The Three Effort Systems
Workout intensity can be quantified in multiple ways. The three most commonly used in modern fitness apps are RPE (Rate of Perceived Exertion), RIR (Reps in Reserve), and Heart Rate Zones. Understanding how each works helps you pick the right one for your training and use your app more intelligently.
RPE (Rate of Perceived Exertion)
Scale: 1–10, where 10 is maximum effort (complete failure)
Best for: All training types — versatile across strength, cardio, and mixed workouts
How to log it: Add an RPE score as a note to each set (e.g., "Squat: 100kg × 5, RPE 8"). Over time, a pattern emerges: your "RPE 7" sessions consistently produce certain reps, allowing the app to better estimate your 1RM and suggest appropriate loads.
Limitation: Requires calibration. RPE accuracy varies between individuals and improves with experience.
RIR (Reps in Reserve)
Scale: 0–4+, where 0 = went to failure, 4 = 4 more reps were possible
Best for: Strength and hypertrophy training with barbells or dumbbells
How to log it: Note RIR per set alongside your weight and reps. "Bench: 80kg × 8 @ 2RIR" is a fully specified set. Research shows training between 0–4 RIR is the productive intensity range for hypertrophy; 3–5 RIR for strength with heavy loads.
Limitation: Requires strong body awareness. Beginners often misjudge how many reps remain.
Heart Rate Zones
Scale: Zone 1–5, based on percentage of maximum heart rate
Best for: Cardio and conditioning training
How to log it: Apps connected to HR monitors automatically categorise session time in each zone. Most fitness platforms display zone distributions for cardio sessions.
Limitation: Not applicable to pure strength training; HR response is highly individual and affected by hydration, caffeine, and stress.
Which System Should You Use?
Strength-focused athletes benefit most from RIR or RPE. Endurance athletes benefit from HR zones. Most gym-goers benefit from a hybrid: RPE or RIR for strength work, HR zones for cardio. Apps like Fitblues support all three — you can log RPE notes on strength sets and have cardio sessions automatically zone-classified from connected wearables, keeping everything in one place.
