Morpho-functional response of the elbow extensor muscles to twelve-week self-perceived maximal resistance training

The purpose of this study was to examine the effects of different contraction times and delay times prior to a positioning task. While blindfolded, each of 25 subjects learned to produce elbow-extension movements to a short and a long target using a kinesthesiometer. The subject then produced 30 trials without feedback to each target. These control trials were preceded by a foreperiod of 0-, 3-, or 6-sec. delay. The 60 experimental trials were identical to control trials except the subject isometrically contracted elbow extensor muscles for 3 or 6 sec. prior to each trial. Following each isometric contraction the subject delayed movement for 0, 3, or 6 sec. The 3-sec. and 6-sec. prepositioning contractions produced greater undershooting and variability than no prepositioning contractions, and the 0-sec. delay produced less constant error than either the 3- or 6-sec. delay. It was concluded that following isometric contraction, undershooting a target occurred and this effect did not dissipate within a 6-sec. period.

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Effects of fatigue of elbow extensor muscles voluntarily induced and induced by electromyostimulation on multi-joint movement organization

Neuroscience Letters ◽

10.1016/j.neulet.2006.04.025 ◽

2006 ◽

Vol 403 (1-2) ◽

pp. 109-113 ◽

Cited By ~ 11

Author(s):

Anne-Fabienne Huffenus ◽

Nicolas Forestier

Keyword(s):

Joint Movement ◽

Movement Organization ◽

Extensor Muscles ◽

Elbow Extensor

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The synergy of elbow extensor muscles during dynamic work in man

European Journal of Applied Physiology and Occupational Physiology ◽

10.1007/bf00421625 ◽

1980 ◽

Vol 44 (3) ◽

pp. 255-269 ◽

Cited By ~ 32

Author(s):

S. Le Bozec ◽

B. Maton ◽

J. C. Cnockaert

Keyword(s):

Dynamic Work ◽

Extensor Muscles ◽

Elbow Extensor

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The effects of isometric resistance training on stretch reflex induced tremor in the knee extensor muscles

Journal of Applied Physiology ◽

10.1152/japplphysiol.00917.2011 ◽

2013 ◽

Vol 114 (12) ◽

pp. 1647-1656 ◽

Cited By ~ 8

Author(s):

Rade Durbaba ◽

Angela Cassidy ◽

Francesco Budini ◽

Andrea Macaluso

Keyword(s):

Resistance Training ◽

High Intensity ◽

Stretch Reflex ◽

Knee Extensor ◽

Training Group ◽

Control Group ◽

Force Matching ◽

Level Of Activity ◽

Extensor Muscles ◽

Knee Extensor Muscles

This study examines the effect of 4 wk of high-intensity isometric resistance training on induced tremor in knee extensor muscles. Fourteen healthy volunteers were assigned to either the training group ( n = 7) or the nontraining control group ( n = 7). Induced tremor was assessed by measuring force fluctuations during anisometric contractions against spring loading, whose compliance was varied to allow for preferential activation of the short or long latency stretch reflex components. Effects of high-intensity isometric resistance training on induced tremor was assessed under two contraction conditions: relative force matching, where the relative level of activity was equal for both pre- and post-training sessions, set at 30% maximum voluntary contraction (MVC), and absolute force matching, where the level of activity was set to 30% pretrained MVC. The training group experienced a 26.5% increase in MVC in contrast to the 0.8% for the control group. For relative force-matching contractions, induced tremor amplitude and frequency did not change in either the training or control group. During absolute force-matching contractions, induced tremor amplitude was decreased by 37.5% and 31.6% for the short and long components, respectively, with no accompanying change in frequency, for the training group. No change in either measure was observed in the control group for absolute force-matching contractions. The results are consistent with high-intensity isometric resistance training induced neural changes leading to increased strength, coupled with realignment of stretch reflex automatic gain compensation to the new maximal force output. Also, previous reported reductions in anisometric tremor following strength training may partly be due to changed stretch reflex behavior.

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Moment distribution among human elbow extensor muscles during isometric and submaximal extension

Journal of Biomechanics ◽

10.1016/s0021-9290(99)00157-8 ◽

2000 ◽

Vol 33 (2) ◽

pp. 145-154 ◽

Cited By ~ 27

Author(s):

Li-Qun Zhang ◽

Gordon W. Nuber

Keyword(s):

Moment Distribution ◽

Extensor Muscles ◽

Elbow Extensor

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Reflex and Intrinsic Changes Induced by Fatigue of Human Elbow Extensor Muscles

Journal of Neurophysiology ◽

10.1152/jn.2001.86.3.1086 ◽

2001 ◽

Vol 86 (3) ◽

pp. 1086-1094 ◽

Cited By ~ 54

Author(s):

Li-Qun Zhang ◽

W. Zev Rymer

Keyword(s):

Small Amplitude ◽

Joint Stiffness ◽

Rest Period ◽

Equation Model ◽

Joint Torque ◽

Intracellular Acidosis ◽

Extensor Muscles ◽

Reflex Gain ◽

Intrinsic Stiffness ◽

Elbow Extensor

Fatigue-induced changes in intrinsic and reflex properties of human elbow extensor muscles and the underlying mechanisms for fatigue compensation were investigated. The elbow joint was perturbed using small-amplitude and pseudorandom movement patterns while subjects maintained steady levels of mean joint extension torque. Intrinsic and reflex properties were identified simultaneously using a nonlinear delay differential equation model. Intrinsic joint properties were characterized by measures of joint stiffness, viscous damping, and limb inertia and reflex properties characterized by measures of dynamic and static reflex gains. Fatigue was induced using 15 min of intermittent voluntary isometric (submaximal) exercise, and a rest period of 10 min was taken to allow the fatigued muscles torecover from acute fatigue effects. Identical experimental and data analysis procedures were used before and after fatigue. Our findings were that after fatigue, joint stiffness was significantly reduced at higher torque levels, presumably reflecting the reduced force-generating capacity of fatigued muscles. Conversely, joint viscosity was increased after fatigue potentially because of the reduced crossbridge detachment rate and prolonged relaxation associated with intracellular acidosis accompanying fatigue. Static stretch reflex gain decreased significantly at higher torque levels after fatigue, indicating that the isometric fatiguing exercise might be associated with a preferential change in properties of spindle chain fibers and bag2 fibers. For matched pre- and postfatigue torque levels, dynamic reflexes contributed relatively more torque after fatigue, displaying higher dynamic reflex gains and larger dynamic electromyographic responses elicited by the controlled small-amplitude position perturbations. These changes appear to counteract the fatigue-induced reductions in joint stiffness and static reflex gain. The compensatory responses could be partly due to the effects of increasing the number of active motoneurons innervating the fatiguing muscles. This shift in operating point gave rise to significant compensation for the loss of contractile force. The compensation could also be due to fusimotor adjustment, which could make the dynamic reflex gain much less sensitive to fatigue than intrinsic stiffness. In short, the reduced contribution from intrinsic stiffness to joint torque was compensated by increased contribution from dynamic stretch reflexes after fatigue.

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