Heat: Performance Enhancer or Inhibitor?
I’ll be honest, training to any extreme is not my cup of (lukewarm) tea, especially when it comes to extreme temperatures. Even with recovery, I’m not running to – or heading anywhere near – an ice bath or sauna, though there can be benefits to both if done safely and at the right time.
Sometimes however, training in the heat may be unavoidable or even advantageous… but only to a certain degree (literally).
So let’s discuss:
When heat works as a performance enhancer
When it becomes a performance inhibitor
How to identify if the benefits outweight the negatives (and vice versa)
What you can do to cool down when heat is not advantageous but unavoidable
Heat as a Performance Enhancer
Heat can actually enhance your performance, but it depends on a lot of factors and preparation.
Warming up the body
When it comes to “warming up” (the aptly named term for preparing the body for more intense physical exertion and performance), being in a warmer climate or even layering up can shorten your warm up time, provided you’re not breaking a sweat after just a couple reps or a gentle stretch.
By physically heating the body, it allows the soft tissues (muscles, tendons, ligaments, fascia) to become more malleable and able to stretch further, allowing for greater range of motion (mobility) and greater muscular contraction. Just because you’ve physically warmed the body, doesn’t mean it’s a good idea to sit in front of a heater for a couple minutes then jump right into heavy lifts or high intensity sprints. Another important part of warming up is lubricating the joints through movement (preferably similar to or the same movements as the ones you’ll be performing).
Side note, if you’re so lucky as to have access to a sauna pre or post session, that can help to either kickstart your warm up or promote recovery after by increasing blood flow.
Improved physiological response
When properly acclimatized to the heat, your body better regulates and responds to hotter temperatures with:
Increased plasma volume leading to higher sweat rate
Earlier onset sweating, helping to keep the core temperature down
Reduced salt loss in sweat, better maintaining electrolyte levels
Reduced skin blood flow, indicating a lower metabolic rate (lowered intensity)
Increased intensity & output
Training in hotter temperatures will increase cardiac output, increasing the intensity with which your body has to perform at to produce the same or similar results in more moderate conditions.
Heat as a Performance Inhibitor
Let’s go a little deeper into what’s actually going on when the negatives outweigh the potential positives…
Core temperature is too high
If you’re in extreme heat and humidity for too long without the ability to cool down, your core temperature will rise. The blood flow to your heart will actually decrease as your blood then pools in your limbs, sending it to the skin in an attempt to radiate the heat and cool your internal temperature. This brings you into an anaerobic state, using up the energy in your muscles more quickly, leading to quicker rates of fatigue and decreased performance.
Dehydration
In addition to the effects on your core temperature, and the effect most commonly thought of when it comes to heat is dehydration. Dehydration occurs as a consequence of sweating out liquids (and electrolytes) faster than you are replenishing them. Even if you are drinking liquids (with electrolytes) throughout your training, if it’s so hot that you simply can’t drink enough to replace what you’re losing, you’re at a huge risk not just for dehydration but, more seriously, heat exhaustion and heat stroke.
Muscle cramps
Even if you are simply dehydrated though, muscle cramps may sideline you first, due to the lack of oxygen being sent to your muscles. It’s not always enough to just keep drinking liquids, you’ll eventually need to reduce your internal core temperature.
Reduced performance
Even before becoming too hot, dehydrated, and/or cramping, your performance will suffer:
Muscles fatigue more quickly
Cardiovascular function is impaired
Central Nervous System (CNS) is impaired
Simply put, at a certain point, your body’s systems aren’t keeping up with the intense demands placed on it, leading to a reduction in overall performance and diminishing returns.
When it comes to training in heat, it all comes down to WHY and HOW you’re training in heat that determine whether the benefits outweigh the negatives…
The benefits outweigh the negatives:
Acclimatization for a warm climate outdoor event/activity. If you’re training for an event or style of training that takes place outside in a hot/humid climate, slowly adjusting your body to higher temperatures is advantageous. This should be done over a 1-2 week period. Acclimatizing to warmer conditions can also improve your performance in cooler climates. If you’re repeatedly (and gradually) exposing yourself to training in warmer temperatures, your blood vessels will be better able to dilate, causing more oxygen rich blood flow, allowing for greater overall performance.
Staying within a weight class for a short term sporting event. I’m not here to debate whether this is a healthy practice but it is a fact that some sports require you to maintain a specific weight range to participate in a specific weight class. Purposefully increasing the heat in order to shed water weight is common practice and can be done relatively safely if done under supervision.
The negatives outweigh the (potential) benefits:
You’re unable to perform your activity with proper form. I say potential benefits here because, at a certain point, you’re no longer actually benefiting from the added intensity. If you’re unable to perform exercises with proper form your body is now unable to keep up with the demands placed on it and it’s better to cool down and restart when you’ve rehydrated (with electrolytes) and successfully cooled your core body temperature. Otherwise, you’re only going to see diminishing returns and greatly increase your risk of injury.
You’re strength training. Under no circumstances should you lift heavy weights while in extreme heat. Sure, you’ll likely be fine doing some bodyweight or relatively light resistance exercises (provided you’re still doing so with proper form) but lifting heavy in the heat is a recipe for disaster and there are ZERO benefits that outweigh the extreme risks.
When & How to Cool Down
When
It’s time to cool down when, as mentioned before, you’re not able to continue your training with proper form. Even more pressing, you should cool down ASAP if you’re experiencing even the slightest signs of dehydration or heat exhaustion, including:
Muscles cramps
Dizziness
Headache
Extreme thirst
Feeling or being sick
Cramps in the arms, legs, and stomach
Fast breathing or heartbeat (more than you’d normally experience during training)
Extreme weakness or fatigue (more than you’d normally experience during training)
Excessive sweating and skin becoming pale and clammy or getting a heat rash (note that change in skin color can be harder to see on darker skin tones)
How
So, how can we reduce that internal temperature to avoid dehydration, muscle cramps, or other more serious negative effects?
Lay down with your feet above heart level. Not only are you stopping movement, you’re also directing blood flow back to your heart to help re-oxygenate the blood flowing through your body.
Step into the shade if in the sun.
Take it off! Wear as little as possible, as loose as possible. Loose, breathable, and light colored.
Ice packs to cool the skin.
Find a fan (there are plenty of wearable options out there).
Takeaway
While there may be some benefits to training in slightly higher temperatures and increasing body heat, it’s clear that there is a certain threshold where it will greatly reduce athletic performance. Any theoretical increase in intensity or output during a heated training session will be so marginal that it’s likely not worth it unless:
You have a specific, short term goal (i.e. losing water weight to stay within a weight class).
You have to perform in unavoidably hotter climates (i.e. a marathon in Hawaii).
You are a professional/olympic level athlete where those tiny margins matter.
You’re doing so gradually over the span of couple weeks (acclimatizing).
If you’ve determined that training in heat is something you want to pursue, here’s a good resource that goes more in depth and demonstrates how to acclimate safely: “Heat Acclimatization to Improve Athletic Performance in Warm-Hot Environments”
