The verb kommen is a "half modal". It's sometimes used as it was a modal verb, with a bare infinitive:
Kommst du laufen?
Wir gehen schwimmen.
Sie sieht ihn stürzen.
There are a lot more of such verbs, most about moving to practice another action, or perception.
Kommst du auch zu laufen?
This is ungrammatical. You may actually hear it in some some dialects but it means
Are you having time for running?
That is because to make it grammatical, one inserts a dazu
Kommst du auch dazu, dass du läufst?
Kommst du auch dazu, zu laufen?
and dazu kommen means Are you having time for it?. This is tricky. The verb dazukommen in contrary means coming to the group. The difference is all in the stress. See 'umfahren vs um'fahren.
You could write
Kommst du auch zum Laufen?
instead, making laufen a noun. This phrase may mean both depending on the stress, and that's why the modal phrase is often preferred.