This is the DC stretch for biceps, one variation of an anabolic stretch for biceps. Grab a barbell or bar in a smith machine with the palms as shown. Then squat down while holding the bar and feel the stretch in your biceps. Go as far down as you can go. Hold that position for a minute or as close to a minute as possible. If you can get into a squat position and want to handle more pain, then kneel down on your knees instead. If you need more pain than that, you're not doing it right.