Power-to-weight ratio is the single most important factor when climbing.
Put simply, your power to weight ratio is how many watts you can produce divided by how much you weigh. The more watts you can sustain and the less you weigh, the faster you will be able go uphill.
A lot of bike races are won or lost when the road heads uphill and so power to weight ratio is a key calculation in the pro ranks, but the principle is also important if you want to improve your climbing ability, or you're targeting a mountainous sportive with long climbs.
When climbing the major factor that stops us from riding quicker is gravity, so the more you weigh (or, more accurately, the greater your mass in kilogrammes), the greater the effect of gravity and, therefore, the more difficult it is to get to the top of a climb. Therefore, when climbing, the lighter you are, the better, and, as with any aspect of cycling, the more power you can put out, the better.
With that in mind, power to weight ratio is simply a way of quantifying how much power you can put out in relation to how heavy you are. Power to weight is measured in w/kg and this gives a rough idea of your climbing ability.
Power to weight ratio is also a useful figure to compare riders. For example, we couldn’t expect a 65kg climber to put out the same sprint power as 80kg sprinter, but what would happen if the two went up against each other on a climb? The respective power to weight ratios of the two riders would give us a good idea to what might happen. If the climber can put out 350 watts over the course of they climb then their power to weight ratio is 6.1w/kg, whereas the sprinter can produce 440 watts but has a lower power to weight ratio of 5.5w/kg.
But what do those figures mean? Let's take a closer look at some typical power to weight measurements.
Typical power to weight figures
A lot of numbers get thrown around with regards to power to weight ratios.
The first thing to highlight is the time period you are talking about when quoting a power to weight ratio. For example, most cyclists will be able to produce 6w/kg - the benchmark for top-level professional riders - however, some may only be able to sustain this intensity for twenty seconds, while others will be able to climb like mountain goats at this figure for an hour.
In one of my previous articles I covered lactate threshold and functional threshold power (FTP) - or the power that a rider can sustain for one hour. This is considered the golden standard in terms of sustainable power production and climbing ability in the high mountains like the Alps and Pyrenees, and so is typically the length of time considered when quoting power to weight. You can read my piece on lactate threshold to find out how to calculate your FTP (and later in this article we'll consider how you can use power to weight if you don't have a power meter) but, for now, let's look at typical power to weight ratios for various levels of rider.
Starting with World Tour professionals, the likes of Chris Froome. They are understandably very secretive about their exact power outputs but a good estimate would be around 6-6.2 w/kg. A good climber on a domestic professional team might have a FTP of around 5.2-5.7w/kg. A good first cat might be around 4.5-4.8w/kg mark, A second cat might be excepted to be around 4w/kg and a third cat at around 3.5-3.8w/kg. On the women’s side of things, a world class climber in the mould of former British pro Emma Pooley would likely be able to sustain around 5.2w/kg.
So should we all become obsessed by our power to weight ratio? Needless to say, it has its limitations as a measurement by which to determine cycling ability.
Limitations to power to weight
These numbers are all well and good but, unless you are regularly racing up Alpe d’Huez or the Col du Tourmalet, your power to weight ratio for one hour isn’t the be all and end all of cycling performance.
Power to weight is particularly relevant on long climbs, and while it's still a factor on short, steep like those found in the Tour of Flanders, outright power is also significant. It's why riders like Fabian Cancellara thrive in the Spring Classics, but falter in the high mountains.
As we've already covered, power to weight ratio is important when gravity is the overwhelming limiting factor on cycling speed. Therefore, when riding on the flat, power to weight becomes less important. Obviously to ride quickly on the flat a lot of power is still required, but aerodynamics become much more important than weight - the resistance caused by moving though the air has a much greater effect on how fast we ride than our weight. A big, heavy rider who can produce a lot of power will often be able to ride much faster on the flat than a skinny climber with a much better power to weight ratio but ultimately less power. It's about making the most of what you have.
Time trials - power:wind resistance
The same is true for time trialists. During a time trial, the most important factor you are trying to overcome is the resistance caused by moving through the air, which is why top riders use TT bikes and helmets, wear skinsuits, and spend so much time in the wind tunnel. Therefore, the key to performance in a time trial is not power to weight but a power to aerodynamic coefficient. As a result, time trialists typically focus on producing the maximum power they can sustain over a flat or rolling course, with the lowest aerodynamic penalty.
As you can see, power to weight ratio is simply one component of cycling performance. If you race in a very hilly area, or are targeting a sportive in the high mountains, then it will be an important factor in the outcome of your performances, but if you live in a flat area where lots of races finish in sprints then you may be better off focusing your training on other aspects of fitness such as sprint power, as this has a far more direct application in the type of races you are riding.
Still, there's no denying that power to weight is a key figure and most of us want to climb quicker, so how do you go about improving your ratio?
Increase power or decrease weight?
If you are looking to improve your power to weight ratio, what is the best way to do it?
You have two options: increase your power or lose weight. If you are carrying a fair amount of additional weight then it'd be beneficial to first concentrate on shedding that through your day-to-day training programme and healthy eating. However, I typically advise my coaching clients to focus on increasing their power (we'll look at a training session to improve your power at the end of this article) and there are four main reasons for this.
- Increasing the amount of power you put out will have benefits across all terrains, from the mountains to time trials to rolling roads, and possibly even on descents. The harder you can pedal, the faster you go.
- Trying to lose weight can often impact negatively on your lean muscle mass and, subsequently, your power output. Dieting is also very stressful on your body and can seriously impact on your ability to recover from hard training sessions. In the long run this affects your overall training load and can result in a decrease in power. By dieting you may have lost weight but you may also have lost some precious watts.
- Bradley Wiggins is famous for losing weight to increase his power to weight ratio and convert from a Olympic medalist on the track to the winner of the Tour de France - a race where power to weight ratio is absolutely vital. However, he did this after already maximising his power output. Most riders haven't got to the point where they have maximised their power potential and, therefore, they can still make significant progress in that area. Wiggins was already at his physiological potential in terms of power output and therefore had no other choice than to reduce his weight in order to improve his power to weight ratio.
- With the increased training load that it takes to improve your power output, chances are you will lose a little bit of weight naturally because you are simply training harder. That, of course, is as long as you are sensible with your food intake.
We aren’t all lucky enough to have a power meter to be able to measure our FTP power and calculate our power to weight ratio. However, if you have a GPS cycling computer then there is another option to estimate your climbing ability and, crucially, help with pacing on long climbs - VAM.
VAM stands for ‘velocità ascensionale media’ or, in English, ‘average climbing speed’.
VAM is a measurement of your climbing rate expressed as how many vertical meters you will climb in one hour. Let's use Alpe d’Huez as an example: the bottom of the climb is at 744m and the summit is at 1,815m. Therefore, if you climb the famous 21 hairpins in exactly one hour - and that is the goal many riders established riders set themselves - then your VAM will be 1,071m per hour. To offer a comparison with professional cycling, during the Tour de France the best riders will be able to sustain 1,600-1,700m/h.
Your GPS computer will most likely be able to give you a current VAM reading, given as meters per hour. This is a great tool to use to gauge your effort on a long climb. If you are aiming for the golden hour for l’Alpe then you know you can’t let your VAM drop below 1,071m/h. Likewise, it's best not to set off at 2,000m/h as at some point you will blow up.
VAM is something I have used successfully with my coaching clients who don't have access to a power meter, but who want to judge their pace and effort on long climbs during tough, mountainous sportives like the Marmotte and Etape du Tour. As a result, it's a useful figure if you are targeting a particular time as climbing takes up a significant proportion (of time and effort) of such events.
Unfortunately, if you are looking to use VAM as a guide to pacing during your next sportive it can only really be calculated accurately by doing a test on a long climb. You can calculate a sustainable VAM using a similar method to an FTP test. If you are lucky enough to have a local twenty-minute climb then ride as hard as possible from top to bottom, record your VAM and then take 95 per cent of that figure for the VAM you can sustain for one hour.
Pacing using VAM
When using VAM as a pacing aid you also need to take a three other factors into account.
Firstly, wind. When riding with a tailwind your VAM will be much higher as you are effectively being pushed up the climb and so less effort is required for the same rate of ascent. On the flip side, when riding into a headwind the additional resistance will mean that your VAM figure will drop for the same effort.
Gradient also has a small affect on VAM. On steeper climbs you will find that you be able to sustain a higher VAM figure than on shallow climbs. VAM is most useful when climbing on a gradient of between six and 15 per cent. Any shallower and wind resistance has too much of an effect, any steeper and you are simply going so slow that you aren’t making enough forward progress to sustain a high VAM figure.
Finally, the length of the climb also affects VAM. You need to take into account the length of the climb when calculating the VAM figure to aim for. If, for example, you know you can sustain 1,000m/h for one hour then on a twenty-minute climb you need to aim a little higher - around five per cent. On the other hand, if you will be climbing for one-and-a-half to two hours then you need to aim for five per cent less than your one-hour VAM figure.
It can be difficult to follow VAM on climbs with irregular gradients - for example, a lot of Pyrenean climbs. In this case, some computers have a 30-second average VAM figure and this is really useful as it smoothes out the peaks in VAM during the steep hairpins and the lulls on the flatter sections, and so it gives a much more stable number to ride to.
VAM and power to weight ratio are intrinsically linked, and by now it's likely you'll want to hit the road to improve your climbing ability. Flick through to the final page for a training session to do just that.
A session to improve your power to weight ratio
George Scott/Factory Media
As we've already covered, the best - and most sustainable - way to improve your power to weight ratio is to focus on improving your power.
Power to weight on long climbs is all about sustainable power - your anaerobic threshold - so here is a session to work on that all important Functional Threshold Power. This session refers to your training zones - find out how to set your zones here.
- Warm up for 15 minutes in zone two
- 2 x 20 minutes progressive zone four effort - start at the bottom of zone four and finish right at the top of zone four/bottom of zone five
- 10 minutes zone one recovery between efforts
- 10 minutes cool down