I bought a treadmill + standup desk 2.5 years ago, and to this day, it remains the best investment I've made to avoid sitting for most of the day.

Before I started using the treadmill desk, I averaged around 2.5-3k steps per day. On days when I exercised, it could go up to 8-10k steps, although I wasn't exercising regularly at that time. Now, 2.5 years later, I consistently reach 10k-12k steps on a bad day (about 2 hours of walking) and can go up to 18-24k steps on a good day (3-4 hours). Occasionally, I hit 30k steps, but that's quite rare, to be honest.

I was hesitant about the idea, but a friend who got one himself and shared his experience encouraged me to give it a try.

Pros:

- Feels more natural than just standing on the desk (after 20 min I get tired of standing still, whereas I can walk 2h without even realizing)

- I can work comfortably with the computer when typing, using the mouse (programming, writing... and even playing games), at speeds up to ~4.5km/h (~2.8 miles per hour). Beyond that the thoughts don't flow in the same way. Below this threshold I don't notice much difference in my work. I initially found 3 km/h (~1.8 mph) fast enough, but over time, 4 km/h (~2.5 mph) has become my sweet spot.

- You can enter a flow state just as easily as when seated (or at least that's my feeling)

Cons:

- Space: The treadmill takes up room, so I keep it next to my desk when not in use for convenience. Setting up the treadmill desk takes around 1 minute.

- Meetings: It felt awkward at first. Initially, I avoided attending meetings while walking, but I gradually started participating in 1:1s and eventually team meetings. Nowadays, I’m comfortable walking during most meetings, although I avoid it during large group or company-wide calls. My webcam is positioned to show only my shoulders and face, minimizing visible movement and reducing distractions for others during calls (probably the others won't care anyway).

- Limited Upper Body Movement: The upper body remains relatively still since my hands are usually on the keyboard or mouse. This limits overall activity compared to walking outside. However, when reading, my arms and hands move off the desk, mimicking the motion of walking, so it really depends.

- Noise: I live in a flat, and while the treadmill isn't very noisy, it could be bothersome if people are sleeping (whether in the next room or in the floor below). I avoid using it early in the morning or late in the evening.

My treadmill automatically beeps after 2 hours and shuts off for 30 minutes. It does force me to take a break (or even take a shower depending on the speed I was walking). After the break, I switch to a seated position. I typically have one walking session in the morning, and on some days, another in the afternoon. When it beeps and I'm in the zone I just move it aside and continue seated (sometimes I just continue standing still for some minutes), so it does not get in the way if you are focused.

Overall I think it is an improvement over staying still for most of the day (seated or standing), and also an improvement over forcing regular/spaced interruptions (I honestly tried several times, but it breaks my concentration and prevents me from going into the zone). Standing desk + treadmill: Totally worth the investment.