Let me help all you fools who are "playing it cool", "taking your time", etc.
The girl never puts you in the friend zone. You do that to yourself. A girl approaches you and says she wants to perform a vigorous physical activity with you. You're both in your teens or twenties. Hello, what do you think is going on here?
The girl is EXPECTING you to make a move...and not some friend-zone-inducing maneuver like kissing their hand. You have no excuse for not trying other than your own pathetic fear.
Be direct and arrogantly humorous with the innuendo. As soon as the run is finished: "Hey, now let's go back to my place and do a real workout", whatever, something that says it so directly that your position on things is clear.
Then you make a real move, at least attempt to kiss the lips. Who cares if you fail?
You succeed...bingo.
You fail but she makes another running date with you...your position is already clear and she hasn't said no. No awkward tension exists and you won't have to overanalyze what everything she did and said might have meant. Continue being randy until you either succeed or fail.
You fail and she does not make another running date with you...you just saved yourself from being a workout rabbit for a cocktease.
You do not have to apologize for being a horny man, it's biological reality. She chose to approach you knowing this in advance.
Maybe you think "but I might lose a potential platonic friend who only wanted to run with me." That's the cost of being a man. If you surround yourself with women who aren't putting out for you, all the other women out there who you might hope to connect with are also going to move you into the "safe but gay" category. Are you really so desperate for someone to run with that you would accept blue-balls? Go find some dude to function as your running partner and save yourself the humiliation.
Thank me later for saving you a lot of wasted time.