Dynamic tests

Barefoot recording was undertaken after the static capture and at the beginning of the testing. Ten walking trials of acceptable quality were recorded and saved for further analysis for each subject. Once data collection for barefoot was finished, one of the shoes used was randomly selected as a test condition and donned, and the retro-reflective markers were repositioned again on the area where the circles had previously been drawn on the foot and through the holes cut in the uppers of the shoes. The testing order for each shoe test was randomised for all subjects throughout their walking trials. After donning each pair of shoes, a static test was recorded and then a small number of walking trials were performed to monitor the walking speed for repeatability and to identify the optimal gait initiation point before walking data were recorded. It typically took five minutes to record the walking trials and five minutes to replace the shoes for each footwear test condition and to ensure that

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the leg muscles being tested were not getting fatigued. A five minute period of habituation was given for each test condition, and also a number test runs were performed for each shoe test condition to ensure each subject could walk confidently for each run by striking the force plates in the correct area and also maintaining gait speed within the set time parameters using the timing gates.

At the end of the testing session the subject’s weight and height was measured with the clinical equipment available in the gait laboratory.

5.7.2.1Walking speed

Various sources from the literature and scientific articles for the effect of walking speed on kinematic, kinetic and EMG data for lower limb suggest that it has a significant impact on these changes (Kirtley et al., 1985, Chen et al., 1997, Holden et al., 1997a, Waters and Mulroy, 1999, Hof et al., 2002, den Otter et al., 2004, van Hedel et al., 2006, Byrne et al., 2007, Chiu and Wang, 2007, Stoquart et al., 2008, Chung and Wang, 2010, Sousa and Tavares, 2012).

It was therefore decided that the best method for kinematic, kinetic and EMG data collection for this study was to closely control walking speed during the gait laboratory trials. Previous studies have demonstrated that speed of walking effects gait patterns and EMG data, and would therefore have an effect on the results obtained with regards to muscle properties, which were based on Qualisys kinematic motion capture data. Chung and Wang (2010) conducted research to investigate the gait performance of subjects aged between 20-60 years of age utilising walking speeds of 80%, 100%, 120%, 140% of their preferred walking speed. The most significant alterations to gait parameters were noted once subjects attained walking speeds greater than 20% of their preferred walking speed. Holden et al (1997a) demonstrated that if subjects walk at lower natural speed by a factor of 25%, it results in reduced knee flexion and lower knee moments. Additional research, which investigated the effect of varying walking speed and the effects of additional weight on lower limb muscles and gait, has demonstrated that significant changes in joint kinematics for healthy subjects at walking speeds slower than 3 km/h (kilometres per hour) versus the 5 km/h figure (van Hedel et al., 2006) can occur.

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Figure 5.28: Influence of walking speed on joint trajectories for (a) hip, (b) knee and (c) ankle joint at 10 different walking speeds (van Hedel et al., 2006).

Chiu and Wang investigated the effect of speed and gender on muscle activity, joint motion in lower extremity plus GRF values and demonstrated that walking speed had a significant influence on the perceived extension of the whole body, as well as the buttock, rear thigh, front thigh and rear shank areas. An increased walking speed caused significant increases in the muscle activity of erector spinae, bicepc femoris, and medial gastrocnemius, as well as GRF values as shown in figure 5.29.

Figure 5.29: The gait speed effect on (a) EMG activity, (b) vertical ground reaction force (Chiu and Wang, 2007).

One recent study of the effect of gait speed on muscle patterns and magnitude during stance phase on thirty-five healthy individuals for gastrocnemius medialis, bicepcs femoris and rectus femoris muscles showed significant changes due to walking speed. In general, muscle activity was significantly higher at + 25% of self-selected walking speed and significant lower at -25% of self-selected walking speed (Sousa and Tavares, 2012).

Most adults prefer to walk at a speed of between 3600 and 6012 metres/hour. The average walking speed observed by Walters and Mulroy (1999) for adult pedestrians aged between 20-60 years old (who were unaware they were observed) was 4932 meters per hour. The

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participants who volunteered for this thesis were young, aged 25.3 ± 2.73 years with an average height of 1.74 ± 0.06 m, and were healthy. Therefore, the ideal selected walking speed for all subjects to attain during the walking trials in this study was chosen as 5 kilometres per hour. The evidence demonstrates that walking speeds within a range of ±5% have no significant comparative effects on knee and ankle kinematics or EMG readings for lower extremities during stance phase. Therefore, the acceptable speed range within the trials was set at 5km/h ± 5% for this research.

5.7.2.2The timing gates

Timing gates were utilised to ensure each walk taken with each footwear test condition was performed within set time parameters. A short period of habituation was allowed for each subject prior to walking in each test condition. No evidence was found in the literature of the existence of carry-over effects when walking with rocker-soled footwear. The timing gates utilised were manufactured by Brower SpeedTrap II (figure 5.30) and gave an audible sound when passed through by the subject both on commencement and completion of the walk in question.

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The speed of walking was shown using the remote controller of the system. If a walk was seen to not be within the prescribed limits of time, then further walks were undertaken to ensure an adequate number of walks for subsequent analysis were performed.

5.7.2.3Gait laboratory synchronisation equipment setup

Qualisys Track Manager (QTM) software and hardware had complete integration with the Noraxon’s wireless EMG system. All the basic settings below were selected:

 The muscle channel name;

 The sampling rate;

 The channel output;

 Trigger synchronisation;

 Device setup and synchronisation check.

The EMG settings for EMG devices were set using the QTM software and all data were captured directly to the Qualisys software. Only one single desktop computer was used for integration. The EMG integration was added to the existing integration with four force plates. It was possible to start Qualisys recording EMG, force and motion capture data from the QTM software. An external trigger was used to control the start of recording. The basic experimental setup for the gait analysis and synchronisation is shown on figure 5.31. The EMG capture frequency was set at 3000 Hz. Motion data capture frequency was set at 100 Hz and the force plate frequency for all plates was set at 100 Hz.

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