We just had our first HOT weekend of the year here in Kentucky. Temperatures were in the 40s last weekend, but this weekend they crept into the low 80s with lots of sunshine.

Springtime greenery


The first heatwave of the season always takes a toll on athletes. After several months of cold training, we are ready to quickly shed the winter clothes, but unfortunately our bodies are not yet adapted to handling the new heat. Friends, colleagues, clients, and myself struggled through tough runs this weekend…Why?

Why the Struggle?

We all know your body cools itself by sweating and evaporation. When you are hot, blood is routed to the skin where it can be cooled. There is, therefore, less blood/oxygen being transferred to the working muscles, which decreases performance. Additionally, exercising in hot temperatures naturally speeds up glycogen depletion and increases lactate levels.

Heat acclimation on Bourbon Street, NOLA – 2015


Heat Acclimation

Your body will automatically acclimate to the heat, as it does every summer. You will sweat sooner and increase the number of activated sweat glands. Blood volume will increase, thus more blood will be available to exercising muscles. And heart rate increase will be less than before acclimation.

Heat acclimation typically takes place over the first 5-10 runs of an hour or longer in the heat. Cardiovascular adaptations will start within the first 5 days. Sweating changes typically occur in the first 10 days.

What to do in the meantime?

Slow down! Because of the reasons mentioned above, your body has to work harder than it would in cooler weather to achieve the same output. Adjust your pace in the heat to compensate. For example, if you are used to running 9:00 minute miles at a heart rate of 140bpm in cooler weather, on a hot day you may find your heart rate escalates to 150bpm to hold the same 9:00 min pace. You will need to slow your pace to settle your heart rate back down into your preferred zone. Studies have shown that marathon performance can degrade 10% or more on 85 degree versus 55 degree race days.

Hydrate! Hydration is always important but even more so in the heat. Start your workout well hydrated, and then hydrate early and often. Understand your hourly sweat rate and drink accordingly. Supplement with electrolyte tablets or drinks as required. Proper hydration is an involved and important topic that I won’t discuss fully in this blog post, but stay tuned for a hydration-only post in the near future.

What else? I have a few other simple tips to keep in mind for making the heat transition bearable. Wear sunscreen! Not only does it protect your skin, but it helps keep your skin cooler. Dress in breathable, wicking fabrics to pull moisture from your body and aid in the evaporation process. Modify your training route to keep yourself near accessible water sources. Lastly, understand the warning signs of heat illness, and cut your workout short and take appropriate action as required to stay healthy!