Power meters: Do I really need one for triathlon?

Power measurement is becoming synonymous with cycling. It’s now not uncommon to hear individuals milling around talking wattages and watts per kilogramme for training and racing. This is because the power you put into riding a bike is what you get back on the road, and it speaks volumes about training or racing prowess.

But while there are plenty of technological advances that mean we’re losing fewer and fewer watts to drag, it’s important to remember that what really matters is the engine you’re driving the bike with – you. If you have your power measured in a maximal test it’ll show what you are – and aren’t – capable of. And the numbers can be sobering…

• How to use a bike power meter

Why do triathletes need to measure power?

1. QUALITY

Power measurement keeps quality work honest. While stationary bike classes may get your legs going, they don’t measure your effort. Similarly, turbo-trainer sessions using heart rate alone can be susceptible to heat build-up as well as inconsistency of resistance on the rear wheel, which can distort the numbers – you can end up training 30-50 watts lower at the finish than at the start of a 35-40min interval session. It’s not just about sending your heart rate into the required training zone, though. It’s about doing precise work, seeing what that does to your
heart rate and comparing that with what your heart rate should be doing.

• Best heart rate zones for running
• Best heart rate training zones for cycling

2. PERFECT PACING

Racing at the correct pace for you isn’t an intuitive ability, unfortunately, but power allows you to pace your bike leg precisely. Recent research has shown that variable cycle effort over a 1hr period negatively affects 9km run performance by 42secs compared to smooth, controlled riding. Riding consistently near average target power is the key to efficient triathlon biking.

3. FATIGUE AWARENESS

Training with power catches fatigue early. By assessing actual work done rather than inaccurate metrics like average speed or feel, you have your own early-warning system that looks out for fatigue or illness. Power takes all the extraneous information that can cloud your judgement and looks at simple work done against heart rate and perceived exertion. It doesn’t ignore your feelings, but rather heightens your sensitivity of yourself as an athlete.

4. TESTING, TESTING

A power meter gives you the ability to test power-to-heart rate anywhere, anytime. Once, power was only available in the lab, but now it’s accessible to almost anyone. Over 60% of my clients use power in some format, many on their race bike. There is a flipside, however – most power systems are probably more costly than many readers’ bikes. But for the serious, time-crunched or tech-minded trier, they’re a very worthy investment.

5. PITFALLS OF POWER

Nobody should ride with wattage all the time. You also have other sports that you’re training for, generating fatigue from other muscles – not just your legs – that needs to be taken into account. If you’re doing a base ride to increase stamina, then zone one (60-80% of max) is the goal. It’s all too easy to try and see how hard you can go while staying in the correct zone, but leave power at home on those days, and get it out for intervals, hill strength or race pacing.

Similarly, using power doesn’t mean you’ll suddenly become hugely powerful and discover the legs of a Rachel Joyce or Frederick Van Lierde. Across a whole range of athletes, from those with a peak power output (PPO) of 200w to those with 450w, once trained I rarely see power increase significantly in 30-40-year-old athletes.

6. MARGINAL GAINS

You can now purchase systems that measure the left/right balance of your pedal stroke, like the Rotor Power Cranks or Garmin Vectors. This left/right efficiency is at the cutting-edge of understanding what we can and can’t do to a rider’s efficiency and power. Research suggests that becoming more efficient is difficult, though long-term analysis of pros reveals a 1-2% improvement is possible when riding more than 20,000km per year. It’s an ever-evolving area, but its early adopters and those with a clear left/right imbalance are ahead of the curve.

• Power meters: 6 of the best reviewed

Jargon buster

PPO – peak power output, defined as max average 1min power output in a test.

Watts per kilo – an athlete’s average race or peak power data compared to their weight (for example, 3.5w/kg Kona bike).

HIIT – high-intensity interval training, which is done at somewhere between 85 and 92% of max heart rate.

More power training advice

• 12-week power meter training plan
• What’s the difference between cycling power meters and running power meters?
• How can power meters help you perform better?
• Cycling power secrets: how to increase and understand it so you can apply it effectively
• Cycling speed versus wattage calculator: how much power do you need to reach your target speed?
• What’s the difference between average power and normalised power on the bike?