torques and powers during gait. J Appl Physiol. 2000; 88(5): 1804-11.

48. Ostrosky KM, VanSwearingen JM, Burdett RG, Gee Z. A comparison of gait characteristics in young and old subjects. Phys Ther. 1994; 74(7): 637-44.

49. Winter DA, Patla AE, Frank JS, Walt SE. Biomechanical walking pattern changes in the fit and healthy elderly. Physical Therapy. 1990; 70: 340-7.

50. Laufer Y. Effect of age on characteristics of forward and backward gait at preferred and accelerated walking speed. J Gerontol A Biol Sci Med Sci. 2005; 60(5): 627-32.

51. Kerrigan DC, Todd MK, Della Croce U, Lipsitz LA, Collins JJ. Biomechanical gait alterations independent of speed in the healthy elderly: evidence for specific limiting impairments. Arch Phys Med Rehabil. 1998; 79(3): 317-22.

52. Kirkwood RN, Gomes HA, Sampaio RF, Culham E, Costigan P. Biomechanical analysis of hip and knee joints during gait in elderly subjects. Acta Ortop Bras. 2007; 15(5): 267-71.

53. Bruijn SM, van Dieën JH, Meijer OG, PJ. B. Is slow walking more stable? J Biomech. 2009; 42(10): 1506-12.

54. Stergiou N. Innovative Analysis of Human Movement: Human Kinetics;2004.

55. Dingwell JB, Robb RT, Troy KL, Grabiner MD. Effects of an attention demanding task on dynamic stability during treadmill walking. J Neuroeng Rehabil. 2008; 12: 1-5.

56. Beauchet O, Dubost V, Herrmann FR, Kressig RW. Stride-to-stride variability while backward counting among healthy young adults. J Neuroeng Rehabil. 2005; 26: 1-2.

57. Beauchet O, Allali G, Annweiler C, Bridenbaugh S, Assal F, Kressig RW, et al. Gait variability among healthy adults: low and high stride-to-stride variability are both a reflection of gait stability. Gerontology. 2009; 55(6): 702-6.

58. Dubost V, Kressig RW, Gonthier R, Herrmann FR, Aminian K, Najafi B, et al. Relationships between dual-task related changes in stride velocity and stride time variability in healthy older adults. Hum Mov Sci. 2006; 25(3): 372-82.

59. Bridenbaugh SA, Kressig RW. Laboratory review: the role of gait analysis in seniors’ mobility and fall prevention. Gerontology. 2011; 57(3): 256-64.

60. Hausdorff JM, Schweiger A, Herman T, Yogev-Seligmann G, Giladi N. Dual-task decrements in gait: contributing factors among healthy older adults. J Gerontol A Biol Sci Med Sci. 2008; 63(12): 1335-43.

61. van Iersel MB, Kessels RP, Bloem BR, Verbeek AL, Olde Rikkert MG. Executive functions are associated with gait and balance in community-living elderly people. J Gerontol A Biol Sci Med Sci. 2008; 63(12): 1344-9.

62. Abbud GAC, Li KZH, DeMont RG. Attentional requirements of walking according to the gait phase and onset of auditory stimuli. Gait Posture. 2009; 30(2): 227-32.

63. Coppin AK, Shumway-Cook A, Saczynski JS, Patel KV, Ble A, Ferrucci L, et al. Association of executive function and performance of dual-task physical tests among older adults: analyses from the InChianti study. Age Ageing. 2006; 35(6): 619-24.

64. van Iersel MB, Ribbers H, Munneke M, Borm GF, Rikkert MGO. The Effect of Cognitive Dual Tasks on Balance During Walking in Physically Fit Elderly People. Arch Phys Med Rehab. 2007; 88(2): 187-91.

65. Laessoe U, Hoeck HC, Simonsen O, Voigt M. Residual attentional capacity amongst young and elderly during dual and triple task walking. Hum Mov Sci. 2008; 27(3):496-512.

66. Hall CD, Echt KV, Wolf SL, Rogers WA. Cognitive and Motor Mechanisms Underlying Older Adul Ability to Divide Attention While Walking. Phys Ther. 2011;91(7): 1039-50.

67. Beauchet O, Dubost V, Gonthier R, Kressig RW. Dual-task-related gait changes in transitionally frail older adults: the type of the walking-associated cognitive task matters. Gerontology. 2005; 51(1): 48-52.

68. de Bruin N, Doan JB, Turnbull G, Suchowersky O, Bonfield S, Hu B, et al. Walking with music is a safe and viable tool for gait training in Parkinson’s disease: the effect of a 13-week feasibility study on single and dual task walking. Parkinsons Dis. 2010; 48: 30-5.

69. Verghese J, Kuslansky G, Holtzer R, Katz M, Xue X, Buschke H, et al. Walking while talking: effect of task prioritization in the elderly. Arch Phys Med Rehabil. 2007; 88(1): 50-3.

70. Byrne JE, Stergiou N, Blanke D, Houser JJ, Kurz MJ, Hageman PA. Comparison of gait patterns between young and elderly women: an examination of coordination. Percept Mot Skills. 2002; 94(1): 265-80.

71. Haddad JM, van Emmerik RE, Wheat JS, Hamill J, Snapp-Childs W. Relative phase coordination analysis in the assessment of dynamic gait symmetry. J Appl Biomech.2010; 26(1): 109-13.

72. Haddad JM, van Emmerik RE, Whittlesey SN, Hamill J. Adaptations in interlimb and intralimb coordination to asymmetrical loading in human walking. Gait Posture. 2006; 23(4): 429-34.

73. Lu TW, Yen HC, Chen HL. Comparisons of the inter-joint coordination between leading and trailing limbs when crossing obstacles of different heights. Gait Posture. 2008; 27(3): 309-15.

74. Yen HC, Chen HL, Liu MW, Liu HC, Lu TW. Age effects on the inter-joint coordination during obstacle-crossing. J Biomech. 2009; 42(15): 2501-6.

75. Shemmell J, Johansson J, Portra V, Gottlieb GL, Thomas JS, Corcos DM. Control of interjoint coordination during the swing phase of normal gait at different speeds. J Neuroeng Rehabil. 2007; 10: 1-4.

76. Chiu SL, Chou LS. Effect of walking speed on inter-joint coordination differs between young and elderly adults. J Biomech. 2012; 45(2):275-80.

77. Toulotte C, Thevenon A, Watelain E, Fabre C. Identification of healthy elderly fallers and non-fallers by gait analysis under dual-task conditions. Clin Rehabil. 2006; 20 (3): 269-76.

78. Mirriam-Webster Collegiate Dictionary. 11th ed. Springfield, Massachusetts, USA.: Mirriam-Webster, Inc.; 2004. Mirriam-Webster Collegiate Dictionary; p. 1623.

79. Lord SR, Smith ST, Menant JC. Vision and falls in older people: risk factors and intervention strategies. Clin Geriatr Med. 2010; 26(4): 569-81.

80. Yogev-Seligmann G, Hausdorff JM, Giladi N. The role of executive function and attention in gait. Mov Disord. 2008; 23(3): 329-42.

81. Oatis C. Kinesiology: The Mechanics and Pathomechanics of Human Movement.5th ed: Lippincott Williams & Wilkins; 2004.

82. Sparrow WA, Begg RK, Parker S. Variability in the foot-ground clearance and step timing of young and older men during single-task and dual-task treadmill walking. Gait Posture. 2008; 28(4): 563-7.

83. Shumway-Cook A, Brauer S, Woollacott M. Predicting the probability for falls in community-dwelling older adults using the Timed Up & Go Test. Phys Ther. 2000; 80(9): 896-903.

84. Delbaere K, Close JC, Heim J, Sachdev PS, Brodaty H, Slavin MJ, et al. A multifactorial approach to understanding fall risk in older people. J Am Geriatr Soc. 2010; 58(9): 1679-85.

85. Plummer-D’Amato P, Altmann LJP, Reilly K. Dual-task effects of spontaneous speech and executive function on gait in aging: Exaggerated effects in slow walkers. Gait Posture. 2011; 33(2):233-7.

86. Reelick MF, van Iersel MB, Kessels RP, Rikkert MG. The influence of fear of falling on gait and balance in older people. Age Ageing. 2009;38(4):435-40.

87. Springer S, Giladi N, Peretz C, Yogev G, Simon ES, Hausdorff JM. Dual-tasking effects on gait variability: the role of aging, falls, and executive function. Mov Disord. 2006;21(7):950-7.

88. Ansari NN, Naghdi S, Hasson S, Valizadeh L, Jalaie S. Validation of a Mini-Mental State Examination (MMSE) for the Persian population: a pilot study. Appl Neuropsychol. 2010; 17(3): 190-5.

89. Mosallanezhad Z, Salavati M, Hellstr MK, Reza Sotoudeh G, Nilsson Wikmar L, Fr Ndin K. Cross-cultural adaptation, reliability and validity of the Persian version of the modified falls efficacy scale. Disabil Rehabil. 2011; 33: 2446-53.

90. Thrane G, Joakimsen RM, Thornquist E. The association between timed up and go test and history of falls: the Tromso study. BMC Geriatr. 2007; 1: 1-7.

91. Kristensen MT, Foss NB, Kehlet H. Timed “up & go” test as a predictor of falls within 6 months after hip fracture surgery. Phys Ther. 2007; 87(1): 24-30.

92. Salavati M, Negahban H, Mazaheri M, Soleimanifar M, Hadadi M, Sefiddashti L, et al. The Persian version of the Berg Balance Scale: inter and intra-rater reliability and construct validity in elderly adults. Disabil Rehabil. 2012; 2: 15-18.

93. Malakouti SK, Fatollahi P, Mirabzadeh A, Salavati M, Zandi T. Reliability, validity and factor structure of the GDS-15 in Iranian elderly. Int J Geriatr Psychiatry. 2006; 21(6): 588-93.

94. Kang HG, Dingwell JB. Separating the effects of age and walking speed on gait variability. Gait Posture. 2007; 27: 572-77.

95. Buzzi UH, Stergiou N, Kurz MJ, Hageman PA, Heidel J. Nonlinear dynamics indicates aging affects variability during gait. Clinical Biomechanics. 2003; 18: 435-43.

96. Salavati M, Hadian MR, Mazaheri M, Negahban H, Ebrahimi I, Talebian S, et al. Test-retest reliability [corrected] of center of pressure measures of postural stability during quiet standing in a group with musculoskeletal disorders consisting of low back pain, anterior cruciate ligament injury and functional ankle instability. Gait Posture. 2009; 29(3): 460-4.

97. Danzl P, Nabi A, Moehlis J. Charge-balanced spike timing control for phase models of spiking neurons. DISCRET CONTIN DYN S. 2010; 28(4): 1413-35.

98. Chiu SL, Chou LS. Variability in inter-joint coordination during walking of elderly adults and its association with clinical balance measures. Clin Biomech. 2013; 28(4): 454-8.

99. Chiu SL, Osternig L, Chou LS. Concussion induces gait inter-joint coordination variability under conditions of divided attention and obstacle crossing. Gait Posture. 2013; 38(4): 717-22.Hamill J, van Emmeril RE, Heiderscheit BC, Li L. A dynamical systems approach to lower extremity running injuries. Clin Biomech .1999;14:297-308.

100. Lipsitz LA, Goldberger AL. Loss of “complexity” and aging: potential applications of fractals and chaos theory to senescence. JAMA. 1992; 267:1806-9.

101. Hicheur H, Terekhov AV, Berthoz A. Intersegmental coordination during human locomotion: does planar covariantion of elevation angles reflect central constraints? J Neurophysiol. 2006; 96:1406-19.

102. Nordahl CW, Ranganath C, Yonelinas AP, DeCarli C, Fletcher E, Jagust WJ. White matter changes compromise prefrontal cortex function in healthy elderly individuals, J Cog Neurosci.2006; 18(3): 418-29.

103. Gunning-Dixon FM and Raz N. Neuroanatomical correlates of selected executive functions in middle-aged and older adults: a prospective MRI study, Neuropsychologia. 2003; 41(14): 1929–41.

104. Raz N. Aging of the brain and its impact on cognitive performance: integration of structural and functional findings,” in The Handbook of Aging and Cognition, F. Craik and T. Salthouse, Eds., Erlbaum. 2000; pp.1–90.

105. Raz N, Gunning FM, Head D. Selective aging of the human cerebral cortex observed in vivo: differential vulnerability of the prefrontal gray matter. Cerebr Cort. 1997; 7(3): 268–82.

106. Raz N, Lindenberger U, Rodrigue KM. Regional brain changes in aging healthy adults: general trends, individual differences and modifiers. Cerebr Cort. 2005; 15(11): 1676–89.

107. Park DC and Reuter-Lorenz P. The adaptive brain: aging and neurocognitive scaffolding. An Rev Psych. 2009; 60: 173–96.

108. Grady CL and Craik FI. Changes in memory processing with age. Curr Opin Neurobio. 2000; 10(2): 224–31.
109. Buckner RL. Memory and executive function in aging and ad: multiple factors that cause decline and reserve factors that compensate. Neuron. 2004; 44(1): 195–208.

110. Jonides J, Marshuetz C, Smith EE, Reuter-Lorenz PA, Koeppe RA, Hartley A. Age differences in behavior and PET activation reveal differences in interference resolution in verbal working memory,” J Cog Neurosci. 2000;12(1): 188–96.

111. Krampe RT, Schaefer S, Lindenberger