Whether you do preacher curls or inclined curls, your biceps muscles activate in pretty much the same way if you're using a moderate weight and pushing to failure. Basically, the 'effort' your...

When measuring muscle activity with electrodes during bicep curls, the results can be affected by how the muscle stretches and where the electrode sits — so the numbers aren’t always a perfect measure of effort.

Surface electromyography can measure and distinguish the highest levels of muscle activity in the biceps and triceps when performing exercises like concentration curls and kickbacks in healthy young adults.

Doing bicep curls on an incline bench builds more muscle in the upper part of your biceps than preacher curls do.