Z-CoiL Footwear has been extensively tested both in the Laboratory and in real life. With over 1 million pair sold, there is extensive data regarding the effectiveness of Z-CoiL footwear in the field.Z-CoiL has three special parts that lead to its' exceptional performance for those seeking relief from the pain and stress of walking on hard surfaces.
Ergonomic Implementation to Reduce Plantar Pressure
Research study conducted by Wayne Scheler, New Mexico Highlands University
|This research study was conducted in 2008 as part of the Masters program in the area of Human Performance and Sport at New Mexico Highlands University.NMHU researcher Wayne Scheler teamed up with Z-CoiL Footwear and Novel Electronics to evaluate the ergonomic benefits of Z‑CoiL® shoes worn as occupational footwear.Industrial employees are on their feet 8 to 10 hours per day. This causes an enormous amount of pressure to be placed on the plantar surface of the feet. When external weight is added, this pressure is multiplied.Past studies of Z‑CoiL® footwear have shown a longer force impact curve, which reduces jarring forces, while the heel coil also provides a 40% kinetic energy return. By studying plantar pressure and the effects of an ergonomic device such as Z‑CoiL®, the NMHU researchers were able to gain a better understanding of the effects caused by lowering the initial pressure.For this study, 19 participants were selected from a variety of industrial occupations. Wearing carefully fitted Z‑CoiL® shoes, these subjects were monitored as they moved from station to station, modeling a typical production line. Novel’s Pedar system and data acquisition software were used to capture and analyze real-time data on the pressure the test subjects experienced across the whole foot, the heel, the midfoot, and the forefoot.According to the data, the plantar regions recorded in Z‑CoiL® shoes showed a statistically significant decrease in mean peak pressure. The whole foot averaged a 13% reduction, with a 16% reduction at the heel, 14% at the midfoot, and 0.05% in the forefoot.The reduction of foot pressure is a key element in reducing pressure throughout the kinetic chain. It can be assumed that a decrease in foot pressure transcends the foot and reduces pressure in the ankle, knee, hip, and low back. In Conclusion With the ergonomic implementation of Z‑CoiL® shoes, the plantar surface of the foot experienced a significant decrease in pressure. This decrease helps fight fatigue and injury, while improving joint health.To view the video documenting this study, go to http://www.zcoil.com/NMHU_video.html© 2009 Z-Tech, Inc.|
a = ▲v (2)
▲tWhere a is acceleration, Dv is change in velocity, and Dt is the change in time. The velocity with which an individual’s foot approaches the ground should be the same, regardless of shoe type. By landing on a spring, the time over which the foot comes to a stop is increased. Inspection of the above equation shows that as Dt increase, the resulting acceleration decreases. This is the advantage that the Z-Coils offer over traditional shoes. Experimental setup Each participant was instrumented as shown below in figure 1. The accelerometer (a Crossbow Technologies 3-axis LP model) was attached via a steel clip to the outside of the right shoe. When the test participant was comfortable with the shoes, the attached data logger was triggered to gather data at 512 Hertz. Each participant walked on a flat surface for approximately 60 paces while data were collected for all three accelerometer axes. After data were collected for both types of shoes with the participant walking at a self selected “normal walking pace”, the accelerometer was moved to an elastic band that was attached with Velcro just below the participants’ knee. Fitted like this, the participant jogged, again at a “normal jogging pace” for three recorded segments of approximately 20 paces each in each type of shoe. The accelerometer was moved to the knee for the running portion of the test to ensure accurate data recording. The accelerometer used in these tests is accurate to } 10 times the acceleration due to gravity, or 10 g, and because preliminary tests had shown that heel-based accelerations during jogging could exceed 10 g, the knee mounting was used for running to prevent saturation of the sensor. Data By using a three-axis accelerometer, our results were three channels of data that represent vectors in the x, y, and z directions. With the participant’s foot flat on the floor, the positive x vector point forwards, the positive y is upwards, and the z vector points medially through the ankle. These were vectorially summed to produce a total acceleration vector at each moment in time using equation Where |a| is the summed accelerations, ax, ay, and az are the component accelerations in their respective axes. The output of each axis is displayed on the initial plot that is generated by the Crossbow software as shown in Figure 4A. When the axes are summed as in equation 3, the same five steps appear as in Figure 4B. For comparison, summed accelerations were used. The summed data were analyzed, and the highest peaks (one per gait cycle, or stride) were averaged to produce the statistic we used for further comparison, called here the mean peak acceleration (MPA). The significance of the difference between the statistics for Z-Coils and the other shoes was found using the Student t-test and associated P values are reported in the Appendix. Results In general, the accelerations recorded while individuals were wearing Z-Coils were significantly smaller than those in the others. In the walking trial, all individuals recorded significantly lower accelerations while wearing Z-Coil shoes except participant number 3. In the jogging trial, participant number 3 again had higher accelerations in the Z-Coils, as did another participant, and one individual had the same mean peak acceleration in both pairs of shoes. During the jogging trial, participant number 6 noted that it felt like the shoe was bottoming out, but had not felt that during the walking trial. This is consistent with the data for number 6 who had a lower MPA in Z-Coils while walking and a lower MPA in the competitor’s shoes while jogging. Our hypothesis for these results was that the individuals who had higher accelerations in Z-Coils were bottoming out the spring at heel strike. Without the support of the spring, the participants’ heels were, in effect, hitting the running surface – in this case a concrete floor. This hypothesis seemed reasonable, especially when the weight of participant number 3 (250 lbs) was considered. This was verified by numerically integrating the y-axis acceleration data twice to get vertical heel displacement. This was done for the individual with higher accelerations in the Z-Coils while walking and onerepresentative individual who did not. The results are given below, and all participant’s heights and weights are presented in Table 3 of the appendix. Table 2: Vertical heel displacement during heel strike and weight of participants. In the case of the one individual who experienced higher accelerations in the Z-Coils while walking, the vertical heel displacement was found to be 1.1 inches. This very nearly matches the actual height of the bottom of the Z-Coil shoe above the floor. In this individuals’ case, it is clear that the spring is becoming fully compressed, and the bottom of the shoe is striking the floor. In every other case, the vertical displacement is within the useful travel range of the spring, resulting in reduced accelerations. Conclusions For most participants, the Z-Coil shoes had significantly lower accelerations while walking (5 out of 6), and jogging (4 out of 6). It appears that the use of a stiffer spring in shoes that will be worn by heavier individuals would be beneficial, and should result in reduced accelerations for all wearers of Z-Coil shoes. The analysis technique used in this study is somewhat limited in its utility, and the possibility of gait variation among subjects was not researched. While the conclusion that some individuals are bottoming out the spring is plausible, and mathematically verified, it is possible that some portion of the abnormal gait accelerations are due to another cause, including gait type or a lack of familiarity with the Z-Coil shoes. This work proved that individuals who are properly fitted in their Z-Coil shoes with the correct spring have reduced accelerations when walking and jogging. This finding allows the exclusion of the data from individuals who suffered from inadequate springs. With the exclusion of the data for those subjects who bottomed out the springs, the reduction in walking MPA is changed from 8.7% to 13.4%. The reduction in jogging MPA is changed from 5.1% to17.2%. These are illustrated by Figure7. Further Work This study showed a statistically significant reduction in acceleration for most wearers of Z-Coil shoes. The link between this finding and joint pain is suggested, but not researched. This study could be used as a pilot to future work where matched cohorts of individuals with joint pain could be observed for several months or years to determine long-term benefits of reduced accelerations during everyday activities.