The specific objectives of the study were to (1) examine the effects of a preferred 1-mile walk on standing balance measures and to (2) examine the effects of three alternative footwear types on standing balance measures. Maintaining the center of gravity within the base of support (Winter et al, 1990). Center of Gravity (COG): the point where the weight of the body or system may be.
The bipedal nature of human locomotion presents a unique challenge to the body's balance control systems that maintain this balance (Winter, 1995). The location of the COM depends on body position and is not necessarily located within the body (Rodgers, Cavanagh, 1984). The COG is the point on which the weight of the body can be considered to act (Rodgers, Cavanagh 1984).
By using the plantar flexors to control net ankle motion, the COP can be moved to regulate the position of the COG (Winter, 1995). In the event of a forward swing and an anterior displacement of the COG, the body may activate the plantar flexors to move the COP anterior to the COG. Similarly, when the body senses that a posterior shift of the COG needs to be corrected, the COP moves to a.
The purpose of this study is to see how these alternative types of footwear affect standing balance and postural control.
METHODOLOGY METHODOLOGY
The first part of experimental testing began at the Applied Biomechanics Lab
They were then asked to stand as still as possible on the NeuroCom board for the Sensory Organization Test (SOT) and the Motor Control Test (MCT). After the SOT and MCT, participants moved to the Kevser Ermin Applied Physiology Laboratory and each was assessed while walking one mile on a treadmill at a self-selected pace. This self-selected pace was determined by walking 70 ft on an indoor track 6 times and averaging the pace times.
Each participant was given a short warm-up period at half this selected pace before running a mile on the treadmill. After collecting the necessary data in the physiology laboratory, participants returned to the biomechanics laboratory where the SOT and MCT were again used in the same manner as before to assess balance. After the fourth day, each participant had completed the procedure in each of the three types of shoes.
Statistical analysis: With a default alpha level of 0.05, results were analyzed in SPSS using a 2x3 repeated measures ANOVA [2 measurement times (before/after walking) x 3 shoe types (FF, CC, MIN)] for each of conditions TODAY. and for MCT delay times.
RESULTS
Time Point
Anterior/Posterior Sway Velocity- Eyes Open
Anterior/Posterior Sway Velocity- Eyes Closed
Anterior/Posterior Sway Velocity- Eyes Open, Visual Surround Sway Referenced
Anterior/Posterior Sway Velocity- Eyes Open, Platform Sway Referenced
Because there was no significant shoe-time interaction effect, shoe effects can be generalized to all time points. There were no significant differences in APRMS found for shoe main effects, time main effects, or shoe by time interaction effects for condition 1 and conditions 3 and 4. ® TODAY conditions.
Anterior/Posterior Sway RMS- Eyes Open
Anterior/Posterior Sway RMS- Eyes Closed
Anterior/Posterior Sway RMS- Eyes Open, Platform Sway Referenced
Anterior/Posterior Sway RMS- Eyes Open, Visual Surround Sway Referenced
In the pairwise comparison for condition 3, a significant difference was seen between FF and MIN (p= 0.010). No significant interaction effect was seen for condition 3, so the effects of shoes may generalize across both time points. There were no significant shoe, time, or shoe-time interaction effects for MLVEL in conditions 1, 2, and 4.
Figures: Average sway speed measurements in the medial-lateral direction for each of the four Neurocom® SOT conditions.
Medial/Lateral Sway Velocity- Eyes Open
Medial/Lateral Sway Velocity- Eyes Closed
Medial/Lateral Sway Velocity- Eyes Open, Visual Surround Sway Referenced
Medial/Lateral Sway Velocity- Eyes Open, Platform Sway Referenced
No significant footwear-time interaction effects were found under conditions 3 or 4, so the effects of time are generalizable across footwear types for both conditions. There were no significant effects seen for footwear, time, or footwear-time interaction for MLRMS under conditions 1 and 2. Figures: Average Sway RMS measures in the Medial-Lateral direction for each of the four Neurocom® SOT conditions.
Medial/Lateral Sway RMS- Eyes Open
Medial/Lateral Sway RMS- Eyes Closed
Medial/Lateral Sway RMS- Eyes Open, Visual Surround Sway Referenced
Medial/Lateral Sway RMS- Eyes Open, Platform Sway Referenced
DISCUSSION
Another factor shown in previous studies to have an effect on balance is shoe mass. Other studies have shown that mass may not be as important as other factors in determining balance performance (Chander, 2012). In the current study, the FF was the lightest shoe of the three at 100 grams.
Future research could focus on determining whether there is a threshold shoe mass at which fatigue becomes a factor affecting balance performance. Despite textured insoles, the CC did not perform significantly better than the other two shoes in any of the balance measures or conditions. This seems to support previous findings that textured insoles do not have a significant impact on balance performance (Hatton, Dixon, Martin, & Rome, 2007).
The FF did not perform worse than the CC on any of the trials, as both performed significantly worse than the MIN in two balance measurements. Although future research could compare the flip-flop to a standard running shoe of similar mass and sole thickness to determine if the shoe's thong-like construction is responsible for differences in balance. A significant main effect was observed for time for the MLRMS measure, but as this only emerged as a main effect for one measure, it does not appear that time is an important factor contributing to balancing performance under the conditions of this experiment.
Also, previous studies have shown that changes in swing due to fatigue are usually transient and often disappear within fifteen minutes of exercise (Nardone, Tarantola, Giordano, & Schieppati, 1997). There were also significant differences in APVEL and MLVEL between the flip-flops and Vibrams (MIN). There was only one balance measure where time played a significant role in influencing balance performance (MLRMS).
These results suggest that the reduced sole thickness and increased sole hardness of MIN compared to CC and FF may have played a role in its better balance performance. Fatigue induced during a mile walk may have had a small effect on balance performance, as indicated by the differences in MLRMS over time, but it did not have as strong an effect as footwear. A systematic review of the effects of shoes and other ankle or foot devices on balance in older people and people with peripheral nervous system disorders.
