title: The free moment in walking and its change with foot rotation angle.
abstract: BACKGROUND
  This investigation characterized the time-history pattern of the free moment (FM) during walking and, additionally, assessed whether walking with either an internally or externally rotated foot position altered the FM's time-history.
  
  
  METHODS
  Force plate and foot kinematic data were acquired simultaneously for 11 healthy subjects (6 males, 5 females) while walking at their self-selected comfortable speed in 3 foot rotation conditions (normal, internal and external). The FM was calculated and normalized by the product of each participant's body weight and height prior to extraction of peak FM, occurrence of peak FM in stance and net relative impulse. Differences in these values across foot rotation conditions were assessed using separate one-way, repeated measures analysis of variance and subsequent pair-wise comparisons.
  
  
  RESULTS
  The average FM pattern during normal walking exhibits a biphasic shape: resisting inward rotation during approximately the first half of stance and outward rotation during the latter part of stance. While no differences in peak FM or net relative impulse were observed between the internal foot rotation condition and normal walking, the external foot rotation condition resulted in significantly greater peak FM and relative net impulse in comparison to normal walking.
  
  
  CONCLUSIONS
  The differences in selected FM variables between normal walking and the external foot rotation condition are attributable to individual subject response to walking with an externally rotated foot. In this condition, some subjects displayed a FM pattern that was similar to that recorded during normal walking, while others displayed markedly larger FM patterns that are comparable in magnitude to those reported for running. The larger FM values in these latter subjects are speculated to be a result of excessive transverse plane body movements. Whilst further investigation is warranted regarding the FM time-history characteristics during walking, our results indicate that the FM may provide useful information in assessment of gait.
authors.affiliation: Biomechanics and Ergonomics Laboratory, School of Kinesiology and Health Studies, 69 Union St., Queen's University, Kingston, ON, K7L 3N6, Canada.|Human Mobility Research Centre, Kingston General Hospital, 76 Stewart St., Kingston, ON, K7L 2V7, Canada.
authors.forename: Sivan
authors.initials: S
authors.lastname: Almosnino
authors.affiliation: Biomechanics Laboratory, Department of Kinesiology, McMaster University, 1280 Main St. West, Hamilton, ON, L8S 4K1, Canada.
authors.forename: Tara
authors.initials: T
authors.lastname: Kajaks
authors.affiliation: Biomechanics and Ergonomics Laboratory, School of Kinesiology and Health Studies, 69 Union St., Queen's University, Kingston, ON, K7L 3N6, Canada.|Human Mobility Research Centre, Kingston General Hospital, 76 Stewart St., Kingston, ON, K7L 2V7, Canada.
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Costigan
references.citation: J Biomech. 1991;24(10):887-97
references.pmid: 1744147
references.citation: J Biomed Eng. 1993 Sep;15(5):392-400
references.pmid: 8231156
references.citation: Clin Biomech (Bristol, Avon). 2000 Oct;15(8):583-91
references.pmid: 10936430
references.citation: Med Biol Eng Comput. 1992 May;30(3):343-50
references.pmid: 1453807
references.citation: J Orthop Res. 2001 May;19(3):414-20
references.pmid: 11398854
references.citation: J Exp Biol. 2001 Jan;204(Pt 1):47-58
references.pmid: 11104710
references.citation: Gait Posture. 2005 Jan;21(1):24-38
references.pmid: 15536031
references.citation: J Athl Train. 1992;27(1):64-9
references.pmid: 16558135
references.citation: J Biomech. 1983;16(3):219-33
references.pmid: 6863337
references.citation: Clin Biomech (Bristol, Avon). 2008 Jul;23(6):779-86
references.pmid: 18343001
references.citation: Acta Physiol Scand. 1989 Jun;136(2):217-27
references.pmid: 2782094
references.citation: J Bone Joint Surg Am. 1990 Jul;72(6):905-9
references.pmid: 2365722
references.citation: J Sci Med Sport. 2006 May;9(1-2):67-71
references.pmid: 16621703
references.citation: Gait Posture. 2002 Jun;15(3):212-9
references.pmid: 11983495
references.citation: J Biomech. 2005 Mar;38(3):445-52
references.pmid: 15652542
references.citation: J Biomech. 1993 Jun;26(6):753-9
references.pmid: 8514818
references.citation: Gait Posture. 2007 Jan;25(1):2-8
references.pmid: 16483778
references.citation: J Pediatr Orthop. 1996 Jul-Aug;16(4):489-91
references.pmid: 8784703
references.citation: J Biomech. 2005 Apr;38(4):819-25
references.pmid: 15713303
references.citation: Med Sci Sports Exerc. 1994 Jul;26(7):919-28
references.pmid: 7934769
references.citation: J Biomech. 2006;39(15):2819-25
references.pmid: 16289078
references.citation: Med Sci Sports Exerc. 2008 Sep;40(9):1669-74
references.pmid: 18685523
references.citation: J Orthop Res. 1996 Mar;14(2):289-95
references.pmid: 8648508
references.citation: J Sci Med Sport. 2008 Sep;11(5):444-51
references.pmid: 17768089
references.citation: J Biomech. 1978;11(4):199-202
references.pmid: 690155
references.citation: J Biomech. 1995 Sep;28(9):1115-7
references.pmid: 7559681
references.citation: Gait Posture. 2007 Oct;26(4):611-4
references.pmid: 17337189
references.citation: J Biomech. 2008 Aug 7;41(11):2575-80
references.pmid: 18621376