title: An inverse dynamic analysis on the influence of upper limb gravity compensation during reaching.
abstract: Muscular dystrophies (MDs) are characterized by progressive muscle wasting and weakness. Several studies have been conducted to investigate the influence of arm supports in an attempt to restore arm function. Lowering the load allows the user to employ the residual muscle force for movement as well as for posture stabilization. In this pilot study three conditions were investigated during a reaching task performed by three healthy subjects and three MD subjects: a control condition involving reaching; a similar movement with gravity compensation using braces to support the forearm; an identical reaching movement in simulated zero-gravity. In the control condition the highest values of shoulder moments were present, with a maximum of about 6 Nm for shoulder flexion and abduction. In the gravity compensation and zero gravity conditions the maximum shoulder moments were decreased by more than 70% and instead of increasing during reaching, they remained almost unvaried, fluctuating around an offset value less than 1 Nm. Similarly, the elbow moments in the control condition were the highest with a peak around 3.3 Nm for elbow flexion, while the moments were substantially reduced in the remaining two conditions, fluctuating around offset values between 0 to 0.5 Nm. In conclusion, gravity compensation by lower arm support is effective in healthy subjects and MD subjects and lowers the amount of shoulder and elbow moments by an amount comparable to a zero gravity environment. However the influence of gravity compensation still needs to be investigated on more people with MDs in order to quantify any beneficial effect on this population.
authors.forename: J M N Hans
authors.initials: JM
authors.lastname: Essers
authors.forename: Kenneth
authors.initials: K
authors.lastname: Meijer
authors.forename: Alessio
authors.initials: A
authors.lastname: Murgia
authors.forename: Arjen
authors.initials: A
authors.lastname: Bergsma
authors.forename: Paul
authors.initials: P
authors.lastname: Verstegen
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D005542:Forearm / Q000503:physiopathology*; D006112:Gravitation; D006801:Humans; D008297:Male; D008875:Middle Aged; D009136:Muscular Dystrophies / Q000534:rehabilitation*; D009989:Orthotic Devices / Q000706:statistics & numerical data; D010865:Pilot Projects; D016059:Range of Motion, Articular / Q000502:physiology*; D055815:Young Adult