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Pedal Science Blog: How Does Bike Fit Impact Upon Power Output?

Welcome to Pedal Science, the weekly bike fitting blog by Nick Thomas of The Endurance Coach. This week we look at the subject of BIKE FIT & POWER OUTPUT. 

To ride to your potential you need to be able to maintain the highest average power you’re physiologically capable of for the duration of the event. An effective bike fit will provide a position which enables the cyclist to ride as efficiently and consistently as possible and is achieved by improving comfort and pedaling technique:

  • Comfort:

The riding position should be as comfortable as possible and the longer the event the more important this becomes. Once people feel pain or discomfort the mind becomes focused on the discomfort and power drops as the body tries to relieve cause of the pain. This is evident during the second lap of any Ironman bike leg: numerous people will be sat up, freewheeling, stretching and adjusting their position to relieve the discomfort they’re feeling. Slower second laps are often due to biomechanical deterioration, not lack of calories.

The most common complaints are lower back ache, neck tension and painful feet, all of which can be affected by – or attributed to - the bike set up. Back ache is often due to over stretching and having inadequate weight distribution through the tribars and neck pain can often be caused by handlebars which are set too low. Sometimes a couple of simple adjustments is all that’s needed to alleviate the problem. Sore feet are often caused by cleats which are set too far forward so the pressure is centred directly under the ball of the foot: by pulling the cleats back the pressure is reduced in the foot and the foot plate behind the ‘hot spot’ takes the load instead.

  • Efficient pedaling technique:

To maintain a consistent power output each pedal stroke should be completed with a power distribution which is as consistent as possible. Power meters provide a spin scan which shows the power distribution throughout every pedal revolution in real time and can be invaluable in improving pedaling efficiency. There are two main reasons why power distribution might be too uneven:

Technique:

Many people are unaware of how they should pedal and tend to stamp down and/or pull up instead of applying more consistent through the bottom of the pedal stoke. This is often visible to the naked eye as the pedaling action has a jerky appearance.

Saddle height:

If a saddle is too high there’s often a loss of power at the bottom of the stroke as the primary muscles lose their mechanical advantage. This can lead to hips dropping or feet excessively plantarflexing to reduce the extension at the knee, but both compensations can result in a less efficient technique with resulting lower back pain and unnecessarily fatigued calf muscles.

A saddle set too low can result in different compensations and often lead to knee pain. If there isn’t enough room for the foot to pass over the pedal stroke it will either go around instead or the hips will hitch up to provide the necessary range of movement for it to pass over the top. Rocking hips can cause lower back discomfort, knees that don’t track properly can cause knee pain and both factors reduce efficiency as there’s a loss of continuity in the application of power throughout the pedal cycle.

To improve pedaling efficiency gain access to a power meter if possible: many gyms now have Watt Bikes and the time spent using them would be very well spent. Without a power meter incorporate the following points in your training to improve pedaling efficiency:

Scrape, don’t stamp:

Power distribution should be as even and continuous as possible throughout the pedal stroke. Instead of pushing down (or stamping) think about scraping the foot back through the bottom of the stroke. Single leg drills are an effective way of achieving this, either on the road or a turbo trainer.                       

If riding outdoors find a flat, uninterrupted stretch of road and try the following: keep both feet clipped in but let one leg go dead for 30 seconds so the other leg is doing all the work. If you stamp you will find there is a dead spot at the top of the stroke. To improve stroke momentum you’ll have to maintain pressure through the bottom of the stroke. Complete 30 seconds on the second leg and then spin as normal for 2-3 minutes and repeat the process several times.    

Relaxed but stable:

Leg muscles are the prime movers when cycling so there is nothing to be gained by having a tense upper body. Posture should be correct to reduce stress on the lower back and your upper body should be relaxed with the weight rested into the handlebars. Correct posture will also engage the core muscles which will reduce unwanted upper body ‘rocking’.

To improve posture and core function try climbing short, steep hills in a hard gear with the palms rested on the handlebars instead of gripping. You’ll be surprised how much your torso is working to stabilise the upper body.

Symmetrical power distribution:

Power distribution should be symmetrical through both legs. Many power meters measure power distribution in real time so you can continually adjust your technique throughout a session. It’s not uncommon for someone to have a distribution of 55/45 and although this appears fairly even the effort and concentration required to achieve 50/50 is considerable. Single leg drills on the non-dominant leg are an effective way of increasing function.

Spin and grind:

Too improve pedaling efficiency complete sessions with either very high or very low cadence. High resistance/low cadence reps of 70 RPM or below will highlight dead spots at the top/bottom of the stroke if the power application is not continuous (i.e. the rider is stamping). Low resistance/high cadence reps of 110 RPM or above improve neuromuscular coordination so efficiency at normal cadences is improved.

Let’s off road!:

If you’ve ever driven up an icy hill in your car you’ll know the consequence of applying too much pressure on the accelerator pedal. The effect is the same when climbing up a muddy or gravelly hill on a mountain bike – you’ll wheel spin. It’s no coincidence competitive mountain bikers have high spin scan scores as even application of pressure is essential when traction is inconsistent. Spend as much time during the off-season riding off road and your performance will improve when you return to the road the following season.

Conclusion:

Comfort and effective pedaling technique are essential for anyone who wants to maximise their potential on a bike. By riding on a correctly fitted bike you will be able to ride faster for longer.

Nick Thomas is the resident bike fitter at The Endurance Coach. He is a fully qualified bike fitter and expert in lower limb mechanics, holding a BSc (Hons) in podiatry. You can contact him using the email address: nickthomas@theendurancecoach.com or see more about his fitting services by GOING HERE.



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