Procedure

1. Information Gathering & Baseline Calculation

   • Retrieve the user's age and resting heart rate (RHR) from their profile or via get_user_preferences.
   • If RHR is unavailable, instruct the user to measure it immediately upon waking.
   • Calculate the Heart Rate Reserve (HRR) by subtracting RHR from the estimated Max HR ($220 - \text{Age}$).
   • Use compute_hr_zones with the Karvonen formula: $\text{Target HR} = (\text{HRR} \times % \text{Intensity}) + \text{RHR}$.

2. Zone Personalization

   • Define five training zones based on the following HRR percentages:
     • Zone 1 (50-60%): Recovery/Active Rest.
     • Zone 2 (60-70%): Aerobic Base/Mitochondrial Health.
     • Zone 3 (70-80%): Aerobic Capacity/Tempo.
     • Zone 4 (80-90%): Lactate Threshold/Anaerobic Power.
     • Zone 5 (90-100%): $VO_2 \text{ max}$/Peak Performance.
   • Save these calculated zones to the user's profile using remember.

3. Program Structure Selection

   • Apply the Polarized Training (80/20) model for most users:
     • 80% of volume in Zone 2.
     • 20% of volume in Zones 4 or 5.
   • Avoid "No Man's Land" (excessive Zone 3) unless programming a specific Tempo phase.

4. Progressive Overload Implementation

   • Organize training into three distinct phases using plan_week:
     • Base Phase: Focus on increasing Zone 2 volume (duration).
     • Build Phase: Integrate Zone 3/4 intervals (e.g., 4x5 minutes in Zone 4) to increase intensity.
     • Peak Phase: Incorporate Zone 5 HIIT to maximize $VO_2 \text{ max}$.
   • Sequence progression in this order: Volume $\rightarrow$ Intensity $\rightarrow$ Density (reducing rest).

5. Coaching & Safety Validation

   • Provide the "Talk Test" as a subjective check:
     • Zone 2: Full sentences.
     • Zone 4: One-word gasps.
   • Advise the user to monitor RHR daily. If RHR increases by +5–10 bpm, use update_workout to pivot the current session to Zone 1 (Recovery).
   • Instruct the user to recalibrate zones every 8–12 weeks to account for RHR changes and fitness improvements.

6. Execution

   • Use create_workout to schedule specific cardio sessions with target Karvonen HR ranges in the description.