The science behind warmers

Can arm and knee warmers make you faster?

It is important to cover up when it's cold outside, but not for the reason we first thought

70º Fahrenheit (21.1ºC) is something of a magic number in cycling. It’s the temperature at which many coaches allow their riders to train with uncovered joints. Even coaching legends such as Patrick Lefevere and Chris VanGent tell their riders not to leave home without warmers if it’s colder than 70ºF outside.


While we are unsure where this rule originated, we can only assume it’s something that coaches observed about the way their athletes were performing in different temperatures. It’s common knowledge that muscles perform better when they are warm, but this is only true to a certain extent – and an overheated athlete’s performance will suffer much the same as a cold athlete’s.

You might think that 70ºF sounds like an arbitrary number, but according to Lefevere and VanGent, cold joints and muscles not only hinder performance, but can also contribute to the onset of tendonitis and arthritis. These warnings of deteriorating soft tissue and joints are something that is echoed by many coaches.

Depending on the time of year, and the humidity, sometimes it’s comfortable to head off without warmers at 60ºF (15ºC), while at other times you’d need a jacket and full finger gloves.

So was this magic temperature based in science, or coaching folklore?

Folklore v2.0

Australian cyclist Scott Sunderland found great success racing in Europe, and developed an affinity for the cold Belgian classics. More recently, he worked on the other side of the bike as Sports Director for CSC and Team Sky – but as a young rider, Sunderland was taught to follow a similar rule regarding warmers.

Sunderland told BikeRadar: “Back then coaches used to draw a number (read: pick a temperature) and stick to it, and I think it had something to do with guys burning fat on their legs –  they were essentially trying to get guys to sweat off extra weight. Now with diets the way they are, you don’t see many guys needing to burn fat anywhere.”

Since then there have been a lot of innovations, not only with the way pro riders and everyday people are eating, but also in the way they are training and what they are wearing.

When he made the switch from rider to sports director, Sunderland took what he had experienced when riding and racing in the worst conditions into account when he advised his riders.

“The magic number I told my riders for warmers was about 15 to 16ºC (59 to 61ºF), depending on the time of year’, he explained. “You need to be warm, but you also need to be able to do the work necessary without overheating.”

It appeared that Lefevere and VanGent’s magic number may have been slightly outdated. BikeRadar also spoke with Katie Slattery, a sports scientist at the New South Wales Institute of Sport, who reinforced what Sunderland said.

“The magic number I tell my guys is 18ºC (64.4ºF), so if it’s 18ºC or below, they need to be wearing tights and a jacket to train outside,” she said.

“Cycling in the cold, you are exposed to higher wind chill factors, so you get more vasoconstriction, which is essentially reduced blood flow to your muscles – something you definitely don’t want.”

Vasoconstriction not only reduces blood flow to the muscles, but also redistributes blood volume to the core, causing increased stroke volume, and small changes in heart rate. This causes an increased cardiac output to support more metabolic heat production – in layman’s terms, this means that the body is devoting extra energy to keeping itself warm.

Muscles perform better at sprinting and max power efforts when they’re warm, however in some cases, covering up can be at the cost to performance. There have also been many studies which state endurance athletes actually perform better at cooler temperatures. Once such study states that the optimal temperature for marathon runners is between five and 10ºC. This temperature is less relevant for cyclists, because, as pointed out by Slattery, cyclists are subject to more severe wind chill factors.

According to Slattery, it’s okay to be cold for a one off performance, but for day-in day-out training you are better off protecting yourself from the cold, because it not only puts extra stress on your vascular system, but is also taxing on your immune system.

This is one reason why we often see riders forgoing warmers during cold and wet races. But another reason is the availability of embrocation and warming oils. These help to create an insulative barrier against the cold, and don’t take on water the way many warmers and tights do. There is a down side to these though. Both Sunderland and Slattery pointed out that while the oils create a warming sensation and help to prevent vasoconstriction in the skin, it also means warm blood is flowing close to the skin is more likely to cool down before it makes it way back to the heart. While you may feel warmer initially, the embrocation or warming oil may actually reduce your core temperature.

While a drop in core temperature is cause for concern, Slattery explained that the cold has little affect on ligaments and tendons, and is not linked as a cause to tendonitis or arthritis.

Dr Josh Murphy, a sports chiropractor at the Body of Life Health Centre, agreed with Slattery, saying: “All the research I have seen says that the cold doesn’t have an effect on the tendons. It is a common misconception that cold temperatures can make tendons brittle or stiff. It’s more of an anecdotal thing; there is no science to back it up.

“People come into the practice all the time saying, ‘Its cold today and all my joints have stiffened up’, but the science does not agree with that.”

Performance-based gains

There is another school of thought working here as well, as there are more studies taking place that are looking into the performance gains of riding in the heat.

“There is a lot of research coming out that suggests that training in the heat actually boosts your performance, allowing you to get more benefits than altitude training,” Slattery said. “In a nutshell, training in the heat promotes increases in your blood volume, which will increase performance. While they may not have realised it, telling their athletes to wear warmers, even when they may not have needed them, was helping their training. ”

Despite all this, both Slattery and Sunderland stressed the most important thing is to be comfortable while on the bike.

“It’s important to find the right combination of clothing for each temperature, and to also remember that you generate quite a lot of heat while you are riding, so it’s ok to be a little chilly at the beginning of your ride,” says Sunderland.

So what can we take away from all this? Do we need to religiously wear warmers? The answer seems to be not really. While you can benefit from wearing extra layers, the most important thing is to stay comfortable while you are riding. Finding the right combination of clothes for each temperature range takes a bit of trial and error, but in the end the most important thing is to be comfortable.


What do you think? Do you subscribe to the 70ºF rule, or are you happy to be a bit chilly while out riding?