One band, full biceps tension, zero gym needed.
Keep your elbows locked at your sides and squeeze at the top.
Standing on a loop band and curling puts the biceps under a tension that ramps up as your hands rise, so the peak of the squeeze coincides with the band's peak pull. There's no dropping the tension at the bottom either, the band never fully slackens, which keeps the muscle working through the entire set. For home arm training it covers everything a curl needs, and the resisted lowering phase alone makes cheap bands feel expensive.
For building biceps, tension and effort matter more than the tool. Band curls load the top half hardest while dumbbells load the middle, so they complement each other. Taken near failure with a controlled negative, band curls absolutely grow arms.
That's the band's nature, minimal stretch means minimal tension. Fix it by widening your feet on the band or gripping further down so there's real resistance from the very start of the curl.
Pin your elbows to your sides and think of your hands curling around them, not up in front of you. If they still drift, the band is too heavy for strict reps, adjust your grip up the loop.
