Hot Weather Marathon Tips

It's looking like the conditions will be challenging for Monday's Boston Marathon. If the current forecast holds, most of the race will be run with temperatures in the low to mid-70's, which is far from ideal, but also better than the mid-80's that are predicted as the day's high. High temperatures can lead to dehydration and overheating. Your body tries to stay cool by sweating and by sending more blood to the skin where it's cooled. That's all well and good, except that your working muscles want that blood for themselves. As such, you're having an internal tug of war over your finite blood supply. Either you slow down because your muscles get less blood, or you overheat because your body isn't using its resources to cool you. One way or another, something's gotta give.

The other issue is that your sweat rate will increase in an effort to keep your body cool.  This will put you at greater risk for dehydration. It's especially important that you maintain proper hydration leading up to the race, and certainly during the race.

Even under the best of conditions, it's important to pace intelligently. There's no such thing as "banking time", and going out too fast will result in losing more time later than you gained early in the race. Rather than trying to ignore the adverse conditions, it's best to make adjustments in your plan before the race, rather than waiting until your body gives you no choice. While everyone is different, most of the science seems to suggest a 2-3% decrease in performance when racing in the conditions that are expected on Monday. (Obviously the decrease will be greater if the temps reach the 80's earlier.)  If you're starting later, you'll probably encounter more challenging conditions and need to adjust more. Similarly, slower runners should probably make a bigger adjustment. The level to which you have acclimated to the heat (which is presumably not at all for east coast runners at this time of year) and your general tolerance of hot weather should also be taken into consideration

Here are a few tips for race day:

  • Drink 20+ ounces before bed and when you wake up. Keeping your blood volume up is valuable.
  • Salt with breakfast and during the race can be beneficial
  • While you may be able to gauge your hydration by thirst under other circumstances, you need to be more proactive in Boston. Drink liberally before the race and don't wait until you're thirsty during the race to start replenishing.
  • Sports drinks may be favorable due to the electrolyte content
  • Wear sunscreen, a cap or visor, sunglasses, and light, wicking clothing
  • Pour cold water over your head. If they offer ice, put some under your hat. Dip a bandana in cool water and wear it around your neck.

Adjusting your goal pace by even 2-3% is obviously frustrating and disappointing, but it's far better than sticking to the original plan until you crash and burn (no pun intended), in which case you will lost far more time. Your 3-hour marathon may turn into a 3:03-3:06, or even a 3:10, and your plan to negative split may go out the window since the heat will increase as the race progresses, but if you plan intelligently and fuel wisely, there's no reason why you can't still have a great race in Boston.

Have fun and be safe.