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Power meter guide

Quara Elsa Power Meter
Marc Abbott
27 May 2015

Power Meters. Why you need one, how you choose it and how to best use it to help your training.

With great power comes great responsibility. But whether you’re strong as an ox or simply want to add a scientific measure to your training progress, the increasingly affordable option of a power meter has many benefits. Although available in a number of forms – at the hub, the cranks or pedals – all cycling power meters work on the same theory, using strain gauges to accurately measure the torque you make with each pedal stroke, and convert that measurement into a reading in watts on your cycling computer. This allows you to keep track of your performance on the road and then spend hours poring over the data on your computer screen once you’ve uploaded your ride.

Who needs heart rate?

So what exactly is a power meter going to give you that a heart rate monitor can’t? Well, for one thing, there’s consistency. James Gullen, head coach at Go Faster Coaching (gofastercoaching.co.uk), explains, ‘Heart rate can be affected by a lot of other factors – if you’re ill or tired, for example – but power is a constant.’

And according to Dan Fleeman, director of Dig Deep Coaching (digdeepcoaching.com), if you’re using heart rate alone, it’s impossible to perform interval training accurately due to the lag time while your heart rate rises to the desired level and return to a resting state. ‘Using heart rate for a time trial isn’t too bad, because it’s a constant effort,’ Fleeman says, ‘but for anything that includes on/off efforts, such as intervals, it’s not a great tool.’

Don’t go chucking your heart monitor strap in the bin just yet, though, as many coaches still believe there’s a place for it in your training. ‘It’s true that “perceived rate of effort” measurements are still a valuable tool, especially in conjunction with heart rate readings,’ says Tobias Bremer, clinical director and lead physiotherapist at Physio Clinic in Brighton (physioclinicbrighton.co.uk). He adds, ‘A study in 2011 by the University of Florida found that there was no difference in improvement between cyclists using heart rate monitors versus power meters while doing interval training sessions. Both groups improved significantly.’

Nonetheless, Gullen maintains that using your power output to measure performance improvements is far more reliable than heart rate: ‘If you’re putting out more watts in June than you were in January, you know that’s because you’re stronger, but if you’re relying on heart rate across time, the variables involved in working out why your HR is elevated or lower make it an unreliable way to gauge any real-world performance gains.’ He adds that power data makes it easier to compare yourself to your mates (or rivals), suggesting, ‘If your mate’s 90kg and you’re only 60kg, you might not make the same numbers on your absolute power output, but if you use your power to weight ratio, you can track how you compare.'

 

Power Meter Garmin Vector

‘I’m here to read the meter’

It’s clear, then, that power meters have their advantages. What’s not clear is how to make the most of those advantages to make yourself a stronger rider. Fleeman warns, ‘I know some people who’ve spent more than £2,000 on an SRM, and just use it to go riding with. Basically, what they’ve bought is a really pricey speedo.’ In other words, it’s only worthwhile investing in a power meter if you know how to read the data it provides.

It’s fine for the pros: they don’t need to know how to use their expensive power measuring equipment because most teams provide coaching staff. They set a training plan and monitor riders’ data online using websites such as Training Peaks. ‘Teams like Sky do so well because they can look at their riders’ numbers and pretty much know how their riders will perform in certain races if they hit the right watts,’ says Gullen. However, us mortals, unless we’re paying for coaching, won’t have this luxury. So it’s important you learn how to analyse your data to get the best out of your training.

‘It doesn’t matter what websites you use to store your rides,’ Gullen says. ‘You can even use Strava (strava.com) to see what watts you’re making on each segment, and compare identical rides over time. It’s even better if you have access to Training Peaks (trainingpeaks.com), because there you can see your power peaks for five seconds, 10 seconds, five minutes and so on. This is really useful for analysing interval sessions.’

Fleeman would direct you to a book (remember them?) called Training And Racing With A Power Meter. Written by Hunter Allen, it laid the foundations for the metrics used by Training Peaks, such as the Training Stress Score (TSS) and Intensity Factor (IF). ‘Using these measurements gives you a way of quantifying the load of your training,’ he says. ‘You can use the website’s performance management chart too, which plots your TSS over time to plot a graph. From this, you can work out when you’re tired or how to peak for an event.’

Power meter data can benefit your riding in other distinct ways too. ‘A power meter can help flag up strengths and weaknesses in your physiology and bike set-up,’ says Bremer. ‘For instance, you may work at your most efficient at a cadence of 98 while generating 220 watts rather than a lower cadence producing the same power output. Triangulating heart rate readings, cadence and power will help you see this and you could change your gearing accordingly to make you a more efficient rider.’ This may mean poring over a lot of numbers and doing difficult sums, but the reward of smoother, faster riding may well be worth the effort.

Power Tap Wheel Hub Power Meter

Make it work for you

You don’t even need to be hitting the big numbers of a professional rider to benefit from a power meter. ‘It doesn’t matter if you can’t do the same watts as Fabian Cancellara; monitoring your power over time and working on it will bring improvements,’ according to Gullen. ‘Though it helps if you’re actually training for a specific discipline or event,’ he adds.

For most sportive riders, Fleeman recommends that regardless of how hilly your local roads are, you should combine your climbs. ‘I usually go out for a few hours and try to do a combined hour of climbing; it’s best to do this at Zone 4 (see Pro Power Training Plan, opposite) or a little bit above,’ he advises. ‘Or if you’ve no climbs nearby, do five or 10-minute efforts in a bigger gear, so you can still get your power into Zone 4. It’s just as useful for replicating the power you’ll need for the big ascents.’

Racers, meanwhile, can look at their power data after the event and find the areas they need to work on. ‘You can analyse the spots where you’re making big power and work out whether it was because you were out in the wind, or even if your brakes were rubbing!’ says Fleeman. And for time trials? Gullen adds, ‘You can use your average power display to measure the sort of watts you want to be generating, to make sure you don’t blow after five minutes.’

What’s the big news?

One of cycling’s most exciting developments in recent years is the increased affordability of power meters, which puts ownership firmly within the grasp of the recreational rider or club racer. ‘They’re now at a place where a power meter will cost you about the same as a set of wheels, where a few years ago they were the price of a new bike,’ says Gullen.

Dan Fleeman adds: ‘The more inexpensive meters like a Stages crank, which just measures left-leg power, while they only estimate power based on one leg, are forcing everyone else to lower their prices.’ This has to be good news for the consumer, as long as the cheaper models are still accurate and reliable, right? ‘The cheaper power meters are absolutely fine,’ says Fleeman. ‘The most important thing is that you use the same tool every time to get consistent data.’

The danger is you can become a bit Dave Brailsford about these things, and Fleeman is the first to point out that it’s easy to become obsessed with data. ‘Some people will come to me and say “I’m doing this power or that power,” to which I’ll reply, “Yes, but you’re getting dropped in races!” It’s a tool for measuring your progression and performance, it’s not really much use to go out there and keep trying to smash your peak power.’ If racing is your goal, he offers this advice: ‘If you’re looking to win a race, often the winner is the one who pedals least, so hitting big watts is less important. Look at Christian Vande Velde in the Tour de France… In 2008, when he finished fourth, his data showed there were two hours on each day when he wasn’t pedalling. He wasn’t the strongest guy in the race, but in the final week he had the advantage.’

Stages Crank Power Meter

A final thought on the benefits of power measurement from physiotherapist Tobias Bremer: ‘I’ve sometimes used power meters to prevent injuries or manage knee, hip and back conditions by setting the maximum wattage to below the rider’s pain threshold.’ So using a power meter means you can continue riding while completing a rehabilitation programme? ‘Yes, usually at a higher cadence but with lower wattage.’ That ultimately means less down time and getting back to full strength sooner. One thing is for sure – there are going to be thousands more riders with power meters this time next year, so whether you’re a racer or a café-stop wattage boaster, your competition is about to get tougher.

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