If you’re cruising along on a runner’s high while your partner has yet to feel that sweet euphoria, is that a nod toward your superior running ability? Sorry, no. The more likely reason could simply be in your genes, according to a recent study published in Medicine & Science in Sports & Exercise. Researchers looked at 25 collegiate runners, both male and female, and tested their saliva before and after a long-distance run. They also asked them about whether or not they experienced a runner’s high, which they gauged based on four criteria: mood, lost sense of time, run quality,...