The idea being that the actual track uniform, typically a pair of shorts, is worn underneath the track pants. The zippers allow the athlete to remove the pants while still wearing their shoes. Track pants are intended to be worn as coverups before and in between events.
How do you wear adidas Tiro pants?
https://www.youtube.com/watch?v=bS2430c3-Rw
How do I make my Adidas pants tighter?
https://www.youtube.com/watch?v=OFcfhtWTzKM
How do Adidas Tiro 19 pants fit?
The Tiro 19 size medium compared to the 17 are very different. The 19's are much baggier, I thought they were just the newer version but they fit very differently. I'd recommend the 19 if you have big thighs/butt or like a more relaxed fit but still want the tapered look.