There is a common belief that if you get older, you should slow down and take it easy. A lot of people reduce the intensity of their workouts. However, training intensity remains essential for strength, cardiovascular health, and metabolic function. If you reduce it too much it fails to counteract the physical decline. Therefore your goal should not be ‘less intensity’ but ‘smarter intensity’.
WHAT ‘INTENSITY’ ACTUALLY MEANS IN THE CONTEXT OF EXERCISING
Intensity is often misunderstood as simply lifting very heavy or pushing to exhaustion, but it is more precise than that. We typically measure training with the concept of ‘relative intensity’ which describes how close you are to your maximum output.
In strength training a widely used concept is how close you are to “failure” during a specific set. ‘Failure’ should be understood as not being able to crank out one more repetition with proper form (technical failure). This concept is independent from the weight that you actually use: with a very heavy weight you reach the point of technical failure faster, let’s say at 5 reps, with a lighter weight you might reach the point of technical failure at 15 reps.
In cardiovascular training, it reflects how much the training demands your heart and lungs, typically measured by heart rate.
WHAT ACTUALLY CHANGES WITH AGE (AND WHAT DOESN’T)
With age, your body does not lose its ability to adapt to training, but it does become less forgiving in how it recovers. Muscle, strength and endurance can still be built well into later decades if the stimulus is sufficient, yet recovery between sessions tends to take longer. This is because your hormones and your nervous system are changing. Your joints, tendons and connective tissue already have accumulated some mileage. Your body becomes less efficient in utilizing protein. However, what does not change is that your body still responds to challenge. It will still adapt to the training. The key difference is that you have to put more attention on your increased recovery demands and apply intensity in a smart way.
THE KEY PRINCIPLE FOR TRAINING INTENSITY IN YOUR MIDLIFE
A Balanced Approach
You want to balance the intensity of your training sessions with volume (how much you train) and frequency (how often you train) in such a way that you create a strong enough stimulus without overwhelming your ability to recover.
Going all out with maximum effort will lead to a disproportional increase in recovery time. In other words: while it creates the maximum stimulus, it will take its toll and you need some days off to recover from it before you can go back to training. Hence, your training frequency drops which will set you back on your overall progress. You want to create consistent, repeatable effort. This is why frequent training with maximal effort is counterproductive in midlife.
Intensity in Strength Training
In strength training we typically measure intensity with the concept of “reps in reserve” (RIR). It is a measure of how many more repetitions you could have performed. A good trade-off between stimulus and fatigue is typically at 1-2 RIR, meaning you stop your set when you feel that you could do only 1-2 more repetitions in good form. If you are a beginner, you might want to add +1 RIR to stay on the safer side. You should also consider the nature of the exercise: if you work smaller muscles in isolation (like bicep curls), going close to failure is less fatiguing than if you do big compound lifts like a barbell squat.
Intensity in Cardiovascular Training
To gauge the intensity of cardiovascular training in a simple way, you can use the ‘talk test’. If you are able to talk comfortably in full sentences your training level is at ‘moderate intensity’ (or in more technical terms referred to as ‘Zone 2 training’). You are purposefully moving, but not struggling. Once you increase the intensity level, your breathing gets deep and rapid and you are no longer able to pass the ‘talk test’: you can’t say more than a few words at a time without stopping to catch your breath. This is considered ‘vigorous intensity’.
Lower-intensity work builds the aerobic base and supports recovery, while occasional higher-intensity efforts improve cardiovascular capacity (VO₂ max) and metabolic health. Avoiding intensity altogether limits these benefits, but overusing it quickly leads to fatigue. A balanced approach – around 80% low intensity with 20% selective, well-placed higher-intensity sessions – delivers the best long-term results.
PUTTING THINGS TOGETHER IN PRACTICE
As you already know, I am advocating 4-6 days of training per week, which is on the higher end of training frequency. Therefore, controlled, smart intensity is required.
In your 2-4 strength training sessions, don’t go all out but keep 1-2 RIR.Complement this with 2-3 cardio sessions that are mostly low intensity with the occasional higher-intensity work. Minimum 1 rest day is essential to absorb the training stimulus.
However, the response to training is highly individual. So the above serves as a fundamental guiding principle but you need to listen to your body, observe how you recover and if you feel that fatigue is setting in make incremental adjustments of intensity, frequency and volume as you go about your training. The emphasis is on consistency and repeatability—training in a way you can maintain week after week without accumulating fatigue or risking injury.