title: Age and sex differences in steadiness of elbow flexor muscles with imposed cognitive demand.
abstract: OBJECTIVE
  These studies determined (1) age- and sex-related differences in steadiness of isometric contractions when high cognitive demand was imposed across a range of forces with the elbow flexor muscles (study 1) and; (2) sex differences in steadiness among older adults when low cognitive demand was imposed (study 2).
  
  
  METHODS
  36 young adults (18-25 years; 18 women) and 30 older adults (60-82 years; 17 women) performed isometric contractions at 5, 30 and 40 % of maximum voluntary contraction (MVC). Study 1 involved a high-cognitive demand session (serial subtractions by 13 during the contraction) and a control session (no mental math). Study 2 (older adults only) involved a low-cognitive demand session (subtracting by 1s).
  
  
  RESULTS
  Older individuals exhibited greater increases in force fluctuations (coefficient of variation of force, CV) with high cognitive demand than young adults, with the largest age difference at 5 % MVC (P = 0.01). Older adults had greater agonist EMG activity with high-cognitive demand and women had greater coactivation than men (P < 0.05). In study 2, CV of force increased with low cognitive demand for the older women but not for the older men (P = 0.03).
  
  
  CONCLUSIONS
  Older adults had reduced steadiness and increased muscle activation when high cognitive demand was imposed while low cognitive demand induced increased force fluctuations in older women but not older men. These findings have implications for daily and work-related tasks that involve cognitive demand performed simultaneously during submaximal isometric contractions in an aging workforce.
authors: Department of Physical Therapy, Marquette University, P.O. Box 1881, Milwaukee, WI, 53201, USA.
authors: Hugo M
authors: HM
authors: Pereira
authors: Vincent C
authors: VC
authors: Spears
authors: Bonnie
authors: B
authors: Schlinder-Delap
authors: Tejin
authors: T
authors: Yoon
authors: Kristy A
authors: KA
authors: Nielson
authors: Sandra K
authors: SK
authors: Hunter
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001007:Anxiety / Q000503:physiopathology; D003071:Cognition; D004550:Elbow / Q000502:physiology; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000254:growth & development / Q000502:physiology*; D012737:Sex Factors
references: Exp Brain Res. 1998 Apr;119(4):467-74
references: 9588781
references: Med Sci Sports Exerc. 2007 Mar;39(3):469-79
references: 17473773
references: J Neurophysiol. 1993 Jun;69(6):2108-15
references: 8350134
references: Exp Brain Res. 1997 Feb;113(2):207-13
references: 9063707
references: J Appl Physiol (1985). 2014 Apr 1;116(7):767-78
references: 24526582
references: Am J Ind Med. 2002 Apr;41(4):221-35
references: 11920966
references: Psychol Rev. 2000 Jul;107(3):411-29
references: 10941275
references: Neurosci Biobehav Rev. 2011 Jan;35(3):715-28
references: 20833198
references: Muscle Nerve. 2007 Oct;36(4):515-24
references: 17626289
references: Neuropsychol Dev Cogn B Aging Neuropsychol Cogn. 2006 Sep-Dec;13(3-4):366-84
references: 16887779
references: Exerc Sport Sci Rev. 2011 Apr;39(2):77-84
references: 21206281
references: J Appl Physiol (1985). 2005 Jun;98(6):2072-80
references: 15691902
references: Electroencephalogr Clin Neurophysiol. 1990 Dec;76(6):509-19
references: 1701119
references: J Neurophysiol. 1998 Dec;80(6):2870-81
references: 9862891
references: J Appl Physiol (1985). 2001 Aug;91(2):821-31
references: 11457799
references: J Appl Physiol (1985). 2008 Oct;105(4):1199-209
references: 18687979
references: Front Aging Neurosci. 2014 May 22;6:97
references: 24904410
references: Muscle Nerve. 2005 Oct;32(4):533-40
references: 15986419
references: J Neurophysiol. 2007 May;97(5):3206-18
references: 17360826
references: Acta Physiol (Oxf). 2014 Apr;210(4):768-89
references: 24433272
references: J Electromyogr Kinesiol. 2000 Oct;10(5):361-74
references: 11018445
references: Biol Psychol. 2005 Apr;69(1):113-32
references: 15740829
references: J Appl Physiol (1985). 2002 Mar;92(3):1004-12
references: 11842033
references: Eur J Neurosci. 2012 Nov;36(10):3365-75
references: 22882424
references: Neural Plast. 2012;2012:131608
references: 22848845
references: J Neurosci. 2013 Mar 20;33(12):5301-11
references: 23516294
references: Neurobiol Aging. 2009 Apr;30(4):507-14
references: 19231028
references: Scand J Work Environ Health. 1998 Oct;24(5):418-24
references: 9869314
references: Cereb Cortex. 2005 Nov;15(11):1676-89
references: 15703252
references: Neuropsychologia. 2012 Jun;50(7):1578-93
references: 22450197
references: PLoS One. 2013;8(2):e55970
references: 23409099
references: Exp Brain Res. 2007 Jan;176(3):448-64
references: 16896977
references: Am J Physiol. 1994 Jul;267(1 Pt 2):H344-53
references: 8048600
references: J Electromyogr Kinesiol. 2003 Feb;13(1):1-12
references: 12488083
references: Eur J Appl Physiol. 2007 Nov;101(5):629-36
references: 17701201
references: J Appl Physiol (1985). 2004 Jul;97(1):225-35
references: 15220319
references: Psychoneuroendocrinology. 2006 Feb;31(2):151-78
references: 16139959
references: J Neurophysiol. 2000 Apr;83(4):2030-9
references: 10758113
references: Neurosci Lett. 2001 Nov 2;313(1-2):33-6
references: 11684333
references: J Neurophysiol. 2008 Oct;100(4):1800-12
references: 18684903
references: Front Psychol. 2013 Apr 08;4:165
references: 23579267
references: J Physiol. 2009 Dec 15;587(Pt 24):5925-38
references: 19840996
references: Muscle Nerve. 2000 Apr;23(4):600-12
references: 10716772
references: J Appl Physiol (1985). 2000 Jul;89(1):61-71
references: 10904036
references: Exp Brain Res. 2010 Jun;203(2):307-16
references: 20358188
references: Eur J Appl Physiol. 2010 Dec;110(6):1251-7
references: 20737167
references: J Appl Physiol (1985). 2012 Jun;112(11):1897-905
references: 22442023
references: Compr Physiol. 2012 Oct;2(4):2629-82
references: 23720261
references: Diabetes Metab Rev. 1992 Dec;8(4):355-72
references: 1307524
references: J Appl Physiol (1985). 2009 Nov;107(5):1486-96
references: 19729594
references: J Appl Physiol (1985). 2005 Oct;99(4):1483-93
references: 15947031