How to Fuel For Success on HOT Days

Common mistakes and keys for success.

Updated for 2024

INTRODUCTION

We’ve all experienced it in some variation – it’s basically a rite of passage for any serious endurance athlete who’s ever pinned on a number and, inevitably, started a workout or race with insufficient hydration on board. Everything seems to be going well, and then it hits. Catastrophic cramping, crippling GI distress, exhaustive vomiting, and life-changing diarrhea – the stories you later recount to your friends and training buddies in response to “What’s the worst that could happen?”

If you’re lucky, you can get through it and struggle to the line. Those are the fortunate days. But more often than not, it’s the end of the road. It’s not pretty, and the risk of experiencing it is absolutely multiplied by the kind of hot weather that tends to correspond with target races and big events.

Training and racing in the cold is entirely different than training and racing in heat. Strange things seem to happen in hot conditions, with some athletes thriving while others fall apart; however, there is a science to it, and your nutrition program has a lot to do with how well you handle extreme conditions.

Dehydration, cramping, and GI distress can wreak havoc on your performance. Your best weapon against them is smart, intentional hydration.

THE DANGERS OF DEHYDRATION

Dehydration significantly reduces your ability to absorb calories and nutrients, and ergolytic (performance decreasing) effects begin to compound the worse dehydration gets.

At just a 1% drop in internal fluids, your heart rate increases in order to sustain an adequate sweat rate. If you suffer a 2% drop in total internal fluids, you’ll experience a serious decrease in your exercise performance and efficiency. You could even suffer from heatstroke, and those compounding effects add up to DNF. Obviously, that’s not what any endurance athlete wants, so – though it’s an athletic axiom – it’s worth reiterating that maintaining hydration is critical to performance, especially in hot conditions.

3 KEYS TO SUCCESS ON HOT DAYS

HYDRATION COMES FIRST

Training and racing in the heat will most likely be derailed by dehydration way before it’s affected by a nutrition bonk, and dehydration can actually contribute to bonking by compromising nutrition absorption.

Most athletes prioritize caloric intake and consume water arbitrarily without considering concentration percentages or osmolality, which is exactly what you shouldn’t be doing.

The most important consideration, when racing on hot days, is hydration, not carbs. If you don’t make sure your hydration requirements are being met before consuming additional calories, then cramping, dehydration, and GI distress can wreck your day.

You probably won’t experience cramping or dehydration issues when training or racing for an hour or less. For longer sessions, however, it’s essential to stay on top of your hydration and electrolyte consumption.

To do that correctly, it’s critical to maintain an internal balance between electrolytes and your basic hydration level, so the First Endurance system – EFS, EFS-PRO, and Liquid Shot – is engineered to keep you replete with all five electrolytes (sodium, potassium, calcium, magnesium, chloride).

That ensures your electrolytes levels stay balanced with each other and with internal fluid levels, in turn ensuring proper muscular contraction and cellular respiration. When electrolytes are in balance, performance improves and the risk of cramping is eliminated. If you’re just loading up on water alone or only consuming one or two electrolytes, then you risk throwing the whole system out of whack, which impedes muscle function and creates cramping risk.

DRINK WITH INTENTION

Sweat is your body’s mechanism to cool itself in hot environments. The more trained you are, the better your mechanism to sweat and cool yourself becomes. If you have a high sweat rate, it’s a sign that your body has acclimated to the heat. To sustain a high sweat rate, which is ultimately what you want in hot conditions, you have to maintain the appropriate amount of fluid.

Humidity levels can also affect hydration needs. In very arid environments (like in Arizona and Utah), sweat can evaporate almost immediately, which can make it difficult to consciously track your sweat rate, thereby impeding your own perception of how much fluid you’re losing. In dry conditions, your sweat rate can be at its highest – even though you don’t see or feel any moisture on your skin – so it’s especially critical to drink with intention rather than drinking to thirst in hot, dry conditions.

DIAL YOUR APPROACH IN TRAINING

It’s always best to test your hydration and fueling strategies in training in order to figure out what works best for you. As the duration of training and racing increases, it becomes more and more important to pay attention to your fluid and caloric intake so you can balance the two appropriately in order to ensure success. Only consume the maximum calories that match your hydration consumption.

Your pace also affects how many calories you need, of course, but that also requires an adjustment to hydration volume. A threshold pace will require significantly more calories than a slow pace, and thus, significantly more fluid.

As the temperatures and/or pace change in training and racing, you should change your hydration and fueling strategies to match. That applies to each session or race individually – if it starts out cold and heats up as the day progresses, then be sure to adjust your caloric intake and hydration accordingly.

GUIDELINES FOR HYDRATING IN THE HEAT

Every athlete responds differently in the heat. In extremely hot and long sessions, it’s not out of the question for some athletes to push 40-50oz of liquid per hour to sustain efforts, while others can get away with as little as 24-30oz.

Though hydration volume is personal, we can provide general fuel : liquid ratios. On hot days, we recommend drinking 21oz fluid for every 100 calories. If you know you will only consume 42oz of fluid per hour, then your maximum caloric intake during exercise should be 200. Attempting to force calories in without proper hydration is a recipe for gastric distress, cramping, and poor performance – see our dire, but not exaggerated, warnings in the intro.

Finally, the effects of a workout don’t end with the workout. Following every workout you should gauge your hydration levels, and don’t be shy about topping off your fluids and electrolytes with a hit of EFS or EFS-PRO in 21-26oz of water. Your body probably wants the carbs to restock glycogen levels, and it almost certainly wants the water and minerals to restore homeostasis.