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Effect of ankle support on leg muscle activation, kinematics, and kinetics during drop landings
598
Abstracts
HAND PRESSURES AS PREDICTORS OF RESULTANT AND PROPULSIVE HAND FORCES IN SWIMMING Anne M. Thayer Department of Exercise Science, The University of Iowa, Iowa City, IA 52242 The purpose of this study was to determine the extent to which the resultant and propulsive forces acting on the hand of a swimmer can be satisfactorily predicted from measures of local pressure on the hand. Tests were conducted in a recirculating water hand models instrumented with 127 flume using two full-scale, mechanically-driven pressure taps. Motions simulating the freestyle stroke and the propulsive phase of the breaststroke pull were each tested in two orientations, yielding four test conditions. The forces (measured via strain gages mounted on the shaft supporting the hand model) and pressures were recorded throughout the range of motion of the hand through the water. Under each of the four conditions, taps associated with correlations between pressure and the resultant or propulsive force which met the criterion of eO.92 (~~20.85) were termed good predictors. The locations on the hand of these good predictors were shown to vary with the stroke being simulated and the orientation of the hand to the flow stream. No single pressure tap was able to predict the resultant (or propulsive) force with acceptable accuracy under all conditions of motion and orientation. When the data sets for all four conditions were combined and an allpossible-regressions procedure used, a minimum of eight taps was needed to predict the resultant force, and a minimum of eleven taps was needed to predict the propulsive force with acceptable accuracy. The results of this study indicate that the resultant and propulsive forces on a swimmer's hand can not be satisfactorily predicted from cl small number of pressure measures on the hand.
EFFECT OF AGE AND SPEED ON THE BIOMECHANICS OF SITl-ING DOWN ONTO A CHAIR M. Melissa Gross Department of Movement Science, The University of Michigan, Ann Arbor, MI 48109-2214, USA Chair trzinsfer is an important activity of daily living that is particularly challenging to the elderly. Although the biomechanics of rising from a chair have been studied for both young and elderly subjects, little is yet known about the biomechanics of sitting down onto a chair for either age group. In this study, the biomechanics of sitting down onto a chair were examined in young and elderly women when moving at three self-selected speeds. Movement times were similar for the young and elderly women, except in the fast speed trials when young subjects moved faster. Even when moving at the same speeds, however, the elderly subjects spent relatively more time in the descent portion of the task, thus generating less downward momentum compared with the young subjects. Joint torques were similar for the young and the elderly subjects at all movement speeds. Although the magnitude of the joint torques did not change with movement speed, the role of the hip muscle torque changed with movement speed, especially for the young subjects. Hip muscle torque was used primarily to counteract the effects of the gravity torque at slow speeds, but at faster speeds, the hip torque was used increasingly to generate body acceleration. The center of pressure position at chair contact tended to move anteriorly as movement time decreased for the elderly subjects. Differences in the biomechanics of the task between young and elderly subjects may represent a strategy by the elderly subjects to enhance stability at the time of chair contact.
EFFECT OF ANKLR SUPPORTON LEG MUSCLE ACTIVATION, KINRMATICS,AND KINJ$TICX WRING DROP LANDING9
Jon W. Feuezbach,l%mas M. Luudin,MarkD. Grabiner Departmentof BicuuedicalEngiueeaing ‘Ihe Cleveland Clinic Foundation,Cleveland,OH44195.USA. l%e purposeof thisstudywasto uxupate theeffectaof threetypesof anklesupporton lower limb muscle activation, kinematic&kinetks, and energeticaduringdrop laadings. Eve uninjuredmale subjectsperformedfive drop landingsunderfour bii conditions: (1) no ankle support; (2) applicationof tape; (3) applicationof Aircasts;and (4) applicationof Swede-O ankle breces. EMG signak wez collectadfrom the gastrocnemius, penmeuslongus,and tibialisanteriorof tbe rightleg. Right foot, &auk, aad thighpositionswere mcordedusinga MotionAnalysisSystemand groundreaction fm and mome.nIswerefeuxdedusingtwo Abfl’Ifonxplates,onebeneatheacbfoot. Inversedynamicswerepaionmedtoobtainlower~blrineticsand~~. Difkrences in muscle activationlevel pmduced by anklesupportwereuot stadsticallysiguificaut,but the uwd of inarased pemneuslongus aUivationwhich was observedduriagthe aakle supportconditionsdesems fmthcxattenth. Signilicaotlyleas planmrfkxionwas observed~totouchdownintbesnlrlesupportconditions~~totbatofthenoeopportoondition. Iuvwsionaadadduction duringtbedesceatwtrenotsignifkaatlyaffectedbyaaklesuppM Aredu*iwiuplanwflexioncouldbeame&mismfortbe aecreasC~anLlein]uriesthatbavebeenrepoltedwiththe~~ofankle~. Obseaxdhxeasesinkneeflexioaduringtie anLles~cmditionsmayhaveaaed~nconcertwith~ip~~~~~~t~zcronetchangeinthelpolmdreaction forces. Itbasbeensuggestedthatalterationsio~~byanklesupportmayproduceImeinjuries. However,aakle supporthad litde effect on maximumknee joint moments,or kaeejoint fznerge?ica. Thus, tbeseresultspmvide littleevidencethat applicationofathletictape~commercialanblesupports(duringadrcrplanding)iacrrasetheriskofkneejoiatinjmy. A-could beutilizedtoimprovetbermderstandingofthebi~~signlficcmceoffactonrwhicbinn~saessinthelateralanLlejoint ligaments. In conclusion,with the exceptionof kaee fkxkm aad plantion angle priorto touchdown,aakle supportbad few statisticallysignificanteffects on lower limb muscle activation,kiaematica,aud kineticslo noxmalsubjecta.
Abstracts
HAND PRESSURES AS PREDICTORS OF RESULTANT AND PROPULSIVE HAND FORCES IN SWIMMING Anne M. Thayer Department of Exercise Science, The University of Iowa, Iowa City, IA 52242 The purpose of this study was to determine the extent to which the resultant and propulsive forces acting on the hand of a swimmer can be satisfactorily predicted from measures of local pressure on the hand. Tests were conducted in a recirculating water hand models instrumented with 127 flume using two full-scale, mechanically-driven pressure taps. Motions simulating the freestyle stroke and the propulsive phase of the breaststroke pull were each tested in two orientations, yielding four test conditions. The forces (measured via strain gages mounted on the shaft supporting the hand model) and pressures were recorded throughout the range of motion of the hand through the water. Under each of the four conditions, taps associated with correlations between pressure and the resultant or propulsive force which met the criterion of eO.92 (~~20.85) were termed good predictors. The locations on the hand of these good predictors were shown to vary with the stroke being simulated and the orientation of the hand to the flow stream. No single pressure tap was able to predict the resultant (or propulsive) force with acceptable accuracy under all conditions of motion and orientation. When the data sets for all four conditions were combined and an allpossible-regressions procedure used, a minimum of eight taps was needed to predict the resultant force, and a minimum of eleven taps was needed to predict the propulsive force with acceptable accuracy. The results of this study indicate that the resultant and propulsive forces on a swimmer's hand can not be satisfactorily predicted from cl small number of pressure measures on the hand.
EFFECT OF AGE AND SPEED ON THE BIOMECHANICS OF SITl-ING DOWN ONTO A CHAIR M. Melissa Gross Department of Movement Science, The University of Michigan, Ann Arbor, MI 48109-2214, USA Chair trzinsfer is an important activity of daily living that is particularly challenging to the elderly. Although the biomechanics of rising from a chair have been studied for both young and elderly subjects, little is yet known about the biomechanics of sitting down onto a chair for either age group. In this study, the biomechanics of sitting down onto a chair were examined in young and elderly women when moving at three self-selected speeds. Movement times were similar for the young and elderly women, except in the fast speed trials when young subjects moved faster. Even when moving at the same speeds, however, the elderly subjects spent relatively more time in the descent portion of the task, thus generating less downward momentum compared with the young subjects. Joint torques were similar for the young and the elderly subjects at all movement speeds. Although the magnitude of the joint torques did not change with movement speed, the role of the hip muscle torque changed with movement speed, especially for the young subjects. Hip muscle torque was used primarily to counteract the effects of the gravity torque at slow speeds, but at faster speeds, the hip torque was used increasingly to generate body acceleration. The center of pressure position at chair contact tended to move anteriorly as movement time decreased for the elderly subjects. Differences in the biomechanics of the task between young and elderly subjects may represent a strategy by the elderly subjects to enhance stability at the time of chair contact.
EFFECT OF ANKLR SUPPORTON LEG MUSCLE ACTIVATION, KINRMATICS,AND KINJ$TICX WRING DROP LANDING9
Jon W. Feuezbach,l%mas M. Luudin,MarkD. Grabiner Departmentof BicuuedicalEngiueeaing ‘Ihe Cleveland Clinic Foundation,Cleveland,OH44195.USA. l%e purposeof thisstudywasto uxupate theeffectaof threetypesof anklesupporton lower limb muscle activation, kinematic&kinetks, and energeticaduringdrop laadings. Eve uninjuredmale subjectsperformedfive drop landingsunderfour bii conditions: (1) no ankle support; (2) applicationof tape; (3) applicationof Aircasts;and (4) applicationof Swede-O ankle breces. EMG signak wez collectadfrom the gastrocnemius, penmeuslongus,and tibialisanteriorof tbe rightleg. Right foot, &auk, aad thighpositionswere mcordedusinga MotionAnalysisSystemand groundreaction fm and mome.nIswerefeuxdedusingtwo Abfl’Ifonxplates,onebeneatheacbfoot. Inversedynamicswerepaionmedtoobtainlower~blrineticsand~~. Difkrences in muscle activationlevel pmduced by anklesupportwereuot stadsticallysiguificaut,but the uwd of inarased pemneuslongus aUivationwhich was observedduriagthe aakle supportconditionsdesems fmthcxattenth. Signilicaotlyleas planmrfkxionwas observed~totouchdownintbesnlrlesupportconditions~~totbatofthenoeopportoondition. Iuvwsionaadadduction duringtbedesceatwtrenotsignifkaatlyaffectedbyaaklesuppM Aredu*iwiuplanwflexioncouldbeame&mismfortbe aecreasC~anLlein]uriesthatbavebeenrepoltedwiththe~~ofankle~. Obseaxdhxeasesinkneeflexioaduringtie anLles~cmditionsmayhaveaaed~nconcertwith~ip~~~~~~t~zcronetchangeinthelpolmdreaction forces. Itbasbeensuggestedthatalterationsio~~byanklesupportmayproduceImeinjuries. However,aakle supporthad litde effect on maximumknee joint moments,or kaeejoint fznerge?ica. Thus, tbeseresultspmvide littleevidencethat applicationofathletictape~commercialanblesupports(duringadrcrplanding)iacrrasetheriskofkneejoiatinjmy. A-could beutilizedtoimprovetbermderstandingofthebi~~signlficcmceoffactonrwhicbinn~saessinthelateralanLlejoint ligaments. In conclusion,with the exceptionof kaee fkxkm aad plantion angle priorto touchdown,aakle supportbad few statisticallysignificanteffects on lower limb muscle activation,kiaematica,aud kineticslo noxmalsubjecta.