Activity Target Methodology

Inputs and outputs

Formula

healthy_body_fat_upper = female 30, male 20
body_fat_excess = max(0, body_fat_percent - healthy_body_fat_upper)
zone2 = clamp(round_to_step(105 + activity_delta + goal_delta + age_delta + body_fat_delta, 15), 90, 240)
activity_delta = sedentary -15, light 0, moderate 15, active 30, veryactive 45
goal_delta = lose 30, gain 15, maintain 0
age_delta = age >= 70 ? -15 : age >= 55 ? -10 : 0
body_fat_delta = excess >= 12 ? 45 : excess >= 8 ? 30 : excess >= 4 ? 15 : 0
strength_sessions = clamp(2 + gain_bonus + body_fat_bonus + age_bonus - high_activity_reduction, 2, 4)
steps = clamp(round_to_step(7000 + low_activity_bonus + loss_goal_bonus, 500), 7000, 11000)

Calculation steps

1. Use WHO 150 minutes per week as the public guideline floor and 300 minutes as the extensive-benefit reference.
2. Estimate a practical Zone 2 target around the user goal, current activity, age, and body-fat context.
3. Set strength training at 2 to 4 sessions per week.
4. Set steps between 7000 and 11000 per day, with higher targets for sedentary/light activity and fat-loss goals.

Guardrails

• The app target is not a clearance to exercise with chest pain, fainting, acute injury, or unstable medical disease.
• Users with chronic disease, pregnancy, disability, or medication constraints may need a tailored plan.

Sources

• Physical activity World Health Organization