Effects of repetitive dynamic contractions upon electromechanical delay

Gabriel, David A.; Boucher, Jean

doi:10.1007/s004210050470

Cited by 31 publications

(16 citation statements)

References 17 publications

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“…As indicated by our definitions of L on and L off , we assumed an electromechanical delay of 25ms when we calculated active shortening and active lengthening. We are not aware of studies done on the ILPO to confirm this assumption, but this time period falls within values measured for other muscles (Cavanagh and Komi, 1979;Moritani et al, 1987;Winter and Brookes, 1991;Zhou et al, 1995;Gabriel and Boucher, 1998;Muraoka et al, 2004;Roberts and Gabaldon, 2008). The equation used to calculate a given length change was dependent on the timing of L on and L off relative to other lengths measured during a stride.…”

Section: Length and Velocity Changesmentioning

confidence: 55%

Differential segmental strain during active lengthening in a large biarticular thigh muscle during running

Carr

Ellerby

Marsh

2011

Journal of Experimental Biology

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SUMMARYThe iliotibialis lateralis pars postacetabularis (ILPO) is the largest muscle in the hindlimb of the guinea fowl and is thought to play an important role during the stance phase of running, both absorbing and producing work. Using sonomicrometry and electromyography, we examined whether the ILPO experiences differential strain between proximal, central and distal portions of the posterior fascicles. When the ILPO is being lengthened while active, the distal portion was found to lengthen significantly more than either the proximal or central portions of the muscle. Our data support the hypothesis that the distal segment lengthened farther and faster because it began activity at shorter sarcomere lengths on the ascending limb of the length-tension curve. Probably because of the self-stabilizing effects of operating on the ascending limb of the length-tension curve, all segments reached the end of lengthening and started shortening at the same sarcomere length. During shortening, this similarity in sarcomere length among the segments was maintained, as predicted from force-velocity effects, and shortening strain was similar in all segments. The differential active strain during active lengthening is thus ultimately determined by differences in strain during the passive portion of the cycle. The sarcomere lengths of all segments of the fascicles were similar at the end of active shortening, but after the passive portion of the cycle the distal segment was shorter. Differential strain in the segments during the passive portion of the cycle may be caused by differential joint excursions at the knee and hip acting on the ends of the muscle and being transmitted differentially by the passive visco-elastic properties of the muscle. Alternatively, the differential passive strain could be due to the action of active or passive muscles in the thigh that transmit force to the IPLO in shear. Based on basic sarcomere dynamics we predict that differential strain is more likely to occur in muscles undergoing active lengthening at the beginning of contraction than those undergoing only shortening.

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Section: Length and Velocity Changesmentioning

confidence: 55%

Differential segmental strain during active lengthening in a large biarticular thigh muscle during running

Carr

Ellerby

Marsh

2011

Journal of Experimental Biology

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“…This change was also associated with a significant training-related reduction in voluntary EMD associated with repeated testing. This reduction in voluntary EMG but “not” evoked EMG, and highlights the change in neural control (Gabriel and Boucher 1998). We suggest that the greater Q 30 and reduction in voluntary EMD for females were associated with a different motor unit activity pattern at the onset of muscle contraction.…”

Section: Discussionmentioning

confidence: 76%

Neural, biomechanical, and physiological factors involved in sex-related differences in the maximal rate of isometric torque development

2016

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ObjectiveRecent research has reported that lower maximal rate of torque development (dτ/dt max) exhibited by females, relative to males, during knee extension can be accounted for by normalization to a maximal voluntary contraction (MVC); however, this was not seen in the upper limb.PurposeThe aim of the current work was to examine the contribution of maximum strength (τmax), twitch contraction time (CT), muscle fiber condition velocity (MFCV), and rate of muscle activation (Q30) to sex-differences in the dτ/dt max during maximal isometric dorsiflexion.MethodsThirty-eight participants (20 males; 18 females) performed both maximal voluntary and evoked isometric contractions of the tibialis anterior across 3 days. Ten maximal compound muscle action potentials were elicited and subsequently followed by three, 5-s contractions. From the recordings, MFCV, dτ/dt max, τmax, CT, electromechanical delay (EMD), root-mean squared (RMS) amplitude, peak-to-peak voltage (Vpp), and Q30 were calculated.ResultsAn ANCOVA showed that τmax accounted for all the sex-differences in dτ/dt max (p = 0.96). There were no significant differences between groups with respect to MFCV, RMS amplitude, Vpp amplitude, or CT. However, there was a significant sex-difference in dτ/dt max, τmax, and Q30. Females had longer evoked EMD times compared with males (15.69 ± 10.57 ms versus 9.95 ± 3.46 ms; p = 0.01), but the voluntary EMD times were not different.ConclusionThe current research supports the work by Hannah et al. Exp Physiol 97:618–629, (2012) that normalization to MVC in the quadriceps is able to account for all sex-differences in rate of toque development in the lower limb.

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“…EMD appears to be strongly dependent on the magnitude of the reflex response [10], [18], [54], [57], [58] and [63]. Time delays in force production have been shown to decrease with increasing contractions intensity (%MVIC) [58] and [63] and reflex stimulus intensity [63], and to be correlated with rate of force development [54] and absolute force production [57].…”

Section: Introductionmentioning

confidence: 99%

“…Although EMD has been defined and measured in many ways, 'true' EMD is described as the time delay from the earliest onset of EMG activity to the initial onset of force generation [64]. Thus, EMD represents that portion of movement where activation of the motor units and shortening of the series elastic component is occurring [8], [18], [59] and [66]. Of the many physiological processes that are thought to account for this mechanical delay [8], the time needed to stretch the series elastic component is thought to be the primary factor [8], [43], [54] and [63].…”

Section: Introductionmentioning

confidence: 99%

The differential effects of fatigue on reflex response timing and amplitude in males and females

Moore

Drouin

Gansneder

et al. 2002

Journal of Electromyography and Kinesiology

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SJ. The differential effects of fatigue on reflex response timing and amplitude in males and females. Journal of Electromyography and Kinesiology. 2002; 12:351-360 Abstract:We examined the effects of fatigue on patellar tendon reflex responses in males and females. A spring-loaded reflex hammer elicited a standardized tendon tap with the knee positioned in an isokinetic dynamometer and flexed to 85°. We recorded vastus lateralis activity (SEMG) and knee extension force production at the distal tibia (force transducer). Reflex trials were performed before and after (immediate, 2, 4, and 6 min) an isokinetic fatigue protocol to 50% MVC (90°/s). For each event, pre-motor time (PMT), electromechanical delay (EMD), and total motor time (TMT) were obtained, as well as EMG amplitude (EMGamp), time to peak EMG (EMGtpk), peak force amplitude (Famp), time to peak force (Ftpk), EMG:force ratio (E:F), and rate of force production (Frate=N/ms). TMT increased significantly in females following fatigue, while males showed no change. The increased TMT was due to an increased EMD with fatigue, while PMT was unaffected. EMGamp and Famp were somewhat diminished in females yet significantly augmented in males following fatigue, likely accounting for the differential changes in EMD noted. Results suggest males and females may respond differently to isokinetic fatigue, with males having a greater capacity to compensate for contraction force failure when responding to mechanical perturbations.

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Effects of repetitive dynamic contractions upon electromechanical delay

Cited by 31 publications

References 17 publications

Differential segmental strain during active lengthening in a large biarticular thigh muscle during running

Differential segmental strain during active lengthening in a large biarticular thigh muscle during running

Neural, biomechanical, and physiological factors involved in sex-related differences in the maximal rate of isometric torque development

The differential effects of fatigue on reflex response timing and amplitude in males and females

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