By sport
Swimrun Training Zones
Swim and run alternate with no rest. Blend CSS swim pace with run HR/pace zones. Transitions keep you near threshold.
Max Heart Rate Calculator
Your maximum heart rate is the highest your heart can beat at all-out effort. Age formulas estimate it: Tanaka gives 208 − 0.7 × age, the classic 220 − age runs high. At age 35 that is 184 and 185 bpm, but true values vary by ±10–12 bpm, so test it.
Heart Rate Zone Calculator
Heart-rate zones are percentages of your maximum heart rate: Zone 1 is 50–60%, Zone 2 60–70%, Zone 3 70–80%, Zone 4 80–90% and Zone 5 90–100%. At a max of 185 bpm, Zone 2, the aerobic-base zone, is 111–130 bpm. Most easy training belongs in Zones 1–2.
Critical Swim Speed (CSS) Calculator
Critical Swim Speed is your swimming threshold pace, found from two time trials: CSS = 200 ÷ (t400 − t200) in meters per second, and pace per 100 m = 100 ÷ CSS. A 400 m in 6:00 and 200 m in 2:50 give a CSS of about 1.05 m/s, or roughly 1:35 per 100 m, your sustainable threshold pace.