In this post, we discuss resistance training and intensity, and how to get it right to avoid injury, pain, and muscle tightness.
At a glance
Dramatic transformations grab attention, but in fitness the line between progress and injury is thin.
More training doesn’t always equal better results—even elite athletes monitor intensity carefully.
The general population, especially older adults, have a smaller margin for error.
Repetitions in reserve (RIR) is a practical way to adjust training intensity safely.
The best guide is how you feel after:
- Energised, freer movement, less pain → on the right track.
- Exhausted, tight, more pain → probably overdoing it.
Introduction
We all love a dramatic transformation: the alcoholic who lost everything and then turned his life around, the woman who nearly died and then won gold at the Olympics. The more extreme the better.
The narrative arc is usually the same: a leap from one end of the spectrum—whether in business, fitness, or sport—to the other, often in record time, driven by hard work and determination.
In fitness, and to a certain extent sport, the concept that doing more leads to greater gains is pervasive.
The sense that if you ask a question of your body, it will respond by adapting. That there are infinite reserves available—if you try hard enough.
Is there a limit to physical capacity when training?
In elite sport, where most of the research on this subject takes place, the answer is an unequivocal yes.
There is generally a sweet spot to be found between doing enough training to receive a benefit, and not doing so much that you wind up injured or sick.
Training of athletes is closely monitored to avoid this very situation. It’s why we have sports medicine, to treat individuals who have overcooked it.
In my experience however, the most difficult people to train aren’t elite athletes, but rather older adults, especially if they’ve had no previous exercise experience.
Why?
Because the line between gaining a positive benefit from exercise and injury is so much smaller.
That’s not to say incredible transformations can’t take place. It’s just that these may take months to achieve, rather than weeks.
How do you get the intensity right when resistance training?
The American College of Sports Medicine (ACSM) suggests the following rule of thumb: if you hit 1-2 repetitions beyond your target two sessions in a row, nudge the weight up by 2-10%.
They recommend increases of 2-5% for upper body / single joint exercises and 5-10% for lower body / multi-joint exercises.
This presumes there will be neat linear progressions to your training. Of course the reality is often very different.
For this reason, researchers suggest a repetitions in reserve (RIR) strategy might be more effective.
Anchor most sets around 1–3 RIR. Meaning you could complete a maximum of 3 further repetitions for any given set but no more.
If RIR drops to 0 hold or reduce load next time; if RIR is >3, consider a small increase in weight.
This method of auto regulation allows for fluctuations in performance that may occur day to day. This study found it to be effective in college age American Football players.
How to tell you’ve got the intensity right when resistance training
One of the best indicators is how you feel after the session.
If you’re exhausted, suffering from muscle tightness, and in more pain than when you started, you’re likely overdoing it.
If, on the other hand, you feel energised and you’re moving more freely with less pain, you’re probably on the right track.
The tricky bit is monitoring these changes over time. In particular range of motion, as this can be thought of as the canary in the coal mine with respect to injury.
If you find you’re losing range of motion around a joint, restore it with light, targeted exercise and proceed with caution.
Summary
Pushing harder in training doesn’t always mean better results. Even elite athletes have limits, and finding the right balance between effort and recovery is key to avoiding injury.
For everyday people—especially older adults—the margin between progress and overdoing it may be even smaller. Using strategies like repetitions in reserve (RIR) helps regulate intensity and keep training safe and effective.
The best guide is how you feel after a workout. If you finish moving better and with less pain, you’re on the right track.