Influence of Sneakers versus Flip-flops on Attack Angle and Peak Vertical Force at Heel Contact: 1920: Board #84 May 29 3:30 PM- 5:00 PM

Shroyer, Justin F.; Weimar, Wendi H.; Garner, John C. III; Knight, Adam C.; Sumner, Andrea M.

Medicine & Science in Sports & Exercise: May 2008 - Volume 40 - Issue 5 - p S333
doi: 10.1249/01.mss.0000323655.89417.90
D-29 Free Communication/Poster - Gait and Movement Disorders: MAY 29, 2008 1:00 PM - 6:00 PM ROOM: Hall B

Auburn University, Auburn, AL.

(Sponsor: Dr. David Pascoe, FACSM)


(No relationships reported)

Flip-flops are becoming a common footwear option and casual observation indicates that individuals are wearing flip-flops beyond the structural limit of flip-flops, and individuals alter their gait while wearing flip-flops. These observations suggest that flip-flops are a cause of pain in the lower extremities and are counterproductive to alleviating the pain if pain is present.

PURPOSE: To investigate the influence of sneakers versus flip-flops on the angle constructed from the anterior and vertical force vectors (attack angle) and peak vertical force at heel contact.

METHODS: Thirty-nine (20 F and 19 M) subjects were randomly assigned to a footwear order (flip-flip or sneaker first) and asked to wear the assigned footwear on the day prior to and the day of testing. Each participant walked at a normal pace, and force plate data yielded attack angles and peak force at heel contact. Data was analyzed with a 2 (sex) x 2 (footwear) ANOVA with repeated measures on the last factor. It was hypothesized that a person alters his/her gait while wearing flip-flops in such a manner that would result in a decreased attack angle and smaller peak vertical forces at heel contact when compared to his/her gait while wearing sneakers.

RESULTS: There was a significance interaction in attack angle between sex (p = 0.042), with females producing a more vertical attack angle while wearing flip-flops (M = 82.9 degrees, SD = 2.0) than when wearing sneakers (M = 81.8 degrees, SD = 1.7). No significant difference was noted for males. Further, a significant difference (p = 0.005) was found in peak vertical force at heel strike between sneakers (M = 167 N, SD = 33) and flip-flops (M = 163 N, SD = 34) but no significant interaction (p = 0.459) was found between sex.

CONCLUSION: While the attack angle yielded a significant difference, the amount of difference does not have any practical implications since it was so small. However, peak vertical force was statistically different between type of footwear, resulting in smaller peak vertical forces while wearing flip-flops. This decreased force could explain the anecdotal evidence that persons who wear flip-flops alter their normal gait and therefore experience lower leg pain as a result. Further research is needed to determine other kinetic and kinematic differences in gait while wearing flip-flops versus sneakers.

©2008The American College of Sports Medicine