Changes in muscle fascicles of tibialis anterior during anisometric contractions are not associated with motor-output variability of the ankle dorsiflexors in young and old adults

Jesunathadas, Mark; Rudroff, Thorsten; Enoka, Roger M.

doi:10.1007/s00421-010-1606-4

Cited by 6 publications

(3 citation statements)

References 55 publications

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“…This length specifi city to the steadiness of torque application could be in accordance with a previous study showing that the fl uctuations in net torque are increased with modulations in activation strategy of agonist muscles that are induced with altered muscle length [ 29 ] . However, this seems in disagreement with another recent study demonstrating that changes in fascicle length in the tibialis anterior are not associated with variability during anisometric actions [ 18 ] . A possible explanation for the observed diff erences in torque variability could be related to diff erences in the architectural characteristics between the 2 antagonistic muscles.…”

Section: Muscular Lengthcontrasting

confidence: 94%

Wrist Flexors are Steadier than Extensors

Salonikidis¹,

Amiridis²,

Oxyzoglou³

et al. 2011

Int J Sports Med

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To examine torque variability in 2 antagonistic muscles 20 individuals performed maximal and submaximal (5, 10, 20, 50 and 75% of Maximal Voluntary Contraction, MVC) isometric wrist flexions and extensions (5 s) at 5 different angles (230, 210, 180, 150 and 130°). The EMG activity of Flexor Carpi Ulnaris (FCU) and Extensor Digitorum (ED) was recorded and quantified as the integral of EMG. Participants showed higher maximal isometric torque (32.43±11.17 vs. 17.41±3.84 Nm) and lower coefficient of variability during wrist flexion compared to extension. The normalized agonist EMG increased across higher levels of torque for both wrist muscles. Interestingly, the coactivation of ED during wrist flexion was greater compared to the coactivation of FCU during wrist extension at 50 and 75% of MVC, regardless of wrist angle (f.e.: at 180° and 75% of MVC the normalised EMG of ED as antagonist was 14.84±5.18% vs. 9.33±6.94 of the FCU). It is concluded that a stronger isometric wrist flexion is more steadily produced, with greater coactivation compared to a weaker wrist extension, independently from muscle length and torque level. Even if the relative contribution of antagonists to the resultant torque is to be considered, altered activation patterns responsible for differences in force fluctuations could be suggested.

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Section: Muscular Lengthcontrasting

confidence: 94%

Wrist Flexors are Steadier than Extensors

Salonikidis¹,

Amiridis²,

Oxyzoglou³

et al. 2011

Int J Sports Med

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show abstract

“…Changes to sEMG can be due to many different reasons such as skin-electrode contact, subcutaneous thickness, neural drive to the muscle and muscle properties. Age-related increase in the sEMG's amplitude can be attributed to a number of factors: (i) increased antagonistic co-activation [10,36], (ii) motor unit remodelling [10,36] and (iii) change in muscle architecture [16,20,21,37,38]. We have considered the effect of each of these below.…”

Section: Differential Age-related Changes In the Ta And Ts Semgmentioning

confidence: 99%

“…The muscles investigated are all pennate and have short fibre lengths [47], with the TS muscles having higher pennation angle and shorter fibres than TA [47]. The pennation angles of TS are known to decrease with age [20], while the angle for TA does not change [37]. Modelling has shown that increased pennation angle would increase the nonpropagating components of sEMG [48], and thus broaden the power spectrum and decrease the P M [49].…”

Section: Change In Muscle Architecturementioning

confidence: 99%

Difference in age-related changes in surface electromyogram of tibialis anterior and triceps surae

Siddiqi¹,

Arjunan²,

Kumar³

2016

Biomed. Phys. Eng. Express

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We have investigated the dissimilarity between age-associated changes of surface electromyogram (sEMG) of tibialis anterior (TA) and triceps surae (TS) muscles. Thirty-six participants from two cohorts with equal representation of younger (20-30 years) and older (60-85 years) cohorts performed isometric dorsi and plantar-flexion at 30% maximal voluntary contraction and their surface electromyograms (sEMG) of TA and TS were recorded. The maximal power spectral density (P M ) was computed for the recordings and an analysis of variance statistical test was performed with age and muscle as factors (α=0.05). The results show that age-associated change of P M was significantly higher for TA compared with TS muscles. This could be attributed to soleus which has been earlier found to have smaller age-related changes. The study highlights the need to consider the disproportionate age-associated changes in sEMG of the two muscles while examining the muscle strength of the elderly.

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Computational model to investigate the relative contributions of different neuromuscular properties of tibialis anterior on force generated during ankle dorsiflexion

Siddiqi

Arjunan

Kumar

2018

Med Biol Eng Comput

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This study describes a new model of the force generated by tibialis anterior muscle with three new features: single-fiber action potential, twitch force, and pennation angle. This model was used to investigate the relative effects and interaction of ten age-associated neuromuscular parameters. Regression analysis (significance level of 0.05) between the neuromuscular properties and corresponding simulated force produced at the footplate was performed. Standardized slope coefficients were computed to rank the effect of the parameters. The results show that reduction in the average firing rate is the reason for the sharp decline in the force and other factors, such as number of muscle fibers, specific force, pennation angle, and innervation ratio. The fast fiber ratio affects the simulated force through two significant interactions. This study has ranked the individual contributions of the neuromuscular factors to muscle strength decline of the TA and identified firing rate decline as the biggest cause followed by decrease in muscle fiber number and specific force. The strategy for strength preservation for the elderly should focus on improving firing rate. Graphical abstract Neuromuscular properties of Tibialis Anterior on force generated during ankle dorsiflexion.

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Changes in muscle fascicles of tibialis anterior during anisometric contractions are not associated with motor-output variability of the ankle dorsiflexors in young and old adults

Cited by 6 publications

References 55 publications

Wrist Flexors are Steadier than Extensors

Wrist Flexors are Steadier than Extensors

Difference in age-related changes in surface electromyogram of tibialis anterior and triceps surae

Computational model to investigate the relative contributions of different neuromuscular properties of tibialis anterior on force generated during ankle dorsiflexion

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