«A Thesis Submitted to the Graduate Faculty of the Louisiana State University and Agricultural Mechanical College in partial fulfillment of the ...»
Grand Mean 3.01E-04 CV(Subject*Heel) 23.98 CV(Subject*Locomotion) 44.88 CV(Subject*Heel*Locomotion) 7.91 Analysis of Variance Table for Tibialis
Grand Mean 4.76E-04 CV(Subject*Heel) 18.37 CV(Subject*Locomotion) 43.35 CV(Subject*Heel*Locomotion) 13.94 22.214.171.124.Hypothesis 1 The ANOVA measurements reveal a significant difference in the normalized EMG results (MAV) between the muscle activities without heel and with heel at 2 and 3 mph on the treadmill. The gastrocnemius results show a ( 0.05) result when using the heel at 3 mph with a p value of 0.0012. The tibialis anterior results show a ( 0.05) result when using the heel at 3 mph with a p value of 0.0005.
This proves that wearing the heel reduces muscle activity, and thus rejects the null hypothesis and proves the alternative hypothesis true.
126.96.36.199.Hypothesis 2 As Table 6.3 indicates, the “locomotion” factor impacts the activity level for both muscles in accordance with the EMG measurements as ( 0.05) results indicate p values of
0.0006 and 0.0010 in the gastrocnemius and the tibialis anterior, respectively. Again, both p values being lesser than 0.05, it can be deduced that a change of speed from 2 mph to 3 mph is associated with significant change in muscle activity, as the participants switch from walking with heels to walking without heels.
However, although Figures 6.3 and 6.4 show speed has some impact on the amount of muscle activity decrease from wearing the heel according the EMG, Table 6.3 reveals no statistically significant interaction between speed and presence / absence of heel, based on the heel*locomotion p values of 0.0583 in the gastrocnemius and 0.4730 in the tibialis. This means that speed influences the amount of relief provided by the heel, but not at a statistically significant level for these selected speeds.
6.2. Body Maps The subjects were asked to assess and compare the discomfort / pain they endure during the tests, with and without heels. The target areas are 20-27 on the body map displayed in Figure 5.11.
. Wilson and Corlett (1995) explained that “because „pain‟ is sometimes seen as a specific and localized experience, the term „discomfort‟ is used.” Discomfort / pain is expressed on the standard ergonomics scale established by Borg‟s category-ratio scale (CR-10), from 0 to 10, as detailed in the chart displayed in Figure 5.12. Results were averaged for all participants;
Figure 6.9: Average discomfort when walking without heels and walking with heels All subjects experienced a greater discomfort without the heel than they did with the heel.
The discomfort difference was thus calculated by subtracting the discomfort value without the heel from the value with the heel, which indicates the subjective change in comfort level triggered by the biomechanical modification. The results obtained indicate that the removable heel provides an average discomfort relief of 2.67 points on Borg‟s CR-10 scale in the knees,
2.61 points in the calves, 3.89 points in the ankles, and 4.22 points in the feet. Thus, an observation of the results indicates a greater relief at the ankles and the feet.
6.2.1. Statistical Results: Hypothesis 3 As the statistical equation is applied to each area and each hypothesis, the following
categorized series of formulas is obtained:
This above SAS table displays the ANOVA results from the hypotheses‟ equations in table 6.4. The p values for each area help conclude that there is a significant difference in discomfort between walking without heels and walking with heels, as they are lesser than 0.05.
The following figure displays the graphed results of Table 6.4 before and after heel installation (Detailed results of the ANOVA are displayed in Table B.0.3 in the Appendix).
Each spot represents the mean for the 9 participants. The chart shows the lines are not parallel, which shows the presence of an interaction. The divergence of lines toward the end shows that there is more interaction in the last 2 areas, which indicates that participants experienced more discomfort in areas 24-27 when performing without the removable heel.Relevance of the Participants‟ Athletic Background As the body map survey results are grouped and averaged by participant category, the
Figure 6.11: Average discomfort difference by participant athletic category Table 6.
7 and Figure 6.10 reflect the fact that non-athletes seem to experience the greatest relief from the removable heel as a whole. Effectively, they reported the greatest difference in discomfort values upon completion of the exercise, with heels in all areas except for the calves, an area for which distance runners experienced the greatest relief. This is due to the fact that having the least athletic experience in track, they constitute the group that needs the most leg support as they are not used to walking in spike shoes. Unsurprisingly, sprinters experienced the least relief from the removable heel, even though the biomechanical modification was designed especially for this target group. This is due to the fact that sprinters are most accustomed to walking in spike shoes. Nevertheless, the amount of relief they felt was still very significant for all areas, which confirms their need for leg support while walking in spike shoes and the efficiency of the heel in addressing such a need.
Unlike the EMG data, the body map offers relatively subjective results. Thus, the absence of a statistical analysis or inclusion of the body map results in ANOVA is due to the fact that even though it provides insight as to the level of relief the modified spike shoes bring about, the data is not as rigorously reliable as the EMG data is on a scientific level.
6.2.3. Remaining Discomfort Even though these results are much more subjective than the EMG calculations, they perfectly illustrate and confirm the efficacy of the removable heel. Effectively, Table 6-7 reveals that the subjects felt an significant decrease of pain and discomfort when performing with the heeled spikes.
The results, however, reveal that some discomfort remains, even after installation of the heel. The main complaints the subject mentioned were the relative hardness of the heel material, and the fact that the heel‟s square shape provided no curving for walking particularly fast.
This project began with the problems that track athlete experience all the time, but have never really been addressed with a concrete solution that enables them to continue running and to do so healthily. Many athletes experience pain in the foot and knee areas while practicing and competing. The track spikes in which runners are competing are designed to keep them on their toes. This is a good design for certain events, but only during those events. When the athlete is not competing, the same design presents bad posture to the foot, which causes pain in multiple places.
The proposed solution to this problem is a removable heel that gives the runner more support. The heel allows the runner to quickly attach or detach the extra support whenever needed. The experiment reveals that the heel does, in fact, lessen the pain in the major affected areas and provides the runner with more comfort overall.
7.1.Shortcomings 7.1.1. Limited Number of Participants The shoe is only tested on a limited number of participants. Due to that fact and the limited amount of time to prepare, it is impossible to fully and/or accurately identify the portion of pain felt by the subject due to their own, individual gait, bone structure, age, experience in running, or gender, and the portion of pain due to the shoe.
7.1.2. Limited Prototype Quantity The second downfall is that because there is only one prototype, there is only one size – size 10 – available. This limits the number of subjects fit for the experiment, especially in terms of trained athletes. Furthermore, because of the prototype‟s quantitative limitation, any technical malfunction delays the experiment considerably, reducing the already limited size of the population tested.
7.2. Further Developments 7.2.1. Running and Monitoring Conditions In the future, it is agreed to make the experiment more accurate by allowing the athlete participants to run at their speed of choice, that is, to have them run at the same speed they would on the track before wearing the removable heel. In the same purpose to make the conditions more faithful to real track performance, the participants will run, and then walk, for the same amount of time they would in a race, rather than limiting the experiment to one minute.
Additionally, electrodes should be placed on both legs to ensure better accuracy of muscle activity.
7.2.2. Participants Selection and Shoe Characteristics In the future, the experiment will be conducted on more trained subjects, both males and females. The participants‟ remarks, concerning the material and shape of the heel, will also be taken into account: a softer material (probably rubber; though it is not long-lasting material, due to the friction on the mondo surface) with a more curved shape. The heel being removable, it could be replaced when needed. In addition, considering the works from other inventors of removable heels together with time considerations, a faster attaching mechanism should be considered, such as sliding instead of screwing the heel to the sole.
7.2.3. Further Assessment Considering research such as Wakeling et al. (2001) who measured the reaction force that triggers muscle activity during normal walking, a future study to this thesis might measure the amount of intensity absorbed when the removable heel is applied, which would serve to quantify the ergonomic worth and value of the heel.
Also, angular measurements could help identify the gait modification brought about by the removable heel. To do so, technology and methodology similar to those used by Orchard et al. (1996) who utilized a 3D Motion Analysis System to perform a biomechanical evaluation of heel elevation devices of 50 mm and 150 mm.
7.3. Final Remarks Although the experiment is not a success in all categories, it can be concluded that the removable heel would be ideal for a mid-distance or long distance runner. As a whole, the project was a success since a more ergonomic product was designed for the track athlete. This project presented a valued learning experience. Investigating those problems that had not been previously addressed was enlightening. Hopefully, the concept presented here will aid track athletes in the future.
In addition, ergonomics must to be further implemented in sports. Indeed, there are too many long-term injuries in sports that can be prevented by devices as simple as a removable heel. The removable heel could constitute one step forward in protecting the health of many athletes.
Nevertheless, considering research such as Wakeling et al. (2001) who measured the reaction force that triggers muscle activity during normal walking, a future study to this thesis might measure the amount of intensity absorbed when the removable heel is applied, which would serve to quantify the ergonomic worth and value of the heel.
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