By the end of the past weekend, more than half of all Americans will have suffered from temperatures of 90 degrees or higher. Blazing heat and humidity toasted states from Texas to Massachusetts. Records fell or were tied: New York City 90F, Washington, DC, 92F; Austin, TX 99F, Richmond, VA, 95F, Philadelphia, PA 95F, Worcester, MA 88F.
Aging and Heat
Some physiological changes that affect heat tolerance are inevitable with age:
- Decreased cardiac output. How much blood the heart pumps decreases by about 30% between the ages of 20 and 80. Cardiac output is a function of heart rate and stroke volume, how much blood your heart pumps per beat. While your maximum HR inevitably declines, through exercise you can maintain your ability to sustain a reasonably high HR and slow the decrease in the elasticity of your heart, which is what reduces stroke volume.
- Decreased skin blood flow. Blood flow to the skin is 25-40% less in older athletes. The reduced flow is due to changes with the blood vessels in the skin. Staying very fit does not prevent the skin from aging.
- Sweating rate. Compared to younger equivalently fit athletes, most older athletes have lower sweating rates. Although the same number of sweat glands are activated each gland produces less sweat. Genetics plays a large role in determining sweating rate and there is wide variability among older athletes. Decreased sweating is more of a problem in hot, dry environments than in humid ones.
This column provides more information: Heat Tolerance and Aging
You’re the Reason Why You Get Hot.
The human engine is very inefficient. Only about 20 – 40% of the calories you burn move you down the road. The other 60 – 80% generate heat, which must be dissipated. This is why you can feel hot when you’re riding briskly on a cool day.
You also gain some heat from radiation from the sun, from breathing hot air, from hot air on your skin and from hot bike parts. However, the primary source of heat is your engine, which has important implications for heat management.
Effects of Heat on Your Riding.
As your core temperature starts to rise, your body circulates more blood through your core and to your skin to provide cooling and to protect your vital organs from overheating. As a result, less blood flows to the muscles to deliver oxygen and nutrients. As your core temperature rises, it’s also more difficult for your brain to recruit your muscles to contract forcefully, i.e., put out high power. You also can’t ride as hard for psychological reasons — in short, it feels harder to ride when you are hotter.
Sweating is Your Primary Cooling Mechanism
Increasing your sweat rate and radiation from increased blood flow to the skin account for about 85% of your body’s cooling. The rest comes from conduction and convection from your body the air.
The harder you exercise, the more sweating is the dominant mechanism for cooling. Because the primary source of heat is your working muscles, internal cooling to keep your core organs cool is much more important than external cooling. Think of your body like a car’s engine. Most of the cooling is provided internally by coolant, which flows through the engine and then through the radiator. Only a little cooling comes from heat given off directly to the air around the engine. Your blood is the coolant, your muscles are the engine, and your skin is the radiator. Thus, managing your internal coolant — hydration and electrolyte levels — is critical.
Although it may feel good to dump water on your head while riding this only cools your skin. If you drink the water it helps to cool your core, which is much more important. Of course, if you have an ample supply of water, e.g., at a minimart then dumping.
Riding in Hot Conditions
Here’s how you can still have fun on your bike and maintain – even improve – your fitness
- Study the weather and plan around it. Plan your longest or hardest rides for the cooler days.
- Do intensity indoors:
Research demonstrates the value of intensity for older riders:
- Anti-Aging Benefits of Training with Intensity
- Anti-Aging Interval Training Increases Longevity
- Anti-Aging Intervals or Fartlek for Longevity
- Intensity workouts can be hard to do when it’s hot. Try riding your intensity workouts on the trainer with a huge fan blowing on you and with two water bottles. It’s not much fun to do trainer rides like this, but at least they are short—and better than doing them in the sun!
- Adjust your expectations. When it’s really hot you can’t ride as hard or as long as you can when it’s just 10F (5.5C) cooler.
- Ride by effort, not pace. Heat drives up your heart rate to increase blood flow to the skin, so your heart rate monitor doesn’t provide useful information about how hard your muscles are working. Gauge your effort by perceived exertion, not by your computer.
- Slow down. Since most of the heat comes from your working muscles, slowing down to reduce the internal heat generated internally helps you deal with the external heat. If you ride a bit more slowly but don’t have heat-related problems, you’ll finish sooner than if you pushed the pace!
- Ride early. Get out before the heat of the day. I have clients in Arizona who train before sunrise.
- Take frequent breaks. If you are doing an endurance ride, stop as needed to cool down by resting in a cool environment. For example, get a healthy snack at a fast-food place or minimart and eat it inside — I recommend ice cream. You could do laps from your house and stop periodically back home to cool down.
- Split your workouts. Exercise accumulated in smaller amounts is almost as beneficial as longer workouts. Start your endurance ride in the morning, take a break indoors for lunch (or breakfast) and to cool down, and then ride more after your break. Your cumulative riding time can be longer so you’ll get more training benefit than trying to push through without a significant break.
- Practice technique. During an easy endurance ride, throw in a few 20- to 30-second flat-out sprints in a hard gear. The purpose is to improve how your nervous system coordinates the firing of your muscle fibers, not to reach a specific power or heart rate. By improving your neuromuscular facilitation, you’ll increase your power. Because you aren’t trying to sustain a hard effort, allow plenty of recovery in between each sprint. I wrote this column on 10 Essential Bike Handling Skills.
- Smile. In an experiment a group of trained cyclists was asked to ride at the same perceived effort they would expend if riding a 20 to 40K time trial. They repeated the trial rides at 15, 25 and 35C (59, 77, 95F). Based solely on perceived effort, their power output declined as the temperature rose. Instead of complaining about the heat accept it.
Because you are sweating replacing fluid is important. You’ve probably been advised to, “Drink before you’re thirsty, eat before you’re hungry.” The current recommendation is to drink to satisfy your thirst, but don’t overdrink. However, the sensation of thirst may decline with age. The ACSM’s specific recommendation is helpful: drink enough to prevent more than 2% dehydration and to prevent more than 2% weight gain. If you weigh 150 lbs, then your hydration should keep your weight between 147 lbs (2% less) and 154 lbs (2% more). To check if you’re drinking the right amount on a ride weigh yourself nude before and after the ride. (Eating before you’re hungry is a good idea!)
Why is weight gain from hydration a concern? Studies of athletes and hydration have found drinking too much fluid can dilute the concentration of sodium in your blood to a dangerous level, a condition known as hyponatremia (low sodium). Instead of sweating, your body may start to retain fluid, which dilutes the sodium level in your blood. This is exercise-associated hyponatremia (EIA). Sports drinks as well as water contribute to EIA because the concentration of sodium in sports drinks is less than then concentration of sodium in your blood.
I had a client in a cross-country event who was urinating infrequently in small amounts. Because the rider thought he was getting dehydrated he drank more fluid but still didn’t urinate. The next day he still felt crappy and rode poorly. That evening he went to the emergency room where he was diagnosed with EIA. They treated him with IV fluids with lots of sodium. He recovered and rode the rest of the way across the county.
If you aren’t peeing and your body is getting puffy then the problem is fluid retention, not dehydration. If your wrists are puffy around your glove, a finger puffy around a ring or your ankles are puffy around the top of your socks, then stop drinking until the swelling goes down. I’ve written several related columns:
- 12 Myths about Hydration
- Learning from the Pros about Heat and Hydration
- Nature Breaks, Dehydration and Hyponatremia
- What Should a New Rider Drink
Your sweat is composed of water and salt. The trace amounts of potassium, calcium, magnesium is sweat are orders of magnitude less than what your regular diet provides. Sport nutrition companies promote electrolyte supplements to make a profit, not because electrolytes are necessary for you to ride well. Skip the supplements. You can read more in these columns:
According to the ACSM if your ride is less than four hours, you probably don’t need to supplement with electrolytes unless your jersey is caked with salt or you cramp. Sodium depletion may be one of the causes of cramps, so if you suffer from cramps try supplementing with sodium.
With summer almost here we’re riding our bikes more, which is terrific! Most of our available hours we’re getting moderate and perhaps more intense aerobic exercise. Aerobic exercise most days a week totaling at least 2:30 hours or more is the primary recommendation for good health and longevity from the US Department of Health and Human Services (HHS) and the American College of Sports Medicine (ACSM). You can read the recommendations here Anti-Aging New Exercise Recommendations. In addition to aerobic exercise the HHS and ACSM make recommendations in these areas, about which I’ve written columns:
- Muscle strength training:
Anti-Aging 4 Essential Year-Round Home Resistance Exercises
Anti-Aging Core Strength in 1 Hour a Week
6 Strength Training Exercises to Prevent Cramps
2. Flexibility: Anti-Aging Flexibility in 30 Minutes a Week
Anti-Aging Why Practicing Balance Skills is Important
4. Weight-bearing: Anti-Aging: 9 Weight-Bearing Activities for Strong Bones
Your normal daily activities could include some of these activities. You could walk briskly with your spouse after dinner, which is aerobic exercise and a weight-bearing activity. At the grocery store you could park away from the store. Instead of using a cart to roll your groceries to the car you could carry them for leg strength and weight-bearing. I’ve written a column: Anti-Aging: Value of Multi-component Physical Activities. Because multi-component activities usually are activities of daily living, they’re a great way to get exercise without taking time away from cycling.
- Cycling in the Heat 101
- How To Ride Safely in the Heat
- Tactical Tips for Riding in the Heat
- Cycling in Low and High Humidity
- Effective Cooling
- Hot Feet
You can learn more about the science of riding in the heat, and managing your fluids and electrolytes, in my two-part eArticle series:
- Cycling in the Heat, Part 1: Ride Management is 19 pages and covers how to acclimatize to hot conditions, how to train in hot months, what to wear, eat and drink, how to cool down if you overheat, and how to deal with heat-related problems.
- Cycling in the Heat, Part 2: Hydration Management is 21 pages and covers how to determine how much you should drink depending on your physiology and sweat rate, how best to replace your fluids and electrolytes, the contents of different sports drinks, how to make your own electrolyte replacement drinks, how to rehydrate after a ride, and how to deal with hydration-related problems.
The cost-saving bundled eArticles totaling 40 pages Cycling in the Heat Parts 1 and 2 are just $8.98 (a 10% savings).
- Cycling in the Heat, Part 1: Ride Management, 19 pages
- Cycling in the Heat, Part 2: Hydration Management, 21 pages
- Preventing and Treating Cramps, 10 pages A detailed look into the causes of cramps, prevention techniques, and tips (both on-bike and off-bike, including photos) for breaking and flushing cramps.
- Eating and Drinking Like the Pros, 15 pages What pro riders consume before, during and after a stage and the benefits for cyclists at all levels. Eating and drinking like the pros offers recreational riders the same nutritional benefits, which you can customize to your own needs at a fraction of the cost of commercial sports food and drink, if you choose to make your own. I worked with a professor of nutrition and an expert on hydration and electrolytes (both experts are cyclists) in creating recipes for both sports drinks and food.
The cost-saving bundled 65 pages of eArticles Summer Riding are just $15.96 (a $4 savings).
My eBook Anti-Aging: 12 Ways You Can Slow the Aging Process includes chapters on how to meet the American College of Sports Medicine’s recommendations on aerobic, high intensity aerobic, strength training, weight-bearing exercises, balance and flexibility. I include sample weeks and months for different types and amounts of exercise. I give you plans to build up to 100-km and 100-mile rides. I include a plan to increase over two years your annual riding from around 4,000 miles (6,500 km) to over 5,000 miles (8,000 km) a year. You can easily modify the plans for different annual amounts of riding. I discuss the importance of recovery and how to gauge if you are getting enough recovery. I combine the different kinds of training into programs that balance training and recovery. The 106-page Anti-Aging: 12 Ways You Can Slow the Aging Process is $14.99.
Coach John Hughes earned coaching certifications from USA Cycling and the National Strength and Conditioning Association. John’s cycling career includes course records in the Boston-Montreal-Boston 1200-km randonnée and the Furnace Creek 508, a Race Across AMerica (RAAM) qualifier. He has ridden solo RAAM twice and is a 5-time finisher of the 1200-km Paris-Brest-Paris. He has written over 40 eBooks and eArticles on cycling training and nutrition, available in RBR’s eBookstore at Coach John Hughes. Click to read John’s full bio.
Kerry Irons says
On the few (3 or 4) times over the decades when I have struggled with heat/hydration issues, I can pretty much always trace it back to lack of salt intake relative to sweat losses. You can’t drink more because of that “sloshing feeling” of a gut full of water that isn’t being transported to your blood stream. And this is because you have upset the sodium balance between gut and blood. More salt intake fixes this.
Regards dumping water on yourself, there is a benefit beyond cooling. When your sweat evaporates it leaves the salt on your skin. Due to colligative properties, that extra salt depresses the vapor pressure of the water on your skin and thereby reduces the sweat evaporation rate. Rinsing off the salt improves sweat evaporation. And besides, it feels good!