Run Stress Score (RSS) is a single number to help runners understand their day-by-day training. It takes into account the volume and intensity of your training session to give you a single number, or “score.” The Running Stress Score is similar to TSS (training stress score) which allows you to compare the stress of workouts of various duration and intensities. The difference between TSS and RSS is small, the difference coming from the fact that the equation for RSS is intended to account for the additional biomechanical stress put on your body from running whereas cycling is largely aerobic stress.
RSS is calculated by comparing your power during your run with your critical power. Therefore, accurate critical power is essential for RSS calculations. If you have auto-CP disabled, it is recommended to repeat the critical power test every 4 - 6 weeks.
In the TrainingPeaks platform, the term Training Stress Score (TSS) is used. Here is how you would calculate TSS compared to RSS:
TSS = (duration of workout in seconds x NPx IF)/(FTP x 3600) x 100
The primary input to RSS is running power (collected each second) along with the time
spent at different training intensity levels and can be calculated as follows:
RSS for each second of your run = a * (one second power / critical power)^b
where a and b are both constants developed by sports physiologists.
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