The Science Of Staying Warm

Find out how can to regulate your body temperature, ride in more comfort and improve cycling performance this winter.

Through the year and even within a single ride, riders can be exposed to a wide range of environmental conditions. Temperature and moisture levels can fluctuate significantly between seasons and even within rides, due to changing weather conditions or through the impact of altitude. Also, whilst we often think about staying warm in winter, with many riders spending increasing amounts of time on the turbo-trainer and with the abundance of winter clothing available, it’s also important to avoid getting too hot!

In this feature, we explore how environmental conditions can influence cycling performance, health, comfort, explain how to minimise potential negative effects and even use the environment to your advantage!

Humans Are Inefficient

Biological systems, including our bodies, are notoriously inefficient. As our metabolism transforms the chemical energy stored in food and body tissues into the mechanical work of cycling, average efficiency may range between 20-25% but could be considerably lower (1). The remaining 75% of energy is released as heat. As work-rates increase (i.e. you ride faster or harder), more heat will be released. When exercising, body temperature rises through a combination of this metabolic heat production, environmental conditions (temperature/humidity) and wearing clothing, which may reduce your ability to lose heat through evaporation (e.g. non-breathable jerseys or rain jackets).

The human body works best when it’s operating in a fairly narrow temperature range. Our metabolism relies on a complex series of chemical reactions to perform well and stay healthy. These reactions can be compromised if body temperature gets too hot or cold. With the exception of the most severe and freakish weather conditions (think Milan – San Remo), by selecting the appropriate garments, cyclists can ride in broad range of weather conditions and still maintain a temperature which facilitates both performance and comfort.

Don’t Dress Like Your Friends (Necessarily)

It’s widely accepted that the best way to clothe yourself for outdoor sports, including cycling, is to use multiple layers. Using layers, you can ‘tune’ clothing requirements to your individual needs and the conditions, even adding or removing layers during a ride if the weather changes.

Riders with heavier builds have a smaller surface area to body mass ratio relative to cyclists with a  more ‘slight’ build. This puts heavier riders at a disadvantage for heat removal, but may mean that they find it easier to stay warmer in winter and don’t require so much clothing. If you’ve ever wondered why pro-cyclists wear so much clothing when they’re training, it’s because their slight, super-lean build means that they feel the cold more than mere mortals! It’s important to remember this individual difference and select the most appropriate clothing for your needs, rather than relying on looking at what others around you have chosen.

There Are No Prizes For Wearing The Least Clothing

Even if you feel you are particularly resistant to the cold, there are no prizes for wearing the least clothing. Despite the fact that you may feel comfortable, if you don’t keep joints and ligaments warm, you may increase your risk of injury. A 2003 study (2) found that the training season had a statistically significant effect on the incidence of achilles tendon injuries. This may be due to the fact that decreased temperatures increase the thickness of the fluid which lubricates the tendon. Consequently, it’s beneficial to conduct a specific, progressive warm-up before training in winter and to use clothing such as tights, long-sleeve jerseys, leg/knee-warmers and arm-warmers to protect joints and ligaments from cold conditions.

Dress For The Wind-Chill

Remember wind-chill: when cycling outdoors the apparent temperature acting on the body is decreased by the flow of air. Wind chill increases the body’s rate of heat loss. For example, if the ambient temperature was 15°C, but you were riding in a group at 20mph, the apparent temperature would be reduced by 2°C, to 13°C. Consequently, it’s important to select clothing according the the apparent temperature (what you will feel with wind-chill), rather than the ambient temperature. It’s an old cliché, but it’s true; you can always take clothes off on a ride, but you can’t add them if you didn’t bring them with you!

General Guidelines For Layering

• 19°C-21°C: Base layer; short-sleeved jersey; shorts; racing mitts; socks
• 17°C-19°C: Add arm warmers
• 15°C-17°C: Add knee warmers or 3/4 length tights; swap for thicker socks; swap mitts for thin full-finger gloves
• 13°C-15°C: Swap knee warmers for leg warmers; add gilet
• 11°C-13°C: Swap warmers for full medium-weight tights, thicker full-finger gloves; add long-sleeved jersey; toe covers or over-socks; head-band
• 9°C-11°C: Swap to long-sleeved base layer; thin hat, add race-cape/packable water-proof for changeable conditions
• 7°C-9°C: Swap to full over-shoes or winter shoes; thicker hat
• 5°C-7°C: Swap for heavier-weight tights; lobster gloves or mittens
• 3°C-5°C: Add a second long-sleeved jersey; a midlayer sock
• 1°C-3°C: Add additional base-layer; knee warmers under tights
• 0°C and below: High-risk of ice on the road so consider an indoor session! 

Hydrate Appropriately

Even in winter when conditions are cool, it’s still important to remember to hydrate appropriately.

Dehydration, if sufficiently severe can cause: 

• Reduced exercise performance
• Reduced blood volume
• Increased heart rate
• Reduced skin & muscle blood flow
• Impaired thermoregulation
• Increased perception of effort
• Headache, nausea, insomnia
• Impaired mental function
• Increased risk of heat illness (3)

The majority of your body’s heat loss will take place through the evaporation of sweat. Heat production may increase 15-20 times compared with at rest, even on relatively low-intensity rides.

The aim of hydration during riding should be to avoid gaining weight (i.e. don’t drink too much) but avoid losing too much. Though some weight loss is common, most riders will tolerate losing 2% of their body weight during a ride in cold to temperate conditions (between 5°C 22°C). To find out how your body responds, try weighing yourself before and after a ride noting how much fluid you consumed during the outing.

For example, if a rider weighed 70kg at the start of a ride, but returned weighing less than 68.6kg, it’s likely that they did not drink enough.

In addition, a rider may monitor urine output (see the free infographic at the end of this feature) to assess frequency, volume and colour, in order to conduct an individualised self-assessment of hydration status.

The amount of fluid that a rider should drink varies, so it’s difficult to make specific recommendations. However, the general consensus is that riders should aim to consume between 400ml-800ml hour. A rider may adjust this based on weight and urine observation experiments pre and post ride. Small amounts of sodium (0.3 to 0.7 grams per litre) may be useful in some contexts (‘e.g. for salty sweaters’) and added to sports drinks, but the amounts of electrolytes a rider should consume also varies between individuals. Electrolyte powders and dissolvable tablets, containing sodium, are available from a number of manufacturers. Hydration advice should be specific to the task, the environment and the individual.

You Can Still Overheat In The Cold

Heat stress is strongly related to prolonged intense activities such as cycling. In addition to impairing performance, getting to hot also increases the risk of heat illness. Heat illness can occur even in relatively cool conditions. In their book ‘Cutting Edge Cycling’ (4) Allen & Cheung cite the case of a male runner who collapsed following a marathon due to heat stress, despite the fact that the ambient temperature was ‘only’ 6°C.

Why Getting Too Hot Can Slow You Down

There is a large body of work in the fields of medicine, sports science and exercise physiology looking at the impact of heat. For example, in 1997 Galloway and Maughan (5) explored the effects of ambient temperature on cycling performance, measuring a group of rider’s time to exhaustion at 4°C, 10°C, 20°C and 30°C whilst riding at 70% VO2 max (the upper boundary of training zone 2 in a 6 zone system). The subjects performed best at 10°C and progressively worse at 20°C and 30°C.

However, it’s not simply environmental conditions and their impact on chemical processes which limit performance. Our perception of the environment plays a huge role.

Is It All In The Mind?

In 2011, Castel et al. (6) conducted a study requiring subjects to carry out a 30 minute cycling time-trial in a range of temperature conditions. However, the researchers deceived the riders by providing incorrect feedback, tricking them into thinking that the room and their body temperature were lower than in reality.

The findings were compelling:

“Deception improved performance in the heat by creating a lower RPE, evidence of a subtle mismatch between the subconscious expectation and conscious perception of the task demands.” 

The control temperature was 26.0°C. As expected, when the room was heated to 31.6°C, the rider’s performance dropped. However, when the room was kept at 31.6°C, but the riders were told it was 26.0°C, their performance was equal to when the room was 26.0°C in reality. So, if you want to improve your performance in the heat, convince yourself it’s 5°C cooler than it actually is!

Read more about how perception can influence pacing, here. 

Protect Yourself

Simply being fit provides protection against the negative effects of increasing core body temperature. It appears that individuals who possess greater levels of aerobic fitness are more resistant to heat, likely due to a number of adaptations which take place in relation to improving fitness which also enhance heat resistance. Examples include improved sweat response, lowering the threshold that sweating begins in addition to lower resting and a higher maximum tolerated core temperatures.

“There’s no such thing as bad weather, just bad clothing!” 

For good reason, this quote, apparently of Scandinavian origin, has become the mantra for many a hardy cyclist. In contrast to the cyclists of yesteryear who were forced to choose between braving freezing, wet conditions in wool jerseys which stretched until they touched the rear wheel, or boil in a bag thanks to waterproof but completely impervious winter jackets, the modern cyclist is spoilt for choice when it comes to knowledge and technical clothing. We now have the opportunity to enjoy cycling in more conditions than ever before, but if you’re still looking for an excuse, remember this: cold air is more dense and creates more drag, so if you’re planning a Strava PB or world-record, wait until summer!

Top Tips To Regulate Your Body Temperature This Winter 

• Select appropriate clothing for the conditions.
• Consider wind-chill and individual differences (body-mass).
• Use a fan when training indoors.
• Hydrate appropriately, even in cool conditions.
• Use your mind to your advantage: If you can’t do anything about it, don’t dwell on thoughts of being ‘too hot’ and even try to convince yourself that it’s cooler than it is!
• Keep training! – The fitter you are, the better it seems that you can acclimatise.

References

McArdle et al. (2010) Exercise Physiology: Nutrition, Energy, and Human Performance. Section 2: Energy For Physical Activity. Lippincott Williams & Wilkins.

Milligram et al. (2003) Cold Weather Training: A Risk Factor for Achilles Paratendinitis among Recruits. Foot & Ankle International May 2003 vol. 24 no. 5 398-401 http://fai.sagepub.com/content/24/5/398.short

Maughan (2013) Dietary strategies to maintain proper hydration for endurance athletes in the heat. International Sport Nutrition Conference. Paris, France.

Allen & Cheung (2012) Cutting Edge Cycling. Chapter 10: Dealing With Environmental Stress. Human Kinetics.

Galloway & Maughan (1997) Effects of ambient temperature on the capacity to perform prolonged cycle exercise in man. Med Sci Sports Exerc. Sep;29(9):1240-9. http://www.ncbi.nlm.nih.gov/pubmed/9309637

Castle et al. (2012) Deception of ambient and body core temperature improves self paced cycling in hot, humid conditions. European Journal of Applied Physiology. January 2012, Volume 112, Issue 1, pp 377-385 http://link.springer.com/article/10.1007/s00421-011-1988-y