In sports and exercise contexts, it also describes the use of non-standard or extra body movements to help complete a physical action, such as using torso or leg motion to assist an upper body exercise
Anything between 5-30 reps is inside the hypertrophic sweet spot, but for isolation exercises you probably want to aim for ~12 reps and up.
My biggest concern reading this is that you seem quite fixated to the weight of the dumbells. Some body English is fine, but be careful to not make what should be a biceps exercise into a full body exercise.
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