- slip last, which involves sewing the upper directly to the sole
- board last, which uses a board to attach upper and lower elements
- combination last, which uses a board last in the heel area, while the forefoot is slip lasted.
The method used can be worked out by removing the in-sole and examining the interior - a full length piece of card indicates board lasting, stitching indicates slip-lasting and both, a combination last.
Slip lasts tend to provide less control and more absorption than board lasts. Board lasted shoes are usually more stable, while combos provide rear foot control with forefoot absorbency.
Sole (or Out-sole)
There are numerous types of sole. For instance, some combine various types of materials to maximise traction on and off the road, while a number of new soles are made from moulded, composite materials. Other than for use in extreme conditions such as fell running, many designs don't really have a great deal of bearing on function.
Mid-sole
The mid-sole is the thick layer of rubber that sits between the outsole and foot bed. The mid-sole absorbs impact, flexes in the ball of the foot at toe off and determines the level of foot control. It is usually constructed of foam type compound, frequently EVA (ethylene vinyl acetate).
Manufacturers have developed 'technology' such as air bags, gel and structures of other material which are designed to provide various functions. The best new materials improve shock absorbency without increasing weight, which is beneficial.
Three factors determine how good a mid-sole is:
1 Shock absorbency
This can be tested by pressing the material. If it's extremely spongy then it may not provide the shock absorbency required by heavier runners, and conversely, if it's too taut it may be inappropriate for lighter runners. When longitudinal creases develop - those parallel to the ground - the mid-sole will be losing its shock absorbency.
2 Heel height
Most people require a small heel to help reduce forces within the foot and stress on the Achilles' tendon. Heel height can be determined by taking the thickness of the sole at the ball of the foot from the thickness at the heel. An increased heel height is preferable for calf problems or rigid feet.
3 Pronation control
Some trainers incorporate a wedge within the mid-sole - making the sole thicker on the inside than it is on the outside - to increase foot control. Other shoes use plastic inserts to achieve this. A more popular method is to use two densities of material within the sole. Typically, the material on the inside of the heel is harder than it is on the outside, so when a load is applied there is more compression on the outside of the foot forming an effective wedge.
Arch Fill
This is the area of mid-sole and sole under the arch. It should be designed to let the shoe flex with movement of the foot, whilst still providing it enough support. A large number of shoes have less material here. In most cases this does not provide enough support, and any trainer which is weak at this point should be avoided. A simple test is to bend the shoe and see if the arch correspondingly flexes - if it does it is too weak. Shoes that are strengthened in this area will not bend as easily.
Upper
This fits around the foot holding the shoe in place when the laces are tied. It can be made of nylon or nylon mesh, or a combination. It sometimes incorporates design features such as light weight, reflective or waterproof (and breathable) material.
Sometimes parts of the upper which are prone to wear, such as the outer toe box and area around the lower heel, are reinforced with a leather type material or rubber.
For comfort, increased cushioning may be used around the ankle collar at the top of the shoe where it meets the ankle, in the heel tab and in the tongue, under the laces to prevent them rubbing. Some shoes use an inner sleeve to improve fit, but there is little evidence that this has a significant effect.
Toe box
This is the part of the shoe that holds your toes, the height of which it should comfortably accommodate. A small toe box will constrict your toes and increase the risk of bruising on the toenails.
Lacing
This secures the upper and therefore the rest of the shoe to the foot. An eyelet is the hole the lace passes through - this should be strong enough not to snap when the lace is done up at normal tension. There are a few types eyelet used:
- traditional eyelets, which are punched out of a (usually reinforced) part of the upper
- 'D' ring eyelets, which are designed to lace up quicker. Some manufacturers call a lacing system comprised of D ring eyelets a 'ghilly' lacing system
- multi hole eyelets which are often staggered to accommodated a wider variety of foot widths.
Heel
Heel counter
This is the portion of the heel that is stiffened. Research indicates that a stiffer heel does not necessarily improve control, but it is preferable to the side to side displacement of more flexible designs. You can squeeze the heel to see whether it will be firm and supportive. For runners who require specialist in-soles or orthoses, a stiffer heel will prevent the insert from slipping. Any insert within a shoe is known as an orthoses.
Heel tab
This is the top part of the heel counter. It is important it is not so high that it protrudes into the Achilles tendon, which could cause inflammation. Some heel tabs have small straps attached to help pull your trainer on.
In-sole
This sits on the foot bed, inside the bottom of the shoe. The in-sole is cushioned material, frequently made of low density foam, which manufactures insert into the shoe to provide additional shock absorbency and shape. Most removable in-soles do not provide enough arch support, resulting in a loss of control. However, if additional inserts are placed on to an existing in-sole - particularly one that already has an arch support - then there may be a problematic increase in control.
Carry out safe and fair experiments to test the suitability for materials used in your
footwear:
Grip:
- Grip can be tested by using a weighted trainer and a Newton meter on a running track. Shoes/boots of different sports could be tested to compare the best grip on other surfaces. For my experiment, I used a 1kg weight.
Here are my results:
I have concluded that the trainer has the best grip on grassy surfaces, and also has a fair amount of grip on tarmac. I would definitely recommend this trainer to cross country runners, as they do most of their running in fields and grassy surfaces.
Impact absorption:
- Impact absorption could be tested by a trolley on an inclined slope with a test block on it. By altering the ramp’s inclination, the angle at which the block falls off provides the means of testing. The greater the angle the more energy is absorbed by the shoe.
Here are my results:
To conclude, I would say that these trainers have a very high impact absorption level. This can mean many things. Firstly, it can mean that the trainers could be comfortable to wear. Secondly, it means that the outsole can absorb large amounts of impact and can prevent knee and ankle injuries because of its ‘suspension’.
Resistance to wear:
- A wear-wheel can be used to test the trainer’s resistance to wear.
- Density can be tested with a Eureka can and a digital measuring scale. By recording the amount of water pouring out of the Eureka can and finding out the mass of the material with the scales, you can work out the density of the material.
- Resistance to chemical corrosion can be tested by placing the piece of material into a weak acid, into water and under intense lighting. I will then note any physical changes.
Conclusion:
Evaluation:
Comparison to manufacturing aspects:
Compare footwear designs:
