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 & RUNNING PERFORMANCE.
When setting up a bike most triathletes (and bike fitters) are aware that the riding position will affect comfort and efficiency and that a correctly fitted bike will result in a faster bike split. However what appears to be overlooked in the majority of cases we see is how the position affects the run split.
Physical deterioration can be considerable during the run in a triathlon and the longer the event the more apparent this can be. People who are good runners are often reduced to a walk with a run split much slower than they’re potentially capable of. There are various contributing factors to this deterioration but correct bike fit is essential to be able to run to your potential. The most common problems we see which can adversely affect the run split are as follows:
- Front end is too low:
The lower the front end the more the flexed the torso and hips become as the person is bent over more than if the handlebars were higher. A low front end can cause a blockage at the top of the pedal stroke if hip mobility is restricted and can also cause discomfort in the lower back if flexibility in the back is limited.
Once the person dismounts the bike the hip flexors will be tight as a result of the closed hip angle and this will affect running gait from the outset as the pelvis is anteriorly rotated due to the tension in the hip flexors. This can be seen in people running in a bent/leaning forward position at the beginning of the run: running efficiency is compromised and it can take several miles for the tightness to subside.
Anyone who has begun the run with a sore lower back knows how debilitating it can be. Once the core postural muscles are unable to support the body in motion force production will drop, stride length will decrease and the ‘Ironman shuffle’ begins.
- Rider is overstretched:
Excessively low handlebars are often accompanied by an overstretched riding position which compounds the problems described above and often causes mid-upper back and neck pain. Trirars are designed to support weight and reduce tension throughout the posterior chain of muscles but this can only be achieved if the bars are in the correct position at the right angle. An overextended position prevents the rider from weight bearing into the bars and tension consequently increases throughout the back and neck. This is especially common on road bikes with tribars as the bars are usually too long and often provide very little adjustability. Unless they can be shortened sufficiently they’re useless and it often makes more sense to race without the tribars.
- Saddle is too high:
A saddle set too high will usually cause one or both of the following compensations:
1. Rocking hips
2. Plantar flexed feet
These compensations help the leg to reach the pedal at the bottom of the stroke without the knee having to extend too far but both can impact on the run. Rocking hips can lead to excessive lower back fatigue and pain and a plantarflexed foot (toes pointing down) causes unnecessary stress within the lower leg muscles as these muscles are forced to plantarflex at the foot at the bottom of every pedal stroke.
This should be avoided at all costs as the same muscles are essential during gait to limit the amount of foot pronation and internal leg rotation as the leg is loaded and then supinate the foot as the person drives forward and pushes off the ground. If these muscles are excessively tired from the bike they’ll be unable to function effectively during the run. The result is an inefficient gait, recruitment of secondary muscles and a disappointing run.
- Cleats are too far forward:
The further forward the cleats are positioned the more tension there will be on the lower leg muscles described above when cycling: the same problems consequently arise so it often makes sense to pull the cleats back to reduce the muscle tension. Triathletes often require the cleats to be positioned further back than cyclists but it’s very unusual for this to be considered during the fitting process.
It’s possible to lose more time during the run than the bike in a triathlon but this factor is commonly overlooked by triathletes and bike fitters. By achieving a riding position which reduces unnecessary muscular stress the body will be able to run more efficiently and for longer without deteriorating. Triathletes should always be fitted with the run in mind, not just the bike.
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: email@example.com or see more about his fitting services by GOING HERE.