"To isolate the biceps" means to focus on working out or exercising only the biceps muscles, without involving other muscles.
Sentences with «to isolate the biceps»
Keep your elbows to your sides to isolate the biceps better and keep the movement under control at all times. (fitnessandpower.com)
One of the best ways to isolate the biceps when doing particular work out that includes your arms is to perform the barbell curl. (directlyfitness.com)