Tuesday, 22 July 2014

Training and competing in the Heat - what can you do to help?

As Britain enjoys one of the warmest summers I remember, I was asked the question, 'how does heat effect your training and what can you do to help your training and racing in the heat?'

One of the main effects of heat is an increase in perceived effort and the decreased motivation to go out and perform. Training or competing seem much harder and therefore times can suffer either in training or competition.

But what are the physiological effects of the heat?

The main ones are:
  • Dehydration
  • Increased Heart Rate
  • Reduced Blood Flow (and subsequently oxygen) to the working muscles.
Dehydration - I have already covered dehydration and why and what we should drink in a previous posts. But why does the risk of dehydration increase as the environmental temperature increases? 

Thermoregulation is the body's way of maintaining a consistent internal temperature, vital for bodily functions which keep us alive.  One of the ways that the body looses heat is via sweating, with the rate of evaporation linked to how well the body is cooled and the atmospheric humidity. When humidity is low evaporation increases, when humidity is high the rate of evaporation decreases and less cooling occurs.

Sweating leads to fluid loss, and dehydration occurs from the inadequate replacement of fluids. It is thought that every 2% loss of body weight through sweat can lead to about a 4-6% decrease in performance.  If this fluid is not replaced an athletes blood volume decreases, less blood returns to the heart and less oxygen rich blood reaches the muscles. You produce less energy aerobically and you run slower for a given effort level.  As it gets hotter, this effect is increased. The more heat that needs to be dissipated, the greater the proportion of blood diverted to the skin.

What can you do?

Training in itself provides some adaptation to the heat. It increases the total plasma volume which is why the fittest athletes (and likely those with the highest plasma volume) typically adapt more easily to the heat and perform better.

Regular training in the heat can result in it becoming easier to maintain a faster pace and reduce perceived exertion by increasing blood plasma volume, increasing sweat rate, reducing heart rate at a given pace and speeding up the onset of sweating. These adaptations make it easier to perform in the heat and can be noticed after only a week or two of heat exposure.  Training in the same temperatures as you would be competing at can have a massive positive affect.

Heat also effects intensity. Some athletes may benefit from moving training focus away from a certain time goals to running at an equivalent efforts. Sessions could be moved away from a track, to make it easier to pay attention to feel and perceived exertion rather than split times

What can you do for racing in the heat?
  • Adjust preparation - increase the layers in training to replicate warmer temperatures when you race. I have known triathletes preparing for Kona do bike sets next to a radiator with additional layers to prepare themselves for the heat they could expect when they race
  • Increase fluid and electrolyte intake in the days prior to racing to make sure you are hydrated
  • Stay as cool as possible before the race (sponges)
  • Perhaps have a shorter warm up
  • Pay more attention to perceived effort rather than race splits 
The other bit to recognise is the signs and symptoms of heat stroke:
  • Headache
  • Dizziness and light headedness
  • Lack of sweating despite exercising in the heat
  • Dry Skin
  • Muscle weakness or cramps
  • Nausea and Vomiting
If you do train in the heat and experience any of the above, try to get in a cool environment and drink plenty of water.

1 comment:

  1. As Rachael mentions, humidity plays an important role in thermoregulation. Endurance athletes, marathon runners in particular, often have to weight up the benefits of training at altitude in the run up to a big race, against the relative costs. Increased altitude is associated with reduced humidity, and though altitude will help increase performance in a number of ways, it will not prepare you for competing in high humidity environments, not matter how warm it is. If you are planning on competing in high humidity, either skip the altitude training altogether, or allow 10 days or so after your return to sea level to acclimatise to the humidity.

    Similarly, air conditioned environments will not help you adjust to heat and humidity. If you are preparing to compete in the heat, hiding away in your air conditioned hotel room will do little for your performance. Of course, you need to get a balance, as you don't want to get sun stroke, sunburnt or dehydrated in the day or two leading up to your event