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.

Upper Extremity Kinematics and Muscle Activation Patterns in Subjects With Facioscapulohumeral Dystrophy

“…Investigating the involvement of rotator cuff muscles and deeper muscles such as the serratus anterior would require more invasive techniques such as fluoroscopy or intramuscular needle electromyography. As part of a complementary approach to understanding rotator cuff muscle contributions, biomechanical musculoskeletal models 21,36,37 could also be used. As a long-term research perspective, it would be interesting to further evaluate whether the use of arm supports would result in more efficient movements that require less effort and would therefore enable the performance of tasks such as eating for longer periods.…”

Recommendations for studies on dynamic arm support devices in people with neuromuscular disorders: a scoping review with expert-based discussion

“…Two articles were added after reference cross cheques. Finally, eight articles were included for reviewing after the inclusion process [18][19][20][21][22][23][24][25] ( Table 1). Two studies, ongoing until 31 December 2020 and 2019, respectively, were identified from the goverenment clinical trial source [26,27] (Table 2).…”

“…The evaluated DAS were a prototype A-gear [19,28], and commercially available devices Armon Ayura [26,27,29], Armon Edero [25,29], Gowing [24,30], JAECO MultiLink Arm with Elevation Assist [25,31], JAECO WREX [21,23,26,27,31], SLING [20,22,30], and Top-Help [22,30], and a JAECO WREX modified with a trunk support prototype [18] (Table 1). These DAS provide gravity compensation through adjustable counter-weights (SLING) or springs (A-gear, Armon Edero, JAECO MultiLink Arm with Elevation Assist, JAECO WREX, Top-Help) with an additional actuator that adjusts the springs' tension (Armon Ayura, Gowing).…”

“…Our mixed-method approach revealed that literature focuses on selected framework cells which are often considered separately, thus limiting the evidence on the interaction between cells. For instance, current evidence shows that muscle activity and joint mobility are both influenced by load reduction [18][19][20][21][22][23]. However, as also pointed out by experts, the interaction between (1) muscle activity and joint mobility and (2) how this is affected by disease and (3) how this could be restored by the device should be investigated.…”

Upper extremity exomuscle for shoulder abduction support

“…Instead, we constructed a low-inertia, large workspace sling support [35], [36]. We suspended an arm rest from the ceiling using 165 cm of high-strength nylon rope.…”