Cribratge d’una quimioteca de composts sols formada per sals de

Footwear profiles were designed in this research so that only one footwear feature was altered. For example, previous studies have investigated the effect of altering the apex position, but at the same time they also changed the thickness of the sole and the resulting

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weight. This may have resulted in an additional parameter alteration (i.e. large differences in weight) which could have affected the results. Therefore this research has a systematic approach to more fully understand the precise effect of footwear features by reducing factors that can influence the results (such as walking speed, previous injuries and current pathologies, and differences in age groups).

This research used same standard shoe profile without changing thickness of the sole or significant weight of the shoe, to facilitate a better understanding than previously as to how rocker shoes alter gait and muscle function. Additional software was used to analyse muscle properties and it is discussed in the methodology chapter. The summary biomechanical result of footwear features, which can result in alteration of triceps surae muscle work, is presented in table 4.8 below.

Table 4.8: Biomechanical evidence of footwear features. Footwear features (FF) Definition (Biomechanical explanation in text) Hypotheses Measures Back of heel Heel Height (HH)

The heel height of shoes can be varied by increasing the heel height or reducing it. Different heel heights will have an effect on the anatomical shape of the shoe and raised heels can also affect apex position in relationship to the toe angle.

A high heel places the ankle in a plantarflexion position during the whole stance phase as it alters the pitch of footwear as well. A low heel shoe may be called negative shoe as the sole apex position is lower than heel height level with the shoe on a level surface (the heel is lower than the front of the foot).

A Heel height profile would theoretically alter direction of ground reaction force (GRF), moment arm of external moment and therefore reduce/increase moment generation about the ankle and knee. Heel height can shift the ankle kinematics to be into more dosiflexion or plantarfelxion position during stance phase. It may change muscle-tendon properties, velocity and type of muscle contraction during stance phase. Consequently, it may change the magnitude of the EMG for lower leg muscles. Gastrocnemius is responsible for knee flexion as well and increased HH of the shoe will place the knee into a more flexed position during stance phase, therefore it may also affect the gastrocnemius muscle activity. Heel height can change the triceps surae muscle moment arm. When moving from a DF position into PF, the muscle moment arm is increasing. There should be an optimal heel height at which the MTU can be at its optimal length during

Different heel heights in relationship to different measurements detailed below: 1. GRF point of application. 2. GRF direction. 3. Kinematic and kinetic data.

4. EMG activity during stance phase.

5. Muscle-tendon length and velocity of

contraction.

6. The type of muscle contraction.

7. The muscle moment arm.

8. Shank angle (reclined or inclined).

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mid-stance and terminal-stance to make the calf muscles work efficient and offload them.

Curved heel (CH) or SACH heel

A curved heel could be designed purely by shape or changing the material property of the heel. For example, a SACH heel will also allow the heel to deform into a curved heel shape during IC phase. A curved heel places the ankle into a more dorsiflexion position after IC phase (in MBT) compared with normal shoes.

CH changes the point of application during IC and shifts it closer to the ankle, and therefore it reduces the dorsiflexion moment (as ankle moment arm is reduced) which can result in tibialis anterior (TA) muscle activity being reduced during 0-10% of the gait cycle. If the point of application of the GRF is closer to or forwards of the ankle it may activate triceps surae group prematurely. Therefore, CH may alter kinematics, kinetics, muscle-tendon length and contraction velocity of the muscles acting on the ankle, which may result in EMG changes for the lower limb during IC, LR and partly mid-stance phases.

Different material properties of the heel in relationship to different measurements below: 1. Point of application. 2. GRF direction. 3. Kinematic and kinetic data.

4. Level of EMG during stance phase.

5. Muscle-tendon length, velocity. 6. Type of muscle contraction

7. Muscle moment arm. 8. Shank angle (reclined or inclined). 9. Walking speed. Midsole area Bending flexibility or stiffness (BF)

Stiffness of the sole is defined by how much force is required to bend the mid sole of the shoe. Baseline stiffness occurs during barefoot walking, and an extremely stiff sole is produced when reinforced by steel plating or by a deep rocker sole. A low level of stiffness (i.e. a more easily bent sole) approximates more to barefoot walking.

Shoe flexibility of the mid-shoe area may alter plantar flexor moment during end of mid stance, terminal stance and pre-swing phases, and therefore alter lower limb (particularly calf muscle) activity. If the sole is more flexible, it may require less plantarflexor moment and power to plantarflex the ankle during the end of mid stance, terminal stance and pre- swing phases. If the sole has increased the level of bending stiffness in the middle of the sole it means bending resistance is increased and it can alter walking strategy, for example, it may affect the knee and increase flexion during second half of the stance phase. Stiffness of the sole may alter calf muscle firing patterns during the end of mid stance, terminal stance and pre-swing phases, and it may also alter type of contraction, velocity of muscle contraction, reduce ankle range of motion, muscle-tendon properties and consequently EMG activity.

Different flexibility levels of the mid area of the sole in a relationship to different measurements below:

1. Point of application. 2. GRF direction. 3. Kinematic and kinetic data.

4. Level of EMG during stance phase.

5. Muscle-tendon length, velocity. 6. Type of muscle contraction

7. Muscle moment arm. 8. Shank angle (reclined or inclined).

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(AP)

Shoes with angled rocker soles have a single apex position on the sole where the shoe contacts a level surface. In a baseline shoe this defined by the last the shoe is made from and decided by heel height and toe spring. In the MBT shoe, the apex position is positioned at approx 50% shoe length as a result of the curve shape of the sole. The apex position of a shoe may be varied by adding a rocker sole, and the apex position will still be the point at which the sole contacts the ground on a level surface. If there is a flat surface from heel to apex position, it is the position after which the toe shape raises above the flat surface. The apex position can be anywhere between the heel and the sole.

Moving the apex position alters direction of ground reaction force (GRF) during different percentages of the stance phase, and changes kinematics and kinetic data of lower limbs as well. It can also affect the flexibility by changing the thickness of the sole at the apex position. If the apex is further forwards towards the toe, there is more material behind the apex position and therefore the shoe may be stiffer. An apex position at 50% of shoe length may alter stability, because the metatarsal head area during plantar flexion phase, positioned at the area of 60% of the shoe would be shaped upward. This may force an increased acceleration of the ankle and increase muscle activity of the ankle and knee to control balance. Muscle tendon properties and the type of contraction can be rapidly changed. AP can be varied and tuned to be optimal at the stance phase by keeping muscle fibres and tendons close to their optimal length, and therefore muscle force can be more efficiently applied. Also, less oxygen can be used.

1. Point of application. 2. GRF direction. 3. Kinematic and kinetic data.

4. Level of EMG during stance phase.

5. Muscle-tendon length, velocity. 6. Type of muscle contraction.

7. Muscle moment arm. 8. Shank angle (reclined or inclined).

9. Walking speed.

Toe (forefoot) area Angle of the toe area (toe spring angle)

The toe spring angle is determined by the position and orientation of the sole at the apex. The higher the angle the deeper the sole unit and stiffer the sole for a given material.

This will have an effect on the GRF position and direction. Therefore ankle external ankle dorsiflexion and/or plantarflexion moments may be altered.

1. Point of application. 2. GRF direction. 3. Kinematic and kinetic data of ankle, knee and pelvis.

4. Level of EMG during stance phase.

5. Muscle-tendon length, velocity and acceleration. 6. Type of muscle contraction

7. Muscle moment arm. 8. Shank angle (reclined or inclined).

9. Walking speed. Curve level of

the toes area (toe spring).

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