MMG Amplitude Research Articles

Effect of the Wingate Test on Mechanomyography and Electromyography

The purpose of this investigation was to examine mechanomyographic (MMG) and electromyographic (EMG) amplitude responses of the superficial quadriceps femoris muscles during the Wingate Anaerobic Test (WAnT). Ten healthy adults (age 21 +/- 1.2 years) volunteered to perform the WAnT on a calibrated Monark 894E cycle ergometer while the EMG and MMG signals were recorded. The EMG and MMG amplitude and power output (W) values per 5-second segments of the test were averaged and normalized to the highest value found during the test, respectively. The statistical analysis indicated that EMG amplitude did not change significantly over the 30-second test, but W and MMG amplitude decreased significantly. There is dissociation between EMG and MMG amplitude over the 30-second anaerobic test, providing evidence that MMG amplitude could be used as a monitor of W during such a task. MMG amplitude could potentially be used as a direct monitor of mechanical activity, which could be of benefit to those who train athletes when a direct assessment of mechanical contribution from a given muscle to a fatiguing activity is desired (such as when monitoring an injury), but it must be studied under various conditions, such as the current study, before such applications are made.

Mechanomyographic and Electromyographic Responses During Submaximal to Maximal Eccentric Isokinetic Muscle Actions of the Biceps Brachii

The purpose of this investigation was to determine the mechanomyography (MMG) and electromyography (EMG) amplitude and mean power frequency (MPF) vs. eccentric isokinetic torque relationships for the biceps brachii muscle. Nine adults (mean +/- SD age = 23.1 +/- 2.9 years) performed submaximal to maximal eccentric isokinetic muscle actions of the dominant forearm flexors. After determination of isokinetic peak torque (PT), the subjects randomly performed submaximal step muscle actions in 10% increments from 10 to 90% PT. Polynomial regression analyses indicated that the MMG amplitude vs. eccentric isokinetic torque relationship was best fit with a quadratic model (R(2) = 0.951), where MMG amplitude increased from 10 to 60% PT and then plateaued from 60 to 100% PT. There were linear increases in MMG MPF (r(2) = 0.751) and EMG amplitude (r(2) = 0.988) with increases in eccentric isokinetic torque, but there was no significant change in EMG MPF from 10 to 100% PT. The results suggested that for the biceps brachii, eccentric isokinetic torque was increased to approximately 60% PT through concurrent modulation of the number of active motor units and their firing rates, whereas additional torque above 60% PT was produced only by increases in firing rates. These findings contribute to current knowledge of motor-control strategies during eccentric isokinetic muscle actions and could be useful in the design of training programs.

Effects of KAATSU on muscular function during isometric exercise

Generally, a threshold intensity of 65% 1-RM will induce muscle hypertrophy; however, recent studies using low-intensity (20% 1-RM) exercise combined with vascular restriction (KAATSU) have demonstrated increases in muscle size and strength. PURPOSE: To investigate the EMG and MMG responses, and percent voluntary activation (PVA) of the vastus lateralis (VL) following exposure to low-intensity intermittent isometric exercise in combination with moderate vascular restriction.METHODS: Twelve males (Age = 23.7 ± 4.1 yrs) participated in 1 familiarization trial and 2 experimental trials (with or without KAATSU) each separated by 48 h. Testing order was: a) Resting blood pressure after 5 min rest; b) 5 min warm-up on a cycle ergometer (50 W, 50-70 rpm); c) 2 preexercise 5-s isometric MVCs, 1 min rest between trials; d) 5 sets of 20 intermittent isometric contractions (2-s on / 1-s off) at 20% of MVC, 30-s interset rest periods; and e) 2 post-exercise isometric 5-s MVCs. RESULTS: There were no significant interactions or main effects for time or session for pre- and post-exercise isometric MVCs, with and without KAATSU, for the following parameters: MVC, PVA, EMG amplitude, EMG mean power frequency (MPF), MMG amplitude, and MMG MPF. Average normalized EMG amplitude increased significantly from repetitions 1-4 to 5-8 to 9-12 and MMG amplitude increased significantly from set 1 to 2 for both the KAATSU and no-KAATSU sessions. CONCLUSION: Intermittent isometric contractions at 20% 1-RM, with or without vascular restriction, are not intense enough to cause significant muscular fatigue.

Mechanomyographic amplitude and frequency responses during dynamic muscle actions: a comprehensive review.

The purpose of this review is to examine the literature that has investigated mechanomyographic (MMG) amplitude and frequency responses during dynamic muscle actions. To date, the majority of MMG research has focused on isometric muscle actions. Recent studies, however, have examined the MMG time and/or frequency domain responses during various types of dynamic activities, including dynamic constant external resistance (DCER) and isokinetic muscle actions, as well as cycle ergometry. Despite the potential influences of factors such as changes in muscle length and the thickness of the tissue between the muscle and the MMG sensor, there is convincing evidence that during dynamic muscle actions, the MMG signal provides valid information regarding muscle function. This argument is supported by consistencies in the MMG literature, such as the close relationship between MMG amplitude and power output and a linear increase in MMG amplitude with concentric torque production. There are still many issues, however, that have yet to be resolved, and the literature base for MMG during both dynamic and isometric muscle actions is far from complete. Thus, it is important to investigate the unique applications of MMG amplitude and frequency responses with different experimental designs/methodologies to continually reassess the uses/limitations of MMG.

Mechanomyographic and electromyographic responses to repeated concentric muscle actions of the quadriceps femoris

In comparison to isometric muscle action models, little is known about the electromyographic (EMG) and mechanomyographic (MMG) amplitude and mean power frequency (MPF) responses to fatiguing dynamic muscle actions. Simultaneous examination of the EMG and MMG amplitude and MPF may provide additional insight with regard to the motor control strategies utilized by the superficial muscles of the quadriceps femoris during a concentric fatiguing task. Thus, the purpose of this study was to examine the EMG and MMG amplitude and MPF responses of the vastus lateralis (VL), rectus femoris (RF), and vastus medialis (VM) during repeated, concentric muscle actions of the dominant leg. Seventeen adults (21.8 ± 1.7 yr) performed 50 consecutive, maximal concentric muscle actions of the dominant leg extensors on a Biodex System 3 Dynamometer at velocities of 60° s −1 and 300° s −1. Bipolar surface electrode arrangements were placed over the mid portion of the VL, RF, and VM muscles with a MMG contact sensor placed adjacent to the superior EMG electrode on each muscle. Torque, MMG and EMG amplitude and MPF values were calculated for each of the 50 repetitions. All values were normalized to the value recorded during the first repetition and then averaged across all subjects. The cubic decreases in torque at 60° s −1 ( R 2 = 0.972) and 300° s −1 ( R 2 = 0.931) was associated with a decline in torque of 59 ± 24% and 53 ± 11%, respectively. The muscle and velocity specific responses for the MMG amplitude and MPF demonstrated that each of the superficial muscles of the quadriceps femoris uniquely contributed to the control of force output across the 50 repetitions. These results suggested that the MMG responses for the VL, RF, VM during a fatiguing task may be influenced by a number of factors such as fiber type differences, alterations in activation strategy including motor unit recruitment and firing rate and possibly muscle wisdom.

Non-invasive characterization of single motor unit electromyographic and mechanomyographic activities in the biceps brachii muscle

The aim of the study was to investigate amplitude and frequency content of single motor unit (MU) electromyographic (EMG) and mechanomyographic (MMG) responses. Multi-channel surface EMG and MMG signals were detected from the dominant biceps brachii muscle of 10 volunteers during isometric voluntary contractions at 20%, 50%, and 80% of the maximal voluntary contraction (MVC) force. Each contraction was performed three times in the experimental session which was repeated in three non-consecutive days. Single MU action potentials were identified from the surface EMG signals and their times of occurrence used to trigger the averaging of the MMG signal. At each contraction level, the MUs with action potentials of highest amplitude were identified. Single MU EMG and MMG amplitude and mean frequency were estimated with normalized standard error of the mean within subjects (due to repetition of the measure in different trials and experimental sessions) smaller than 15% and 7%, respectively, in all conditions. The amplitude of the action potentials of the detected MUs increased with increasing force (mean ± SD, 244 ± 116 μV at 20% MVC, and 1426 ± 638 μV at 80% MVC; P < 0.001) while MU MMG amplitude increased from 20% to 50% MVC (40.5 ± 20.9 and 150 ± 88.4 mm/s 2, respectively; P < 0.001) and did not change significantly between 50% and 80% MVC (129 ± 82.7 mm/s 2 at 80% MVC). MU EMG mean frequency decreased with contraction level (20% MVC: 97.2 ± 13.9 Hz; 80% MVC: 86.2 ± 11.4 Hz; P < 0.001) while MU MMG mean frequency increased (20% MVC: 33.2 ± 6.8 Hz; 80% MVC: 40.1 ± 6.1 Hz; P < 0.001). EMG peak-to-peak amplitude and mean frequency of individual MUs were not correlated with the corresponding variables of MMG at any contraction level.

EMG and MMG of agonist and antagonist muscles as a function of age and joint angle

The aim of this study was to determine the effect of elbow joint position on electromyographic (EMG) and mechanomyographic (MMG) activities of agonist and antagonist muscles in young and old women. Surface EMG and MMG were recorded from the triceps and biceps brachii, and brachioradialis muscles during isometric elbow extensions in young and old women. The measurements were carried out at an optimal joint angle ( A o), as well as at smaller ( A s = A o − 30°) and larger ( A l = A o + 30°) angles. The normalized to force EMG amplitude (RMS-EMG/ F) was smaller in old women compared to young in all muscles. The RMS-EMG/ F of the triceps brachii muscle was not affected by muscle length while that of the biceps brachii and brachioradialis muscles increased at shortest muscle length in both groups. The normalized to force MMG amplitude (RMS-MMG/ F) was smaller in old than in young in the triceps brachii muscle only. There was an increase in RMS-MMG/ F with triceps brachii and biceps brachii muscle shortening in both groups, and in the brachioradialis muscle – in young only. Compared to young, older women exhibited a bigger force fluctuation during maximum voluntary contraction, but these did not contribute significantly to the RMS-MMG. Skinfold thickness accounted for the RMS-EMG/ F and RMS-MMG/ F differences seen between old and young women in the biceps brachii muscle only. It is concluded that, the EMG and MMG response to muscles length change in agonist and antagonist muscles is generally similar in old and young women but the optimal angle shifts toward a bigger value in older women.

Relationships For Mechanomyographic Amplitude And Mean Power Frequency Vs. Torque During Isometric And Eccentric Isokinetic Muscle Actions

PURPOSE To examine the mechanomyographic (MMG) amplitude and mean power frequency (MPF) versus torque relationships during isometric and eccentric isokinetic muscle actions. METHODS Eight women (mean age/SD = 20.4/1.3 y) volunteered to perform isometric and eccentric isokinetic leg extension muscle actions at 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100% of maximal voluntary contraction (MVC) and peak torque (PT) on a Cybex 6000 dynamometer. An accelerometer (Entran, EGAS-FT-10- /V05) was placed on the vastus medialis to detect the MMG signal. The amplitude of the MMG signal was expressed as root mean square (rms), while frequency data were expressed as mean power frequency (MPF). Torque (Nm) was recorded by the dynamometer. RESULTS Polynomial regression analyses indicated that the relationship for MMG amplitude versus MVC was linear (r∧2 = 0.930) for the isometric muscle actions, but there was no significant relationship between MMG amplitude and PT for the eccentric isokinetic muscle actions. For the isometric and eccentric isokinetic muscle actions, the MMG MPF versus % MVC or % PT relationships were linear (r∧2 = 0.957 and 0.920, respectively). CONCLUSIONS The different torque-related responses for MMG amplitude and MPF may reflect differences in the motor control strategies that modulate torque production for isometric versus eccentric isokinetic muscle actions. These results suggested that isometric torque production was modulated by a combination of recruitment and firing rate, while eccentric isokinetic torque production was modulated primarily through firing rate.

The Effect Of Mechanography As A Biofeedback Mechanism For Muscle Relaxation And Performance

Mechanomyography (MMG) is the recording of muscular vibrations that has been shown to be helpful in providing biofeedback to subjects when attempting to control an external prosthesis (Barry et al., Arch Phys Med Rehabil 67:267–269, 1986). No previous studies however, have determined whether MMG can be utilized to provide information to subjects on their muscle function that will allow for enhanced muscular relaxation and/or performance. PURPOSE The purpose of the present study was to examine the MMG signal as a biofeedback mechanism during muscular relaxation and with isotonic repetitions to fatigue. METHODS On two separate occasions twelve adult (mean±SD; age=22.0±1.1 yrs) subjects (weight=82.3±29.2 kg; height=165.7±49.0 cm) were instructed to relax their biceps brachii muscle as much as possible while being provided with (by viewing a computer screen graphically displaying the MMG signal) MMG biofeedback (BIO) and then without MMG biofeedback (NOBIO). EMG and MMG were detected midway over the biceps brachii during testing. Following the relaxation protocol, subjects performed as many repetitions as possible at 85% of their 1-RM with BIO and NOBIO using the seated preacher curl bar. RESULTS Paired t-tests revealed significantly (p<0.05) lower MMG amplitude (mean±SEM; BIO=0.6±0.1 mV; NOBIO=1.1±0.2 mV) but no significant difference in EMG amplitude (BIO=6.6±0.7 μ NOBIO=10.4±2.4 μ) for BIO when subjects were instructed to relax their muscle. There was no significant difference in the number of forearm flexion repetitions performed for BIO (mean±SD=7.9±0.4 reps) versus NOBIO (8.1±0.6 reps). CONCLUSION The results of the present study revealed that using MMG as a biofeedback technique can enhance the development of muscle relaxation but was not useful when performing forearm flexion repetitions to fatigue. Future studies are necessary to determine if MMG can be used for other purposes (ie., pain control, improved athletic performance for other activities, diagnosis of muscle diseases) that may be sensitive to biofeedback.

Gender Comparisons of Mechanomyographic Amplitude and Mean Power Frequency versus Isometric Torque Relationships

This study compared the patterns of mechanomyographic (MMG) amplitude and mean power frequency vs. torque relationships in men and women during isometric muscle actions of the biceps brachii. Seven men (mean age 23.9 +/- 3.5 yrs) and 8 women (mean 21.0 +/- 1.3 yrs) performed submaximal to maximal isometric muscle actions of the dominant forearm flexors. Following determination of the isometric maximum voluntary contraction (MVC), they randomly performed submaximal step muscle actions in 10% increments from 10% to 90% MVC. Polynomial regression analyses indicated that the MMG amplitude vs. isometric torque relationship for the men was best fit with a cubic model (R(2) = 0.983),,where MMG amplitude increased slightly from 10% to 20% MVC, increased rapidly from 20% to 80% MVC, and plateaued from 80% to 100% MVC. For the women, MMG amplitude increased linearly (r(2) = 0.949) from 10% to 100% MVC. Linear models also provided the best fit for the MMG mean power frequency vs. isometric torque relationship in both the men (r(2) = 0.813) and women (r(2) = 0.578). The results demonstrated gender differences in the MMG amplitude vs. isometric torque relationship, but similar torque-related patterns for MMG mean power frequency. These findings suggested that the plateau in MMG amplitude at high levels of isometric torque production for the biceps brachii in the men, but not the women, may have been due to greater isometric torque, muscle stiffness, and/or intramuscular fluid pressure in the men, rather than to differences in motor unit activation strategies for modulating isometric torque production.

Mechanomyographic and Electromyographic Responses of the Vastus Medialis Muscle During Isometric and Concentric Muscle Actions

The purpose of this study was to examine the patterns for the mechanomyographic (MMG) and electromyographic (EMG) amplitude and mean power frequency (MPF) vs. torque relationships during submaximal to maximal isometric and isokinetic muscle actions. Seven men (mean +/- SD age, 22.4 +/- 1.3 years) volunteered to perform isometric and concentric isokinetic leg extension muscle actions at 20, 40, 60, 80, and 100% of maximal voluntary contraction (MVC) and peak torque (PT) on a Cybex II dynamometer. A piezoelectric MMG recording sensor was placed between bipolar surface EMG electrodes on the vastus medialis. Polynomial regression and separate 1-way repeated-measures analysis of variance were used to analyze the EMG amplitude, MMG amplitude, EMG MPF, and MMG MPF data for the isometric and isokinetic muscle actions. For the isometric muscle actions, EMG amplitude (R(2) = 0.999) and MMG MPF (R(2) = 0.946) increased to MVC, mean MMG amplitude increased to 60% MVC and then plateaued, and mean EMG MPF did not change (p > 0.05) across torque levels. For the isokinetic muscle actions, EMG amplitude (R(2) = 0.988) and MMG amplitude (R(2) = 0.933) increased to PT, but there were no significant mean changes with torque for EMG MPF or MMG MPF. The different torque-related responses for EMG and MMG amplitude and MPF may reflect differences in the motor control strategies that modulate torque production for isometric vs. dynamic muscle actions. These results support the findings of others and suggest that isometric torque production was modulated by a combination of recruitment and firing rate, whereas dynamic torque production was modulated primarily through recruitment.

The acute effects of static stretching on peak torque, mean power output, electromyography, and mechanomyography

The purpose of this study was to examine the acute effects of static stretching on peak torque (PT), the joint angle at PT, mean power output (MP), electromyographic (EMG) amplitude, and mechanomyographic (MMG) amplitude of the vastus lateralis (VL) and rectus femoris (RF) muscles during maximal, voluntary concentric isokinetic leg extensions at 60 and 240 degrees x s(-1) of the stretched and unstretched limbs. Twenty-one volunteers [mean age (SD) 21.5 (1.3) years] performed maximal, voluntary concentric isokinetic leg extensions for the dominant and non-dominant limbs at 60 and 240 degrees x s(-1). Surface EMG (muVrms) and MMG (mVrms) signals were recorded from the VL and RF muscles during the isokinetic tests. PT (Nm), the joint angle at PT, and MP (W) were calculated by a dynamometer. Following the initial isokinetic tests, the dominant leg extensors were stretched using four static stretching exercises. After the stretching, the isokinetic tests were repeated. PT decreased (P< or =0.05) from pre- to post-stretching for the stretched limb at 60 and 240 degrees x s(-1) and for the unstretched limb at 60 degrees x s(-1). EMG amplitude of the VL and RF also decreased (P< or =0.05) from pre- to post-stretching for the stretched and unstretched limbs. There were no stretching-induced changes (P>0.05) for the joint angle at PT, MP, or MMG amplitude. These findings indicated stretching-induced decreases in force production and muscle activation. The decreases in PT and EMG amplitude for the unstretched limb suggested that the stretching-induced decreases may be due to a central nervous system inhibitory mechanism.

Resting Mechanomyography After Aerobic Exercise

A number of mechanisms have been proposed for the elevation in oxygen consumption following exercise. Biochemical processes that return muscle to its preexercise state do not account for all the oxygen consumed after exercise. It is possible that mechanical activity in resting muscle, which produces low frequency vibrations (i.e., muscle sounds: mechano-myographic [MMG] activity), could contribute to the excess postexercise oxygen consumption. Therefore the purpose of this study was to determine whether the resting MMG amplitude changes after exercise, and whether the change is related to the elevation in oxygen consumption (VO2). Ten young male subjects (22.9 yrs) performed 30 minutes of exercise on a cycle ergometer at an intensity corresponding to 70% peak VO2. Oxygen consumption was measured by indirect calorimetry, and MMG by an accelerometer placed over the mid-quadriceps before exercise and for 5.5 hours after exercise. MMG activity, expressed as mean absolute acceleration, was significantly elevated for the 5.5 hours of measurement after exercise (p < 0.05). MMG and VO2 decayed exponentially after exercise with time constants of 7.2 minutes and 7.4 minutes, respectively. We conclude that muscle is mechanically active following exercise and that this may contribute to an elevated VO2.

Mechanomyographic Responses of the Vastus Medialis to Isometric and Eccentric Muscle Actions

The mechanomyographic (MMG) signal may be used to examine the motor control strategies used to modulate torque during various types of muscle actions. Therefore, the purpose of this study was to examine the MMG amplitude and mean power frequency (MPF) versus torque relationships during isometric and eccentric isokinetic muscle actions. Eleven adults (mean age +/- SD = 20.8 +/- 1.4 yr) volunteered to perform isometric and eccentric isokinetic leg extension muscle actions at 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100% of peak torque on a Cybex 6000 dynamometer. A piezoelectric crystal contact sensor was placed on the vastus medialis to detect the MMG signal. Polynomial regression analyses indicated that for the isometric muscle actions, the relationships for MMG amplitude (r2 = 0.984) and MPF (r2 = 0.989) versus torque were linear. For the eccentric isokinetic muscle actions, the relationships for MMG amplitude (r2 = 0.580) and MPF (r2 = 0.961) versus torque were also linear. The patterns for MMG amplitude and MPF may reflect the motor control strategies that modulate torque production for isometric and eccentric isokinetic muscle actions. Based on the results of this and previous studies, it appears that for the vastus medialis, torque is modulated in a similar manner for isometric, concentric, and eccentric isokinetic muscle actions. Specifically, these findings suggest that gradation of torque involves increases in recruitment and firing rate to 100% voluntary torque production.

Mechanomyographic amplitude and mean power frequency versus torque relationships during isokinetic and isometric muscle actions of the biceps brachii

The purpose of this investigation was to determine the mechanomyographic (MMG) amplitude and mean power frequency (MPF) versus torque (or force) relationships during isokinetic and isometric muscle actions of the biceps brachii. Ten adults (mean±SD age=21.6±1.7 years) performed submaximal to maximal isokinetic and isometric muscle actions of the dominant forearm flexors. Following determination of isokinetic peak torque (PT) and the isometric maximum voluntary contraction (MVC), the subjects randomly performed submaximal step muscle actions in 10% increments from 10% to 90% PT and MVC. Polynomial regression analyses indicated that MMG amplitude increased linearly with torque during both the isokinetic ( r 2=0.982) and isometric ( r 2=0.956) muscle actions. From 80% to 100% of isometric MVC, however, MMG amplitude appeared to plateau. Cubic models provided the best fit for the MMG MPF versus isokinetic ( R 2=0.786) and isometric ( R 2=0.940) torque relationships, although no significant increase in MMG MPF was found from 10% to 100% of isokinetic PT. For the isometric muscle actions, however, MMG MPF remained relatively stable from 10% to 50% MVC, increased from 50% to 80% MVC, and decreased from 80% to 100% MVC. The results demonstrated differences in the MMG amplitude and MPF versus torque relationships between the isokinetic and isometric muscle actions. These findings suggested that the time and frequency domains of the MMG signal may be useful for describing the unique motor control strategies that modulate dynamic versus isometric torque production.

Mechanomyographic and Electromyographic Responses to Repeated, Concentric Muscle Actions

0815 PURPOSE: The purpose of this study was to examine the mechanomyographic (MMG) and electromyographic (EMG) amplitude and mean power frequency (MPF) responses of the superficial quadricep femoris muscles during repeated, concentric muscle actions of the dominant leg. METHODS: Fifteen adults (21.8 ± 1.7 yrs) performed 50 consecutive, maximal concentric muscle actions on a Biodex System 3 Dynamometer at a velocity of 60°×s−1. Bipolar surface electrode arrangements were placed over the mid portion of the vastus lateralis (VL), rectus femoris (RF) and vastus medialis (VM) muscles with a MMG contact sensor placed adjacent to the superior EMG electrode on each muscle. Torque, power, and MMG and EMG amplitude and MPF values were calculated for each of the 50 repetitions. All values were normalized to the value recorded during the first repetition and then averaged across all subjects. RESULTS: Polynomial regression analysis indicated cubic decreases in torque (R2 = 0.976) and power (R2 = 0.973) across all 50 muscle actions. EMG amplitude increased quadratically for the VL (R2 = 0.362) and cubically for the RF (R2 = 0.528) and VM (R2 = 0.419). EMG MPF decreased across muscle actions with a quadratic relationship for the VL (R2 = 0.865) and VM (R2 = 0.821) and a cubic relationship for the RF (R2 = 0.979). MMG amplitude decreased cubically for the VL (R2 = 0.316) and RF (R2 = 0.563), but there was no change in the MPF for the VM (R2 = 0.043). MMG MPF decreased quadratically for the VL (R2 = 0.601) and linearly for the RF (R2 = 0.788) and VM (R2 = 0.457). CONCLUSION: These findings indicate muscle-specific dissociations between EMG and MMG amplitude across the 50 repetitions where EMG amplitude increased and MMG amplitude decreased. The decrease in MMG amplitude and MPF may be due to a decrease in motor unit discharge rates associated with “muscle wisdom”. Further, these results suggest that “muscle wisdom” may be muscle specific. Future studies should examine the applicability of muscle wisdom during dynamic muscle actions.

Peak Torque, Mechanomyographic, And Electromyographic Responses Of The Vastus Medialis To Isometric Strength Training

2335 PURPOSE: The present investigation examined the peak torque (PT), mechanomyographic (MMG), and electromyographic (EMG) responses of the vastus medialis (VM) to eight weeks of isometric leg extension strength training. METHODS: Thirteen adult male volunteers (age19-29) were randomly assigned to a training (TRN) group (n = 6) or a control (CTL) group (n = 7). Maximal isometric PT for leg extension was measured along with EMG and MMG amplitude at leg flexion angles of 30°, 60°, and 90°. Measurements were collected three times during the study (weeks 0, 4, and 8). The TRN subjects performed unilateral isometric muscle actions with the non-dominant (ND) limb at 60° of leg flexion. The first two weeks, subjects performed two sets of muscle actions at 80% of their maximal isometric PT at 60°. For the remaining six weeks, subjects performed three sets of muscle actions at 80% of their maximal isometric PT. Maximal PT at 60° was reassessed at the end of the fourth week of training to adjust the training torque values. Each set consisted of ten repetitions lasting six seconds each. The subjects trained three times a week. RESULTS: The results indicated significant (p<0.05) increases in PT for the ND limb of the TRN group between week 0 and week 4 and between week 0 and week 8 of 9.8% and 14.8% respectively, at 60°. There was also a significant (p<0.05) increase in EMG amplitude for the ND limb of the TRN group between week 0 and week 8 of 46% at 60°. There was no training effect on MMG amplitude. CONCLUSION: These findings indicated that changes in muscle activation of the vastus medialis might be responsible for the training-induced increase in PT. The findings also indicated that there was no cross-training effect in the untrained limb of the TRN group for PT, MMG amplitude, and EMG amplitude.

Peak Torque, Mechanomyographic, And Electromyographic Responses Of The Vastus Medialis To Isometric Strength Training

2335 PURPOSE: The present investigation examined the peak torque (PT), mechanomyographic (MMG), and electromyographic (EMG) responses of the vastus medialis (VM) to eight weeks of isometric leg extension strength training. METHODS: Thirteen adult male volunteers (age19-29) were randomly assigned to a training (TRN) group (n = 6) or a control (CTL) group (n = 7). Maximal isometric PT for leg extension was measured along with EMG and MMG amplitude at leg flexion angles of 30°, 60°, and 90°. Measurements were collected three times during the study (weeks 0, 4, and 8). The TRN subjects performed unilateral isometric muscle actions with the non-dominant (ND) limb at 60° of leg flexion. The first two weeks, subjects performed two sets of muscle actions at 80% of their maximal isometric PT at 60°. For the remaining six weeks, subjects performed three sets of muscle actions at 80% of their maximal isometric PT. Maximal PT at 60° was reassessed at the end of the fourth week of training to adjust the training torque values. Each set consisted of ten repetitions lasting six seconds each. The subjects trained three times a week. RESULTS: The results indicated significant (p<0.05) increases in PT for the ND limb of the TRN group between week 0 and week 4 and between week 0 and week 8 of 9.8% and 14.8% respectively, at 60°. There was also a significant (p<0.05) increase in EMG amplitude for the ND limb of the TRN group between week 0 and week 8 of 46% at 60°. There was no training effect on MMG amplitude. CONCLUSION: These findings indicated that changes in muscle activation of the vastus medialis might be responsible for the training-induced increase in PT. The findings also indicated that there was no cross-training effect in the untrained limb of the TRN group for PT, MMG amplitude, and EMG amplitude.

Time and Frequency Domain Analyses of the Surface Mechanomyogram During Submaximal to Maximal Isokinetic Muscle Actions of the Biceps Brachii

2346 PURPOSE: The purpose of this study was to examine the mechanomyographic (MMG) amplitude and mean power frequency (MPF) versus torque relationships during isokinetic muscle actions of the biceps brachii. METHODS: Ten adults (mean ± SD age = 21.6 ± 1.7 yrs) performed submaximal to maximal isokinetic muscle actions of the dominant forearm flexors at a velocity of 30°·s−1 on a calibrated Cybex II dynamometer. Following determination of isokinetic peak torque (PT), the subjects randomly performed submaximal step muscle actions in 10% increments from 10% to 90% PT. RESULTS: Polynomial regression analyses indicated that MMG amplitude increased linearly (r2 = 0.982), while MMG MPF was best fit with a cubic (R2 = 0.786) model with increases in isokinetic torque from 10% to 100% PT. There were no significant mean differences, however, in MMG MPF from 10% to 100% PT. CONCLUSION: The linear increase in MMG amplitude and relatively stable MMG MPF with increases in isokinetic torque to 100% PT may indicate that recruitment of additional motor units, with little change in the global motor unit firing rate, is the primary motor control strategy for increasing torque production during dynamic muscle actions of the biceps brachii.

Time and Frequency Domain Analyses of the Surface Mechanomyogram During Submaximal to Maximal Isokinetic Muscle Actions of the Biceps Brachii

2346 PURPOSE: The purpose of this study was to examine the mechanomyographic (MMG) amplitude and mean power frequency (MPF) versus torque relationships during isokinetic muscle actions of the biceps brachii. METHODS: Ten adults (mean ± SD age = 21.6 ± 1.7 yrs) performed submaximal to maximal isokinetic muscle actions of the dominant forearm flexors at a velocity of 30°·s−1 on a calibrated Cybex II dynamometer. Following determination of isokinetic peak torque (PT), the subjects randomly performed submaximal step muscle actions in 10% increments from 10% to 90% PT. RESULTS: Polynomial regression analyses indicated that MMG amplitude increased linearly (r2 = 0.982), while MMG MPF was best fit with a cubic (R2 = 0.786) model with increases in isokinetic torque from 10% to 100% PT. There were no significant mean differences, however, in MMG MPF from 10% to 100% PT. CONCLUSION: The linear increase in MMG amplitude and relatively stable MMG MPF with increases in isokinetic torque to 100% PT may indicate that recruitment of additional motor units, with little change in the global motor unit firing rate, is the primary motor control strategy for increasing torque production during dynamic muscle actions of the biceps brachii.