Originally Posted by
prathmann
Lots of factors contribute to slower riding when it's cold and I'm surprised you only see a drop of 2 k/hr. They include:
1) denser air when it's cold - therefore greater air resistance
2) more clothing which restricts the movement of your legs and also adds air resistance
3) colder air in your lungs results in slower exchange of oxygen into your blood
4) body uses more energy to stay warm so less is available for leg muscles
5) more mechanical resistance when cold due to thicker grease/oil in bearings and less flexible rubber tires.
2) has more impact in my mind especially when wearing unstretchable pants/tights on the knee area.
4) It would be true if our body was a closed system but as everybody knows we can eat and drink and breath more when needed and our body can make glucose via gluconeogenesis.
There is definitively something there though. I believe that probably there could be as many different outcomes as people.
What is known is that blood pressure increase when the body get colder and that blood pressure can decrease after a time of exposure to hot temperatures but is also higher first.
http://www.colorado.edu/eeb/courses/...%202007/17.htm
But because we wear more clothes in winter, more clothes usually means than it becomes harder to regulate the temperature well and it also means possibly that clothes could generate more compression on the body parts so depending on each and every one of us outcomes could be everything between hyperthermia and hypothermia, restricted blood flow or not.
Futhermore, lack of blood flow should lead to less nutrient and oxygen to the muscles leading to lower performance in winter but one study has shown that results could be the opposite temporarily depending on training. So there is no way to know the outcomes for everyone.
http://www.wired.com/playbook/2010/1...econditioning/