We won't do a huge amount of exercise in a warm running tops - but they are very useful for between reps and also for travelling around and waiting about at competitions.

As such, you don't need a hugely specialised top for it to perform the functions it needs to.

A top that is large enough that you can fit base layers underneath, but isn't so big it flops everywhere (or worse still - acts like a big sail!) is good - probably made of some kind of fleece / sweatshirt material which is relatively thick and warm.

You might want it to have an external waterproof layer - or buy a separate waterproof for rainy days.

One bug bear of may coaches is when athletes pull their jumpers over their hands when they run - this creates tension in the forearms which can transfer all the way up the arms and across the shoulders. So - either buy some gloves or the sort of top that has thumbholes to keep your hands warmer. Maybe elasticated wrists would be good to help you not do this too.