Bike fit clinic

Lee Prescott from the Velo Atelier Bicycle Studio in Warwickshire, UK, has a background in ergonomics and bicycle design. He shares one of his more subtle bike fits from recent weeks.

Cyclist gender: Female

Age bracket: 45-55

Discipline: Road

Level: Experienced club rider

Complaint: Exponential foot numbness after one hour of regular cycling

This rider came into the studio for an initial assessment and was getting increasing numbness in her feet after one hour of cycling at any intensity. It was affecting both feet and would continue even whilst resting at coffee stop breaks. After getting home the pain would subside within five minutes.

Bike fit Observations

A check of the client's overall position on the bike showed no obvious issue: It was well balanced and muscle recruitment was well distributed by the saddle position and body angle. Her closed hip angles were well within safe limits, so restriction of the iliac artery was ruled out.

Focus turned to the client’s shoe setup. Firstly, she was measured correctly with a Brannock device, which showed that she was a B width on both feet. Her shoes were standard last Sidis, which looked to be wide enough for her. However, the standard Sidi Insoles were being used, which didn’t match her extremely high arch (see photo, next page). Due to this she suffered from a little over-pronation. The rest of her foot was a little hypermobile.

Theory

Based on the basic information it looked like the shoes should be fine apart, from the insole not being quite supportive enough. Lee’s theory was that given the symptoms the problem had to be due to a restriction of the venous system of the foot. All signs pointed to a restriction of blood flow causing the numbness.

The fact that the numbness continued until the shoes were eventually removed — and that once removed it was a short period before feeling returned — seemed likely to be the blood flow being restored to the foot, backing up this thesis.

Following these observations, Lee interviewed the client a little more to find out more of her medical history. It appeared she also suffered from Reynaud’s, which is a whitening and coldness in the extremities caused primarily by low blood pressure. Deeper consultation identified that she had none of the other symptoms of peripheral Arterial Disease (PAD) but she was instructed to consult a GP to be sure. It seemed likely that with a history of low blood pressure that it would only require a minor constriction of the foot to cause the numbness being seen.

The athlete was asked to put her foot into the Windlass position by lifting her toes whilst maintaining contact with the ground through her heel and transverse arch (see photo, above). Given her mobility in the foot and already high arches, it could be seen that the instep was extremely high volume. The shoes she was wearing were the correct width for her, but were also of a low volume through the rest of the foot. This was the issue that was causing foot to be constricted in the mid foot, creating the slight blood restriction.

Intervention

Now the issue had been identified it was a relatively simple task of correcting the problem.

Firstly, Lee had to select a different shoe that catered for the athlete’s foot type. The shoe selected was the Lake CX241, which has the upper split into several segments that can be individually tensioned by Boa dials. Secondly, a set of custom insoles were moulded to hold the foot correctly and prevent the small overpronation seen.

Once fitted, the foot was supported inside the shoe allowing the knee to track naturally and facilitate the efficient communication of the power into the pedal. The separate sections of the shoe allowed both the small volume forefoot and the high volume midfoot to be correctly supported by the upper of the shoe, without causing any restriction of blood flow.

Result

Two weeks following the session the foot numbness was completely gone, while power production had increased as the athlete didn’t feel held back by something in her physiology “not working right”. She had also consulted a specialist who confirmed there were no further signs of PAD.

Take home

1. Just because a foot is narrow doesn’t mean that it is small in every dimension: Think in three dimensions when looking at any biological structure.

2. If you are not an expert in a field then own that fact and ensure you refer your clients to someone who is if you are even in the slightest bit concerned about symptoms you are seeing.

3. Ensure you are well-versed in the product ranges available and how the differ in terms of fit and function to help solve your clients problems.

4. Don’t overlook the importance of what’s going on inside the body as well as how the external components are working.

Have an unusual case you'd like to share: Email lee@ibfi-certification.com