Intensity

In the gym, the term 'intensity' is used in two completely different ways, and confusing them is a common mistake. Objective intensity is the load expressed as a percentage of your 1RM. Subjective intensity, or perceived effort, indicates how fatigued you feel during a set, measured with scales like RPE or RIR. You can use a light load with high perceived effort (many reps close to failure) or a heavy load with low perceived effort (few reps with a wide margin).

Intensity ranges drive different adaptations. Loads above 85% of 1RM (1-5 reps) primarily develop maximal strength. Between 70% and 85% (6-12 reps) is the classic hypertrophy range. Below 67% (12-25 reps) you're working on muscular endurance, although recent studies show that even higher rep ranges can stimulate growth if you push sets close to failure.

In practice, you don't need to calculate the exact percentage on every set. Use your 1RM as a reference to set the initial loads of a program, then manage daily intensity with RPE and RIR. What matters is that the load is high enough to represent a real stimulus. If you finish a set and could have done another 8 reps, the load is too low regardless of what the percentage on paper says.