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December 15, 2011
TECH NEWS BROUGHT TO YOU BY BIKEEXCHANGE
All too often we forget about our feet. The only time we ever notice them are when they fail and start to cause us pain. But there may be some simple solutions to eliminate pain – not only in the feet, but elsewhere too – and also improve your power.
Let us examine the foot closer……but not too close.
Movement within the structure of the foot can cause associated problems-pain, injuries, and inefficiencies. The impact of this can be quite profound with faulty foot mechanics often to blame for knee, hip and lower back pain. Locking the foot, within the shoe, to cause less movement has been proposed as a mechanism to reduce these injury risks.
The most common type of foot pain for cyclists generally falls into two categories: hot spot/friction injuries and compressive injuries. Hot spots and blisters are typically created by friction – sweating, swollen feet with consistent rhythmic force being applied to them for hours on end is almost guaranteed to cause friction and pressure injuries to the soft tissues of the foot.
Well-fitting footwear, good quality wicking socks (that conform to the pro requirement of a six-inch cuff which rises smoothly to the first bulge of the calf!), non-slip footbeds, appropriate cleat positioning and bike setup will almost always clear these problems up.
Compressive injuries (like numbness and sharp, stabbing pain) can occur due to footwear that is ill fitting (particularly across the ball of the foot which causes compression and squeezes the delicate neural structures within the foot), small surface area on the pedal, the sole of the shoe, and again poor cleat positioning.
These foot problems are typically easy to resolve with appropriate equipment selection — footbeds with metatarsal buttons, good personal hygiene, good bike fit and well fitting shoes. Internet shoe shopping has created many problems with people compromising on fit because they cannot try different makes, models and sizes of shoes.
Cycling shoes are designed for different purposes and different shaped feet. As much as we may like Brand X they may not be the right shape for our feet and can cause injury. Trying on shoes prior to purchasing is very important; it is the only way to determine if the shoe fits!
Where things get really interesting with the foot is when we begin to discuss it in relation to injuries and force generation. Footwear and cleat positioning play a major role in injury management and prevention.
Most of you will be nauseated to know that from a biomechanical perspective most cycling shoes are only as good as the footbeds that are in them. You pay $400 for a magnificent, artisan-crafted, kangaroo leather, BOA-strapped pair of ‘White Ladies’ (as one of my friends disconcertingly calls his shoes) but the reality is that if the foot is not locked, or it moves within the shoe, they may cause injury and can create inefficiency.
If you remove the footbed (the dodgy liner in the bottom of the shoe that most of us ignore) and twist it in your hands, odds on (unless it is a Mavic, Bontrager or to a much lesser extent Specialized) it will probably be a flimsy low profile bit of foam/plastic/cork/cardboard. It has very little structure, support or shape to it. This can be problematic.
Standard foot bed on the left and carbon rigid custom footbed on the right.
The foot is designed to walk on, not ride a bike. When walking we have three stance phases of foot movement: heel strike, mid-foot stance and toe-off. Riding a bike most parallels mid-foot stance. It is at this point in the gait cycle that the ligaments in the foot come marginally off tension and it is unstable, which assists us when walking to shock absorb and conform to the shape of the ground. In bike riding this instability is exaggerated due to it being non-weightbearing.
Note: The ‘mid-foot’ posture of the foot while cycling
There is a debate raging amongst runners regarding what is called ‘natural’ or ‘barefoot’ running whereby they make use of this inherently more mobile part of the gait phase to reduce the risk of injury and increase shock attenuation. Great for running; terrible for cycling. We don’t need to shock absorb.
Cyclists need their foot to be a rigid lever – working as one with a rigid shoe to transfer every watt of power to the pedal. Any aberrant movement through the foot, ankle or knee is at best a waste of power, and at worst a real injury risk. Footbeds need to be different for cycling and walking due to the different biomechanical requirement; one needs to be rigid and the other not.
Examples of cycling specific footbeds- standard, eSole modular, Solestar custom carbon.
Everyone has a finite amount of watts they can generate. Every spot where you ‘leak watts’ is a cause of concern. You could be excessively recruiting muscles to stabilise due to the bars being too low or reaching too far, saddle too high, saddle too low, cleats too far forward making the foot more unstable and recruiting calves unnecessarily, lateral movement of the knee, or hips dropping. All these movements are unnecessary, yet they demand energy through metabolic activity.
This is a demand your body must meet and it means there is less to go around for the working muscle groups which in turn results in less power. Almost all the great cyclists show very little unnecessary movement.
One answer for this can be properly fitted footbeds. The theory with the new footbeds, be they Solestars, Superfeet, eSoles or any number of other custom designed orthotics, is that they allow you to use the inherent stability of the foot. They lock up the foot, typically from the rear with pressure under the sustentaculum tali.
Because the ligaments and bones in the foot are now ‘locked in’ it requires less muscle effort from the intrinsic muscles of the foot and lower leg to stabilise the foot in the shoe. In turn this means there is less aberrant movement in the foot and ankle, and also of the foot within the shoe. Left unchecked this movement at the foot can create knee and back pain.
Internal tibial torsion loads the knee (creating dreaded ITB symptoms) and internal rotation of the femur which alters the way the glutes, hip flexors, quads and hamstrings fire. The sacro iliac joints or lumbar spine then have to cope with the movement.
Right: Normal footbed- note internal tibial rotation Left: Custom footbed-no internal rotation
We objectively analyse movement when assessing and treating injuries and time and again we see poor lower limb biomechanics starting at the foot. These are often not as a result of the shoe but what is in it.
Studies have shown that custom orthotics in cyclists dramatically reduce the rate of injury. O’Neill et al (April 2011) in their study ‘Custom Formed Orthoses in cycling’ found “…custom foot orthoses can significantly alter subject specific parameters of cycling biomechanics including tibial internal rotation and knee position during the power phase of the pedal cycle…”.
But here is the kicker: “…they do not have a systematic effect on cycling biomechanics…”. In the context of the study they mean that the same footbed does not have the same effect for everyone. What works for me might not work for you.
Footbeds must be designed around your particular needs, recruitment patterns, posture, or foot structure. They must be fitted by someone understands the demands of cycling. Typically a podiatrist, physiotherapist or osteopath.
Some shoe manufacturers currently have a uniform forefoot wedge in their shoe which is great for some of the population but not for all. The data indicates shoemakers should keep the shoe neutral and let professionals fit footbeds to cater for the individual’s foot. Not all of us need the wedge, just as not all of us need rear foot posting. One size doesn’t fit all.
What about power generation? Solestar claims its footbed can improve power over an eight-second sprint by 7%. That is a lot. At 800 watts that is a claimed extra 56 watts. I have a pair and I still can’t beat Albury Pro Rhys Pollock in the Tuesday night World Cup (although I suspect it may not be my carbon footbeds!)
Intuitively, it makes sense that a rigid foot in a rigid shoe will transfer power better than a ‘loose bag of bones’. It also makes sense that if the knee and ankle are tracking straighter that there will be less leaked power. I feel there is something in Solestar’s assertion but more rigorous study needs to be performed.
Nothing causes a reduction in power faster than being unable to ride due to injury. From my perspective as a health practitioner this is where there are real-world benefits for the majority of cyclists-injury management, injury prevention and increased efficiency. You may get more power with footbeds, but it has been proven you will reduce your injury risk with appropriate foot mechanics.