Category: Winter Training

Why are winter time trials so much slower?

It’s January which means one thing only – TT season is round the corner (ok maybe it also means other things). Races are popping up from mid February which means some early season form testing is on the cards. You might find that, as a result of a really consistent winter, your power numbers are really good this time of year yet you churn out a couple of slow time trials before it warms up. New kit, new bike fit, more watts and still going slower, but why? Winter time trials are slow!

Rest assured, it’s probably nothing to do with how powerful or inherently aero you actually are yourself and is more to do with the conditions. Of course, by subscribing to myWindsock you will have confidence in knowing this as the conditions are taken into account and you’ll know it was a slow day with high Weather Impact.

Cold is slow!

The speed you ride at for a given power on a given day with some given cda is proportional to one over the square root of the density of the air that you’re riding through. This basically means that as air density goes up, our speed will go down. Air density is impacted primarily by temperature. Hot molecules move faster and spread out more. This means more air occupies some given space when it’s cold compared to when it’s hot. In a time trial, the amount of space we need to pass through is fixed at the distance of the race, but the amount of air occupying this space varies quite a lot from one day to the next. 

If you have left your house at any point since October, you might have noticed it’s become rather chilly. As time trialists, we think “gosh, the air is rather dense today” and people look at us like we have just started speaking Spanish. Cold days are slow days. It’s just the laws of physics. 

If it’s slow, what’s the point of racing in February? 

Time trialing is part art, part science. The ratio of art to science will vary depending on who you ask but everyone agrees, to get good at time trials you have to do them. As with anything though, blind practice only gets you so far. Practising with purpose is the key. 

What would be handy is some kind of service which analyses your winter time trials and tells you how much impact the weather would have and how aero you are. Of course, you can see all of that information here. 

Use myWindsock to dial in your pacing and kit choices so that by the time summer comes around you’re dropping massive PB performances with confidence. 

Planning an interval session

Doing just enough to elicit the maximum training affect is the most efficient way to train. myWindsock can help you pick out the best locations for your intervals and plan their intensity.

I’ll show you how to get an interval plan looking like this. Three intervals depleting similar amounts of W’, your work above Critical Power.

Creating the intervals

I begin by picking a chart that will assist us in planning our intervals. For this paticular session, I am attempting to deplete the same amount of W’, or Kilojoules above Critical Power, on hills with differing lengths. I would like to know how much power to put out on each hill to deplete the same Kiljoules of work above Critical Power.

As I am interested in the W’, it makes sense to plan our intervals with the W’ Bal chart.

W’ Balance Chart is under Power in the Chart Menus

Next I simply drag, or highlight a selection of the chart. When I am happy the correct part of the route is in the chart view and highlighted on the map, I click “New Interval”.

Click New Interval when you are happy with the selection.

I now add the interval parameters. I’ll start with 340 Watts.

I finish by clicking “Save Interval”. I then will repeat this for the next two hills, creating three intervals in total. Remember to click “Apply Changes” to reveal the result of the intervals.

Three intervals, W’ Balance graph shows the depletion of energy above Critical Power.

However due to the differing length of the hills this workout wouldn’t deplete all of the require W’ for the session. Let’s see if we can even them up.

Clicking the edit button on the interval marker will open the interval edit.

Opening up the interval editor, we can add a few extra Watts to each of the hills we were short of Kilojoules. After a little adjustment we can now see even W’ depletion for all three intervals/hills.

The Navigator menu reveals key selections including Intervals we have created.

I now have a power plan for the interval training session. Let’s see what couple more charts tells us.

Power Profile shows the planned power for my interval session
Rolling Weight Power, how our Weighted Power evolves during the session.