Treading Energy Cost Calculator

This calculator estimates calories burned while treading water — specifically the eggbeater kick that keeps a water polo player's upper body free to handle the ball. It works from a MET (metabolic equivalent) table tied to four intensity levels: light warm-up treading sits at 3.5 MET, moderate practice pace at 5.0, vigorous game-speed treading at 7.0, and maximum-effort pressing or wrestling at 10.0. Because colder water pulls heat from the body faster, forcing the muscles to work harder to maintain core temperature, the calculator adds roughly 2% to the effective MET for every degree the water sits below 26°C (FINA's standard pool temperature) — so a chilly 20°C session runs noticeably hotter metabolically than a heated 28°C one, even at identical intensity.

From there, calories per minute follow the standard MET formula (MET × 3.5 × body weight in kg ÷ 200), multiplied out by session duration for the total burn. The equivalent-swim-meters and fat-burn figures are simple downstream conversions (roughly 0.9 meters of moderate freestyle per calorie, and 7.7 kcal per gram of fat) meant to make the number feel tangible, not independently measured quantities. Intensity level is the input most worth getting right: it's a self-reported 1–4 estimate of effort, not a heart-rate-derived measurement, so honestly picking "vigorous" versus "moderate" matters more to accuracy than any other input, including body weight itself.