If bigger biceps are a goal you're after, traditional barbell curls may not necessarily be the best bang for your buck exercise. While a go-to staple in most arm workouts, traditional curls fail to provide much resistance at the bottom of the movement when the elbows are extended, and elbow flexors are in a lengthened position. And to get the most out of your bicep-building efforts, you also must program exercises that challenge the muscles at longer lengths, according to Menno Henselmans, a personal trainer and exercise scientist.