How these resources work together. The sweat sodium collection protocol is designed to capture a clean, uncontaminated sample for sodium concentration analysis -- sample integrity is the priority. The sweat rate calculator is a separate tool: all you need is a scale, a timer, and a record of your fluid intake. Both inform your race-day hydration strategy, but they answer different questions. As your fitness, body composition, and race conditions change, retest and recalculate -- neither sweat sodium nor sweat rate is a fixed number.