Weather has a huge influence on the cycling experience. It's summer as I'm writing this in Alabama and the temperature exceeds 100º F almost daily. However, I can ride in comfort throughout the winter. If you live in higher latitudes, you may experience more pleasant summers than I, but your winters may be brutal.
There are various ways to make cycling in adverse conditions tolerable, if not always comfort able. But it's more than just a matter of comfort: the riding environment also affects performance and can have serious implications for your health.
RIDING IN THE HEAT
The human body performs best when its core temperature stays within a small range anchored around 98.6º F; it becomes stressed even a few degrees outside that range. When we exercise, our bodies produce heat as a metabolic by-product.
Typically 30 to 40 percent of the energy we pro duce generates movement, and 60 to 70 percent is dissipated as heat. Should anything interfere with the dissipation of heat, our core body tempera ture will increase, with potentially serious health consequences.
Due to increased temperatures during exercise, blood flow to the skin is greatly increased to aid in cooling the core. Plasma, the fluid part of the blood, is an ideal medium for heat transfer due to its high water content. The blood absorbs heat from the body's core and carries it via capillaries to the periphery of our bodies, where the heat dissipates at the skin. The blood, now cooled, then returns to cool the core and absorbs more heat to be carried back to the skin. For this process to work, the skin must remain at a lower tempera ture than the core.
------------ Take precautions when riding in a hot environment.
Failure to do so can have severe health consequences.
The body relies on two main strategies to achieve this optimum core temperature: evaporation and convection. When you exercise you sweat, which keeps your core temperature at a manage able level. The more heat that is generated through metabolism and the hotter the environment, the more you sweat. For sweat to cool the body, it must evaporate on the skin. Any sweat that rolls off the body rather than evaporating is wasted.
Relative humidity has a large effect on sweat evaporation. (Relative humidity is a measure of the percentage of air that is saturated with moisture.) If the relative humidity is 40 percent, the air can absorb 60 percent more moisture. If the relative humidity is 90 percent, evaporation will be slow and much of the sweat will roll off the body.
Cycling aids evaporation by continually moving air that is not completely saturated over the skin.
Convection also plays an important role in keeping a healthy core temperature. The act of air passing over the cyclist allows for heat dissipation through transfer from the rider to the air. The heat from the body transfers to the boundary layer of air that surrounds it. When cycling, this boundary layer is continually being replaced with cooler air, allowing for greater heat transfer from the body to the environment.
Dehydration has a strong negative effect on the body's ability to cool itself. A cyclist's body temperature is negatively affected by a fluid loss that is equal to about 2 percent of body weight. (This assumes that the cyclist was fully hydrated at the start of the ride.) Many cyclists who ride in hot, humid conditions stay chronically dehydrated.
To make a long and complicated story short, sweat is basically filtered plasma. If you sweat a lot and do not replace the liquid through an adequate hydration program, you will experience a significant drop in plasma volume, meaning less fluid available for heat exchange. There will also be a drop in blood pressure due to a decrease in whole blood volume, which will further reduce the circulation of blood flowing to the skin to promote cooling. The core temperature will then increase significantly. Dehydration can also lead to an electrolyte imbalance, which can cause mental confusion and cardiovascular complications.
Heat-Related Illnesses
If left untreated, heat-related illnesses can lead to serious complications or death. It is imperative to know the symptoms of the two main categories of heat-related illness: heat exhaustion and heatstroke. Heatstroke is a life-threatening condition that must be treated immediately. Some of the symptoms of heat exhaustion, which are listed below, cross over from one category to the other, and heat exhaustion can quickly turn into heatstroke.
Heat Exhaustion
__headache
__tingling sensation in the skin
__chills
__feeling of weakness
__dizziness
__pale, moist skin
__rapid, weak pulse
Heatstroke
__core temperature greater than or equal to 104° F
__headache
__chills
(This may occur if the body's thermoregulatory system is askew and behaves as though the body is cold. This will cause the body to attempt to further raise the temperature instead of cooling itself.)
__confusion
__hot, dry reddish skin
__cessation of sweating
__rapid, strong pulse
If a heat-related illness is suspected, stop training and move to a cool environment. Don’t attempt to keep pushing on: your condition will only get worse. Use wet towels, ice, or a cold shower or bath to reduce body temperature. Drink plenty of water to restore proper hydration levels.
If you can’t get your core temperature down or if it continues to rise, seek medical attention immediately. If heatstroke is suspected, go straight to the emergency room.
Prevention of (and Acclimatization to)
Heat Stress
If possible, avoid riding in the hottest part of the day (usually between noon and 3 P.M.). Beat the heat by riding as early in the morning as possible.
This will take dedication on your part, but it beats frying like an egg.
Acclimatization is the body's process of adapting to heat stress. A lack of acclimatization plays a key role in many heat-related illnesses. It takes about ten days of riding in the heat to become fully acclimatized.
Don’t ride hard during this period. Start slowly and work up to your normal training schedule.
If you live in a region where summers aren't excessively hot but you're planning to race some where really hot and humid, you should acclimatize before the event. If possible, travel to the event at least three days prior, giving yourself that much time to adapt. If that's not possible, try one or more of these methods to acclimatize before you travel:
__Wear an extra layer of clothing while riding in your normal environment. This will create a microenvironment under the clothing, simulating increased heat and humidity.
__Build a heat chamber for training in your garage or a work shed, adding heat lamps as necessary to increase the temperature.
You might have a hard time convincing your significant other to allow you to build such a chamber in the house itself. Sitting in a sauna may help, but it will not be as effective as a more active method.
When using either of these methods, be extra careful to avoid a heat-related illness. Don’t become overzealous in your training. The idea is to slowly adapt to a hot, humid environment.
Use common sense and listen to your body.
Specific adaptations occur in the body during acclimatization that help the body remain healthy and perform better in the heat. You will begin to sweat earlier than normal, before your core temperature rises significantly. You will also sweat more, and sodium levels within the sweat will decrease to assist in sodium retention and electrolyte balance. Training in the heat increases glycogen use, which will deplete energy stores much faster compared to training in cooler environments. This effect will be minimized once you acclimatize to the heat, which will spare energy.
(See Section 10 for more on the physiology of glycogen production.)
Hydration
Even though the importance of hydration is well known, athletes who train in hot environments have a tendency to stay chronically dehydrated.
This places them behind the curve before they even begin their training day. Many cyclists use thirst as a marker of hydration, but it is a poor indicator. If you're thirsty, you are already dehydrated and performing sub-optimally.
You can monitor hydration levels by tracking changes in body weight. Record your weight, in the buff, before and after you ride. The difference in weight is the water loss from your ride. If you are two pounds lighter, you need to replenish that difference. This process requires a reliable scale that produces the same weight rating when you step on and off it repeatedly.
Clothing
To promote evaporation, clothing must be breath able to allow heat to escape and air to come in contact with sweat. Clothes should also be light in color to reflect sunlight, not absorb it and convert it into heat, as dark clothes do.
Unfortunately, almost all cycling shorts are black, and they become extremely hot in bright sunlight. On the other hand, I don’t recommend white cycling shorts. You can see skin through them, and they show permanent grease marks, whereas black ones do not.
----When riding in cold conditions, pay close attention to the windchill and
the type of clothing and number of layers you wear. (Barbara Dowd)
RIDING IN THE COLD
When the weather turns cold, you can still ride outdoors; you just need to take proper precautions to ensure a safe and tolerable, if not entirely comfortable, ride.
When evaluating cold weather, check the temperature and the windchill factor.
Windchill--a combination of temperature and wind speed- measures how cold it actually feels. Some weather stations report windchill as the "feels like" temperature. For example, a temperature of 40º F and a wind speed of 10 mph feels like 28º F.
The principle of convection applies to cold weather as well as hot weather. Your skin gives up heat to the surrounding air. If the air is not moving, convection results in a boundary layer of warmer air forming around your body. If the air is moving (as in windy conditions) or you are moving through the air (as when riding), the boundary layer is continually replaced with cooler air; this prevents the warm boundary layer from forming, so your skin cools more rapidly.
The body is inclined to maintain a steady internal temperature. In cold weather, the blood cools through convection through the skin, then circulates back to the body's core, where it tends to bring the temperature below the preferred 98.6º F. The body reacts by narrowing the blood vessels (a process known as vasoconstriction), which limits the circulation of blood to the periphery of the body and concentrates it in the core, where it will stay warmer. Although this helps maintain the body's metabolic processes and keeps internal organs functioning, it has two negative consequences.
Leg and arm muscles are deprived of the oxygen rich blood they need to generate power, reducing cycling performance. And the extremities and skin are deprived of warm blood, increasing the risk of frostbite (the freezing of body tissues) in extreme conditions. Thankfully, however, only rare circum stances will cause you to ride in temperatures that could lead to frostbite.
A second mechanism helps keep the body warm: its metabolic rate can be cranked up to increase internal heat production. This is accomplished in two ways. As the body's core temperature begins to lower, the body starts to shiver. This rapid, repeated flexing and un-flexing of the muscles generates heat.
There is also evidence that the body reacts to cold temperatures by automatically increasing its metabolism even with no increase in muscular movement.
As mentioned earlier, about 60 to 70 percent of energy production is dissipated as heat during exercise. Although this is not economical, and it creates a problem in hot environments, it can be useful in cold environments.
Cold-Related Illnesses
Hypothermia occurs when the body's core temperature drops below 95º F. Here are the symptoms:
__shivering (begins before core temperature reaches 95º F)
__weakness
__confusion
__impaired speech
__loss of dexterity and coordination
__pale gray-tinged skin
As hypothermia progresses and the body's core temperature continues to drop, symptoms worsen in this order:
__increasing mental confusion
__stiffening of muscles; sluggish movement
__slowing of heart rate and breathing
__loss of consciousness
__pulmonary edema, in which fluid accumulates in the lungs due to a significant decrease in the depth and frequency of breaths
__cardiac arrest
If hypothermia is suspected, get into a warm environment immediately. Dry, warm blankets or a hot bath or shower are good ways to bring the body's temperature back to normal. If a warm environment is not readily available, at least find shelter from the wind. Even after you have moved to a warm environment, wet clothing will continue to lower your core temperature, so change into dry clothes as soon as possible. If you are stranded on the road, take off your clothes long enough to wring the moisture out of the inner layer, then put them back on immediately. (This assumes your clothing is soaked with sweat.) This will eliminate some of the water next to the skin and keep you slightly warmer. You can also huddle together with friends for increased warmth. In severe cases, which entail a strong possibility of cardiovascular complications, seek medical attention immediately.
Though extremely rare in cycling, severe hypothermia can occur in stranding situations.
When riding in remote areas in cold weather, it is a good idea to ride with a buddy, carry a cell phone, or let someone know your exact route and when you will return.
Training in a cold, dry environment can trigger an asthmatic episode. Cyclists with asthma need to be aware of this and take precautions, as described in Section 15.
Prevention of (and Acclimatization to)
Cold Stress
The body does acclimatize to cold stress, but not to the dramatic extent it does when subjected to heat stress. Individuals who are acclimatized to a cold environment start shivering much later than those who are not acclimatized. It is theorized that this occurs due to a slight increase in resting metabolism and increased blood flow to the extremities. Because of the limited adaptations that occur, however, the prevention of cold-related illnesses must focus on clothing selection and riding strategies.
Clothing
Layering is the key to riding in the cold. At least three layers are usually required. The innermost, base layer should be a wicking material (such as CoolMax or polyester) to move moisture away from your skin. Don’t wear a cotton or wool base layer: both retain moisture and lead to rapid cooling. The outermost layer should be wind- and waterproof but must also allow the dissipation of excess moisture that would otherwise accumulate underneath the fabric. It does so by means of vents designed into the clothing or through the fabric itself, as in the case of materials such as Gore-Tex, which allow moisture to pass in only one direction-away from the body.
The layers in between provide insulation, trap ping the warmth given off by your body through convection to create a cozy microclimate. The type and number of insulating layers are determined by the air temperature and your ability to move freely. Light weight or heavyweight polyester fleece (depending on the temperature) is a good choice for an insulating layer. All insulating layers should be breathable, so that moisture wicked by the base layer can continue to travel away from the body and out through the outer layer's venting system. Be careful not to overdress, which will restrict your freedom of movement and lead to the production of more moisture (sweat) than your clothes can dispel. Layering pro vides you with the opportunity to remove garments when riding if you become too hot.
Don’t ignore your extremities when preparing for a winter ride. Cover your head and face to block the wind and retain heat. Arm warmers and leg warmers are good choices because you can peel them off if you become too hot. Gloves should be windproof and water resistant. Cold, wet feet will make for a miserable ride, so use shoe covers over your normal cycling shoes or buy a pair of winter cycling shoes.
Don’t base your clothing choices on what someone else is wearing because people respond differently to the cold. Cyclists with a high body fat index are typically able to tolerate cold temperatures better than cyclists with little body fat.
Older cyclists typically feel the cold more than younger adults due to a blunted thermoregulatory response. In cold environments children lose heat at a much faster rate than adults, due to a larger surface area in relation to their body mass.
The best way to determine what to wear in cold weather is to create a chart listing wind chill and clothing. For each ride keep a log of the windchill and the clothes you wear. After the ride, record whether the clothing was too much, not enough, or just right. Note the clothing that works well at a given windchill. It will probably take you most of one winter to develop a reason ably complete chart, but thereafter you can refer to it for years to easily determine what you should wear. You should begin a ride feeling somewhat cool. If you are warm before you start, you will be drenched in sweat within the first two miles. During short rides you can actually overheat if you are overdressed. On long rides, excessive sweating can lead to rapid cooling as the ride progresses.
Ride Strategies
The distance traveled, the length of time exposed to the environment, and the speeds traveled all make cycling unique among sports. During the winter it is a good idea to ride shorter routes and/or consecutive loops rather than riding long out-and-back or one-loop routes. Although it may sound boring to ride a 25-mile loop four times, it is better than riding a 100-mile loop or a 50-mile out-and-back route because you'll never be more than 12 1/2 miles from home. If the weather takes a turn for the worse or you suffer a mechanical breakdown or you begin to get hypothermic, you'll return home that much quicker. Even if you can call someone to pick you up, the shorter route will allow a quicker response.
Limit the frequency and duration of stops when riding in cold weather. When you stop, al though the windchill diminishes, your core temperature remains elevated for a brief period, which can promote increased sweating, which leads to rapid cooling of the body. In addition, your metabolism rate drops when you rest, resulting in lower heat production. The longer you stop, the more heat you lose, and you may be unable to maintain core temperature for the rest of the ride.
RIDING AT HIGH ALTITUDES
Racing and training at altitude is an important issue for cyclists. As altitude increases above 5,000 feet, its physiological effects increase accordingly. Traveling from sea level to train or race at altitude has a negative impact on performance and possibly health. However, training at altitude does have potential ergogenic benefits. (Ergogenics are any outside factors with a positive influence on performance.) Many people think that there is less oxygen in the air at high altitudes, but this is not the case.
Air contains 20.93 percent oxygen at sea level as well as atop Mount Everest. The issue is oxy gen availability, which depends on the barometric pressure and the partial pressure of oxygen at any given altitude.
Barometric pressure can be thought of as the "weight" of the atmosphere. As you move up in altitude, there is less atmosphere above you, hence less "weight" pushing down. This translates to lower air pressure.
The partial pressure of oxygen (PO2) is the pressure of oxygen at any given barometric pressure. Because the percentage of oxygen in the atmosphere does not change, the formula is simple:
barometric pressure × 20.93% = PO2
Barometric pressure at sea level is typically about 760 mm of mercury (mm Hg), therefore:
760 mm Hg × 20.93% = 159 PO2 (mm Hg)
When examining the table above, you will notice that as altitude increases, barometric pres sure decreases, with a corresponding decrease in PO2. Gas diffuses from high to low pressure.
Oxygen diffusion from the lungs into the blood is affected by its partial pressure in the atmosphere in relation to its partial pressure in the blood.
The greater the pressure differential between the two, the better the oxygen transfer. A lower PO2 creates less of a pressure differential and has a strong negative effect on oxygen absorption into the blood.
----------- TYPICAL PARTIAL PRESSURE OF OXYGEN BY ALTITUDE
At altitude, hemoglobin saturation drops significantly due to lower PO2 values. The pres sure gradient between the arterial blood and the tissues also drops at altitude, so less oxygen is transferred into the tissues. This puts the body into a hypoxic state, in which oxygen delivery to the tissues is significantly decreased. At altitude, because less oxygen is being delivered to the tissues, such as muscle, an un-acclimated body usually feels weak. It is common to feel fatigued and un able to ride at your normal intensity.
Your body will attempt to compensate for a low PO2 by increasing the rate and depth of breathing. At high elevations and exercise levels, it may seem as though you are hyperventilating. Through a series of biochemical reactions, increased ventilation will ultimately impede your body's ability to buffer lactic acid during high intensity work, resulting in a decrease in performance at or above threshold.
Altitude-Related Illnesses
Altitude sickness is common in individuals who travel from sea level to high altitudes. The sever ity of altitude sickness varies among cyclists, as does the altitude at which it occurs. The faster you change altitudes, the more pronounced the symptoms. But until you have experienced high altitudes, you will not know how your body will respond. Symptoms of altitude sickness include the following:
__decreased ability to breathe at a normal rate and depth
__headache
__nausea and vomiting
__weakness
__mental confusion
__insomnia
Two other more serious conditions can occur, but usually only above 9,000 feet. Pulmonary edema is a condition in which fluid accumulates in the lungs. It is marked by wheezing, skin discoloration, weakness, and coughing up pink phlegm.
Cerebral edema is excess pressure on the brain, caused at high altitudes by an increase in fluid volume in and around the brain. Cerebral edema is marked by neurological symptoms such as loss of coordination, mental confusion, slurred or confused speech, and fatigue. Pulmonary and cerebral edema can lead to serious complications and death. If any of these symptoms occur, move to a lower altitude and immediately seek medical attention. Thereafter, acclimatize by increasing your altitude by about 1,000 feet a day as long as you remain asymptomatic.
Prevention of (and Acclimatization to) Altitude Stress
To participate in an event at high altitude, it would be ideal to show up two to three weeks early to acclimatize. Or you can use training equipment that simulates a hypoxic (low oxygen) state to elicit the same response as training at altitude.
This is accomplished by lowering the percent of oxygen available in an enclosed space as opposed to altering pressure to affect oxygen saturation.
The enclosed space can be anything from an oxy gen tent to a converted room.
Although these adaptation strategies are beneficial, they will not allow you to achieve the level of performance that is normal for you at a significantly lower altitude. They reverse themselves two to three weeks after you return to sea level.
Nevertheless, there may be some positive effects to altitude training.
Hydration
Dehydration can occur quickly at altitude due partly to excessive water loss through respiration. Air at high altitudes tends to be dry, so as we breathe in, the lungs transfer a lot of moisture into the air, which is then exhaled. (Less moisture transfer occurs when breathing humid air.) Because breathing greatly increases at altitude, there is an increase in water loss due to respiration. Urination also increases significantly at altitude. This situation leads to a greatly reduced plasma volume, leading to a higher heart rate at any given sub-maximal intensity (or, any physical exertion below maximal effort). To counter these effects, it is important to stay adequately hydrated.
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ALTITUDE AS AN ERGOGENIC AID
Using altitude to increase performance seems like a good idea. A number of adaptations occur that will increase your aerobic capacity, especially when you return to sea level.
These adaptations include increases in erythropoietin (EPO), hemoglobin, myoglobin, and capillary and 2,3 diphosphoglycerate (2,3-DPG) concentrations, all of which are designed to increase delivery and utilization of oxygen at the working muscles. However, due to low PO2 and a decreased ability to buffer lactic acid, you will not be able to train as hard or as long at altitude, possibly offsetting some or all of the benefits. Research has provided mixed results on training at altitude and racing at sea level.
The reverse-living at altitude and training at sea level-on the other hand, appears to be a promising scenario, for which most research shows a significant increase in performance.
Although there is currently no research to support this theory, I think that living at altitude and a combination of training at sea level and at altitude elicits the best response. The reasoning is that training at sea level most of the time would allow you to work at a higher intensity to increase VO2 max, threshold, and overall performance.
(These terms are discussed in Section 10.) Then training at altitude just one or two days per week would create a hypoxic state that would increase oxygen absorption and transfer under the stress of exercise, whereas living there would keep you in a slightly hypoxic state for improved oxygen dynamics.
Much attention has been paid to the effects of altitude on performance, but many questions remain unanswered, and no one knows which of these scenarios is most beneficial: living at altitude and training at altitude, living at altitude and training at sea level, or living at sea level and training at altitude. Also unknown is the optimum dosage of each variable. Keep in mind that there are huge differences in how each individual responds. Does altitude training work? Maybe. Is the probably small payoff worth the time, money, and effort? That's up to you to decide.
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