Authors: Tim Farin and Dr Katharina Kremser
In summer, it’s clear to most people. But in Central Europe, we do, after all, have distinct seasons and transitional periods: how should we dress our legs when we get on our bikes in autumn or spring? There are widely differing views, feelings and even traditions on this matter. “You shouldn’t cycle in shorts when it’s below 20 degrees,” said Sebastian Klaus, an expert on asphalt and ‘Köpfchen’ ergonomics. Our trainer, Dr Andrea Jeschke, on the other hand, admits that, when it comes to this topic, she has so far only gone “by her own sense of temperature”. Is that enough? Or are there objective guidelines beyond that?
Not all temperatures are the same
Whether short, mid-length or long cycling tights are the best choice does not depend solely on the displayed air temperature. Wind, rain, riding speed, elevation gain, duration and the planned intensity all influence how much your body cools down. Whilst you do generate heat on the bike through your working muscles, But you’re constantly exposed to the wind. This can carry away a lot of heat. A study[1] on cycling under real-world conditions also showed that the cooling effect of the wind significantly alters the thermal stress compared to training indoors on an ergometer. Anyone who’s ever done a race on a trainer in the basement knows this all too well.
What science says about thermoregulation: four factors
Movement generates heat
Working muscles generate heat. Greater exertion also means more heat. Anyone cycling up an alpine pass in snowfall can work up a sweat despite the weather. Downhill, however, it’s a different story. During a leisurely ride, heat production is lower.
Clothing insulates or regulates body temperature
Clothing influences several pathways of heat loss: it either retains heat that would otherwise be released into the environment and carried away by air movement, or allows sweat to evaporate, thereby cooling the body. The sports medicine literature[2] therefore describes clothing as part of thermoregulation. It should keep the body warm without unnecessarily blocking evaporation.
Wind and damp make you feel cold
The weather app usually shows the air temperature. However, your body feels the wind chill. At 12 °C and 50 km/h, a downhill ride can feel significantly colder than the same temperature whilst out for a walk. This is particularly true of the front of the thighs and knees, which are exposed to the airflow. The American College of Sports Medicine (ACSM) therefore recommends[3] that, in cold weather, you take into account not only the air temperature and exercise intensity, but also wind and humidity.
This is because water conducts heat much more effectively than air. Wet trousers or a soaked surface can therefore speed up the process of cooling down. What’s more, when water evaporates from the skin or from fabrics, energy in the form of heat is required for this process.
For short showers, a standard pair of long cycling tights with a water-repellent finish may be sufficient. In the event of cold, persistent rain, strong winds or a long ride, the key question is: how can I stay as dry as possible and put on an extra layer if necessary? A thin, water-repellent or waterproof pair of overtrousers, which protect against wind and rain, is often a better option than particularly thick but absorbent trousers. However, they should be breathable enough to prevent you from getting completely soaked from the inside.
Why you shouldn’t let your knees get cold
Cold can reduce muscle strength and the speed of muscle contraction; at the same time, tendons and other layers of tissue become temporarily stiffer and the synovial fluid more viscous. With regard to the knee, there is evidence[4] that local cooling alters the mechanical properties of the patellar tendon. This suggests that you should keep your knees and thighs warm in a cold draught whilst cycling and warm up sufficiently before any intense bursts of effort. Although a review[5] finds links between the cold and musculoskeletal complaints, it cannot establish a clear cause-and-effect relationship. It would therefore not be entirely sound to claim that shorts can lead to injuries. On the other hand, many of our readers report that they wear long trousers to protect their knees.
Shorts: for warm weather, fast-paced activities and flexible transitions
Short cycling shorts are the best choice if your legs stay warm enough whilst cycling and you don’t expect to face any prolonged periods of cold. This is often the case at temperatures of around 15 to 18 °C – though during intense cycling it may be possible even at lower temperatures, whilst in windy conditions, in the shade or on long descents, it may only be possible later on at higher temperatures.
It has three practical advantages:
- Heat is more easily released through the legs.
- During high-intensity sessions, the risk of your thighs overheating is reduced.
- Worn with leg warmers, it stays flexible: you can start off warm and take a layer off later.
As a general rule, however, you shouldn’t just look at the temperature when you set off. If you set off in the morning at 11 °C and the sun brings the temperature up to 22 °C in the afternoon, leg warmers are often a better option than thick, long winter trousers. Even on a fast training ride with lots of climbs, shorts plus leg warmers can offer better temperature regulation.
Mid-length trousers: the perfect solution for spring and autumn
Knee-length trousers, three-quarter-length trousers or short cycling shorts with leg warmers are particularly practical when you can already dress for summer from the waist up, but your knees still need protection from the wind.
The ideal temperature range is roughly between 8 and 15 °C – depending on the wind, sunshine, pace and duration. Knee-length trousers protect the knees and part of the thighs without restricting heat dissipation as much as lined long trousers. Leg warmers also have the advantage that they can be taken off during the ride and stowed away in a jersey pocket.
For many everyday cyclists, this is the most practical solution in spring and autumn: modular is best. After all, a layer of clothing that you can take off is often more useful on a ride with changeable weather than a supposedly perfect choice made before setting off.
Long trousers: for windy, wet conditions and prolonged periods
Long cycling tights aren’t just necessary when it’s freezing. They become a sensible choice when several factors come together:
- Temperatures below about 10 °C
- strong headwinds or long descents
- thick fog or persistent rain
- A long, leisurely ride with little heat generated
- longer breaks, stops at cafés or waiting times
- high individual sensitivity to the cold
In cold weather, trousers should not only be long but also chosen to suit the situation. A pair of thin, unlined long trousers might be just right at 10 °C. Thick winter trousers can become too warm at 8 °C during high-intensity activity, whilst they remain comfortable on a leisurely three-hour ride.
Wind protection at the front is particularly important. A windproof panel at the knees and thighs can be more effective against wind resistance than simply adding extra thickness all round. At the same time, the trousers must not restrict movement and should fit securely at the ankle to prevent them from getting caught in the chain or crankset.
Overview: Which trousers for when?
The following advice applies to a typical ride of moderate intensity, with dry clothing and an average sensitivity to the cold. It has been compiled from specialist publications, manufacturers’ specifications and feedback from the community. But of course, this is only a rough guide, which may not necessarily correspond to how you feel physically:
- Over 18 degrees: cycling shorts; make sure you have UV protection; leg warmers may be needed on long descents
- 12 to 18 degrees: shorts or shorts with leg warmers; if setting off early, or if it’s windy or overcast, opt for leg warmers or three-quarter-length trousers
- 8 to 12 degrees: mid-length trousers and leg warmers, or light-weight long trousers
- 3 to 8 degrees: long, warm trousers; windproof fabric on the knees and thighs
- Below 3 degrees: long winter cycling tights, windproof or water-repellent
The transition zones are deliberately broad. A well-trained, heavier cyclist riding uphill at high intensity at 10 °C may be dressed differently from a woman returning to cycling who is riding at a leisurely pace on flat terrain for two hours at the same temperature. Age, physique, acclimatisation to the cold, blood circulation and individual experience also play a part.
Trousers fitting: What happens after 15 minutes?
A good practical test is to see how you feel after ten to 15 minutes’ ride. You’re not dressed warmly enough if your legs go numb, you’re shivering uncontrollably, your muscles feel stiff, or you can barely control your hands and feet. In that case, you shouldn’t just ‘grit your teeth and carry on’, but put on an extra layer, cut the ride short or warm yourself up.
You’re dressed too warmly if you’re already sweating heavily early on, the inside of your trousers is getting damp and you therefore start to feel cold during the first long descent. This is because sweat in your clothes can cause you to cool down more quickly later on. In this case, a thinner layer or better ventilation makes more sense than extra insulation.
Important: If it’s so hot outside that you start to overheat and sweat profusely even when wearing a short dress, you should perhaps skip your workout. Extreme heat can cause circulatory and other problems, and may even lead to heatstroke.
