Contractile speed and EMG changes during fatigue of sustained maximal voluntary contractions

1983 ◽  
Vol 50 (1) ◽  
pp. 313-324 ◽  
Author(s):  
B. Bigland-Ritchie ◽  
R. Johansson ◽  
O. C. Lippold ◽  
J. J. Woods
Keyword(s):  
Nerve Stimulation ◽  
Maximal Voluntary Contraction ◽  
Time Course ◽  
Muscle Activation ◽  
Neuromuscular Block ◽  
Voluntary Contraction ◽  
Percentage Change ◽  
Electromyographic Activity ◽  
Excitation Rate ◽  
Voluntary Contractions

Measurements were made from the human adductor pollicis muscle of force, contractile speed, and electromyographic activity (EMG) before, during, and after maximal isometric voluntary contractions sustained for 60 s. The use of brief test periods of maximal nerve stimulation with single shocks or trains of shocks enabled various muscle mechanical properties to be studied throughout each contraction. Electrical activity was measured after rectification and smoothing of the surface potentials and also by counting the total number of potentials per unit time from a population of motor units using fine wire intramuscular electrodes. During a 60-s maximal voluntary contraction, the force fell by 30-50%. Throughout the experiment the voluntary force matched that produced by supramaximal tetanic nerve stimulation. This indicated that, with sufficient practice, full muscle activation could be maintained by voluntary effort. However, the amplitude of the smoothed, rectifed EMG and the rate of spike counts declined. Since no evidence for neuromuscular block was found, the decline in EMG and spike counts was attributed to a progressive reduction of the neural drive from the central nervous system, despite maintained maximum effort. After the prolonged voluntary contractions twitch duration was prolonged, mainly as a result of slowing in relaxation rate. Twitch summation in unfused tetani increased. Both the maximum rate of relaxation and the time course of force decay declined by 50-70%. Similar changes were seen in both voluntary contractions and in test periods of stimulation. The percentage change in muscle contractile speed measured by these parameters approximately equaled the percentage change in the surface EMG measured simultaneously. It is concluded that 1) during a 60-s sustained maximal voluntary contraction there is a progressive slowing of contraction speed such that the excitation rate required to give maximal force generation is reduced, 2) the simultaneous decline in EMG may be due to a continuous reduction in motoneuron discharge rate, and 3) the EMG decline may not necessarily contribute to force loss.

scholarly journals Neuromuscular fatigue during a long-duration cycling exercise

2002 ◽  
Vol 92 (4) ◽  
pp. 1487-1493 ◽  
Author(s):  
Romuald Lepers ◽  
Nicola A. Maffiuletti ◽  
Ludovic Rochette ◽  
Julien Brugniaux ◽  
Guillaume Y. Millet
Keyword(s):  
Time Course ◽  
Muscle Activation ◽  
Mechanical Response ◽  
Vastus Lateralis ◽  
Quadriceps Muscle ◽  
Voluntary Contraction ◽  
Vastus Lateralis Muscle ◽  
Electromyographic Activity ◽  
Cycling Exercise ◽  
M Wave

The effects of prolonged cycling on neuromuscular parameters were studied in nine endurance-trained subjects during a 5-h exercise sustained at 55% of the maximal aerobic power. Torque during maximal voluntary contraction (MVC) of the quadriceps muscle decreased progressively throughout the exercise ( P < 0.01) and was 18% less at the end of exercise compared with the preexercise value. Peak twitch torque, contraction time, and total area of mechanical response decreased significantly ( P < 0.05) after the first hour of exercise. In contrast, changes in M-wave characteristics were significant only after the fourth hour of the exercise. Significant reductions ( P < 0.05) in electromyographic activity normalized to the M wave occurred after the first hour for the vastus lateralis muscle but only at the end of the exercise for the vastus medialis muscle. Muscle activation level, assessed by the twitch interpolation technique, decreased by 8% ( P < 0.05) at the end of the exercise. The results suggest that the time course is such that the contractile properties are significantly altered after the first hour, whereas excitability and central drive are more impaired toward the latter stages of the 5-h cycling exercise.

Nonuniform strain of human soleus aponeurosis-tendon complex during submaximal voluntary contractions in vivo

2003 ◽  
Vol 95 (2) ◽  
pp. 829-837 ◽  
Author(s):  
Taija Finni ◽  
John A. Hodgson ◽  
Alex M. Lai ◽  
V. Reggie Edgerton ◽  
Shantanu Sinha
Keyword(s):  
Achilles Tendon ◽  
Maximal Voluntary Contraction ◽  
Three Dimensional ◽  
Motor Units ◽  
Magnetic Resonance Images ◽  
Voluntary Contraction ◽  
Force Transmission ◽  
Voluntary Contractions ◽  
Nonuniform Strain

The distribution of strain along the soleus aponeurosis tendon was examined during voluntary contractions in vivo. Eight subjects performed cyclic isometric contractions (20 and 40% of maximal voluntary contraction). Displacement and strain in the apparent Achilles tendon and in the aponeurosis were calculated from cine phase-contrast magnetic resonance images acquired with a field of view of 32 cm. The apparent Achilles tendon lengthened 2.8 and 4.7% in 20 and 40% maximal voluntary contraction, respectively. The midregion of the aponeurosis, below the gastrocnemius insertion, lengthened 1.2 and 2.2%, but the distal aponeurosis shortened 2.1 and 2.5%, respectively. There was considerable variation in the three-dimensional anatomy of the aponeurosis and muscle-tendon junction. We suggest that the nonuniformity in aponeurosis strain within an individual was due to the presence of active and passive motor units along the length of the muscle, causing variable force along the measurement site. Force transmission along intrasoleus connective tissue may also be a significant source of nonuniform strain in the aponeurosis.

Initial phase of maximal voluntary and electrically stimulated knee extension torque development at different knee angles

2004 ◽  
Vol 97 (5) ◽  
pp. 1693-1701 ◽  
Author(s):  
C. J. de Ruiter ◽  
R. D. Kooistra ◽  
M. I. Paalman ◽  
A. de Haan
Keyword(s):  
Muscle Activation ◽  
Knee Extensor ◽  
Surface Emg ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Voluntary Activation ◽  
Knee Angle ◽  
Time Integral ◽  
Voluntary Contractions ◽  
Torque Development

We investigated the capacity for torque development and muscle activation at the onset of fast voluntary isometric knee extensions at 30, 60, and 90° knee angle. Experiments were performed in subjects ( n = 7) who had high levels (>90%) of activation at the plateau of maximal voluntary contractions. During maximal electrical nerve stimulation (8 pulses at 300 Hz), the maximal rate of torque development (MRTD) and torque time integral over the first 40 ms (TTI40) changed in proportion with torque at the different knee angles (highest values at 60°). At each knee angle, voluntary MRTD and stimulated MRTD were similar ( P < 0.05), but time to voluntary MRTD was significantly longer. Voluntary TTI40 was independent ( P > 0.05) of knee angle and on average (all subjects and angles) only 40% of stimulated TTI40. However, among subjects, the averaged (across knee angles) values ranged from 10.3 ± 3.1 to 83.3 ± 3.2% and were positively related ( r2 = 0.75, P < 0.05) to the knee-extensor surface EMG at the start of torque development. It was concluded that, although all subjects had high levels of voluntary activation at the plateau of maximal voluntary contraction, among subjects and independent of knee angle, the capacity for fast muscle activation varied substantially. Moreover, in all subjects, torque developed considerably faster during maximal electrical stimulation than during maximal voluntary effort. At different knee angles, stimulated MRTD and TTI40 changed in proportion with stimulated torque, but voluntary MRTD and TTI40 changed less than maximal voluntary torque.

Impulse propagation and muscle activation in long maximal voluntary contractions

1989 ◽  
Vol 67 (5) ◽  
pp. 1835-1842 ◽  
Author(s):  
C. K. Thomas ◽  
J. J. Woods ◽  
B. Bigland-Ritchie
Keyword(s):  
Tibialis Anterior ◽  
Muscle Activation ◽  
Motor Units ◽  
Voluntary Contraction ◽  
Mass Action ◽  
M Wave ◽  
Force Reduction ◽  
Small Decline ◽  
Voluntary Contractions ◽  
Do So

With fatigue, force generation may be limited by several factors, including impaired impulse transmission and/or reduced motor drive. In 5-min isometric maximal voluntary contraction, no decline was seen in the peak amplitude of the tibialis anterior compound muscle mass action potential (M wave) either during or immediately after the voluntary effort, provided maximal nerve stimulation was retained. For first dorsal interosseous (FDI) muscle, M wave amplitudes declined by 19.4 +/- 1.6% during the first 2 min but did not change significantly thereafter, despite the continued force reduction (up to 94% in 5 min for both muscles). The duration of the FDI M waves increased (greater than 30%), suggesting that the small decline in amplitude was the result of increased dispersion between the responses of different motor units. Some subjects kept FDI maximally activated throughout, but when they used tibialis anterior, twitch occlusion and tetanic muscle stimulation showed that most subjects were usually only able to do so for the first 60 s and thereafter only during brief “extra efforts.” Thus force loss during isometric voluntary contractions sustained at the highest intensities results mainly from failure of processes within the muscle fibers.

The Effect of Heating and Cooling on Time Course of Voluntary and Electrically Induced Muscle Force Variation

Medicina ◽  
2011 ◽  
Vol 47 (1) ◽  
pp. 6 ◽  
Author(s):  
◽  
◽  
◽  
◽  
Keyword(s):  
Muscle Fatigue ◽  
Time Course ◽  
Muscle Force ◽  
Peak Torque ◽  
Voluntary Contraction ◽  
Knee Extensors ◽  
Lower Body ◽  
Heating And Cooling ◽  
Force Variation ◽  
Voluntary Contractions

The aim of this study was to investigate the effect of heating and cooling on time course of voluntary and electrically induced muscle force variation. Material and Methods. Ten volunteers performed 50 maximal voluntary and electrically induced contractions of the knee extensors at an angle of 120 degrees under the control conditions and after passive lower body heating and cooling in the control, heating, and cooling experiments. Peak torque, torque variation, and half-relaxation time were assessed during the exercise. Results. Passive lower body heating increased muscle and core temperatures, while cooling lowered muscle temperature, but did not affect core temperature. We observed significantly lower muscle fatigue during voluntary contraction compared with electrically induced contractions. Body heating (opposite to cooling) increased involuntarily induced muscle force, but caused greater electrically induced muscle fatigue. In the middle of the exercise, the coefficient of correlation for electrically induced muscle torque decreased significantly as compared with the beginning of the exercise, while during maximal voluntary contractions, this relation for torque remained significant until the end of the exercise. Conclusion. It was shown that time course of voluntary contraction was more stable than in electrically induced contractions.

Postactivation potentiation in a human muscle: effect on the load-velocity relation of tetanic and voluntary shortening contractions

2007 ◽  
Vol 103 (4) ◽  
pp. 1318-1325 ◽  
Author(s):  
Stéphane Baudry ◽  
Jacques Duchateau
Keyword(s):  
Angular Velocity ◽  
Muscle Activation ◽  
Electrical Stimulus ◽  
Voluntary Contraction ◽  
Muscle Performance ◽  
Postactivation Potentiation ◽  
Muscle Twitch ◽  
Velocity Relation ◽  
Voluntary Contractions ◽  
Shortening Contractions

Recently it was demonstrated that postactivation potentiation (PAP), which refers to the enhancement of the muscle twitch torque as a result of a prior conditioning contraction, increased the maximal rate of torque development of tetanic and voluntary isometric contractions ( 3 ). In this study, we investigated the effects of PAP and its decay over time on the load-velocity relation. To that purpose, angular velocity of thumb adduction in response to a single electrical stimulus (twitch), a high-frequency train of 15 pulses at 250 Hz (HFT250), and during ballistic voluntary shortening contractions, performed against loads ranging from 10 to 50% of the maximum torque, were recorded before and after a conditioning 6-s maximal voluntary contraction (MVC). The results showed an increase of the peak angular velocity for the different loads tested after the conditioning MVC ( P < 0.001), but the effect was greatest for the twitch (∼182%) compared with the HFT250 or voluntary contractions (∼14% for both contraction types). The maximal potentiation occurred immediately following the conditioning MVC for the twitch, whereas it was reached 1 min later for the tetanic and ballistic voluntary contractions. At that time, the load-velocity relation was significantly shifted upward, and the maximal power of the muscle was increased (∼13%; P < 0.001). Furthermore, the results also indicated that the effect of PAP on shortening contractions was not related to the modality of muscle activation. In conclusion, the findings suggest a functional significance of PAP in human movements by improving muscle performance of voluntary dynamic contractions.

Short-Latency Crossed Inhibitory Responses in the Human Soleus Muscle

2009 ◽  
Vol 102 (6) ◽  
pp. 3596-3605 ◽  
Author(s):  
Peter W. Stubbs ◽  
Natalie Mrachacz-Kersting
Keyword(s):  
Electrical Stimulation ◽  
Nerve Stimulation ◽  
Muscle Activation ◽  
Tibial Nerve ◽  
Voluntary Contraction ◽  
Short Latency ◽  
Afferent Feedback ◽  
Medial Plantar Nerve ◽  
Muscle Activation Patterns ◽  
Tibial Nerve Stimulation

Even though interlimb coordination is critical in bipedal locomotion, the role of muscle afferent mediated feedback is unknown. The aim of this study was to establish if ipsilateral muscle generated afferent feedback can influence contralateral muscle activation patterns in the human lower limb and to elucidate the mechanisms involved. The effect of ipsilateral tibial nerve stimulation on contralateral soleus (cSOL) responses were quantified. Three interventions were investigated, 1) electrical stimulation applied to the tibial nerve at stimulation intensities from 0 to 100% of maximal M-wave (M-max) with the cSOL contracted from 5 to 15% of maximal voluntary contraction (MVC) and 15 to 30% MVC, 2) ispsilateral tibial nerve stimulation at 75% M-max prior to, during, and following the application of ischemia to the ipsilateral thigh. 3) Electrical stimulation applied to the ipsilateral sural (SuN) and medial plantar nerves at stimulation intensities from 1 to 3 times perceptual threshold. A short-latency depression in the cSOL electromyogram (EMG; onset: 37–41 ms) was observed following ipsilateral tibial nerve stimulation. The magnitude of this depression increased ( P = 0.0005 and P = 0.000001) with increasing stimulus intensities. Ischemia delayed the time of the minimum of the cSOL depression ( P = 0.04). SuN and medial plantar nerve stimulation evoked a longer latency depression [average; 91.2 ms (SuN); 142 ms (medial plantar nerve)] and therefore do not contribute to the response. This is the first study to demonstrate a short-latency depression in the cSOL following ipsilateral tibial nerve stimulation. Due to its short latency, the response is spinally mediated. The involvement of crossed spinal interneurons receiving input from low-threshold muscle afferents is discussed.

scholarly journals Potentiation Increases Peak Twitch Torque by Enhancing Rates of Torque Development and Relaxation

2013 ◽  
Vol 38 ◽  
pp. 83-94 ◽  
Author(s):  
Christian Froyd ◽  
Fernando Gabe Beltrami ◽  
Jørgen Jensen ◽  
Timothy David Noakes
Keyword(s):  
Electrical Stimulation ◽  
Maximal Voluntary Contraction ◽  
Femoral Nerve ◽  
Voluntary Contraction ◽  
Physically Active ◽  
Isometric Maximal Voluntary Contraction ◽  
Rate Of Torque Development ◽  
Voluntary Contractions ◽  
Torque Development ◽  
Similar Peak

Abstract The aim of this study was to measure the extent to which potentiation changes in response to an isometric maximal voluntary contraction. Eleven physically active subjects participated in two separate studies. Single stimulus of electrical stimulation of the femoral nerve was used to measure torque at rest in unpotentiated quadriceps muscles (study 1 and 2), and potentiated quadriceps muscles torque in a 10 min period after a 5 s isometric maximal voluntary contraction of the quadriceps muscles (study 1). Additionally, potentiated quadriceps muscles torque was measured every min after a further 10 maximal voluntary contractions repeated every min (study 2). Electrical stimulation repeated several times without previous maximal voluntary contraction showed similar peak twitch torque. Peak twitch torque 4 s after a 5 s maximal voluntary contraction increased by 45±13% (study 1) and by 56±10% (study 2), the rate of torque development by 53±13% and 82±29%, and the rate of relaxation by 50±17% and 59±22%, respectively, but potentiation was lost already two min after a 5 s maximal voluntary contraction. There was a tendency for peak twitch torque to increase for the first five repeated maximal voluntary contractions, suggesting increased potentiation with additional maximal voluntary contractions. Correlations for peak twitch torque vs the rate of torque development and for the rate of relaxation were r2= 0.94 and r2=0.97. The correlation between peak twitch torque, the rate of torque development and the rate of relaxation suggests that potentiation is due to instantaneous changes in skeletal muscle contractility and relaxation.

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