Analysis of Physiological Signals of Individuals with Eyes Closed Subjected to Unexpected Direction-Specific Stimuli Causing Instability

Research regarding the cerebral cortex and muscle activity patterns of the body used for postural balance control when sudden instability stimuli occur is lacking. This study analyzed individuals' physiological signals when direction-specific instability stimuli were applied while their eyes were closed. Healthy adults in their 20s maintained their postural balance while looking at the center of gravity provided by a monitor with a three-dimensional dynamic postural balance training system. We performed electroencephalography (EEG) and measured trunk and lower extremity muscle activity of participants with their eyes closed when subjected to four direction-specific instability stimuli (anterior, posterior, left, and right). EEG results showed that gamma waves increased significantly with an unbalanced stimulus when the participant's eyes were open and closed. The increased gamma wave rate with eyes closed was low in the exercise planning area, where information is relatively integrated and exercise is planned without visual information. EMG results showed fewer gamma waves on EEG due to the low focus on postural control because participants could not observe the center of gravity, which is the basis for balance. The trunk and lower extremity muscles tended to be used more due to the larger body perturbation angle. These outcomes can be used as basic data regarding how the human brain and muscles maintain postural balance when an unexpected external instability stimulus occurs. Quantitative postural balance rehabilitation training protocols for the elderly and those with disabilities can be created based on these outcomes.

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Lower-Extremity Muscle Activity During Aquatic and Land Treadmill Running at the Same Speeds

Journal of Sport Rehabilitation ◽

10.1123/jsr.2013-0003 ◽

2014 ◽

Vol 23 (2) ◽

pp. 107-122 ◽

Cited By ~ 5

Author(s):

W. Matthew Silvers ◽

Eadric Bressel ◽

D. Clark Dickin ◽

Garry Killgore ◽

Dennis G. Dolny

Keyword(s):

Lower Extremity ◽

Outcome Measures ◽

Muscle Activity ◽

Tibialis Anterior ◽

Rectus Femoris ◽

Biceps Femoris ◽

Swing Phase ◽

Treadmill Running ◽

Vastus Medialis ◽

Lower Extremity Muscle

Context:Muscle activation during aquatic treadmill (ATM) running has not been examined, despite similar investigations for other modes of aquatic locomotion and increased interest in ATM running.Objectives:The objectives of this study were to compare normalized (percentage of maximal voluntary contraction; %MVC), absolute duration (aDUR), and total (tACT) lower-extremity muscle activity during land treadmill (TM) and ATM running at the same speeds.Design:Exploratory, quasi-experimental, crossover design.Setting:Athletic training facility.Participants:12 healthy recreational runners (age = 25.8 ± 5 y, height = 178.4 ± 8.2 cm, mass = 71.5 ± 11.5 kg, running experience = 8.2 ± 5.3 y) volunteered for participation.Intervention:All participants performed TM and ATM running at 174.4, 201.2, and 228.0 m/min while surface electromyographic data were collected from the vastus medialis, rectus femoris, gastrocnemius, tibialis anterior, and biceps femoris.Main Outcome Measures:For each muscle, a 2 × 3 repeated-measures ANOVA was used to analyze the main effects and environment–speed interaction (P ≤ .05) of each dependent variable: %MVC, aDUR, and tACT.Results:Compared with TM, ATM elicited significantly reduced %MVC (−44.0%) but increased aDUR (+213.1%) and tACT (+41.9%) in the vastus medialis, increased %MVC (+48.7%) and aDUR (+128.1%) in the rectus femoris during swing phase, reduced %MVC (−26.9%) and tACT (−40.1%) in the gastrocnemius, increased aDUR (+33.1%) and tACT (+35.7%) in the tibialis anterior, and increased aDUR (+41.3%) and tACT (+29.2%) in the biceps femoris. At faster running speeds, there were significant increases in tibialis anterior %MVC (+8.6−15.2%) and tACT (+12.7−17.0%) and rectus femoris %MVC (12.1−26.6%; swing phase).Conclusion:No significant environment–speed interaction effects suggested that observed muscle-activity differences between ATM and TM were due to environmental variation, ie, buoyancy (presumed to decrease %MVC) and drag forces (presumed to increase aDUR and tACT) in the water.

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Role of Occupational Footwear and Prolonged Walking on Lower Extremity Muscle Activation during Maximal Exertions and Postural Stability Tasks

Biomechanics ◽

10.3390/biomechanics1020017 ◽

2021 ◽

Vol 1 (2) ◽

pp. 202-213

Author(s):

Harish Chander ◽

Sachini N. K. Kodithuwakku Arachchige ◽

Alana J. Turner ◽

Reuben F. Burch V ◽

Adam C. Knight ◽

...

Keyword(s):

Lower Extremity ◽

Muscle Activity ◽

Repeated Measures ◽

Postural Stability ◽

Muscle Activation ◽

Medial Gastrocnemius ◽

Lower Extremity Muscle ◽

Prolonged Duration ◽

The Mean ◽

The Impact

Background: Occupational footwear and a prolonged duration of walking have been previously reported to play a role in maintaining postural stability. The purpose of this paper was to analyze the impact of three types of occupational footwear: the steel-toed work boot (ST), the tactical work boot (TB), and the low-top work shoe (LT) on previously unreported lower extremity muscle activity during postural stability tasks. Methods: Electromyography (EMG) muscle activity was measured from four lower extremity muscles (vastus medialis (VM), medial hamstrings (MH), tibialis anterior (TA), and medial gastrocnemius (MG) during maximal voluntary isometric contractions (MVIC) and during a sensory organization test (SOT) every 30 min over a 4 h simulated workload while wearing ST, TB, and LT footwear. The mean MVIC and the mean and percentage MVIC during each SOT condition from each muscle was analyzed individually using a repeated measures ANOVA at an alpha level of 0.05. Results: Significant differences (p < 0.05) were found for maximal exertions, but this was limited to only the time main effect. No significant differences existed for EMG measures during the SOT. Conclusion: The findings suggest that occupational footwear type does not influence lower extremity muscle activity during both MVIC and SOT. Significantly lower muscle activity during maximal exertions over the course of the 4 h workload was evident, which can be attributed to localized muscular fatigue, but this was not sufficient to impact muscle activity during postural stability tasks.

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Do Single-Leg Balance Control and Lower Extremity Muscle Strength Correlate with Ankle Instability and Leg Injuries in Young Ballet Dancers?

Journal of Dance Medicine & Science ◽

10.12678/1089-313x.061521f ◽

2021 ◽

Author(s):

You-jou Hung ◽

Jenna Boehm ◽

Morgan Reynolds ◽

Kallee Whitehead ◽

Kaylyn Leland

Keyword(s):

Muscle Strength ◽

Lower Extremity ◽

Ankle Instability ◽

Balance Control ◽

Functional Ankle Instability ◽

Lower Extremity Injuries ◽

Ballet Dancers ◽

Leg Injuries ◽

Lower Extremity Muscle ◽

Extremity Injuries

Ankle injuries are common among young ballet dancers. These injuries may be attributed to ankle instability, insufficient lower extremity strength, and poor balance control. The purpose of this study was to explore whether these dancers exhibit functional ankle instability and if their single-leg balance control and lower extremity muscle strength correlate with functional ankle instability and leg injuries. Twenty-one ballet dancers (aged 10 to 17 years) participated in the study. The Cumberland Ankle Instability Tool (CAIT) questionnaire was used to examine functional ankle stability. Isometric muscle strength of the major lower extremity muscles was measured with a digital hand-held dynamometer. Single-leg balance was evaluated with the Y-Balance Test (YBT) and three Athletic Single-leg Stability Test (ASLST) protocols. Lower extremity injuries (self-reported) within 6 months after testing were recorded for correlation analyses. Both dominant and non-dominant ankles of the subjects exhibited functional ankle instability (26.71 and 25.71, respectively). Raising the center of mass (passé and first arm position) during the ASLST did not significantly affect balance performance (p = 0.104). However, removing extrinsic visual feedback significantly decreased single-leg balance (p < 0.001). In general, there was low correlation (r ≤ 0.49) between muscle strength, CAIT, YBT, and ASLST scores with lower extremity injuries. It is concluded that for young ballet dancers lower extremity muscle strength and single-leg balance control may not be strong contributing factors to leg injuries. This study also suggests that functional ankle stability may not have a direct impact on single-leg balance, and ballet dancers rely heavily on extrinsic visual feedback for single-leg balance control. Teachers might consider minimizing extrinsic feedback to challenge ballet dancers when implementing training protocols for single-leg balance control.

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