title: Sensory Enhancing Insoles Modify Gait during Inclined Treadmill Walking with Load.
abstract: BACKGROUND
  Inclined walking while carrying a loaded backpack induces fatigue, which may destabilize gait and lead to injury. Stochastic resonance (SR) technology has been used to stabilize spatiotemporal gait characteristics of elderly individuals but has not been tested on healthy recreational athletes. Herein, we determined if sustained vigorous walking on an inclined surface while carrying a load destabilizes gait and if SR has a further effect.
  
  
  METHODS
  Participants were fitted with a backpack weighing 30% of their body weight and asked to walk at a constant self-selected pace while their feet were tracked using an optical motion capture system. Their shoes were fitted with SR insoles that were set at 90% of the participant's sensory threshold. The treadmill incline was increased every 5 min until volitional exhaustion after which the treadmill was returned to a level grade. SR stimulation was turned ON and OFF in a pairwise random fashion throughout the protocol. Spatiotemporal gait characteristics were calculated when SR was ON and OFF for the BASELINE period, the MAX perceived exertion period, and the POST period.
  
  
  RESULTS
  Vigorous activity increases variability in the rhythmic stepping (stride time and stride length) and balance control (double support time and stride width) mechanisms of gait. Overall, SR increased stride width variability by 9% before, during, and after a fatiguing exercise.
  
  
  CONCLUSIONS
  The increased stride time and stride length variability may compromise the stability of gait during and after vigorous walking. However, participants may compensate by increasing double support time and stride width variability to maintain their stability under these adverse conditions. Furthermore, applying SR resulted in an additional increase of stride width variability and may potentially improve balance before, during, and after adverse walking conditions.
authors.affiliation: 1Wyss Institute for Biologically Inspired Engineering at Harvard University, Boston, MA; 2School of Engineering and Applied Sciences, Harvard University, Cambridge, MA.
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Miranda
authors.forename: Wen-Hao
authors.initials: WH
authors.lastname: Hsu
authors.forename: Kelsey
authors.initials: K
authors.lastname: Petersen
authors.forename: Stacey
authors.initials: S
authors.lastname: Fitzgibbons
authors.forename: James
authors.initials: J
authors.lastname: Niemi
authors.forename: Nicholas
authors.initials: N
authors.lastname: Lesniewski-Laas
authors.forename: Conor J
authors.initials: CJ
authors.lastname: Walsh
mesh_terms: D000328:Adult; D005080:Exercise Test; D005260:Female; D005528:Foot; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D012775:Shoes; D055698:Touch Perception; D014732:Vibration; D016138:Walking / Q000502:physiology*; D016474:Weight-Bearing; D055815:Young Adult