A recent article in the Wall Street Journal discusses how disruptions to our circadian rhythm (the 24-hour clock that influences sleeping and wakefulness) affect us more than was previously believed, and may contribute to disease. Much research is now focused on how to adjust the “clock genes” within cells of different organs in the body to prevent or help treat conditions such as obesity, colitis, and diabetes. In one area of study, for example, clinical trials are ongoing to determine if there is an optimal time of day to eat in order to gain less weight.
What does this have to do with running? At look at a typical circadian clock cycle based on an average sleep time form 11 p.m. to 7 a.m. provides some clues that lead one (that is, me) to make some general observations on the best times of the day for certain runs:
Best time for long runs (7:30 a.m. – 10 a.m.). Sure, you want to rise early before the heat of the day and before your schedule fills up with other commitments, but don’t start too early. Melatonin secretion, which controls sleep cycles, does not stop until 7:30 a.m.; run too much before that and you’re fighting against the body’s natural sleep cycle. Furthermore, the body’s alertness is on the increase then peaks at 10 a.m., enabling you to be more vigilant then for traffic, potholes, mile markers, barking dogs, and the various signals the body gives off that often go unnoticed until it’s too late. It won't hurt then to give a race's starting time a priority when seeking your next marathon.
Best time for a trail or cross-country run (2:30 p.m. - 3:30 p.m.). We supposedly have our best coordination at 2:30 while our reaction time peaks at 3:30, perfect for dodging and maneuvering around tree roots, rocks, boulders, holes, gullies, and the variable terrain you encounter on trail runs and cross-country rambles.
Best time to run hills (5:00). Hills require leg strength and research has shown that our muscles are strongest at the time most of us knock off from work. How about doing those hill repeats on the way home then?
Best time to run in the cold (7:00 p.m.). Since our body temperature is highest at this time of day, you may want to consider putting off your cold-weather runs until early evening. But make sure you finish by 9:00 p.m. when melatonin secretion begins and your body wants you to (yawn) unwind and relax to prepare for a good night’s sleep.
Best time to dream about winning that Olympic gold medal (2:00 a.m.). When you experience your deepest sleep!