title: Effect of flip-flops on lower limb kinematics during walking: a cross-sectional study using three-dimensional gait analysis.
abstract: BACKGROUND
  Flip-flops are a popular footwear choice in warm weather however their minimalist design offers little support to the foot.
  
  
  OBJECTIVE
  To investigate the effect of flip-flops on lower limb gait kinematics in healthy adults, to measure adherence between the flip-flop and foot, and to assess the effect on toe clearance in swing.
  
  
  METHODS
  Fifteen healthy adults (8 male, mean age 27 years) completed a three-dimensional gait analysis assessment using Codamotion. Kinematic and lower limb temporal-spatial data were captured using the Modified Helen Hayes marker set with additional markers on the hallux and flip-flop sole.
  
  
  RESULTS
  Compared to barefoot walking, there were no differences in temporal-spatial parameters walking with flip-flops. There was an increase in peak knee flexion in swing (mean difference 4.6°, 95 % confidence interval (CI) [-5.8°, -3.4°], p < 0.001) and peak ankle dorsiflexion at terminal swing (mean difference 2°, 95 % CI [-3°, -1°], p = 0.001). Other kinematic parameters were unchanged. Peak separation between foot and flip-flop was 8.8 cm (SD 1.48), occurring at pre-swing. Minimum toe clearance of the hallux in barefoot walking measured 4.2 cm (SD 0.8). Minimum clearance of the flip-flop was 1.6 cm (SD 0.56).
  
  
  CONCLUSIONS
  Healthy adults adapted well to flip-flops. However, separation of the flip-flop from the foot led to increased knee flexion and ankle dorsiflexion in swing, probably to ensure that the flip-flop did not contact the ground and to maximise adherence to the foot. Minimum clearance of the flip-flop was low compared to barefoot clearance. This may increase the risk of tripping over uneven ground.
authors.affiliation: School of Medicine, Royal College of Surgeons in Ireland (RCSI), Dublin, Ireland.
authors.forename: T
authors.initials: T
authors.lastname: Sharpe
authors.affiliation: Gait Laboratory, Central Remedial Clinic (CRC), Vernon Avenue, Clontarf, Dublin 3, Ireland. ailishmcd@gmail.com.
authors.forename: A
authors.identifier: http://orcid.org/0000-0002-7997-4099
authors.initials: A
authors.lastname: Malone
authors.affiliation: School of Physiotherapy, Royal College of Surgeons in Ireland (RCSI), Dublin, Ireland.
authors.forename: H
authors.initials: H
authors.lastname: French
authors.affiliation: Gait Laboratory, Central Remedial Clinic (CRC), Vernon Avenue, Clontarf, Dublin 3, Ireland.
authors.forename: D
authors.initials: D
authors.lastname: Kiernan
authors.affiliation: Gait Laboratory, Central Remedial Clinic (CRC), Vernon Avenue, Clontarf, Dublin 3, Ireland.
authors.forename: T
authors.initials: T
authors.lastname: O'Brien
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D003430:Cross-Sectional Studies; D005260:Female; D005528:Foot / Q000502:physiology; D005684:Gait / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D008297:Male; D012775:Shoes; D016138:Walking / Q000502:physiology*; D055815:Young Adult
keywords: Accidental falls; Footwear; Gait; Gait analysis