Reps-in-Reserve and the Desired Intensity for Meaningful Strength Change

What is “Reps-in-Reserve” or “RIR”?
RIR is an easy way to describe how hard a set feels by estimating how many repetitions you could still do before muscular failure. For example, if you finish a set and feel you had 2 reps left in the tank, that set was performed at 2 RIR. It is a practical, autoregulatory method that coaches and clinicians use instead of only relying on calculating a percentage of or completing the arduous assessment of a 1 Rep Max.

Why RIR matters
RIR helps match training intensity to the individual’s daily readiness, fatigue, and goals. It’s useful because two people lifting the same weight may feel very different. RIR accounts for those differences and helps regulate effort without needing constant retesting. The most recent research suggest RIR scales are feasible and increasingly applied in research and practice, including clinical populations.
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Desired intensity for meaningful change, how your training may look

• Strength (max force): Train fairly close to failure — typically 0-2 RIR on lifts, with heavier loads and lower reps (e.g. 3–6 reps). This produces the strongest neural and mechanical stimulus for strength gains.
• Hypertrophy (muscle size): Similar principles to strength training, however a wider range works. Moderate loads and higher total volume across sets increasing total reps up to 20 reps. Leaving 1–3 reps in reserve across sets is practical and reduces unnecessary fatigue while still driving growth.
• Endurance / Rehab / Frail clients: Principles of muscle strength and hypertrophy continue, however begin at a conservative and tolerance based approach. Leave more in reserve, something like 2-5 RIR, use lighter loads and higher reps; the focus is more on movement quality, safety and progressive overload over time.

These are general targets and it is important to tailor the intensity depending on individual goals, training age, injury status and recovery. ESSA and Australian clinical guidance emphasise tailoring intensity and monitoring signs (eg. pain, excessive fatigue) in rehabilitation and chronic disease populations. 

Tailoring your training on these principles

1. Set goal (eg. strength or size or rehab)
2. Choose load and target reps consistent with the goal.
3. Judge RIR after each set (honest, brief check). This may change the above ranges ongoing.
4. Progress by reducing RIR over weeks, meaning the weights may change. Continue to increase volume of training when RIR feels easier.
5. Again consider your focus; For clinical clients, prioritize movement quality and minimum effective dose; for athletes, periodise RIR across phases with heavier, lower-RIR blocks vs lighter, higher-RIR blocks.

Why exercise physiologists are ideal for this
Accredited Exercise Physiologists (AEPs) are trained to prescribe intensity, monitor response, and adjust programs for both clinical and athletic needs. They blend objective measures including things like strength tests and functional tasks with subjective tools like RIR, pain patterns, etc. to safely progress clients with chronic disease, injury, or high-performance goals. Australian position statements highlight the role of exercise professionals in tailoring intensity for health and rehab outcomes and a clinician will always base their practice on these.

Resources similar to this blog for a deeper dive

• Exercise & Sports Science Australia — Position statement / guidance on exercise intensity and exercise in clinical populations (ESSA documents). Link: https://www.essa.org.au/Web/Web/Resources/Publications/Position-statement-exercise-intensity-terminology.aspx
• Australian Department of Health and Ageing — Choose Health, Be Active. Link: https://www.health.gov.au/sites/default/files/documents/2021/03/choose-health-be-active-a-physical-guide-for-older-australians.pdf
• ACSM's Health & Fitness Journal – Article about progressive overload. Link: https://journals.lww.com/acsm-healthfitness/citation/2022/03000/shareable_resource__ten_ways_to_implement_the.17.aspx#:~:text=A%20modified%20rate%20of%20perceived,rep%20could%20be%20performed%2C%20etc.

Thomas Harrison
​Accredited Exercise Physiologist
​AEP, AES, ESSAM

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