PHYS-45 · Principle
My sRPE and TSS disagree. Which is wrong?
Probably neither. TSS counts the work against a stored threshold; sRPE is what it cost you. Heat, mental fatigue, overreaching or a stale threshold pull them apart: the gap is a question.
How the body works, agreed across the reviews below; a study entry shows what one experiment measured.
Practical Application
My sRPE and TSS disagree. Which is wrong? Probably neither. TSS counts the work against a stored threshold; sRPE is what it cost you. Heat, mental fatigue, overreaching or a stale threshold pull them apart: the gap is a question.
What it means for training: record an external number and sRPE for every session, read the gap across several sessions, and check the ordinary causes first (SYNTH-39).
What it does not mean: that TSS equals fatigue, that one divergent session diagnoses anything, or that agreement proves all is well (SYNTH-39).
Mechanism
External load is the work (power, pace, time-motion); internal load is the response (RPE, heart rate, lactate, TRIMP); a dissociation between them may reveal fatigue (REF-367).
At fixed work, heart rate drifted up 11% over 30 min at 35 °C against 2% at 22 °C (10 trained men, REF-3496), and RPE ran higher at 32 than at 19 °C (10 cyclists, REF-461); after a demanding cognitive task RPE ran higher and time to exhaustion was about 15% shorter, with cardiorespiratory responses largely unaffected (16 subjects, REF-370).
Common misreading
"TSS is fatigue"; "same watts, same day"; "a high sRPE means central fatigue".