Motor unit discharge rate following twitch potentiation in human triceps brachii muscle

Klein, Cliff S.; Ivanova, Tanya D.; Rice, Charles L.; Garland, S. Jayne

doi:10.1016/s0304-3940(01)02389-8

Cited by 52 publications

(75 citation statements)

References 10 publications

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“…This higher level of twitch potentiation at extended compared to more Xexed knee angles has been suggested to underlie the greater endurance time at extended compared to more Xexed knee angles (Place et al 2005). Potentiation of force production, while force output remains constant, is expected to lead to a lower increase in muscle activation; motor unit Wring rates may even decrease during constant force production (Klein et al 2001). A lower increase in the …”

Section: Muscle Activation Between Knee Anglesmentioning

confidence: 99%

“…However, potentiation, the enhancement of contractile response as a consequence of prior activation, has been suggested to contribute to the increased endurance at extended compared to Xexed knee angles (Place et al 2005) as potentiation is greater at short compared to long muscle length in rats (Rassier et al 1997;Rijkelijkhuizen et al 2005). Furthermore, potentiation may lead to a constant force output despite a decline in motor unit Wring rate (Klein et al 2001). Therefore, a muscle length-dependent potentiation could allow for a slower increase in muscle activation at extended compared to Xexed knee angles during constant force production.…”

Section: Introductionmentioning

confidence: 99%

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Knee extensor muscle oxygen consumption in relation to muscle activation

et al. 2006

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Recently, fatigability and muscle oxygen consumption (mVO 2 ) during sustained isometric contractions were found to be less at shorter (30° knee angle; 0°= full extension) compared to longer knee extensor muscle lengths (90°) and, at low torques, less in the rectus femoris (RF) muscle than in the vastus lateralis and medialis. In the present study we hypothesized that these Wndings could be accounted for by a knee angle-and a muscle-dependent activation respectively. On two experimental days rectiWed surface EMG (rsEMG) was obtained as a measure of muscle activation in nine healthy young males. In addition, on day 1 maximal torque capacity (MTC) was carefully determined using superimposed nerve stimulation on brief high intensity contractions (> 70%MVC) at 30, 60 and 90° knee angles. On day 2, subjects performed longer lasting isometric contractions (10-70%MTC) while mVO 2 was measured using near-infrared spectroscopy (NIRS). At 30°, maximal mVO 2 was reached signiWcantly later (11.0 s § 6.5 s) and was 57.9 § 8.3% less (average § SD, across intensities and muscles) than mVO 2 at 60 and 90° (p < 0.05). However, rsEMG was on average only 18.0 § 11.8% (p = 0.062) less at the start of the contraction at 30°. At 10%MTC at all knee angles, maximal mVO 2 of the RF occurred signiWcantly later (28.8 § 36.0 s) and showed a signiWcantly smaller increase in rsEMG compared to both vasti. In conclusion, it is unlikely that the tendency for less intense muscle activation could fully account for the »60% lower oxygen consumption at 30°, but the later increase in RFmVO 2 seemed to be caused by a less strong activation of the RF.

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Section: Muscle Activation Between Knee Anglesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Knee extensor muscle oxygen consumption in relation to muscle activation

et al. 2006

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“…The produced tension depends on the calcium sensitivity of the contractile apparatus and on the force produced per attached cross bridge. Modifications of the force produced by muscle fibers may require an adaptation of the muscle control strategies (11,28).…”

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confidence: 99%

Effect of temperature on spike-triggered average torque and electrophysiological properties of low-threshold motor units

Farina

Arendt-Nielsen²,

Graven‐Nielsen³

2005

Journal of Applied Physiology

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Farina, Dario, Lars Arendt-Nielsen, and Thomas GravenNielsen. Effect of temperature on spike-triggered average torque and electrophysiological properties of low-threshold motor units. J Appl Physiol 99: 197-203, 2005. First published March 10, 2005 doi:10.1152/japplphysiol.00059.2005.-The aim of the study was to jointly analyze temperature-induced changes in low-threshold single motor unit twitch torque and action potential properties. Joint torque, multichannel surface, and intramuscular electromyographic signals were recorded from the tibialis anterior muscle of 12 subjects who were instructed to identify the activity of a target motor unit using intramuscular electromyographic signals as feedback. The target motor unit was activated at the minimum stable discharge rate in seven 3-min-long contractions. The first three contractions (C1-C3) were performed at 33°C skin temperature. After 5 min, the subject performed three contractions at 33°C (T1), 39°C (T2), and 45°C (T3), followed by a contraction at 33°C (C4) skin temperature. Twitch torque and multichannel surface action potential of the target motor unit were obtained by spike-triggered averaging. Discharge rate (mean Ϯ SE, 7.1 Ϯ 0.5 pulses/s), interpulse interval variability (35.8 Ϯ 9.2%), and recruitment threshold (4.5 Ϯ 0.4% of the maximal voluntary torque) were not different among the seven contractions. None of the investigated variables were different among C1-C3, T1, and C4. Conduction velocity and peak twitch torque increased with temperature (P Ͻ 0.05; T1: 3.53 Ϯ 0.21 m/s and 0.82 Ϯ 0.23 mN ⅐ m, T2: 3.93 Ϯ 0.24 m/s and 1.17 Ϯ 0.36 mN ⅐ m, T3: 4.35 Ϯ 0.25 m/s and 1.46 Ϯ 0.40 mN ⅐ m, respectively). Twitch time to peak and surface action potential peak-to-peak amplitude were smaller in T3 (61.8 Ϯ 2.0 ms and 27.4 Ϯ 5.1 V, respectively) than in T1 (71.9 Ϯ 4.1 ms and 35.0 Ϯ 6.5 V, respectively) (P Ͻ 0.05). The relative increase in conduction velocity between T1 and T3 was positively correlated (P Ͻ 0.05) with the increase in twitch peak amplitude (r 2 ϭ 0.48), with the decrease in twitch time to peak (r 2 ϭ 0.43), and with the decrease in action potential amplitude (r 2 ϭ 0.50). In conclusion, temperature-induced modifications in fiber membrane conduction properties may have a direct effect on contractile motor unit properties. twitch torque; surface electromyogram; intramuscular electromyogram

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“…Baudry and Duchateau 8,16) showed changes in the adductor pollicis EMG during a ballistic contraction of 10-50% MVC in intensity after 100% MVC for 6 s. They found no EMG changes before and after this CC. Similarly, EMG changes were not found in the triceps brachii during 10-30% MVC after CC of 75% MVC for 5 s 12,13) . Further, no changes were found for the EMG of the tibialis anterior at the target force of 50% MVC after CC of 100% MVC for 10 s 11) .…”

Section: Discussionmentioning

confidence: 75%

“…Two studies found that the EMG activity did not change during constant sub-maximal contraction [11][12][13] , while another study reported force enhancement when subjects were asked to maintain a target EMG level 14) . These effects of PAP under sub-maximal contraction are controversial and few previous reports have demonstrated the EMG changes during low-level voluntary contraction after a conditioning contraction.…”

Section: Introductionmentioning

confidence: 99%

Changes in Electromyographic Activity after Conditioning Contraction

et al. 2012

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Abstract.[Purpose] Post-activation potentiation is the increase in muscle twitch force in response to electrical stimulation after a conditioning contraction (CC) of maximum or near-maximum intensity. It is controversial whether muscular force during low-level voluntary contractions increases after maximum contraction. This study investigated the changes in electromyographic activity after CC. [Subjects and Methods] Fifteen healthy adults participated in this study. In the first experiment, a supramaximal electrical pulse was applied to the tibial nerve, and the isometric twitch force of plantar flexion was measured. After maximum voluntary contraction (MVC), i.e., CC, the twitch force elicited by electrical stimulation was monitored. In the second experiment, the surface electromyogram were recorded at an intensity of 20% MVC before and after CC. [Results] Results indicated the twitch force significantly increased by 30% within 30 s after CC. In the second experiment, the electromyographic activity significantly decreased by 16% for the gastrocnemius muscle but did not change for the soleus. Correlation coefficients between changes in the twitch force and electromyographic activity at 20%MVC were −0.54 for the gastrocnemius muscle and 0.04 for the soleus muscle.[Conclusion] Post-activation potentiation might work for daily physical activities compensating for reduced force output of the fatigued muscle.

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Motor unit discharge rate following twitch potentiation in human triceps brachii muscle

Cited by 52 publications

References 10 publications

Knee extensor muscle oxygen consumption in relation to muscle activation

Knee extensor muscle oxygen consumption in relation to muscle activation

Effect of temperature on spike-triggered average torque and electrophysiological properties of low-threshold motor units

Changes in Electromyographic Activity after Conditioning Contraction

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