A question for any strength and conditioning enthusiasts;

Generally speaking Intensity would most likely be a percentage of 1RM however this is often not a practical measure as 1RM is hard to test for in certain exercises.

How does one measure intensity for the following exercises? ;

A.Walking lunges
B.Step-ups
C.Farmers Walk

I am trying to put together some assistance exercises in a strength program for a firefighter so grip orientated exercises are what i am struggling with in terms of measuring intensity, i will progress the above exercises through various methods for example

week1 - BW static lunges 3x10 each leg
week2 - DB static lunges 3x10
week3 - DB walking lunges 3x10
week4 - DB walking lunges forwards/backwards 3x10

Are the various methods of progression enough of a measure of intensity?

ROAST