Physiological Workload Engine & ACWR Modeling
The Acute-to-Chronic Workload Ratio is the core mathematical engine inside Caden. It evaluates your short-term fatigue against your historical physical preparation to keep you training in the optimal progress zone.
Understanding Acute and Chronic Load
Acute Workload measures the physical stress accumulated over your past seven days. It reflects short-term metabolic fatigue, muscle damage, and nervous system strain.
Chronic Workload measures your average weekly physical stress calculated over the past twenty-eight to sixty days. It reflects your established aerobic capacity, structural tendon stiffness, and overall fitness foundation.
The ACWR Formula
Your ACWR ratio is calculated by dividing your seven-day rolling acute load by your twenty-eight-day rolling chronic load.
Understanding the Ratio Target Zones
Under-training Zone (Below 0.80). Your acute stress is significantly lower than your historical base. Your body is recovering, but long-term fitness will begin to decay if volume stays low. The Optimal Sweet Spot (0.80 to 1.30). You are increasing your workload at a safe, sustainable pace. Fitness gains are maximized while overuse injury risk remains minimal. Overreaching Warning Zone (1.30 to 1.50). Your recent volume is rising faster than your historical preparation. Pay extra attention to sleep, hydration, and nutrition. Danger Spike Zone (Above 1.50). Your acute workload is more than fifty percent higher than your chronic base. Sports science research shows injury risk increases by three to four times in this zone.
Cardiovascular Strain and Suffer Score Calculations
When Apple Health provides an official Suffer Score, Caden ingests that value directly. If an activity lacks a Suffer Score, Caden calculates an estimated load using moving duration, sport multipliers (Running receives three times impact, Cycling receives one point five times impact, Swimming receives two times impact, Gym receives one point zero impact), and average heart rate intensity scaling.