J1040103 Influence of Posture on the Muscle Activity and Floor Reaction Force in Reach Movement by Healthy Subjects

Repeated high-impact ground forces can lead to injury and decreased performance. While increasing flexor hallucis longus (FHL) muscle activity is known to increase stiffness and elasticity, it is unknown if this also decreases ground reaction forces by shock absorption during landing. This study aimed to determine whether increasing FHL muscle activity affects ground reaction force during landing in healthy subjects. Eight subjects performed single-leg steps onto a force platform for five trials, with and without flexion of the metatarsophalangeal (MTP) joint at the moment of landing. Integrated surface electromyography (sEMG) of the FHL and medial gastrocnemius (MG) and ground reaction forces (GRFs) were measured. sEMG and GRF during the 50 ms before and 100 ms following initial ground contact were analyzed and compared. Flexion of the MTP joint condition significantly decreased the vertical and mediolateral force peaks of GRF, and FHL muscle activity increased. Flexion of the MTP joint at the moment of landing reduces GRF in healthy subjects through force dissipation in the foot, by increased FHL muscle activity. The results suggest that this may contribute to injury prevention by reducing the impact force through flexing the MTP joint at the moment of landing.

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Biomechanical analysis of an unpowered hip flexion orthosis on individuals with and without multiple sclerosis

Journal of NeuroEngineering and Rehabilitation ◽

10.1186/s12984-021-00891-7 ◽

2021 ◽

Vol 18 (1) ◽

Author(s):

Ross M. Neuman ◽

Staci M. Shearin ◽

Karen J. McCain ◽

Nicholas P. Fey

Keyword(s):

Multiple Sclerosis ◽

Muscle Activity ◽

Healthy Subjects ◽

Muscle Activation ◽

Assistive Technologies ◽

Lower Limbs ◽

Biomechanical Analysis ◽

Foot Drop ◽

Plantar Flexors ◽

Hip Flexion

Abstract Background Gait impairment is a common complication of multiple sclerosis (MS). Gait limitations such as limited hip flexion, foot drop, and knee hyperextension often require external devices like crutches, canes, and orthoses. The effects of mobility-assistive technologies (MATs) prescribed to people with MS are not well understood, and current devices do not cater to the specific needs of these individuals. To address this, a passive unilateral hip flexion-assisting orthosis (HFO) was developed that uses resistance bands spanning the hip joint to redirect energy in the gait cycle. The purpose of this study was to investigate the short-term effects of the HFO on gait mechanics and muscle activation for people with and without MS. We hypothesized that (1) hip flexion would increase in the limb wearing the device, and (2) that muscle activity would increase in hip extensors, and decrease in hip flexors and plantar flexors. Methods Five healthy subjects and five subjects with MS walked for minute-long sessions with the device using three different levels of band stiffness. We analyzed peak hip flexion and extension angles, lower limb joint work, and muscle activity in eight muscles on the lower limbs and trunk. Single-subjects analysis was used due to inter-subject variability. Results For subjects with MS, the HFO caused an increase in peak hip flexion angle and a decrease in peak hip extension angle, confirming our first hypothesis. Healthy subjects showed less pronounced kinematic changes when using the device. Power generated at the hip was increased in most subjects while using the HFO. The second hypothesis was not confirmed, as muscle activity showed inconsistent results, however several subjects demonstrated increased hip extensor and trunk muscle activity with the HFO. Conclusions This exploratory study showed that the HFO was well-tolerated by healthy subjects and subjects with MS, and that it promoted more normative kinematics at the hip for those with MS. Future studies with longer exposure to the HFO and personalized assistance parameters are needed to understand the efficacy of the HFO for mobility assistance and rehabilitation for people with MS.

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Effects of expiratory loading on respiration in humans

Journal of Applied Physiology ◽

10.1152/jappl.1980.49.4.601 ◽

1980 ◽

Vol 49 (4) ◽

pp. 601-608 ◽

Cited By ~ 19

Author(s):

B. Gothe ◽

N. S. Cherniack

Keyword(s):

Muscle Activity ◽

Healthy Subjects ◽

Respiratory Muscle ◽

Resistive Load ◽

Similar Magnitude ◽

Occlusion Pressure ◽

Ventilatory Responses ◽

Residual Capacity ◽

Resistive Loads ◽

The Difference

We examined the effects of expiratory resistive loads of 10 and 18 cmH2O.l-1.s in healthy subjects on ventilation and occlusion pressure responses to CO2, respiratory muscle electromyogram, pattern of breathing, and thoracoabdominal movements. In addition, we compared ventilation and occlusion pressure responses to CO2 breathing elicited by breathing through an inspiratory resistive load of 10 cmH2O.l-1.s to those produced by an expiratory load of similar magnitude. Both inspiratory and expiratory loads decreased ventilatory responses to CO2 and increased the tidal volume achieved at any given level of ventilation. Depression of ventilatory responses to Co2 was greater with the larger than with the smaller expiratory load, but the decrease was in proportion to the difference in the severity of the loads. Occlusion pressure responses were increased significantly by the inspiratory resistive load but not by the smaller expiratory load. However, occlusion pressure responses to CO2 were significantly larger with the greater expiratory load than control. Increase in occlusion pressure observed could not be explained by changes in functional residual capacity or chemical drive. The larger expiratory load also produced significant increases in electrical activity measured during both inspiration and expiration. These results suggest that sufficiently severe impediments to breathing, even when they are exclusively expiratory, can enhance inspiratory muscle activity in conscious humans.

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The effect of gait speed and gender on perceived exertion, muscle activity, joint motion of lower extremity, ground reaction force and heart rate during normal walking

Gait & Posture ◽

10.1016/j.gaitpost.2006.05.008 ◽

2007 ◽

Vol 25 (3) ◽

pp. 385-392 ◽

Cited By ~ 109

Author(s):

Min-Chi Chiu ◽

Mao-Jiun Wang

Keyword(s):

Heart Rate ◽

Lower Extremity ◽

Ground Reaction Force ◽

Muscle Activity ◽

Gait Speed ◽

Perceived Exertion ◽

Reaction Force ◽

Joint Motion ◽

Normal Walking ◽

And Gender

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Estimate of Floor Reaction Force Vector Using Foot-Pressure Sensors

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series C ◽

10.1299/kikaic.74.749 ◽

2008 ◽

Vol 74 (739) ◽

pp. 749-751 ◽

Cited By ~ 1

Author(s):

Kazuto MIYAWAKI ◽

Takehiro IWAMI ◽

Goro OBINATA ◽

Yoichi SHIMADA

Keyword(s):

Reaction Force ◽

Pressure Sensors ◽

Force Vector ◽

Foot Pressure ◽

Floor Reaction Force

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The frequency of alternate muscle activity is associated with the attenuation in muscle fatigue

Journal of Applied Physiology ◽

10.1152/japplphysiol.01309.2005 ◽

2006 ◽

Vol 101 (3) ◽

pp. 715-720 ◽

Cited By ~ 37

Author(s):

Motoki Kouzaki ◽

Minoru Shinohara

Keyword(s):

Muscle Fatigue ◽

Muscle Activity ◽

Healthy Subjects ◽

Vastus Lateralis ◽

Rectus Femoris ◽

Knee Extension ◽

Voluntary Contraction ◽

Sustained Contraction ◽

Low Level ◽

Before And After

Alternate muscle activity between synergist muscles has been demonstrated during low-level sustained contractions [≤5% of maximal voluntary contraction (MVC) force]. To determine the functional significance of the alternate muscle activity, the association between the frequency of alternate muscle activity during a low-level sustained knee extension and the reduction in knee extension MVC force was studied. Forty-one healthy subjects performed a sustained knee extension at 2.5% MVC force for 1 h. Before and after the sustained knee extension, MVC force was measured. The surface electromyogram was recorded from the rectus femoris (RF), vastus lateralis (VL), and vastus medialis (VM) muscles. The frequency of alternate muscle activity for RF-VL, RF-VM, and VL-VM pairs was determined during the sustained contraction. The frequency of alternate muscle activity ranged from 4 to 11 times/h for RF-VL (7.0 ± 2.0 times/h) and RF-VM (7.0 ± 1.9 times/h) pairs, but it was only 0 to 2 times/h for the VL-VM pair (0.5 ± 0.7 times/h). MVC force after the sustained contraction decreased by 14% ( P < 0.01) from 573.6 ± 145.2 N to 483.3 ± 130.5 N. The amount of reduction in MVC force was negatively correlated with the frequency of alternate muscle activity for the RF-VL and RF-VM pairs ( P < 0.001 and r = 0.65 for both) but not for the VL-VM pair. The results demonstrate that subjects with more frequent alternate muscle activity experience less muscle fatigue. We conclude that the alternate muscle activity between synergist muscles attenuates muscle fatigue.

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The evaluation of modified foot orthosis on muscle activity and kinetic in a subject with flexible flat foot : Single case study

Prosthetics and Orthotics International ◽

10.1177/0309364613492170 ◽

2013 ◽

Vol 38 (2) ◽

pp. 160-166 ◽

Cited By ~ 3

Author(s):

Hassan Saeedi ◽

Mohammad E Mousavi ◽

Basir Majddoleslam ◽

Mehdi Rahgozar ◽

Gholamreza Aminian ◽

...

Keyword(s):

Ground Reaction Force ◽

Muscle Activity ◽

Sagittal Plane ◽

Single Case ◽

Reaction Force ◽

Vertical Ground Reaction Force ◽

Flat Foot ◽

Case Evaluation ◽

The University ◽

Foot Orthosis

Background:Due to blocking of pronation/dorsiflexion in flexible flat foot and restriction of these movements in using the University of California Berkeley Laboratory orthosis, provided pressures in sole by the orthosis were increased. Therefore, this article describes the evaluation of modified foot orthosis with flexible structure in the management of individuals with flexible flat foot.Case description and method:The patient was a 21-year-old male who had symptomatic flat foot. The modified foot orthosis included movable surface and the outside structure. The modified foot orthosis was evaluated by standing foot X-ray, comfort rate, electromyography of leg muscle and vertical ground reaction force during walking.Findings and outcomes:The modified foot orthosis improved the foot alignment and decreased the symptoms of flat foot with more comfort. Subtalar position by sub-maximum supination had higher position than neutral in sagittal plane. It may increase the muscle activity of peroneus longus by 7% compared to barefoot, and there was a decrease of 11% ground reaction force in mid stance.Conclusion:The result of this single case evaluation only proposed the feasibility of this modified insole as the orthotic treatment in flexible flat foot.Clinical relevanceThe modified foot orthosis, which is mobile in the midfoot, is an orthosis for walking and standing in subjects with flexible flat foot.

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