I play a lot of racquetball, which I started several years before I started vaping. I haven't really noticed a difference in endurance, but I wear a heart rate monitor (to tell me how many calories I burn). I've noticed that since I started vaping my resting heart rate is a bit lower, and the max heart rate I reach during an intense rally is lower. Before the max I would get to was 183, now the highest I seem to get is ~174.