Structure of motor variability in marginally redundant multifinger force production tasks

The hip flexor muscles are major contributors to lumbar spine stability. Tight hip flexors can lead to pain in the lumbar spine, and hence to an impairment in performance. Moreover, sedentary behavior is a common problem and a major contributor to restricted hip extension flexibility. Stretching can be a tool to reduce muscle tightness and to overcome the aforementioned problems. Therefore, the purpose of this systematic review with meta-analysis was to determine the effects of a single hip flexor stretching exercise on performance parameters. The online search was performed in the following three databases: PubMed, Scopus, and Web of Science. Eight studies were included in this review with a total of 165 subjects (male: 111; female 54). In contrast to other muscle groups (e.g., plantar flexors), where 120 s of stretching likely decreases force production, it seems that isolated hip flexor stretching of up to 120 s has no effect or even a positive impact on performance-related parameters. A comparison of the effects on performance between the three defined stretch durations (30–90 s; 120 s; 270–480 s) revealed a significantly different change in performance (p = 0.02) between the studies with the lowest hip flexor stretch duration (30–90 s; weighted mean performance change: −0.12%; CI (95%): −0.49 to 0.41) and the studies with the highest hip flexor stretch duration (270–480 s; performance change: −3.59%; CI (95%): −5.92 to −2.04). Meta-analysis revealed a significant (but trivial) impairment in the highest hip flexor stretch duration of 270–480 s (SMD effect size = −0.19; CI (95%) −0.379 to 0.000; Z = −1.959; p = 0.05; I2 = 0.62%), but not in the lowest stretch duration (30–90 s). This indicates a dose-response relationship in the hip flexor muscles. Although the evidence is based on a small number of studies, this information will be of great importance for both athletes and coaches.

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Optimal Current Allocation Rendering 3-D Magnetic Force Production in Hexapole Electromagnetic Actuation

IEEE/ASME Transactions on Mechatronics ◽

10.1109/tmech.2020.3039258 ◽

2020 ◽

pp. 1-1

Author(s):

Fei Long ◽

Peng Cheng ◽

Ta-Min Meng ◽

Chia-Hsiang Menq

Keyword(s):

Magnetic Force ◽

Force Production ◽

Electromagnetic Actuation ◽

Optimal Current

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The Effects of Spinal Manipulation on Motor Unit Behavior

Brain Sciences ◽

10.3390/brainsci11010105 ◽

2021 ◽

Vol 11 (1) ◽

pp. 105

Author(s):

Lucien Robinault ◽

Aleš Holobar ◽

Sylvain Crémoux ◽

Usman Rashid ◽

Imran Khan Niazi ◽

...

Keyword(s):

Motor Unit ◽

Conduction Velocity ◽

Spinal Manipulation ◽

Maximum Voluntary Contraction ◽

Force Production ◽

Movement Control ◽

Position Sense ◽

Joint Position Sense ◽

Voluntary Contraction ◽

Passive Movement

Over recent years, a growing body of research has highlighted the neural plastic effects of spinal manipulation on the central nervous system. Recently, it has been shown that spinal manipulation improved outcomes, such as maximum voluntary force and limb joint position sense, reflecting improved sensorimotor integration and processing. This study aimed to further evaluate how spinal manipulation can alter neuromuscular activity. High density electromyography (HD sEMG) signals from the tibialis anterior were recorded and decomposed in order to study motor unit changes in 14 subjects following spinal manipulation or a passive movement control session in a crossover study design. Participants were asked to produce ankle dorsiflexion at two force levels, 5% and 10% of maximum voluntary contraction (MVC), following two different patterns of force production (“ramp” and “ramp and maintain”). A significant decrease in the conduction velocity (p = 0.01) was observed during the “ramp and maintain” condition at 5% MVC after spinal manipulation. A decrease in conduction velocity suggests that spinal manipulation alters motor unit recruitment patterns with an increased recruitment of lower threshold, lower twitch torque motor units.

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A soft, synergy-based robotic glove for grasping assistance

Wearable Technologies ◽

10.1017/wtc.2021.3 ◽

2021 ◽

Vol 2 ◽

Author(s):

Ryan Alicea ◽

Michele Xiloyannis ◽

Domenico Chiaradia ◽

Michele Barsotti ◽

Antonio Frisoli ◽

...

Keyword(s):

Daily Living ◽

Power Transmission ◽

Force Production ◽

Output Force ◽

Cord Injury ◽

Closing Force ◽

Block Test ◽

Postural Synergies

Abstract This paper presents a soft, tendon-driven, robotic glove designed to augment grasp capability and provide rehabilitation assistance for postspinal cord injury patients. The basis of the design is an underactuation approach utilizing postural synergies of the hand to support a large variety of grasps with a single actuator. The glove is lightweight, easy to don, and generates sufficient hand closing force to assist with activities of daily living. Device efficiency was examined through a characterization of the power transmission elements, and output force production was observed to be linear in both cylindrical and pinch grasp configurations. We further show that, as a result of the synergy-inspired actuation strategy, the glove only slightly alters the distribution of forces across the fingers, compared to a natural, unassisted grasping pattern. Finally, a preliminary case study was conducted using a participant suffering from an incomplete spinal cord injury (C7). It was found that through the use of the glove, the participant was able to achieve a 50% performance improvement (from four to six blocks) in a standard Box and Block test.

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