If I do walk-run intervals during an Outdoor Walk, will it mess up the walking speed and VOmax measurements?

Open workouts and start your workout, running, say.

You have to let that run for one full minute before the New+ button will allow you to select another workout type.

Select New+ then select the next workout you want to do, let's ride, cycling.

Let that go for one full minute then select New+, let's pick rowing.

Now you have three workouts going -- running, cycling, rowing.

To change from one workout to another, hit pause and select one of the the workouts you've already started.

To end them all, select End.

Scroll down to the bottom and tap done.

Yes because walking and running are 2 different workouts and each has it's own Algorythm,for calculating burnt calories etc.

I do intervals myself, Run/Walk and it does not effect my stats.

I have selected to log it under outdoor running as I run 75% of the time.