In 1996 I put a treadmill in my office so that I could work standing up. My goal was better sleep (the more I stood, the better I slept), not weight loss (the usual reason for a treadmill desk). It was hard to walk a lot. Mostly I stood still. It was noisy, too — my neighbors complained. When the treadmill broke I didn’t replace it.
Now I walk on a treadmill for different reasons: to lower blood sugar and learn Chinese. Above is my current setup. I use the laptop to study Chinese (using Anki) or watch TV or movies. Studying Chinese while walking is much easier than studying Chinese while standing still or sitting. I have used flashcards but Anki (shown on the computer screen) helps space repetitions optimally. The headphones (Bose noise-reduction) are for TV and movies. I don’t need them for Anki.