Fitness adds aerobic fitness and body composition to [Titan Age]. Its two inputs, VO2 Max and lean mass index, contribute 19% of the model.
012 fitness contributors
VO2 Max carries 16%. Titan uses the latest VO2 Max reading in Apple Health from the past 30 days, not a weekly average.
Lean Mass Index carries 3%. It adjusts lean body mass for height, using the latest body mass, body fat percentage, and height from the 30 days before the week ends. Titan calculates lean body mass from weight and body fat percentage, then divides that mass in kilograms by height in meters squared. All three measurements must exist in Health for this row to count.
02Contributions in years
The Fitness total shows how many years its two contributors add to or subtract from Titan Age together. A negative total lowers your estimate. A positive total raises it. Each contributor also shows its own effect in years, so you can see which measurements are lowering or raising your Titan Age.
Tap a row to see its neutral reference value. A missing row also shows the value Titan counted in its place. Once VO2 Max has a recorded reading, the expanded row includes a fitness rating. The row percentages are rounded and may not add exactly to 19%. Titan does not set health targets from these reference values.
03How missing data is handled
Both rows use the latest reading in the past 30 days, so an older reading does not count. A row without a recent reading counts as missing. Titan then fills it from the median of your recorded weeks from the past 26 once you have 6, or from the reference value, which adds zero years. Calculation details on the Titan Age screen shows the coverage for each row.
04Fitness data sources
VO2 Max appears in Health as Cardio Fitness. Apple Watch estimates it from Outdoor Walk, Outdoor Run, and Hiking workouts recorded in the Workout app. Apple's cardio fitness guide explains how readings are collected. Body mass, body fat percentage, and height also come from Health. You can enter measured values there yourself, or a connected scale or app can write them. See your profile for how Titan shows Body & Measurements.
05Find missing fitness data
Start with Set up Apple Health for Titan. Then check these in order.
- For VO2 Max, open Health, tap Browse, then Heart, then Cardio Fitness, and look for a reading in the last 30 days. Apple Watch needs outdoor workouts to produce one, and the first estimate can take several of them.
- For Lean Mass Index, open Health and confirm you have recent weight, height, and body fat percentage. Enter only measurements you have verified.
- Open Health permissions for Titan and confirm Cardio Fitness, Weight, Height, and Body Fat Percentage are on. See Health permissions.
- Wait for the week to close. Titan Age updates after Sunday ends.
Both rows are optional inputs. Titan Age works without them, and you do not need to change your training to record them. If the whole card is blank, see Titan Age missing or not updating.
