Preconditioning Exercise Effect On Biceps Brachii Myotendinous Junction Displacement During Elbow Flexor Eccentric Contractions

Elbow flexor force steadiness is less with the forearm pronated (PRO) compared with neutral (NEU) or supinated (SUP) and may relate to neural excitability. Although not tested in a force steadiness paradigm, lower spinal and cortical excitability was observed separately for biceps brachii in PRO, possibly dependent on contractile status at the time of assessment. This study aimed to investigate position-dependent changes in force steadiness as well as spinal and cortical excitability at a variety of contraction intensities. Thirteen males (26 ± 7 yr; means ± SD) performed three blocks (PRO, NEU, and SUP) of 24 brief (~6 s) isometric elbow flexor contractions (5, 10, 25 or 50% of maximal force). During each contraction, transcranial magnetic stimulation or transmastoid stimulation was delivered to elicit a motor-evoked potential (MEP) or cervicomedullary motor-evoked potential (CMEP), respectively. Force steadiness was lower in PRO compared with NEU and SUP ( P ≤ 0.001), with no difference between NEU and SUP. Similarly, spinal excitability (CMEP/maximal M wave) was lower in PRO than NEU (25 and 50% maximal force; P ≤ 0.010) and SUP (all force levels; P ≤ 0.004), with no difference between NEU and SUP. Cortical excitability (MEP/CMEP) did not change with forearm position ( P = 0.055); however, a priori post hoc testing for position showed excitability was 39.8 ± 38.3% lower for PRO than NEU at 25% maximal force ( P = 0.006). The data suggest that contraction intensity influences the effect of forearm position on neural excitability and that reduced spinal and, to a lesser extent, cortical excitability could contribute to lower force steadiness in PRO compared with NEU and SUP. NEW & NOTEWORTHY To address conflicting reports about the effect of forearm position on spinal and cortical excitability of the elbow flexors, we examine the influence of contraction intensity. For the first time, excitability data are considered in a force steadiness context. Motoneuronal excitability is lowest in pronation and this disparity increases with contraction intensity. Cortical excitability exhibits a similar pattern from 5 to 25% of maximal force. Lower corticospinal excitability likely contributes to relatively poor force steadiness in pronation.

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Influence of forearm orientation on biceps brachii tendon mechanics and elbow flexor force steadiness

Journal of Biomechanics ◽

10.1016/j.jbiomech.2018.05.039 ◽

2018 ◽

Vol 76 ◽

pp. 129-135 ◽

Cited By ~ 5

Author(s):

Rowan R. Smart ◽

Sienna Kohn ◽

Cydney M. Richardson ◽

Jennifer M. Jakobi

Keyword(s):

Biceps Brachii ◽

Elbow Flexor ◽

Force Steadiness ◽

Tendon Mechanics ◽

Biceps Brachii Tendon

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Modulation of Structural Protein Content of the Myotendinous Junction Following Eccentric Contractions

International Journal of Sports Medicine ◽

10.1055/s-2000-3774 ◽

2000 ◽

Vol 21 (5) ◽

pp. 313-320 ◽

Cited By ~ 20

Author(s):

J. Frenette ◽

Côté

Keyword(s):

Protein Content ◽

Eccentric Contractions ◽

Myotendinous Junction ◽

Structural Protein

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Forelimb brachial muscle activation patterns using surface electromyography and their relationship to kinematics in normal dogs walking and trotting

Comparative Exercise Physiology ◽

10.3920/cep13026 ◽

2014 ◽

Vol 10 (1) ◽

pp. 13-22 ◽

Cited By ~ 5

Author(s):

T.C. Garcia ◽

B.K. Sturges ◽

S.M. Stover ◽

K. Aoki ◽

J.M. Liang ◽

...

Keyword(s):

Muscle Activity ◽

Surface Electromyography ◽

Muscle Activation ◽

Biceps Brachii ◽

Elbow Flexor ◽

Median Frequency ◽

Joint Angles ◽

Muscle Activation Patterns ◽

The Right ◽

Elbow Extensor

The objective of this study was to determine activity of the elbow flexor and elbow extensor groups of muscles relative to shoulder and elbow joint kinematics in normal walking and trotting dogs using surface electromyography (EMG), and to determine if muscle activity varies with gait or limb. Ten healthy mixed-breed dogs were walked and trotted across embedded force plates in a 6 m walkway while simultaneously recording muscle activation using surface EMG positioned over the biceps brachii (elbow flexor group) and triceps brachii (elbow extensor group); peak shoulder, elbow, and carpal joint angles from motion capture, and ground reaction forces. EMG magnitude, timing, and power spectral density (PSD) were used to analyse muscle activity. The effects of gait type and limb side on EMG measures and joint angles were assessed using an analysis of variance. Results showed that the elbow flexor group was maximally active at end of stance. The elbow extensor group was maximally active at the beginning of stance. Muscle activity occurred earlier in the gait phase (stance or swing) in the trot compared to the walk. The amplitude, frequency at maximum PSD (elbow flexor group only) and the median frequency were larger on the right side than on the left side. The maximum PSD and integrated PSD were larger on the left side than the right side. These data provide a reference for identifying abnormalities associated with orthopaedic, neurological, or rehabilitative changes. Limb asymmetry observed in muscle activation in clinically normal dogs should be further evaluated.

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Low-frequency fatigue and neuromuscular performance after exercise-induced damage to elbow flexor muscles

Journal of Applied Physiology ◽

10.1152/japplphysiol.01339.2007 ◽

2008 ◽

Vol 105 (4) ◽

pp. 1146-1155 ◽

Cited By ~ 28

Author(s):

James M. Dundon ◽

John Cirillo ◽

John G. Semmler

Keyword(s):

Eccentric Exercise ◽

Biceps Brachii ◽

Maximum Voluntary Contraction ◽

Low Frequency ◽

Elbow Flexor ◽

Triceps Brachii ◽

Force Fluctuations ◽

Flexor Muscles ◽

Elbow Flexor Muscles ◽

Low Frequency Fatigue

The purpose of this study was to quantify the association between low-frequency fatigue (LFF) and the increase in EMG and force fluctuations after eccentric exercise of elbow flexor muscles. Ten subjects performed two tasks involving voluntary isometric contractions of elbow flexors: a maximum voluntary contraction (MVC) and a constant-force task at five submaximal target forces (5, 10, 20, 40, 60% MVC) while EMG was recorded from biceps and triceps brachii. A third task involved electrical stimulation of biceps brachii at 12 frequencies (1–100 Hz). These tasks were performed before, after, and 2 h and 24 h after concentric or eccentric exercise. MVC force declined after eccentric exercise (34% decline) and remained depressed 24 h later (22% decline), whereas the reduced force following concentric exercise (32%) was recovered 2 h later. Biceps brachii EMG and force fluctuations during the submaximal voluntary contractions increased after eccentric exercise (both ∼2× greater) with the greatest effect at low forces. LFF was equivalent immediately after both types of exercise (50–60% reduction in 20:100 Hz force) with a slower recovery following eccentric exercise. A significant association was found between the change in LFF and EMG ( r2values up to 0.52), with the strongest correlations observed at low forces (20% MVC) and at 2 h after exercise. In contrast, there were no significant associations between LFF and force fluctuations during voluntary or electrically evoked contractions, suggesting that other physiological factors located within the muscle are likely to be playing a major role in the impaired motor performance after eccentric exercise.

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The origin of activity in the biceps brachii muscle during voluntary contractions of the contralateral elbow flexor muscles

Experimental Brain Research ◽

10.1007/s00221-006-0570-z ◽

2006 ◽

Vol 175 (3) ◽

pp. 526-535 ◽

Cited By ~ 61

Author(s):

Inge Zijdewind ◽

Jane E. Butler ◽

Simon C. Gandevia ◽

Janet L. Taylor

Keyword(s):

Biceps Brachii ◽

Elbow Flexor ◽

Biceps Brachii Muscle ◽

Flexor Muscles ◽

Elbow Flexor Muscles ◽

Voluntary Contractions

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Eccentric exercise increases EMG amplitude and force fluctuations during submaximal contractions of elbow flexor muscles

Journal of Applied Physiology ◽

10.1152/japplphysiol.01310.2006 ◽

2007 ◽

Vol 103 (3) ◽

pp. 979-989 ◽

Cited By ~ 75

Author(s):

John G. Semmler ◽

Kylie J. Tucker ◽

Trevor J. Allen ◽

Uwe Proske

Keyword(s):

Eccentric Exercise ◽

Biceps Brachii ◽

Maximum Voluntary Contraction ◽

Elbow Flexor ◽

Twofold Increase ◽

Force Fluctuations ◽

Emg Amplitude ◽

Concentric Exercise ◽

Flexor Muscles ◽

Elbow Flexor Muscles

The purpose of this study was to determine the effect of eccentric exercise on the ability to exert steady submaximal forces with muscles that cross the elbow joint. Eight subjects performed two tasks requiring isometric contraction of the right elbow flexors: a maximum voluntary contraction (MVC) and a constant-force task at four submaximal target forces (5, 20, 35, 50% MVC) while electromyography (EMG) was recorded from elbow flexor and extensor muscles. These tasks were performed before, after, and 24 h after a period of eccentric (fatigue and muscle damage) or concentric exercise (fatigue only). MVC force declined after eccentric exercise (45% decline) and remained depressed 24 h later (24%), whereas the reduced force after concentric exercise (22%) fully recovered the following day. EMG amplitude during the submaximal contractions increased in all elbow flexor muscles after eccentric exercise, with the greatest change in the biceps brachii at low forces (3–4 times larger at 5 and 20% MVC) and in the brachialis muscle at moderate forces (2 times larger at 35 and 50% MVC). Eccentric exercise resulted in a twofold increase in coactivation of the triceps brachii muscle during all submaximal contractions. Force fluctuations were larger after eccentric exercise, particularly at low forces (3–4 times larger at 5% MVC, 2 times larger at 50% MVC), with a twofold increase in physiological tremor at 8–12 Hz. These data indicate that eccentric exercise results in impaired motor control and altered neural drive to elbow flexor muscles, particularly at low forces, suggesting altered motor unit activation after eccentric exercise.

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