Why One-Arm Swimming Costs More
A two-arm stroke does more than double the pulling surfaces. It alternates effort from side to side, helping a swimmer move forward without constantly veering off course. Remove one working arm, and each pull creates an uneven force: the body tends to rotate toward the side doing the work.
The Rest of the Body Becomes the Rudder
To keep moving straight, the swimmer must brace the torso and adjust the hips and legs. The core muscles resist the twist, while kicks and small changes in body position help counter the sideways turn. Those movements do little to propel the swimmer compared with a full stroke, but they still consume energy.
The free arm cannot provide an opposing pull or help balance the stroke. Instead, the swimmer must coordinate each one-sided pull with a stabilizing kick and torso rotation. That makes the movement less efficient: effort goes not only into forward motion, but also into controlling the body’s roll and direction.
A Small Imbalance, Repeated Every Stroke
In ordinary swimming, the body’s alternating movements help keep it aligned. With one arm doing the pulling, the same rotational challenge returns again and again. The swimmer is effectively using the trunk and legs to compensate for the missing half of the stroke—so a short distance can feel disproportionately tiring.
