Consider a Bluetooth Accessory
There are actually a variety of factors that can negatively impact the Apple Watch’s accuracy in recording movement and workouts. That could include tattoos and skin perfusion, or how much blood flows through your skin. Some of these factors, of course, you can’t really control.
If you keep getting irregular or inaccurate workout results, Apple actually recommends going with a third-party Bluetooth accessory. That could include an external heart rate monitor or step counter. Just pair these devices with the Apple Watch by going to the Settings app on your watch and navigating to Bluetooth.