Effects of amplitude and predictability of perturbations to the arm on anticipatory and reactionary muscle responses to maintain balance

Forghani, Ali; Preuss, Richard; Milner, Theodore E.

doi:10.1016/j.jelekin.2017.05.006

Cited by 13 publications

(9 citation statements)

References 25 publications

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“…Effects of perturbation predictability have been studied with respect to two characteristics, magnitude of the perturbation (Toussaint et al 1998; Habib Perez et al 2016; Forghani et al 2017a,b) and its direction (Gilles et al 1998; Piscitelli et al 2017). No systematic effects of perturbation direction uncertainty on the latency and rate of increase of ground reaction forces were reported in a study with lateral body perturbations (Gilles et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Stability of vertical posture explored with unexpected mechanical perturbations: synergy indices and motor equivalence

2018

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We explored the relations between indices of mechanical stability of vertical posture and synergy indices under unexpected perturbations. The main hypotheses predicted higher posture-stabilizing synergy indices and higher mechanical indices of center of pressure stability during perturbations perceived by subjects as less challenging. Healthy subjects stood on a force platform and held in fully extended arms a bar attached to two loads acting downward and upward. One of the loads was unexpectedly released by the experimenter causing a postural perturbations. In different series, subjects either knew or did not know which of the two loads would be released. Forward perturbations were perceived as more challenging and accompanied by co-activation patterns among the main agonist-antagonist pairs. Backward perturbation led to reciprocal muscle activation patterns and was accompanied by indices of mechanical stability and of posture-stabilizing synergy which indicated higher stability. Changes in synergy indices were observed as early as 50-100 ms following the perturbation reflecting involuntary mechanisms. In contrast, predictability of perturbation direction had weak or no effect on mechanical and synergy indices of stability. These observations are interpreted within a hierarchical scheme of synergic control of motor tasks and a hypothesis on the control of movements with shifts of referent coordinates. The findings show direct correspondence between stability indices based on mechanics and on the analysis of multi-muscle synergies. They suggest that involuntary posture-stabilizing mechanisms show synergic organization. They also show that predictability of perturbation direction has strong effects on anticipatory postural adjustment but not corrective adjustments. We offer an interpretation of co-activation patterns that questions their contribution to postural stability.

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Section: Introductionmentioning

confidence: 99%

Stability of vertical posture explored with unexpected mechanical perturbations: synergy indices and motor equivalence

2018

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“…This contact may provide proprioceptive input and biofeedback. In some surface EMG studies, proprioceptive input and biofeedback increase muscle activation have been reported (24,25). However, in order to be performed CTAR exercise, a sufficient upper extremity function is needed to keep the ball under the jaw.…”

Section: Discussionmentioning

confidence: 99%

A Comparison of Activation Effects of Three Different Exercises on Suprahyoid Muscles in Healthy Subjects

Kılınç¹,

Yaşaroğlu²,

Arslan³

et al. 2019

Türk Fizyoterapi Ve Rehabilitasyon Dergisi

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Purpose:The most crucial airway protection mechanism during swallowing is adequate laryngeal elevation. Suprahyoid muscles are responsible for laryngeal elevation. Our study aimed to compare the effects of three different exercises, Shaker, resistance chin tuck (CTAR) exercise, and chin tuck exercise with theraband, on suprahyoid muscles activity responsible for laryngeal elevation.Methods: Forty-two healthy subjects with a mean age of 27.92±5.02 years (18-40 years), of which 50% were male were included. All individuals were divided into three groups with computerized randomization. Surface Electromyography (EMG) evaluation was performed to determine electrical activity of the suprahyoid muscles (geniohyoid, mylohyoid, anterior belly of digastric, thyrohyoid, stylohyoid muscles) during maximal voluntary isometric contraction and during performing CTAR, Shaker exercise and chin tuck with theraband. Normalized suprahyoid muscle activations were calculated as the recorded maximum electrical activity during exercise (mV)/recorded maximum electrical activity during maximum isometric contraction (mV).Results: A statistically significant difference was found between three groups regarding normalized suprahyoid muscle activation (p<0.001). The difference between the three groups was caused by the difference between CTAR and Shaker (p<0.001) and between CTAR and theraband (p=0.040) in favor of CTAR. No difference was found between Shaker and theraband (p=0.104). Conclusion:Primarily CTAR exercise should be included in rehabilitation to increase the suprahyoid muscle activation. In addition, chin tuck exercise with theraband can also be considered as an alternative to CTAR.Amaç: Yutma esnasında en önemli havayolu koruması, yeterli laringeal elevasyondur. Laringeal elevasyondan suprahyoid kaslar sorumludur. Çalışmamızın amacı, üç farklı egzersizin; Shaker, dirençli chin tuck (CTAR) egzersizi ve theraband ile yapılan chin tuck egzersizlerin laringeal elevasyondan sorumlu olan suprahyoid kaslarının aktivasyonu üzerine etkilerini karşılaştırmaktı.Yöntem: Yaş ortalaması 27,92±5,02 yıl (18-40 yıl), % 50'si erkek olmak üzere 42 sağlıklı gönüllü çalışmaya dahil edildi. Maksimum istemli izometrik kontraksiyon ve CTAR, Shaker ve theraband ile chin tuck egzersizleri sırasında suprahyoid kasların elektriksel aktivitelerini belirlemek için yüzeyel elektromyografi (EMG) değerlendirilmesi yapıldı. Normalize edilmiş suprahyoid kas aktivasyonları: egzersiz esnasında kaydedilen maksimum elektriksel aktivite (mV)/maksimum izometrik kontraksiyon esnasında kaydedilen maksimum elektriksel aktivite (mV) formülü ile hesaplandı.Sonuçlar: Üç grup arasında normalize edilmiş suprahyoid kas aktivasyonları açısından istatistiksel olarak anlamlı bir fark bulundu (p<0,001). Bu farkın CTAR grubu lehine, CTAR ile Shaker (p<0,001) ve CTAR ile Theraband grupları (p=0,040) arasındaki farklardan kaynaklandığı görüldü. Theraband ve Shaker arasında istatistiksel olarak anlamlı bir fark bulunamadı.Tartışma: Suprahyoid kas aktivasyonunu artırmak için CTAR egzersiz...

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“…In that study, we also showed that the latency difference between the earliest changes in body kinematics and kinetics induced by the perturbation and the response in ankle muscles was not affected by stance width. By varying the amplitude of the perturbation we confirmed that the postural responses to arm perturbations scaled with the magnitude of the perturbation without altering their temporal organization [ 12 ]. From the results of these studies we determined that the rapid response in ankle muscles could not be triggered by signals from sensory receptors in leg muscles or cutaneous receptors in the foot because the ankle did not begin to move and ground reaction force did not begin to change until after the onset of ankle muscle activation.…”

Section: Introductionmentioning

confidence: 87%

“…Subjects subsequently performed the task under several other conditions during the same session. The analysis and results of the subsequent conditions have been presented in previous studies [ 10 – 12 ] cited in the Introduction.…”

Section: Methodsmentioning

confidence: 99%

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Origin of directionally tuned responses in lower limb muscles to unpredictable upper limb disturbances

Forghani

Milner

2017

PLoS ONE

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Unpredictable forces which perturb balance are frequently applied to the body through interaction between the upper limb and the environment. Lower limb muscles respond rapidly to these postural disturbances in a highly specific manner. We have shown that the muscle activation patterns of lower limb muscles are organized in a direction specific manner which changes with lower limb stability. Ankle muscles change their activity within 80 ms of the onset of a force perturbation applied to the hand which is earlier than the onset of changes in ground reaction force, ankle angle or head motion. The latency of the response is sensitive to the perturbation direction. However, neither the latency nor the magnitude of the response is affected by stiffening the arm even though this alters the magnitude and timing of motion of the body segments. Based on the short latency, insensitivity of the change in ankle muscle activation to motion of the body segments but sensitivity to perturbation direction we reason that changes in ankle muscle activation are most likely triggered by sensory signals originating from cutaneous receptors in the hand. Furthermore, evidence that the latency of changes in ankle muscle activation depends on the number of perturbation directions suggests that the neural pathway is not confined to the spinal cord.

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Effects of amplitude and predictability of perturbations to the arm on anticipatory and reactionary muscle responses to maintain balance

Cited by 13 publications

References 25 publications

Stability of vertical posture explored with unexpected mechanical perturbations: synergy indices and motor equivalence

Stability of vertical posture explored with unexpected mechanical perturbations: synergy indices and motor equivalence

A Comparison of Activation Effects of Three Different Exercises on Suprahyoid Muscles in Healthy Subjects

Origin of directionally tuned responses in lower limb muscles to unpredictable upper limb disturbances

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