Stand upright, holding your dumbbells in each hand, arms at your sides, with your knees slightly bent.
Keeping your arms straight and knees slightly bent, slowly hinge forward, bending at your hips (not your waist) and lowering the weights as far as possible without rounding your back, which should remain straight.
Squeeze your glutes to return to standing, keeping your back straight. Once you're standing, pull the weights up the front of your body, bringing them to your chin with elbows going wide. Lower the weights to complete one rep.
Do as may reps as you can with correct form for 45 seconds. Rest for 15 seconds.