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Subjective vs. Objective load

RPE & Perceived Fatigue (sRPE)

Tracking the relationship between how you feel and what your sensors record.

1. Session RPE (sRPE)

Developed by Carl Foster, **sRPE (Session Rate of Perceived Exertion)** is a validated sports science method to quantify training load using only subjective feedback. This is vital when sensors are unavailable, or to complement sensors by showing the emotional and systemic fatigue of a session.

The Formula

sRPE Load = Borg CR-10 Rating × Duration (in minutes)
*For example, a **45-minute** workout rated as a **6 (Hard)** on the Borg scale results in a score of **270 sRPE Load Units**.

2. Borg CR-10 Category-Ratio Scale

We use the Borg CR-10 scale rather than a standard 1-to-10 scale because perceived exertion is non-linear. The jump from 9 to 10 feels much larger than the jump from 2 to 3.

Score Perceived Exertion Physiological Context
0RestingNo exertion (sitting down, sleeping).
1Very LightVery easy pace (leisurely walking, active recovery spin).
2LightAerobic zone. Conversation flows perfectly.
3ModerateSustainable tempo. Steady breathing.
4Somewhat HardSweet spot intensity. Feeling the burn slightly.
5HardThreshold pace. Conversation becomes strained.
6Hard +Slightly above threshold. Focus is required.
7Very HardVO2 Max intervals. Heavy breathing and lactic acid.
8Very Hard +Anaerobic capacity limit. Extremely difficult.
9Near MaximalAbsolute limit of voluntary exhaustion.
10Maximal EffortNeuromuscular sprint limit. Exhaustive failure.

3. The "Fatigue Gap" Recovery Monitor

The **Fatigue Gap** is a premium tool that analyzes the 14-day rolling average difference between subjective stress (**sRPE Load**) and objective sensor load (**TSS/hrSS**).

How We Standardize the Delta

Since sRPE and TSS are measured in different units, the system standardizes both to a daily average and calculates the percentage variance:

Fatigue Gap (%) = ((sRPE_14d_avg - Sensor_14d_avg) / Sensor_14d_avg) × 100
Gap > +20% (Under-Recovered) Your perceived fatigue is significantly higher than your sensor workload suggests. This points to sleep debt, mental stress, heat fatigue, nutrition depletion, or incoming sickness. **Action: Rest.**
Gap ± 20% (Balanced) Your physical feeling matches the metrics from your sensors. Training load matches expectations. **Action: Continue.**
Gap < -20% (Peak Freshness) You feel much fresher and stronger than the sensor training load indicates. A sign of supercompensation and peak adaptation. **Action: Time to Race or Intensity block.**
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