Doing dumbbell raises to failure with 5repmax will bring more pain, discomfort and wear/tear than doing the same exercise with 20repmax.
Why?
Most people don't build up to such a stimulus, so its not surprising if its uncomfortable, if all youve ever done is 20 rep sets.
Not sure what you want to say with 5repmax and 20repmax
Why?
Most people don't build up to such a stimulus, so its not surprising if its uncomfortable, if all youve ever done is 20 rep sets.