5 Ways Heat Affects Running Performance
Stoshew71
Posts: 6,553 Member
Another article I came accross from the same website, since a lot of us are running in higher temperatures (and humidity) as of late.
http://running.competitor.com/2014/06/training/5-reasons-heat-affects-performance_11671
How heat and humidity affect running performance and how to acclimatize to hot conditions.
Changes In Blood Flow And Sweating
The human body has the ability to cool itself in hot conditions by sweating. Actually, it’s the evaporation of sweat that causes cooling, not sweating itself. (This is important with regards to humidity.)
For sweating and cooling to occur, the body must increase blood flow to the surface of the skin. Why blood? Blood is the major carrier of heat, and sweat is composed of plasma, which comes from blood. So when we sweat at high rates, we’re actually losing blood volume, not to mention electrolytes. This is why proper hydration is vital.
Increased skin blood flow is problematic for an endurance athlete because less blood is available to working muscles and vital organs such as the heart, making exercise more difficult.
More Demand On The Heart
Ideally, during exercise we want the heart to pump out as much blood as possible in each beat so that the heart rate doesn’t skyrocket to sustain a given workload. What happens in the heat, however, is less than ideal.
With more blood at the periphery, there is less blood flowing to the heart. This decreases cardiac filling and stroke volume — the amount of blood that is pumped from the heart. To compensate, heart rate increases to sustain the workload. As a result, the relative intensity of exercise increases, more stress is placed on the heart and we max out sooner. In other words, an 8-minute pace may feel like a 6-minute pace because the heart is working that much harder.
Also, if blood volume decreases from high sweat rates (a loss of plasma) there is an increase in blood viscosity — a higher concentration of red blood cells — which puts more stress on the heart and vessels.
Working Muscles Suffer And Anaerobic Modes Kick In
When blood volume is split among competing interests during exercise in heat, the next victim is active muscle.
Muscles engaged in activity suffer because they aren’t getting as much oxygen from the blood. For endurance athletes oxygen is gold; it’s the fuel that allows us to sustain exercise for longer durations, and without it we’re forced to rely more on pain-inducing anaerobic (without oxygen) modes of producing energy.
Increased anaerobic energy production affects exercise at all intensities and causes a slew of issues including higher total energy expenditure and blood lactate accumulation. Also, carbohydrates are used for energy more than lipids (fat), and since carbohydrate fuel stores are extremely limited in the body, exhaustion is reached much sooner.
In the end, this shift from aerobic to anaerobic modes will generally result in a faster onset of muscular fatigue.
VO2 Max Decreases
The heart is hard at work but pumping out less blood than usual; the muscles aren’t getting as much oxygen. These responses play a role in decreasing the all-important VO2 max, which is the maximum amount of oxygen that the body can take in and use to fuel working muscles. Again, for endurance athletes, the higher VO2 max, the better; it’s a marker of exercise efficiency.
Because VO2 max decreases, at any exercise intensity you’ll be working at a higher percent of VO2 max. In other words, relative stress increases at a given workload because you’re less efficient.
Humidity Hinders Cooling
Relative humidity is the amount of water in the air compared to the theoretical maximum amount of water in the air and it directly influences sweating and cooling.
Remember that the body cools itself with the evaporation of sweat — not the sweating itself. The more humid it is, the more saturated the air becomes with water, and the harder it becomes to evaporate sweat. With less evaporation of sweat, we don’t cool as well. Plus, that sweat remains on the skin, making it seem like you’re sweating more, but you’re not — that’s the lack of evaporation.
The bottom line? As temperature increases exercise costs more energy and you’ll tire sooner.
About The Author:
Tawnee Prazak is a certified triathlon coach, exercise scientist and triathlete. Find out more at www.tawneeprazak.com.
Read more at http://running.competitor.com/2014/06/training/5-reasons-heat-affects-performance_11671/5#M4YGy2Szgjo5ePxv.99
http://running.competitor.com/2014/06/training/5-reasons-heat-affects-performance_11671
How heat and humidity affect running performance and how to acclimatize to hot conditions.
Changes In Blood Flow And Sweating
The human body has the ability to cool itself in hot conditions by sweating. Actually, it’s the evaporation of sweat that causes cooling, not sweating itself. (This is important with regards to humidity.)
For sweating and cooling to occur, the body must increase blood flow to the surface of the skin. Why blood? Blood is the major carrier of heat, and sweat is composed of plasma, which comes from blood. So when we sweat at high rates, we’re actually losing blood volume, not to mention electrolytes. This is why proper hydration is vital.
Increased skin blood flow is problematic for an endurance athlete because less blood is available to working muscles and vital organs such as the heart, making exercise more difficult.
More Demand On The Heart
Ideally, during exercise we want the heart to pump out as much blood as possible in each beat so that the heart rate doesn’t skyrocket to sustain a given workload. What happens in the heat, however, is less than ideal.
With more blood at the periphery, there is less blood flowing to the heart. This decreases cardiac filling and stroke volume — the amount of blood that is pumped from the heart. To compensate, heart rate increases to sustain the workload. As a result, the relative intensity of exercise increases, more stress is placed on the heart and we max out sooner. In other words, an 8-minute pace may feel like a 6-minute pace because the heart is working that much harder.
Also, if blood volume decreases from high sweat rates (a loss of plasma) there is an increase in blood viscosity — a higher concentration of red blood cells — which puts more stress on the heart and vessels.
Working Muscles Suffer And Anaerobic Modes Kick In
When blood volume is split among competing interests during exercise in heat, the next victim is active muscle.
Muscles engaged in activity suffer because they aren’t getting as much oxygen from the blood. For endurance athletes oxygen is gold; it’s the fuel that allows us to sustain exercise for longer durations, and without it we’re forced to rely more on pain-inducing anaerobic (without oxygen) modes of producing energy.
Increased anaerobic energy production affects exercise at all intensities and causes a slew of issues including higher total energy expenditure and blood lactate accumulation. Also, carbohydrates are used for energy more than lipids (fat), and since carbohydrate fuel stores are extremely limited in the body, exhaustion is reached much sooner.
In the end, this shift from aerobic to anaerobic modes will generally result in a faster onset of muscular fatigue.
VO2 Max Decreases
The heart is hard at work but pumping out less blood than usual; the muscles aren’t getting as much oxygen. These responses play a role in decreasing the all-important VO2 max, which is the maximum amount of oxygen that the body can take in and use to fuel working muscles. Again, for endurance athletes, the higher VO2 max, the better; it’s a marker of exercise efficiency.
Because VO2 max decreases, at any exercise intensity you’ll be working at a higher percent of VO2 max. In other words, relative stress increases at a given workload because you’re less efficient.
Humidity Hinders Cooling
Relative humidity is the amount of water in the air compared to the theoretical maximum amount of water in the air and it directly influences sweating and cooling.
Remember that the body cools itself with the evaporation of sweat — not the sweating itself. The more humid it is, the more saturated the air becomes with water, and the harder it becomes to evaporate sweat. With less evaporation of sweat, we don’t cool as well. Plus, that sweat remains on the skin, making it seem like you’re sweating more, but you’re not — that’s the lack of evaporation.
The bottom line? As temperature increases exercise costs more energy and you’ll tire sooner.
About The Author:
Tawnee Prazak is a certified triathlon coach, exercise scientist and triathlete. Find out more at www.tawneeprazak.com.
Read more at http://running.competitor.com/2014/06/training/5-reasons-heat-affects-performance_11671/5#M4YGy2Szgjo5ePxv.99
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Another related article: Seven Hot Weather Training Tips By Matt Fitzgerald
http://running.competitor.com/2013/07/training/seven-hot-weather-training-tips_4347
Try pre-cooling
Research has shown that athletes perform better in hot environments when they cool their bodies beforehand. Pre-cooling doesn't make a huge difference, but if you want to gain a little bit of performance in important workouts that must be done in the heat, turn your air conditioning down low or spend time in a cool bath before you head out the door.
Stay hydrated
Drinking during hot-weather workouts will help your sweating system do its job better. By drinking throughout each training session you will keep your blood volume close to normal levels, which in turn keeps your sweat rate high. And since oxygen is delivered to the muscles through the blood, maintaining your blood volume through drinking also enables your heart to deliver more oxygen per contraction, so you perform better than you can if you allow your body to become too dehydrated.
Dress to sweat
Sweating is the body's primary cooling mechanism. When you train in hot weather, be sure to dress in clothes that allow this mechanism to do its job. Avoid wearing everyday clothes such as cotton t-shirts, which trap sweat and heat against the body. Instead wear technical apparel that is designed for your sport and made from moisture-wicking fabrics such as CoolMax, which soak sweat from your skin and transfer it to the outer surface of the garment for evaporation. Light colors that reflect the sun are also preferable.
Run early — or late
If you take the time to acclimatize to the heat, and you adjust your pace properly on hot days, you can train safely in very high environmental temperatures. However, because you have to slow down, you can't train as hard or get as fit in such temperatures as you can in cooler temperatures. That's why very few American runners and triathletes went to "heat camps" ahead of the Beijing Olympics, where very hot days were expected. They preferred to train at a higher level in cooler environments until they left for China, and then acclimatize over there.
By the same rationale, I recommend that you train early in the morning and late in the evening-and perhaps even indoors sometimes-to avoid the highest temperatures of the day. You'll have better workouts and you'll feel more comfortable, too. I lived in Phoenix for one year, where I quickly discovered that the local endurance athletes routinely work out before the sun comes up and after it goes down. After suffering through a few broiling midday workouts I quickly fell in line with the local days, and boy what a difference it made!
Slow down
I said "more or less normally" in the previous photo because it is never possible to train as hard in the heat as in temperate conditions. Research has shown that the brain protects the body during exertion in the heat by constantly monitoring the core body temperature and limiting muscle activity to prevent the core body temperature from rising to dangerous levels. (It's actually the heat produced by the muscles, not environmental heat, that causes heat illness to occur. Environmental heat merely prevents body heat from dissipating.) So don't expect or try to perform at the same level on hot days. Instead, maintain your normal level of exertion and understand that you will not go as fast at this level of exertion as on cooler days.
Take baby steps
The fitter you are, the better your body can tolerate exercise in the heat, so try to build your fitness to a high level in the spring, before the first heat wave of the year. When the first really hot day comes, do a shorter- and slower-than-normal workout. On each subsequent hot day go a little farther and a little faster. It takes about 10 days for the body to full acclimatize to the heat. The body adapts by increasing its sweating capacity and reducing the electrolyte concentration of the sweat to boost your ability to maintain a safe core body temperature. After this process is complete you can train more or less normally through the summer.
Listen to your body
Early signs and symptoms of heat illness include fatigue, discomfort, lightheadedness, cessation of sweating, disorientation and nausea. Stop exercising and find a cool environment as quickly as possible if you begin to notice any of these signs or symptoms while exercising in the heat.
Running in hot weather is not always pleasant, but it’s not always avoidable, either. If you live in an area where the summers are toasty and you want to be in peak shape for a fall half marathon or marathon, then you have to get out there and sweat in July and August.
While running in the heat is not as enjoyable as running on cool days, it need not be any riskier. Heat illness is relatively rare among runners, and if you take the following precautions, it will never happen to you.
Matt Fitzgerald is the author of numerous books, including Racing Weight: How To Get Lean For Peak Performance (VeloPress, 2012). He is also a Training Intelligence Specialist for PEAR Sports. To learn more about Matt visit www.mattfitzgerald.org.
Read more at http://running.competitor.com/2013/07/training/seven-hot-weather-training-tips_4347#eQEG4CS9Bk0zS2wy.990 -
Thanks Stan! I've been reading about this topic a lot, lately. I think the only thing I can really do a little better is making sure I am taking in plenty of water throughout the day, not just during my run......as well as slowing down (Which I have been doing, but it's difficult to do.).0
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Several years ago we had a particularly hot and humid summer here in Ohio. After running in these less than ideal conditions all summer, when fall finally rolled around and the temps and humidity fell, I noticed that I was a much stronger runner than I had been in the spring. Not that I am advocating heading out and going balls to the wall every day in August, but I believe there can be some benefit to training in these conditions. Just exercise your best judgement on when and how hard to run, stay hydrated and listen to your body...pretty much everything stated above.0
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^^I agree. I was amazed at how much faster I was this past fall after running all summer in the sweltering heat. (last summer was my first official summer being a runner).
I just felt soo fast and soo strong! I am hoping that holds true for this coming fall and winter!0 -
Thanks for the links, have been upset at my VO2 max dipping lately, maybe it is heat-related. hadn't considered that. Will check 'em out10
