I have an app which highly depends on maps. Should I allow the user to zoom in, pinch, and other things or should constraint it to only the current location.
My application tracks the users location and tells them how many meters they ran.
The clues to the answer lie in the wording of the question. Should I allow...should I constrain it. i.e. You are asking if you should restrict the user activities.
Typically users have an expectation of interaction with a map via familiarity with other applications. They expect to be able to pan and zoom. Often this functionality comes free with a map interface anyway.
The problem with you constraining the user is that by doing so you are suggesting that you know exactly what people want to do when they use your app, and you understand every use case and every nuance of usage and you have decided that there are no (or insignificant) cases where a user would need to change scale or location.
The problem with that is that there is no accounting for how people will use your app - in what circumstance, in what kind of terrain, or in what part of the world. You cannot know that your runners will be on their first run of a quarter of a mile, or whether they are experienced long distance runners doing a coast to coast run across the UK.
You may have an idea of how you or some percentage of users will want to interact, but you cannot account for everyone. By unnecessarily incorporating restrictions, then you run the risk of alienating a percentage of your potential users, or losing them after some period of use, or even excluding a whole different audience that you had not thought of. For example cyclists may actually find that your app is perfect for them - assuming they could pan/zoom the map.
Never assume you know how all users will use your product.
We have become accustomed to being able to zoom in and pan digital maps. Not allowing that is likely to frustrate your customers and, from what I have read, there is no good reason for it.
Allow zooming and panning unless you have a good reason not to.
It sounds like you want to use a map to tell users how many meters they ran. Say John is using your app. Will John say he wants to see another spot on the map, besides where he currently is? Is there somewhere on the map John wants to run to?