Differential Strength and Endurance Parameters of the Craniocervical and Cervicothoracic Extensors and Flexors in Healthy Individuals

2017 ◽  
Vol 33 (2) ◽  
pp. 166-170 ◽  
Author(s):  
Shaun O’Leary ◽  
Charlotte Loraas Fagermoen ◽  
Hiroyuki Hasegawa ◽  
Ann-Sofi Slettevold Thorsen ◽  
Luke Van Wyk
Keyword(s):  
Maximal Voluntary Contraction ◽  
Voluntary Contraction ◽  
Neck Muscles ◽  
Isometric Strength ◽  
Normal Variation ◽  
Healthy Individuals ◽  
Task Failure ◽  
Load Duration ◽  
Extensor Muscles

This study examined isometric strength (maximal voluntary contraction [MVC]) and endurance of cervical flexor and extensor muscles in healthy individuals at the craniocervical (CC) and cervicothoracic (CT) axes. MVC and endurance measures (time to task failure in seconds [s]) at 50% MVC were recorded in 4 directions (CC flexion, CC extension, CT flexion, and CT extension) in 20 males and 20 females, and 6 strength and endurance ratios were calculated. The findings showed that the cervical extensor muscles are not only much stronger than the flexors (1.3–2 times greater MVC), but also have greater capacity for endurance (2–2.4 times greater). While males produced significantly greater MVC recordings than females (P < .003), strength ratios (P > .06) and endurance measures (P > .11) were similar. Endurance ratios were also similar except the CT extension to CC flexion ratio, which was significantly larger in females compared with males (P = .03). These findings demonstrate that substantial but normal variation exists in strength and endurance parameters between cervical flexor and extensor muscles. This is informative to clinicians when evaluating the performance of these neck muscles or when deciding on exercise parameters (eg, load, duration) when training their performance.

Activation varies among the knee extensor muscles during a submaximal fatiguing contraction in the seated and supine postures

2003 ◽  
Vol 95 (4) ◽  
pp. 1515-1522 ◽  
Author(s):  
L Rochette ◽  
S. K. Hunter ◽  
N Place ◽  
R Lepers
Keyword(s):  
Vastus Lateralis ◽  
Maximum Voluntary Contraction ◽  
Knee Extensor ◽  
Voluntary Contraction ◽  
Emg Activity ◽  
Task Failure ◽  
Rate Of Increase ◽  
Extensor Muscles ◽  
Seated Posture ◽  
Knee Extensor Muscles

Ten young men sustained an isometric contraction of the knee extensor muscles at 20% of the maximum voluntary contraction (MVC) torque on three separate occasions in a seated posture. Subjects performed an isometric knee extension contraction on a fourth occasion in a supine posture. The time to task failure for the seated posture was similar across sessions (291 ± 84 s; P > 0.05), and the MVC torque was similarly reduced across sessions after the fatiguing contraction (42 ± 12%). The rate of increase in electromyograph (EMG) activity (%MVC) and torque fluctuations during the fatiguing contractions were similar across sessions. However, the rate of increase in EMG differed among the knee extensor muscles: the rectus femoris began at a greater amplitude (31.5 ± 11.0%) compared with the vastus lateralis and vastus medialis muscles (18.8 ± 5.3%), but it ended at a similar value (45.4 ± 3.1%). The time to task failure and increase in EMG activity were similar for the seated and supine tasks; however, the reduction in MVC torque was greater for the seated posture. These findings indicate that the time to task failure for the knee extensor muscles that have a common tendon insertion did not alter over repeat sessions as had been observed for the elbow flexor muscles (Hunter SK and Enoka RM. J Appl Physiol 94: 108-118, 2003).

The Effect of an Orthotic Device for Balancing Neck Muscles During Daily Office Tasks

2019 ◽  
Vol 61 (5) ◽  
pp. 722-735 ◽  
Author(s):  
Federico Quinzi ◽  
Martina Scalia ◽  
Arrigo Giombini ◽  
Alessandra Di Cagno ◽  
Fabio Pigozzi ◽  
...  
Keyword(s):  
Neck Pain ◽  
Inertial Mass ◽  
Acute Effect ◽  
Voluntary Contraction ◽  
Neck Muscles ◽  
Erector Spinae ◽  
Orthotic Devices ◽  
Orthotic Device ◽  
Balance System ◽  
Extensor Muscles

Objective: This study aimed at evaluating the acute effect of the combined and single use of two orthotic devices (neck balance system [NBS] and lumbar support [LS]) on muscle activity of neck and back muscles during typical computer working tasks. Background: An excessive activation of neck muscles could threaten the balance between agonist and antagonist muscles, resulting in a lower stability of the head and possibly leading to neck pain. At present, no study evaluated the effect of a specific orthotic device in reducing neck muscles activation. Methods: Surface electromyography (sEMG) from neck flexor (sternocleidomastoid [SCMD]) and extensor muscles (semispinalis capitis [SPC]) and back extensor muscles (erector spinae [ERS]) of 20 healthy individuals was recorded during three computer working tasks performed with the NBS, with NBS and LS, with the LS, and without devices (ND). Results: In the NBS condition, the SPC showed a reduced activation (NBS = 3.97%; NBS + LS = 4.49%; LS = 4.48%; ND = 4.61% of the maximal voluntary contraction) compared to the other conditions. Conclusions: The use of the NBS promotes a reduction of neck extensor muscles, possibly due to the inertial mass added in the occipital part of the head, producing an external neck extensor moment that cooperates with that produced by neck extensor muscles. Application: Orthotic devices such as the NBS may be used by computer workers to reduce the activation of their neck extensor muscles and possible risks of developing neck pain.

scholarly journals Spinal reflexes and coactivation of ankle muscles during a submaximal fatiguing contraction

2005 ◽  
Vol 99 (3) ◽  
pp. 1182-1188 ◽  
Author(s):  
Morgan Lévénez ◽  
Christos Kotzamanidis ◽  
Alain Carpentier ◽  
Jacques Duchateau
Keyword(s):  
Maximal Voluntary Contraction ◽  
Tibialis Anterior ◽  
Voluntary Contraction ◽  
Spinal Reflexes ◽  
Spinal Reflex ◽  
Lateral Gastrocnemius ◽  
Task Failure ◽  
Antagonist Muscles ◽  
Antagonist Coactivation ◽  
Ankle Dorsiflexors

This study examined the involvement of spinal mechanisms in the control of coactivation during a sustained contraction of the ankle dorsiflexors at 50% of maximal voluntary contraction. Changes in the surface electromyogram (EMG) of the tibialis anterior and of two antagonist muscles, the soleus and lateral gastrocnemius, were investigated during and after the fatigue task. Concurrently, the compound action potential (M-wave) and the Hoffmann reflex of the soleus and lateral gastrocnemius were recorded. The results showed that the torque of the ankle dorsiflexors and the average EMG of the tibialis anterior during maximal voluntary contraction declined by 40.9 ± 17.7% (mean ± SD; P < 0.01) and 37.0 ± 19.9% ( P < 0.01), respectively, at task failure. During the submaximal fatiguing contraction, the average EMG of both the agonist and antagonist muscles increased, leading to a nearly constant ratio at the end of the contraction when normalized to postfatigue values. In contrast to the monotonic increase in average EMG of the antagonist muscles, the excitability of their spinal reflex pathways exhibited a biphasic modulation. The amplitude of the Hoffman reflexes in the soleus and lateral gastrocnemius increased to 147.5 ± 52.9% ( P < 0.05) and 166.7 ± 74.9% ( P < 0.01), respectively, during the first 20% of the contraction and then subsequently declined to 66.3 ± 44.8 and 74.4 ± 44.2% of their initial values. In conclusion, the results show that antagonist coactivation did not contribute to task failure. The different changes in voluntary EMG activity and spinal reflex excitability in the antagonist muscles during the fatiguing contraction support the concept that the level of coactivation is controlled by supraspinal rather than spinal mechanisms. The findings indicate, however, that antagonist coactivation cannot simply be mediated by a central descending “common drive” to the motor neuron pools of the agonist-antagonist muscle pairs. Rather, they suggest a more subtle regulation of the drive, possibly through presynaptic mechanisms, to the motoneurons that innervate the antagonist muscles.

A Comparison of Craniocervical and Cervicothoracic Muscle Strength in Healthy Individuals

2010 ◽  
Vol 26 (4) ◽  
pp. 400-406 ◽  
Author(s):  
Luke Van Wyk ◽  
Gwendolen Jull ◽  
Bill Vicenzino ◽  
Mathew Greaves ◽  
Shaun O’Leary
Keyword(s):  
Muscle Strength ◽  
Maximal Voluntary Contraction ◽  
Sagittal Plane ◽  
Testing Procedure ◽  
Voluntary Contraction ◽  
Healthy Individuals ◽  
Axis Extension ◽  
Males And Females ◽  
Separate Measurement ◽  
Flexor Strength

The purpose of this study was to compare maximal torque exerted about the craniocervical (CC) and cervicothoracic (CT) axes in the sagittal plane using a novel dynamometry device. Maximal voluntary contraction (MVC) recordings in newton-meters (N·m) were measured in 20 males and 20 females for each of 4 tests: CT extension, CT flexion, CC extension, CC flexion. Twenty of the volunteers repeated the testing procedure on a second occasion to determine the test–retest repeatability of the measures. MVC recordings at the CT axis (extension, 30.24 ± 12.15 N·m; flexion, 18.90 ± 8.21 N⋅m) were 1.4–2 times greater than recordings at the CC axis (extension, 16.46 ± 7.26 N⋅m; fexion, 13.34 ± 5.97 N·m). Extensor to flexor strength ratios reduced from 1.75 at the CT axis to 1.24 at the CC axis, but were similar for both males and females. Good to excellent test–retest repeatability was demonstrated for all tests (ICC = 0.75–0.99,SEM= 0.50–2.44 N·m). Consistent with differences in the muscle morphology at the CC and CT axes, torque exerted about these axes differ. Separate measurement of torque about these axes potentially offers a more comprehensive profile of cervical muscle strength.

scholarly journals The effects of acute blood flow restriction on climbing-specific tests

2020 ◽  
pp. 7-14
Author(s):  
Atle Hole Saeterbakken ◽  
Vidar Andersen ◽  
Nicolay Stien ◽  
Helene Pedersen ◽  
Tom Erik Jorung Solstad ◽  
...  
Keyword(s):  
Blood Flow ◽  
Maximal Voluntary Contraction ◽  
Peak Velocity ◽  
Dynamic Strength ◽  
Voluntary Contraction ◽  
Peak Force ◽  
Blood Flow Restriction ◽  
Isometric Strength ◽  
Fat Percentage ◽  
Flow Restriction

The aim of the study was to compare climbing specific performance tests with and without blood flow restriction (BFR). Thirty one climbers (age 26.9 ± 5.5 years, height 177.2 ± 7.5 cm, weight 70.5 ± 8.3 kg, fat percentage 11.9 ± 4.1 %, climbing skill 18.9 ± 4.0 IRCRA scale) performed climbing specific grip tests measuring isometric strength (peak force, rate of force development and maximal voluntary contraction (and dynamic strength (power and peak velocity in pull-up) on a 23-mm campus rung. Further, an intermittent finger endurance (7 seconds work, 3 seconds rest at 60% of maximal voluntary contraction) test to failure was conducted. All tests were performed on two separate occasions (separated by 2–5 days) with and without blood flow restriction (200 mmHg) in a randomized order. The results demonstrated no differences in the isometric strength tests (p = 0.496–0.850, ES = 0.060–0.170), dynamic strength test (p = 0.226–0.442, ES = 0.200–0.330) or the intermittent finger endurance test (p = 0.563, ES = 0.160). In conclusion, no differences were observed in the maximal isometric pull-up test, dynamic pull-up test or finger endurance tests including measurements as peak force, MVC, RFD, power output, peak velocity or time to fatigue at 60% of MVC with and without BFR.

scholarly journals Time to task failure and muscle activation vary with load type for a submaximal fatiguing contraction with the lower leg

2008 ◽  
Vol 105 (2) ◽  
pp. 463-472 ◽  
Author(s):  
Sandra K. Hunter ◽  
Tejin Yoon ◽  
Joseph Farinella ◽  
Erin E. Griffith ◽  
Alexander V. Ng
Keyword(s):  
Maximal Voluntary Contraction ◽  
Muscle Activation ◽  
Lower Leg ◽  
Voluntary Contraction ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Time To Failure ◽  
Contraction Force ◽  
Task Failure ◽  
Position Task

The purpose was to compare the time to failure and muscle activation patterns for a sustained isometric submaximal contraction with the dorsiflexor muscles when the foot was restrained to a force transducer (force task) compared with supporting an equivalent inertial load and unrestrained (position task). Fifteen men and women (mean ± SD; 21.1 ± 1.4 yr) performed the force and position tasks at 20% maximal voluntary contraction force until task failure. Maximal voluntary contraction force performed before the force and position tasks was similar (333 ± 71 vs. 334 ± 65 N), but the time to task failure was briefer for the position task (10.0 ± 6.2 vs. 21.3 ± 17.8 min, P < 0.05). The rate of increase in agonist root-mean-square electromyogram (EMG), EMG bursting activity, rating of perceived exertion, fluctuations in motor output, mean arterial pressure, and heart rate during the fatiguing contraction was greater for the position task. EMG activity of the vastus lateralis (lower leg stabilizer) and medial gastrocnemius (antagonist) increased more rapidly during the position task, but coactivation ratios (agonist vs. antagonist) were similar during the two tasks. Thus the difference in time to failure for the two tasks with the dorsiflexor muscles involved a greater level of neural activity and rate of motor unit recruitment during the position task, but did not involve a difference in coactivation. These findings have implications for rehabilitation and ergonomics in minimizing fatigue during prolonged activation of the dorsiflexor muscles.

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