Short-term immobilization has a minimal effect on the strength and fatigability of a human hand muscle

1995 ◽  
Vol 78 (3) ◽  
pp. 847-855 ◽  
Author(s):  
A. J. Fuglevand ◽  
M. Bilodeau ◽  
R. M. Enoka
Keyword(s):  
Wave Amplitude ◽  
Compound Muscle Action Potential ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Emg Activity ◽  
Human Hand ◽  
Contraction Time ◽  
Endurance Time ◽  
M Wave ◽  
First Dorsal Interosseus

The purpose of this study was to determine the association between reduced fatigability typically observed in disused muscle and an improved resistance to the impairment of neuromuscular propagation. Endurance time of an isometric contraction sustained at 35% of maximum voluntary contraction (MVC) force and the fatigue-induced change in the evoked compound muscle action potential (M wave) were measured in the first dorsal interosseus muscle of human subjects before, during, and after 3 (n = 9) or 5 wk (n = 2) of immobilization. The immobilization procedure caused a substantial decline in the chronic electromyographic (EMG) activity (to 4% of control value) of the first dorsal interosseus muscle. Endurance time was found to be significantly correlated to the maintenance of M-wave amplitude during the fatigue task. However, neither of these variables was significantly affected by immobilization. Also, immobilization had no significant effect on the prefatigue values of MVC force and EMG or twitch contraction time or on the postfatigue changes in MVC force and EMG, M wave duration, twitch amplitude, and contraction time. In the unfatigued muscle, immobilization did cause an increase in twitch force (153%) and a decrease in M-wave amplitude (67%). It appears, therefore, that a healthy first dorsal interosseus muscle is generally resistant to adaptation when its use has been reduced for 3–5 wk by immobilization.

Effects of fatigue duration and muscle type on voluntary and evoked contractile properties

1997 ◽  
Vol 82 (5) ◽  
pp. 1654-1661 ◽  
Author(s):  
D. G. Behm ◽  
D. M. M. St-Pierre
Keyword(s):  
Muscle Activation ◽  
Compound Muscle Action Potential ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Contractile Properties ◽  
Plantar Flexors ◽  
Muscle Type ◽  
M Wave ◽  
Time To Peak ◽  
Muscle Action Potential

Behm, D. G., and D. M. M. St-Pierre. Effects of fatigue duration and muscle type on voluntary and evoked contractile properties. J. Appl. Physiol. 82(5): 1654–1661, 1997.—The effects of fatigue duration and muscle type on voluntary and evoked contractile properties were investigated with an isometric, intermittent, submaximal fatigue protocol. Four groups performed contractions of the plantar flexors and quadriceps at various intensities to produce long (LDF; 19 min 30 s)- and short-duration fatigue (SDF; 4 min 17 s). The LDF group had a significantly greater decrease in muscle activation than did the SDF group (12 vs. 5.8%) during recovery, although there was no difference in the impairment of maximum voluntary contraction force beyond 30 s of recovery. The significant decrease in the compound muscle action potential of the LDF group (M-wave amplitude; 14.7%) contrasted with the M-wave potentiation of the SDF group (15.7%), suggesting changes in membrane excitation may affect LDF. The quadriceps group performing contractions at 50% MVC experienced a smaller decrease in agonist electromyograph activity than did other groups, indicating both muscle and fatigue duration specificity. Impairments in excitation-contraction coupling were indicated by changes in quadriceps peak twitch and time to peak twitch while decreases in PF M-wave amplitudes suggested a disruption of membrane potentials. Results suggest that fatigue mechanisms may be duration (activation, half relaxation time) or muscle specific (electromyograph, twitch torque) or a combination of both (M wave, time to peak twitch torque).

Index finger position and force of the human first dorsal interosseus and its ulnar nerve antagonist

1994 ◽  
Vol 77 (2) ◽  
pp. 987-997 ◽  
Author(s):  
I. Zijdewind ◽  
D. Kernell
Keyword(s):  
Ulnar Nerve ◽  
Index Finger ◽  
Maximum Voluntary Contraction ◽  
Normal Subjects ◽  
Voluntary Contraction ◽  
Abduction Angle ◽  
Hand Position ◽  
First Dorsal Interosseus ◽  
Length Analysis ◽  
Neutral Angle

In normal subjects, maximum voluntary contraction (MVC) and electrical ulnar nerve stimulation (UNS; 30-Hz bursts of 0.33 s) were systematically compared with regard to the forces generated in different directions (abduction/adduction and flexion) and at different degrees of index finger abduction. With a “resting” hand position in which there was no index finger abduction, UNS produced about one-half of the abduction force elicited by an MVC (mean ratio 51%). Qualitatively, such a discrepancy would be expected, because UNS activates two index finger muscles with opposing actions in the abduction/adduction plane of torques: the first dorsal interosseus (FDI) and the first palmar interosseus (FPI). The abduction forces produced by MVC and UNS were very sensitive to index finger abduction angle: at a maximum degree of abduction, the UNS-generated force even reversed its direction of action to adduction (with FPI dominating) and the abduction MVC declined to 37% of that in the resting hand position. Inasmuch as these declines in MVC- and UNS-generated abduction force could not be explained by a change in moment arm, the main alternative seemed to be abduction-associated alterations in FDI fiber length (analysis by previously published biomechanical data). The FDI and FPI were further compared by application of a UNS-generated fatigue test (5-min burst stimulation), with the index finger kept at a "neutral" angle, i.e., the abduction angle at which, in the unfatigued state, the forces of the FDI and FPI were in balance (zero net UNS-generated abduction/adduction force).(ABSTRACT TRUNCATED AT 250 WORDS)

Reflex Inhibition of Normal Cramp Following Electrical Stimulation of the Muscle Tendon

2007 ◽  
Vol 98 (3) ◽  
pp. 1102-1107 ◽  
Author(s):  
Serajul I. Khan ◽  
John A. Burne
Keyword(s):  
Electrical Stimulation ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Muscle Cramp ◽  
Emg Activity ◽  
Reflex Inhibition ◽  
Experimental Conditions ◽  
Inhibitory Feedback ◽  
Two Phases ◽  
Stimulation Of

Muscle cramp was induced in one head of the gastrocnemius muscle (GA) in eight of thirteen subjects using maximum voluntary contraction when the muscle was in the shortened position. Cramp in GA was painful, involuntary, and localized. Induction of cramp was indicated by the presence of electromyographic (EMG) activity in one head of GA while the other head remained silent. In all cramping subjects, reflex inhibition of cramp electrical activity was observed following Achilles tendon electrical stimulation and they all reported subjective relief of cramp. Thus muscle cramp can be inhibited by stimulation of tendon afferents in the cramped muscle. When the inhibition of cramp-generated EMG and voluntary EMG was compared at similar mean EMG levels, the area and timing of the two phases of inhibition (I1, I2) did not differ significantly. This strongly suggests that the same reflex pathway was the source of the inhibition in both cases. Thus the cramp-generated EMG is also likely to be driven by spinal synaptic input to the motorneurons. We have found that the muscle conditions that appear necessary to facilitate cramp, a near to maximal contraction of the shortened muscle, are also the conditions that render the inhibition generated by tendon afferents ineffective. When the strength of tendon inhibition in cramping subjects was compared with that in subjects that failed to cramp, it was found to be significantly weaker under the same experimental conditions. It is likely that reduced inhibitory feedback from tendon afferents has an important role in generating cramp.

scholarly journals Influence of Voluntary Contraction Level, Test Stimulus Intensity and Normalization Procedures on the Evaluation of Short-Interval Intracortical Inhibition

2020 ◽  
Vol 10 (7) ◽  
pp. 433
Author(s):  
Cécilia Neige ◽  
Sidney Grosprêtre ◽  
Alain Martin ◽  
Florent Lebon
Keyword(s):  
Healthy Subjects ◽  
Compound Muscle Action Potential ◽  
Short Interval ◽  
Motor Evoked Potential ◽  
Intracortical Inhibition ◽  
Voluntary Contraction ◽  
Experimental Conditions ◽  
Specific Level ◽  
M Wave ◽  
Spinal Motoneurones

Short-interval intracortical inhibition (SICI) represents an inhibitory phenomenon acting at the cortical level. However, SICI estimation is based on the amplitude of a motor-evoked potential (MEP), which depends on the discharge of spinal motoneurones and the generation of compound muscle action potential (M-wave). In this study, we underpin the importance of taking into account the proportion of spinal motoneurones that are activated or not when investigating the SICI of the right flexor carpi radialis (normalization with maximal M-wave (Mmax) and MEPtest, respectively), in 15 healthy subjects. We probed SICI changes according to various MEPtest amplitudes that were modulated actively (four levels of muscle contraction: rest, 10%, 20% and 30% of maximal voluntary contraction (MVC)) and passively (two intensities of test transcranial magnetic stimulation (TMS): 120 and 130% of motor thresholds). When normalized to MEPtest, SICI remained unchanged by stimulation intensity and only decreased at 30% of MVC when compared with rest. However, when normalized to Mmax, we provided the first evidence of a strong individual relationship between SICI and MEPtest, which was ultimately independent from experimental conditions (muscle states and TMS intensities). Under similar experimental conditions, it is thus possible to predict SICI individually from a specific level of corticospinal excitability in healthy subjects.

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).

Aging does not affect voluntary activation of the ankle dorsiflexors during isometric, concentric, and eccentric contractions

2005 ◽  
Vol 99 (1) ◽  
pp. 31-38 ◽  
Author(s):  
Malgorzata Klass ◽  
Stéphane Baudry ◽  
Jacques Duchateau
Keyword(s):  
Electrical Stimulation ◽  
Compound Muscle Action Potential ◽  
Voluntary Contraction ◽  
Voluntary Activation ◽  
M Wave ◽  
Mechanical Responses ◽  
Age Related ◽  
Angular Velocities ◽  
General Slowing ◽  
Ankle Dorsiflexors

This study examines the age-related deficit in force of the ankle dorsiflexors during isometric (Iso), concentric (Con), and eccentric (Ecc) contractions. More specifically, the contribution of neural and muscular mechanisms to the loss of voluntary force was investigated in men and women. The torque produced by the dorsiflexors and the surface electromyogram (EMG) from the tibialis anterior and the soleus were recorded during maximal Iso contractions and during Con and Ecc contractions performed at constant angular velocities (5–100°/s). Central activation was tested by the superimposed electrical stimulation method during maximal voluntary contraction and by computing the ratio between voluntary average EMG and compound muscle action potential (M wave) induced by electrical stimulation (average EMG/M wave). Contractile properties of the dorsiflexor muscles were investigated by recording the mechanical responses to single and paired maximal stimuli. The results showed that the age-related deficit in force (collapsed across genders and velocities) was greater for Iso (20.5%; P < 0.05) and Con (38.6%; P < 0.001) contractions compared with Ecc contractions (6.5%; P > 0.05). When the torque produced during Con and Ecc contractions was expressed relative to the maximal Iso torque, it was significantly reduced in Con contractions and increased in Ecc contractions with aging, with the latter effect being more pronounced for women. In both genders, voluntary activation was not significantly impaired in elderly adults and did not differ from young subjects. Similarly, coactivation was not changed with aging. In contrast, the mechanical responses to single and paired stimuli showed a general slowing of the muscle contractile kinetics with a slightly greater effect in women. It is concluded that the force deficit during Con and Iso contractions of the ankle dorsiflexors in advanced age cannot be explained by impaired voluntary activation or changes in coactivation. Instead, this age-related adaptation and the mechanisms that preserve force in Ecc contractions appeared to be located at the muscular level.

Influence of joint position on ankle plantarflexion in humans

1982 ◽  
Vol 52 (6) ◽  
pp. 1636-1642 ◽  
Author(s):  
D. Sale ◽  
J. Quinlan ◽  
E. Marsh ◽  
A. J. McComas ◽  
A. Y. Belanger
Keyword(s):  
Relaxation Times ◽  
Voluntary Contraction ◽  
Triceps Surae ◽  
Emg Activity ◽  
Optimum Length ◽  
M Wave ◽  
Optimum Position ◽  
Human Muscles ◽  
Slow Twitch ◽  
Torque Development

The contractile properties of the triceps surae (medial and lateral gastrocnemii and soleus) have been studied in humans. In comparison with most other human muscles, the triceps complex had a slow twitch (mean contraction and half-relaxation times 112.4 +/- 11.1 and 99.6 +/- 14.4 ms, respectively) and a low tetanus fusion frequency (60 Hz). Stretching the muscle caused both the contraction and half-relaxation times to become longer. With the knee bent, the optimum length for torque development corresponded to almost full dorsiflexion of the ankle. Similar results were obtained with the knee extended. The optimum position of the ankle differed considerably from the position of the joint when the leg was at rest. Although the position of the ankle joint affected electromyographic (EMG) activity recorded during maximal voluntary contraction, there was little change in the EMG-to-M wave ratio.

scholarly journals External torque as a factor to modify load in abdominal curl-up exercises

2015 ◽  
Vol 7 (1) ◽  
Author(s):  
Alicja Rutkowska-Kucharska ◽  
Agnieszka Szpala
Keyword(s):  
External Force ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Emg Activity ◽  
Electromyographic Activity ◽  
Upper Limbs ◽  
External Torque ◽  
Lever Arm ◽  
Emg Signal ◽  
Ca 50

SummaryStudy aim: the aim of our study was to evaluate electromyography (EMG) activity in exercises where the load to the muscles is determined by the external torque. In a part of the exercises, we changed the value of the external force, while in the other we modified the length of the lever arm at which the force was applied.Material and methods: the study was carried out on a group of 12 subjects (21 ± 2 years, 61 ± 4.8 mass, 172 ± 5 cm height). Electromyographic activity of the rectus abdominis (RA) muscle was evaluated by recording the EMG signal. The length of the lever arm of the external force was changed by using four different positions of the upper limbs, whereas the magnitude of the external force was changed through adding the weights of 0.5, 1.0, and 1.5 kg. The data recorded were normalized with respect to EMG activity measured under maximum voluntary contraction (MVC) conditions.Results: it was found that the change of the lever arm at which the force was applied (any change in the position of the upper limbs) causes a change in EMG activity in each part of the RA muscle from ca. 50% to ca. 100% MVC (p < 0.001). Further, the change in the external load changes statistically significantly the EMG activity only in the left upper part of the RA muscle (p < 0.05).Conclusions: activity in the RA muscle that increased for longer lever arms of the external force, offers opportunities for changing the load used during the exercise in a manner that is safe for the vertebral column.

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