Instructions
Place a pair of dumbbells or kettlebells at your feet. Brace your core and keep your chest up as you kneel down. Pick the dumbbells up, maintaining your form and keeping your gaze straight ahead.
Standing up, walk forward in a straight line, holding the dumbbells at your sides.
The trick is to use very heavy dumbbells. Walk as far as you can then set the weights down. Take a short break and repeat going back the other way.