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Cycle fitting part II – The feet

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FEET-UP
With most sports what we with our feet is crucial to performance. This is further compounded in cycling where your feet are effectively fixed onto a fast turning lever. This makes the act of pedalling a ‘Closed Kinetic Chain’, with the pelvis hip joint at one end and the clamped forefoot at the other. In other words the foot is both the beginning and end of the bio-mechanical chain, where it is often difficult to determine cause from effect. Is an anomaly at the hip-joint causing an issue at the foot? Or is an issue at the foot causing instability at the hip and lower-back? (fig 2).

And does any of this matter as long as we pedal hard enough? Any CycleFit session will spend a significant portion of the two hour session working with: cleat-alignment, footbeds, LeWedge-shims, pedals and shoes, to stabilise and optimise the foot-knee-hip-joint bio-mechanical chain. It is worth pointing out this stage that many incidencies of knee-pain and injury have their root in mal-alignment and bad-set-up, rather than an intrinsic problem within the knee joint itself.

ON TWO LEGS
Let’s back-up a little. We are the only bipedal mammals to have evolved and survived (kangaroos don’t count – they use stored energy in their tendons as massive springs for locomotion). In fact experts still have only unproven theories about what conditions we must have faced in the ancestral environment that required us to stand up straight to survive. Some evolutionary psychologists suggest a sudden change to swamp conditions selected for an ape that could wade. Others are convinced that standing and walking on two legs evolved from showing-off as part of reproductive displays – i.e. a bit like the peacock’s tail – which itself has no intrinsic value other than to catch the female’s eye.

The latest theory concern’s the biped’s inherent ability to develop and recruit powerful glut (hip-extensor) muscle-groups, to help with long-distance running, and therefore cycling. Whatever it was that made us stand up and walk on two feet, now that we do all of our locomotion, power and centre of gravity are concentrated through a very small contact patch with the ground (about the size of two 1st class stamps on a pedal). As a consequence the human foot has evolved amazing function and versatility, consisting of 28 bones and 27 muscles, controlling 33 types of possible mobility.

A FIRST CLASS LEVER SYSTEM
The bipedal foot is our body’s only 1st class lever system, where the load (the pedal) and the force (Calf muscles) are either side of the pivot (ankle) – a perfect see-saw. This gives exceptional mechanical advantage; hence you can elevate your body-weight all-day-long with one calf-muscle, a relatively small muscle-group. In contrast, the lateral quads of the upper-leg work on an inefficient 3rd class lever system, and as a consequence need much more bulk to achieve anything like the same torque (more of this in Part III).

In cycling we are trying to align the inefficient 3rd class levers of the upper leg with the 1st class lever of the foot, for maximum power and efficiency. All the more critical as normally the only natural re-calibration possible when you pedal is with the few degrees float at the pedal/forefoot interface. Put simply, once you are pedalling you have absolutely no choice where your feet are going.

CLEAT AND PEDAL AXLE PLACEMENT
We start by locating a rider’s 1st metatarsal head, adjacent to the ball of the foot (marked ‘1’ in fig3). You will notice that the 2nd metatarsal head (2) is ahead of the 1st met-head. For many people this is where we will start by placing the middle of the pedal axle and cleat. The simple justification being that by taking the pedal-axle out to 2nd met-head we are maximising the mechanical advantage of a very good lever (see above on lever-systems), in addition the 2nd met-head is the natural bipedal toe-off point (i.e. the last point of ground-contact).

BUT 2nd met-head is only a starting point, and there are plenty of situations where it is better for comfort and efficiency to take the pedal-axle back to or behind the 1st met-head, or even on rare occasions in advance of 2nd met-head:

  • Tight calves or Achilles tendon
  • Especially big or small feet
  • Drastically toe-down pedalling style
  • Radical heel-down or ‘ankling’ through pedal-stroke
  • Pre-existing injury or irregularity with rider’s foot
  • Foot or arch length discrepancy
  • Femur length discrepancy
  • Excessive inward rotation or outward rotation of foot during pedal-stroke

The message here is that cleat-placement, like the entire cycle-fit must be in rational empathy with a rider’s dynamic-physiology (your pedalling style). It is insufficient to take measurements and then extrapolate a bike-fit, ignoring what may happen when someone pedals at 100 RPM. Any asymmetry or inflexibility will affect the way the rider interfaces with the bike – and this starts and ends with the pedals.
NEVER GUESS YOUR CLEAT/PEDAL SET-UP!

OLD SCHOOL V’s NEW SCHOOL
Old-school thinking had your feet facing straight-ahead in perfect symmetry, regardless of where your feet naturally wanted to fall. This was thought to give the best power-transference, and if it hurt, well cycling is meant to isn’t it?
Well, no. Most of us are carrying tiny asymmetries that start or end in our feet’s ‘neutral position’.

At CycleFit we assess each foot separately for:

  • Width, length and arch-length
  • Varus or valgus forefoot-tilt (fig 4)
  • Neutral foot-stance – i.e. your foot’s natural stance and bias (a simple way is to get the person to jump a few inches off the ground and observe how they land)
  • Collapsed or high arch (fig 2)

We will align the cleat on the shoe and hence the foot on the pedal in line with a person’s neutral foot posture. The cleat will then be rotated to allow the foot to sit neutrally in the float. Note that more float is not necessarily better. Arguably if the foot is perfectly still and calm throughout the entire the pedal-stroke, then no float would be acceptable? In practice most of us are more comfortable with a few degrees of rotation either side of our neutral foot. Remember that each limb and foot is different. It is not uncommon to see one the cleat one side rotated to allow a heel-in stance, and rotated to allow heel-out on the other (Stand-up Guy Andrews). Often our foot rotation is down to how we were born or developed as children. Occasionally however it can be influenced by an inflexibility or injury such as tightness in the adductor muscle (Guy) [I wish he’d stop picking on me…] or piriformis muscle.

Q-FACTOR (STANCE-WIDTH)
With some pedal-systems the cleats can also be positioned to effect foot stance-width or Q-Factor. In general we align the hip, middle of the patella and 2nd met-head with a laser-line (see fig 5).

PRONATION/SUPINATION
Forefoot pronation is where the foot flattens and rolls towards the crank during the pedal stroke (supination is the opposite and much rarer – about 5% of the population). Often the rider will be rolling over through the foot’s torque-converter bone called the ‘Subtalar Joint’. As well as giving an inefficient articulation to the ankle joint, rolling can cause the foot to feel fidgity on the pedal, and bio-mechanical unstable through the affected leg.

Pronation can cause huge losses in power, efficiency and comfort, both at the feet and more especially all the way up the bio-mechanical chain to the knees, hips, pelvis and back. In effect you are literally wrong from the ground-up (see fig. 2) where a collapsed arch and forefoot-pronation is causing instability in the kinetic chain and movement at the knee and hip. We have a fairly good idea if, and how much, someone is going to pronate by the time we see them pedal by looking at their foot shape (see fig 6 and a substantially fallen arch) and their forefoot tilt.

We use a laser to assess how much movement there is in the kinetic chain from the forefoot pronating or supinating. We will use LeWedge shims to correct a forefoot tilt (figs 7 & 9.) and custom Conform’able footbeds to stabilise the foot and add comfort (fig 8)

The next Installment Part III is on ‘General Bike Set-up’.

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