversely, research on movement economy published in the *Journal of Sports Medicine* indicates that the leg kick is highly energy-intensive, consuming up to four times more oxygen than the arms for the same speed generated. The large muscles of the legs require a massive energy supply, which rapidly accelerates the respiratory rate and causes shortness of breath if they are engaged too actively. In long-distance swimming, observational research shows that adopting a minimal kick (the 'two-beat' kick) serves primarily to stabilize posture and reduce drag in the water rather than to move forward. This advice is therefore particularly rigorous for optimizing one's breath and sustaining effort.

the sources

No named source held this one up — that absence is part of the verdict.