How do I track my steps on my walking pad while my arms are not swinging?

Put the Apple Watch on your ankle.

The Apple Watch does not really know what position your body is in. The Apple Watch uses the accelerometer to determine that your Apple Watch arm is swinging as you are walking. It takes between 30 and 60 complete cycles of back and forth, normal walking, arm swings in a short period of time before the Apple Watch decides you have accomplished your “Stand” for the current hour. If you interrupt the arm swinging for a few minutes, it will reset, and you have to start the 30-60 swings over again. Later in the day, it seems to require more arm swings, or if you keep having incomplete stand attempts, in the Apple Watch's opinion. In reality, you can just gently wave your arm around 30-60 times in a short period of time and get stand credit. Knitters, sitting in a chair, always get their stand credit and huge step counts. Professional Chefs, on their feet, working in a kitchen all day, miss their hourly stands, because their Apple Watch arm is often holding food being chopped, or carrying something when walking, or holding a pot, pan, etc… No 30-60 arm swings in a short period of time, then no stand credit.

Try and calibrate your watch to see if the issue persists. It should be more accurate on a treadmill

1. While wearing your Apple Watch, go to a flat, open outdoor area that has good GPS reception and clear skies.
2. If you have Apple Watch Series 2 or later, you just need your Apple Watch.* If you have Apple Watch Series 1 or earlier, take your iPhone for GPS. Hold your iPhone in your hand, or wear it on an armband or waistband.
3. Open the Workout app, then tap Outdoor Walk or Outdoor Run. To set a goal before starting, tap the More button.
4. Walk or run at your normal pace for about 20 minutes.

See this link for further reference Calibrate your Apple Watch for improved Workout and Activity accuracy - Apple Support

Allieg824 wrote:

So I use a treadmill desk so I can walk and work at the same time. The only bad part is that when I start an indoor walk workout on my watch it inaccurately tracks my steps and mileage because my arm isn’t freely swinging beside me. Yesterday my treadmill said I walked 5+ miles but my watch only logged 1.3 miles. Are there any ways to fix this issue? Thanks!

No, short of wearing the watch on your ankle, as BobHarris suggested. If you're inside, the watch relies on the accelerometer to determine distance.

If you use a third-party app to track your workout from your iPhone and you put the phone in a front pocket, you might get better results. That's what I always did on treadmills before the Apple Watch existed. If you pick an app that syncs to health, you'll see your information there. However, it won't count toward closing your rings.