1. What is the Physical Activity Coefficient?

The Physical Activity Coefficient (PA) is a unitless value that represents the ratio of total energy expenditure to basal metabolic rate. It's used in water requirement calculations to account for different activity levels.

2. How Does the Calculator Work?

The calculator uses the simple formula:

Where:

• \( E \) — Total energy expenditure (kcal/day)
• \( BMR \) — Basal metabolic rate (kcal/day)

Explanation: The PA coefficient adjusts water requirements based on physical activity level, with higher values indicating more active lifestyles.

3. Importance of PA Calculation

Details: Accurate PA estimation is crucial for determining proper hydration needs, especially for athletes, workers in hot environments, and clinical populations.

4. Using the Calculator

Tips: Enter energy expenditure and BMR in kcal/day. Both values must be positive numbers. For accurate results, measure BMR under standard conditions (after overnight fast, at complete rest).

5. Frequently Asked Questions (FAQ)

Q1: What are typical PA values?
A: Sedentary: 1.2-1.4, Light activity: 1.4-1.6, Moderate: 1.6-1.9, Heavy: 1.9-2.5, Extreme: >2.5.

Q2: How does PA affect water requirements?
A: Higher PA values increase water needs due to greater sweat losses and metabolic water production.

Q3: When should PA be measured?
A: Ideally over several days to account for activity variations. Can be estimated from activity diaries or measured via calorimetry.

Q4: Are there limitations to this calculation?
A: Accuracy depends on precise measurement of both E and BMR. Environmental factors (temperature, humidity) also affect actual water needs.

Q5: How is this used in clinical practice?
A: Helps determine fluid prescriptions for patients, especially those at risk of dehydration or with special hydration needs.