"Listen to your body" sounds vague. Modern exercise medicine has actually quantified it. Three measurable signals — RPE, the Talk Test, and Heart Rate Variability — reliably tell you whether the next set should happen.
💡 Why this matters
Three quantifiable signals — Rate of Perceived Exertion (Borg's 1–10 scale), the talk test, and Heart Rate Variability — give you measurable, evidence-based ways to read what your body is telling you.
Rate of Perceived Exertion (RPE)
Developed by Swedish physiologist Gunnar Borg in 1982, the modified RPE scale asks you to rate effort 1 ("nothing") to 10 ("maximal"). RPE correlates well with heart rate, blood lactate, and VO₂ — without any equipment (Borg, 1982). Most strength training should sit at RPE 6–8; conditioning at 7–9; an everyday class at 5–7. RPE 10 should appear rarely.
The Talk Test
A free, ACSM-validated proxy for exercise intensity (ACSM, 2021):
- Light: can sing — too easy
- Moderate: can talk in full sentences
- Vigorous: only a few words at a time
- All-out: can't speak
Heart Rate Variability (HRV)
For tech-inclined trainees, HRV via wearable is a useful longer-horizon recovery signal. Trends matter more than single readings — a sustained HRV drop alongside elevated resting heart rate is a reliable indicator the body is under-recovered (Buchheit, 2014).
Soreness vs. injury
Delayed-onset muscle soreness (DOMS) is normal: dull, diffuse, in muscle bellies, peaks 24–48 hours later, resolves with light movement. Injury is sharp, localised to a joint or specific tissue, gets worse with continued activity, and persists or worsens. The rule of thumb: any pain that gets worse the more you warm up is not soreness.
When to stop and ask
See a clinician if any pain persists more than 7 days, if you have numbness or tingling in a limb, if a "pop" precedes swelling, or if pain wakes you at night. See our medical red flags guide for symptoms that warrant immediate attention.
Perceived exertion is psychophysiologically related to physiological strain and is a useful tool to monitor and prescribe exercise intensity.Source: Borg (1982), Medicine and Science in Sports and Exercise.
By the numbers
The best teacher of body awareness is a coach who watches you for years.
References
- Borg, G. A. V. (1982). Psychophysical bases of perceived exertion. Medicine and Science in Sports and Exercise, 14(5), 377–381. View source →
- American College of Sports Medicine. (2021). ACSM's guidelines for exercise testing and prescription (11th ed.). View source →
- Buchheit, M. (2014). Monitoring training status with HR measures. Frontiers in Physiology, 5, 73. View source →
