Fatigue responses of human triceps surae muscles during repetitive maximal isometric contractions (original) (raw)
Related papers
Journal of Applied Physiology, 2004
This study aimed to investigate central and peripheral contributions to fatigue during repeated maximal voluntary isometric plantar flexions (MVCs). Changes in joint torque, level of activation (LOA), resting twitch amplitude (RT), electromyographic signals (EMG), and presynaptic inhibition of Ia afferents were investigated during 9 bouts of 10 MVCs. MVCs lasted for 2 s and were separated by 1 s. The interval between bouts was 10 s. Electrical stimulation was applied to the tibial nerve; at rest to evoke RTs, M waves, and two (1.5-s interval) H reflexes; with the soleus EMG at 30% of that during MVC to evoke M waves and two H reflexes; and during MVCs to measure LOA. Over the nine bouts, LOA decreased by 12.6% and RT by 16.2%. EMG root mean square during MVCs remained unchanged for the soleus and tibialis anterior muscles, but it decreased for medial gastrocnemius. Peripheral fatigue (decrease in RT) was positively correlated to LOA, whereas central fatigue (decrease in LOA) was not...
Elastic band exercise induces greater neuromuscular fatigue than phasic isometric contractions
Journal of Electromyography and Kinesiology, 2018
This study investigated the neuromuscular fatigue following an elastic band exercise (EB) of the plantar flexors, compared to an intermittent phasic isometric exercise (ISO). Eleven young healthy males (age: 24.2 ± 3.7) took part in the study, consisting of one experimental session involving two 5-min fatiguing protocols separated by 20 min rest and performed randomly. Both exercises were performed at maximal motor output of the plantar flexor muscles, EMG being used as a feedback signal. Neuromuscular fatigue was assessed through changes in maximal voluntary contraction (MVC) and in evoked responses of soleus and gastrocnemii muscles to posterior tibial nerve stimulation (H-reflex, M-wave, V-wave). Both conditions induced significant decrease in MVC force, but to a greater extent after EB (−20.0 ± 5.1%, P < 0.001) than after ISO (−12.3 ± 4.6%, P = 0.037). While no effect was observed in M-wave amplitude after both exercises, EB resulted in greater decrease of normalized H-reflexes compared to isometric condition. Normalized V-wave significantly decreased only after EB. As a conclusion, the greater fatigability found after EB as compared to ISO was underlain by muscular as well as nervous factors. This higher impact was attributed to the dynamic nature of elastic band exercise as compared to isometric contractions.
Isokinetics and Exercise Science
Effect of isotonic and isometric knee extension exercises on mechanical and electromyographical specificity of fatigue. Isokinetics and Exercise Science , 10:167-175 ***Note: Figures may be missing from this format of the document Abstract.: This study investigated the effects of isotonic and isometric knee extension exercises on strength, power, and surface EMG in male and female populations. Using the knee extensors, ten males and ten females performed a 120 s MVIC and 120 maximal isotonic contractions. Prior to each exercise (t = pre) knee extensor isometric peak torque (strength) and average peak power (power) were tested utilizing three, 3 s MVIC's and three maximal isotonic contractions, respectively. Following each exercise, strength and power were assessed immediately after (t =: 00) and at 2.5 (t =: 02.5), 5 (t =: 05), 10 (t =: 10), and 15 (t =: 15) minutes. All strength and power measures were normalized to the respective t = pre value. Vastus lateralis surface EMG signals were collected during all muscle testing and normalized to the respective tire value. Following isometric exercise, both strength and power at t =: 00 (68.7% ± 8.7% & 88.0% ± 8.7%) and t =: 02.5 (82.2% ± 17.8% & 95.2% ± 5.0%) significantly decreased from t=pre (100% ± 0.0%) (p < 0.05) with greater decreases in strength at each time point (p < 0.05). EMG analysis revealed a significant EMG amplitude decrease (p < 0.05) at t =: 00 and t =: 02.5 during strength testing with respect to t=pre. Following isotonic exercise, both strength and power at t =: 00 (68.0% ± 13.2% & 38.8% ± 10.7%) and t =: 02.5 (84.5% ± 14.9% & 81.6% ± 14.5%) significantly decreased from t=pre (100% ± 0.0%) with a greater power decrease at t =: 00 (p < 0.05). The EMG amplitude of males was significantly less at t =: 00 than the respective EMG amplitude for females (p < 0.05) (irrespective of testing condition). We conclude that muscle performance in the fatigued state is dependent upon the type of exercise performed. Article: INTRODUCTION: During the past years of research addressing muscle performance during and following fatiguing exercise, the isometric contraction has been considered the gold standard of muscle force producing capability in the laboratory setting. The muscle force production values acquired from isometric contractions are often referred to as "strength" [11]. However in sporting activities the majority of muscle contractions are dynamic in nature. Power, a variable that takes into account contraction force and velocity, is important in sports that demand explosive movements. Throughout the remainder of this paper strength will refer to isometric torque production and power will refer to dynamic, maximal efforts of the muscle/joint complex.
European Journal of Applied Physiology, 1998
The aims of this study were to investigate if low-frequency fatigue (LFF) dependent on the duration of repeated muscle contractions and to compare LFF in voluntary and electrically induced exercise. Male subjects performed three 9-min periods of repeated isometric knee extensions at 40% maximal voluntary contraction with contraction plus relaxation periods of 30 plus 60 s, 15 plus 30 s and 5 plus 10 s in protocols 1, 2 and 3, respectively. The same exercise protocols were repeated using feedback-controlled electrical stimulation at 40% maximal tetanic torque. Before and 15 min after each exercise period, knee extension torque at 1, 7, 10, 15, 20, 50 and 100 Hz was assessed. During voluntary exercise, electromyogram root mean square (EMG rms ) of the vastus lateralis muscle was evaluated. The 20-Hz torque:100-Hz torque (20:100 Hz torque) ratio was reduced more after electrically induced than after voluntary exercise (P < 0.05). During electrically induced exercise, the decrease in 20:100 Hz torque ratio was gradually (P < 0.05) reduced as the individual contractions shortened. During voluntary exercise, the decrease in 20:100 Hz torque ratio and the increase in EMG rms were greater in protocol 1 (P < 0.01) than in protocols 2 and 3, which did not dier from each other. In conclusion, our results showed that LFF is dependent on the duration of individual muscle contractions during repetitive isometric exercise and that the electrically induced exercise produced a more pronounced LFF compared to voluntary exercise of submaximal intensity.
IEEE Transactions on Biomedical Engineering, 2006
The quantification of the progression of muscle fatigue during a sustained contraction is a valuable tool in several clinical applications, ranging from the evaluation of functional impairment to the development of specific rehabilitative and training protocols. In these fields, great importance is given to isokinetic contractions. The aim of this paper was twofold: first, to propose signal processing methods for assessing the spectral changes of the surface myoelectric signal due to fatigue during isokinetic concentric and eccentric knee flexion-extension movements at a given angular velocity (60 degrees/s); second, to analyze the electrical manifestations of muscle fatigue of four thigh muscles (vastus lateralis, vastus medialis, rectus femoris, and biceps femoris) in the two contraction modalities (i.e. concentric versus eccentric). We demonstrated that, when considering concentric contractions, localized muscle fatigue can be assessed by computing the mean frequency of the frequency marginal of the time-frequency distribution derived from the surface myoelectric signal collected during each contraction cycle. Stronger nonstationarities were observed in the surface myoelectric data recorded within each cyclical movement of the studied eccentric exercise. Thus we propose the computation of the instantaneous mean frequency of the signal based on an original cross-time-frequency algorithm, which proved more sensitive than the frequency marginal in tracking the spectral changes associated with localized muscle fatigue. We derived the average fatigue pattern of the investigated muscles from experimental data recorded from a sample population consisting of twenty healthy subjects and we statistically compared the two contraction modalities. Our results showed that the electrical manifestations of muscle fatigue during concentric contractions were higher than those found during eccentric contractions, although in the latter modality the torque exerted and the mechanical work produced by the subjects were larger than those recorded during the concentric exercise. The results presented in this paper have potential clinical application and they could play an important future role in investigations of muscle behavior during dynamic, highly fatiguing contractions.
2019
Background. Simultaneous tiredness of two or more muscles around a joint can be defined as coordinated fatigue (co-fatigue) and might occur between agonist and antagonist muscles, and vary according to the level of sporting activity levels or gender. Objectives. The aim of this study was to determine the levels of coordinated fatigue in agonist and antagonist muscles during squat-press exercise. Methods. Twenty athletes and twenty sedentary subjects participated in the study. Surface electromyography signals of the rectus femoris, vastus lateralis obliquus, biceps femoris and semitendinosus muscles were recorded at the squat press position for 15 seconds during isometric contraction. Measurements were repeated five times and a 2-minute rest period was allowed between repetitions. After erroneous EMG elimination, movement artefacts were removed by using a 20 Hz high-pass Butterworth filter. Then, as a well-recognized fatigue index, the median frequency (MF) of each filtered middle part of the EMG signal (5 to 10 s. of contraction) was calculated, given that it is known that the MF decreases during isometric contractions. Finally, each MF-based co-fatigue index was calculated by dividing the mean RF and VLO median frequencies by the mean ST and BF median frequencies. The cumulative co-fatigue values of "male vs. female" and "sedentary vs. athlete" comparisons were performed by using a two-sided Student t-test with a Bonferroni correction. Results. There was a statistically significant (Bonferroni corrected p-value < 0.05) difference between the mean female (1.57 0.53) and the mean male (1.23 0.17) co-fatigue values, while there was no statistically significant difference between the mean co-fatigue values of sedentary (1.51 0.52) and athlete (1.29 0.27) subjects. Conclusion. The offered co-fatigue indices might be useful for other sports, physiotherapy and related areas if sufficient scientific proof is accumulated.
Pflügers Archiv - European Journal of Physiology, 2006
The purpose of this investigation was to examine the effects of voluntary muscular fatigue in one lower limb and determine whether a 'cross-over' of fatigue is evident in the contralateral limb. Twenty-eight subjects (13 males and 15 females) performed a series of voluntary and evoked isometric contractions of both the dominant (exercised) and non-dominant (non-exercised) leg extensor muscles, prior to and after a fatigue protocol consisting of a 100-s sustained maximal isometric contraction (MVC) performed by the dominant limb only. Force values and surface electromyography (EMG) from the vastus lateralis muscle were obtained allowing for the determination of twitch and compound action potential (M-wave) values. Maximal twitch tension and peak-to-peak amplitude were significantly decreased after the fatigue test in the dominant limb, as was maximal voluntary force (∼65 N reduction), EMG activity (∼0.1 mV decrease) and voluntary activation (∼17% decline). However, no significant changes were observed in the non-dominant limb with respect to twitch and M-wave properties nor in MVC force. The voluntary activation of the non-dominant limb decreased significantly by 8.7% after the fatigue test, which was performed only on the dominant limb. The results of the present study suggest that the decrease in force production in the exercised limb was primarily related to peripheral fatigue mechanisms, with central fatigue making a lesser contribution. Centrally mediated mechanisms appear to be the sole contributor to fatigue in the non-exercised limb suggesting an anticipatory fatigue response and a 'cross-over' of central fatigue between the exercised and non-exercised contralateral limb.
Journal of Electromyography and Kinesiology, 2006
The purpose of this study was to examine the differences in electromyographic activity of agonist and antagonist knee musculature between a maximal and a submaximal isokinetic fatigue protocol. Fourteen healthy males (age: 24.3 ± 2.5 years) performed 25 maximal (MIFP) and 60 submaximal (SIFP) isokinetic concentric efforts of the knee extensors at 60°s À1 , across a 90°range of motion. The two protocols were performed a week apart. The EMG activity of vastus medialis (VM), vastus lateralis (VL) and biceps femoris (BF) were recorded using surface electrodes. The peak torque (PT) and average EMG (aEMG) were expressed as percentages of pre-fatigue maximal value. One-way analysis of variance indicated a significant (p < 0.05) decline of PT during the maximal (45.7%) and submaximal (46.8%) protocols. During the maximal test, the VM and VL aEMG initially increased and then decreased. In contrast, VM and VL aEMG continuously increased during submaximal testing (p < 0.05). The antagonist (BF) aEMG remained constant during maximal test but it increased significantly and then declined during the submaximal testing. The above results indicate that agonist and antagonist activity depends on the intensity of the selected isokinetic fatigue test.
Electromyographic fatigue thresholds of the superficial muscles of the quadriceps femoris
European Journal of Applied Physiology and Occupational Physiology, 1995
The purpose of this investigation was to compare the thresholds of neuromuscular fatigue determined simultaneously from the vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) muscles using the electromyographic fatigue threshold (EMGFT) test, Eight adult volunteers [mean (SD) age, 33 (10) years] served as subjects for this investigation. The results of a one-way repeated measured ANOVA indicated that there was a significant (P < 0.05) difference among the mean EMGFT values for the VL [248(31)W], VM [-223(43)W] and RF [220(30)W] muscles. Tukey post-hoc comparisons indicated that the EMGFT for the RF was significantly (P < 0.05) lower than that of the VL. These findings suggested that during cycle ergometry there is a dissociation in neuromuscular fatigue characteristics of the superficial muscles of the quadriceps femoris group.