<p>My son had a similar experience. While his running was good he could only do 1 pull up (barely). I put a chin up bar in his room and he worked on it and got up to 9 pull ups about 5 weeks later. He started doing reverse pull ups - using a step he started in the up phase and did controlled ‘downs’. After a while he got so he could do some repetitions and then built up from there. Good Luck!</p>