Excess post-exercise oxygen consumption is not associated with mechanomyographic amplitude after incremental cycle ergometry in the quadriceps femoris muscles

Introduction: The purpose of this study was to understand the relationship between the mechanical activities of the three superficial quadriceps muscles and excess post‐exercise oxygen consumption (EPOC) after incremental cycle ergometer exercise. Methods: Twelve healthy male volunteers had mechanomyographic (MMG) and electromyographic (EMG) activity of the superficial quadriceps muscles recorded 30 minutes before incremental cycle ergometry and 60 minutes after the exercise work bout. Results: The results indicate significant time‐constant values for EPOC and MMG amplitude for the three superficial quadriceps muscles during the 60‐minute post‐exercise recovery period. For EMG amplitude no decay patterns were found for the three muscles. In addition, there were no mean differences between the MMG values for the three muscles that were significantly different from EPOC. Conclusions: These results suggest that EPOC after exercise could not be exclusively attributed to elevated activity of the working muscles. Muscle Nerve 44: 432–438, 2011     

A wavelet‐based analysis of surface mechanomyographic signals from the quadriceps femoris

The purpose of this study was to use a wavelet analysis designed specifically for surface mechanomyographic (MMG) signals to examine the MMG responses of the vastus lateralis (VL), rectus femoris (RF), and vastus medialis (VM) muscles. Fifteen healthy men [age (mean ± SD): 26.4 ± 6.1 years] volunteered to perform isometric muscle actions of the dominant leg extensors at 20%, 40%, 60%, 80%, and 100% of the maximum voluntary contraction (MVC). During each muscle action, surface MMG signals were detected from the VL, RF, and VM and processed with the MMG wavelet analysis. The results show that, for the VL and VM muscles, there was compression of the total MMG intensity spectra toward low frequencies for most force levels above 20% MVC. For the RF, however, the peak of the total MMG intensity spectrum occurred at approximately 30–40 HZ for all force levels. Because the VL, RF, and VM are all innervated by the femoral nerve, the discrepancies among the three muscles for total MMG intensity in each wavelet band may have been due to differences in architecture, muscle stiffness, and/or intramuscular pressure. Muscle Nerve 39: 355–363, 2009     

Comparison of mechanomyographic sensors during incremental cycle ergometry for the quadriceps femoris

The purpose of this study was to examine the mechanomyographic (MMG) amplitude and mean power frequency (MPF) versus power output relationships for the vastus lateralis and rectus femoris muscles during incremental cycle ergometry between the piezoelectric contact sensor (HP) and the accelerometer (ACC) sensor. Nine men performed an incremental cycle ergometry test to voluntary exhaustion. Polynomial regression analyses on a subject‐by‐subject basis indicated that the relationship between the normalized MMG amplitude versus normalized power output was best fit with either a linear, quadratic, or cubic model. These patterns were consistent between sensors for each muscle for each subject. No consistent relationship was found for MMG MPF within subjects and between muscle groups. In addition, there were no significant sensor × power output interactions for normalized MMG amplitude or MPF. These results suggest that, for cycle ergometry, the HP and ACC sensors provide similar information for the interpretation of motor control strategies during continuous exercise. Muscle Nerve, 2010     

Assessment of the reliability of central and peripheral fatigue after sustained maximal voluntary contraction of the quadriceps muscle

The aim of the present study was to further confirm the validity of measurements for characterizing neuromuscular alterations by establishing their reliability both before and after fatigue. Thirteen men (28 +/- 5 years) volunteered to participate in two separate identical sessions requiring the performance of a sustained maximal voluntary contraction (MVC) with the quadriceps muscle for 2 min. MVC and transcutaneous electrical stimulations were used before and immediately after the fatiguing contraction to investigate the reliability of MVC torque, central activation, and peripheral variables (M-wave properties, peak twitch, peak doublet) within and between sessions. Based on previous and present results, we advise the use of (1) voluntary activation level with potentiated doublet as a reference to describe central fatigue, (2) electromyographic activity of vastus lateralis muscle as a surrogate for quadriceps for both voluntary and evoked contraction, and (3) potentiated peak doublet amplitude to investigate contractile fatigue. These findings can be useful in the choice of the parameters describing central and peripheral fatigue of the quadriceps muscle in future studies.     

Comparison of electromyographic responses for the superficial quadriceps muscles: Cycle versus knee‐extensor ergometry

The purpose of this study was to compare the electromyographic (EMG) amplitude and mean power frequency (MPF) versus power output relationships for the three superficial quadriceps muscles during incremental cycle (CE) and knee‐extensor (KE) ergometry in the same subjects. Eight men performed incremental CE and KE tests to exhaustion. Surface EMG signals were recorded simultaneously from the vastus lateralis (VL), rectus femoris (RF), and vastus medialis (VM). Polynomial regression analyses on a subject‐by‐subject basis indicated that the relationship between EMG amplitude versus power output was best‐fit with either a linear, quadratic, or cubic model for CE, whereas the relationship was best‐fit with a linear model for all subjects for the KE test. No consistent relationship was found for EMG MPF within subjects and between muscle groups for CE or KE. Compared with CE, however, the EMG amplitude during KE exercise was, on average, approximately 87% and 30% higher for the RF and VM muscles, respectively. These results suggest that KE exercise may be a better mode of examining EMG amplitude in the quadriceps muscle during incremental exercise than traditional CE. Muscle Nerve, 2009     

Comparison of the fast Fourier transform and continuous wavelet transform for examining mechanomyographic frequency versus eccentric torque relationships

The purpose of this study was to compare the eccentric torque-related patterns for mechanomyographic (MMG) center frequencies (mean power frequency (MPF), median frequency (MDF), and average instantaneous mean power frequency (AIMPF)) determined by the fast Fourier transform (FFT) and continuous wavelet transform (CWT). Eight adults (mean+/-S.D. age=22.5+/-2.4 years) performed submaximal to maximal, eccentric isokinetic muscle actions of the biceps brachii on a Cybex 6,000 dynamometer. The mean MMG MPF, MDF, and AIMPF values for both the absolute and normalized data from 10 to 100% eccentric peak torque (PT) were highly intercorrelated at r=0.908-0.985. Linear models provided the best fit for the absolute MMG MPF (r=0.873), MDF (r=0.831), and AIMPF (r=0.924), as well as normalized MMG MPF (r=0.869), MDF (r=0.816), and AIMPF (r=0.920) versus percentage eccentric PT relationships. There were no significant differences (p>0.05) among the linear slope coefficients for the MMG MPF, MDF, and AIMPF versus percentage eccentric PT relationships for either the absolute or normalized data. These results suggested that Fourier or wavelet transform procedures can be used to examine the patterns of MMG responses during eccentric muscle actions of the biceps brachii.     

An examination of the linearity and reliability of the electromyographic amplitude versus dynamic constant external resistance relationships using monopolar and bipolar recording methods

The purpose of this study was to examine the linearity and reliability of the electromyographic (EMG) amplitude versus dynamic constant external resistance (DCER) relationships for monopolar and bipolar recording techniques during concentric and eccentric muscle actions. Nineteen healthy men (mean ± SD age = 22.9 ± 2.5 years) performed a series of randomly ordered, submaximal to maximal, unilateral DCER muscle actions of the dominant forearm flexors on two occasions separated by at least 48 h. Specifically, the subjects lifted and lowered weights corresponding to 10-100% of the one repetition maximum (1-RM) in 10% increments. During each muscle action, monopolar and bipolar surface EMG signals were detected simultaneously from the biceps brachii. For the monopolar and bipolar methods, the coefficients of determination for the EMG amplitude versus DCER relationships ranged from 0.64-0.98 and 0.38-0.98 for the concentric muscle actions and 0.45-0.98 and 0.45-0.98 for the eccentric muscle actions, respectively. The intraclass correlation coefficients (ICC) and corresponding standard errors of measurement (SEM) for the linear slope coefficients for the EMG amplitude versus DCER relationships were 0.682 (18.4%) and 0.594 (21.8%) with the monopolar method and 0.810 (25.6%) and 0.774 (17.6%) with the bipolar method for the concentric and eccentric muscle actions, respectively. These findings indicated that monopolar and bipolar recording techniques may be used with a similar degree of linearity and reliability for the EMG amplitude versus concentric and eccentric DCER relationships.     

Intersession reliability of the interpolated twitch technique applied during isometric,concentric, and eccentric actions of the human knee extensor muscles

Introduction: Although it has been shown that voluntary activation (%VA) of the knee extensors during isometric contractions can be reliably assessed with the interpolated twitch technique, little is known about the reliability of %VA during concentric and eccentric muscle actions. Therefore, relative and absolute intersession reliability of quadriceps muscle's %VA during different contraction modes was determined. Methods: After a familiarization session, 21 participants (17 males, 25 ± 2 yrs) completed two testing sessions. Paired supramaximal electrical stimuli were administered to the femoral nerve during isometric, concentric, eccentric MVCs, and at rest to assess %VA (stimuli were applied at 70° knee flexion). Results and discussion: Data indicate that %VA of the knee extensors can be reliably measured during isometric [intraclass correlation coefficient (ICC) = 0.89, coefficient of variation (CV) = 4.1%], concentric (ICC = 0.87, CV = 6.6%), and eccentric muscle actions (ICC = 0.86, CV = 7.0%). Muscle Nerve 56 : 324–327, 2017     

The influence of electrode shift over the innervation zone and normalization on the electromyographic amplitude and mean power frequency versus isometric torque relationships for the vastus medialis muscle

The purpose of the present study was to: (a) examine the influence of the innervation zone (IZ) for the vastus medialis on EMG signals from bipolar electrode arrangements that have their center point directly over the IZ, 10mm distal to the IZ, 10mm proximal to the IZ, and 20mm distal to the IZ, and (b) investigate the effects of normalization on EMG amplitude and center frequency values over the IZ. Ten men (mean+/-S.D. age=23.6+/-3.0 years) performed submaximal to maximal isometric muscle actions of the dominant leg extensors, and four separate bipolar surface EMG signals were detected simultaneously from the vastus medialis. One bipolar electrode arrangement had its center point located directly over the IZ, while the other electrode arrangements had their center points 10mm proximal, 10mm distal, and 20mm distal to the IZ. The results showed that there were no consistent patterns among the four electrode arrangements for the absolute and normalized EMG amplitude and mean power frequency (MPF) versus isometric torque relationships. Generally speaking, the IZ had the greatest effect on the EMG signal when the center point of the bipolar electrode arrangement was directly over it or 10mm proximal to it. In addition, normalization reduced the influence of the IZ on the absolute EMG amplitude and MPF values. Thus, these findings supported the practice of normalization, and indicated that it is a useful technique for reducing the influence of electrode location on EMG amplitude and MPF data. Future studies should examine the potential for movement of the IZ during isometric muscle actions.     

Assessment of the reliability of the motor unit size index (MUSIX) in single subject “round-robin” and multi-centre settings

ObjectiveThe motor unit size index (MUSIX) is incorporated into the motor unit number index (MUNIX). Our objective was to assess the intra-/inter-rater reliability of MUSIX in healthy volunteers across single subject “round robin” and multi-centre settings.MethodsData were obtained from (i) a round-robin assessment in which 12 raters (6 with prior experience and 6 without) assessed six muscles (abductor pollicis brevis, abductor digiti minimi, biceps brachii, tibialis anterior, extensor digitorum brevis and abductor hallucis) and (ii) a multi-centre study with 6 centres studying the same muscles in 66 healthy volunteers. Intra/inter-rater data were provided by 5 centres, 1 centre provided only intra-rater data.Intra/inter-rater variability was assessed using the coefficient of variation (COV), Bland-Altman plots, bias and 95% limits of agreement.ResultsIn the round-robin assessment intra-rater COVs for MUSIX ranged from 7.8% to 28.4%. Inter-rater variability was between 7.8% and 16.2%. Prior experience did not impact on MUSIX values. In the multi-centre study MUSIX was more consistent than the MUNIX. Abductor hallucis was the least reliable muscle.ConclusionsThe MUSIX is a reliable neurophysiological biomarker of reinnervation.SignificanceMUSIX could provide insights into the pathophysiology of a range of neuromuscular disorders, providing a quantitative biomarker of reinnervation.     

Development and validation of the hypersomnia-specific beliefs scale

Objective/BackgroundPatients with Central hypersomnia, especially Narcolepsy type 1 and Idiopathic Hypersomnia (NT1 and IHS) often have psychological frustration in their daily lives. We aimed to develop the first scale of hypersomnia-specific beliefs (HSB).Patients/methodsWe developed the HSB scale consisting of three factors (“aversion toward doze”, “hypersensitivity toward others” reactions about my doze”, and “sense of defeat caused by doze”) with 12 items through interviews to 11 patients with NT1 and IHS. Validity and reliability of the HSB were evaluated cross-sectionally with 166 patients with NT1 and IHS and 375 controls. Simultaneously, scores of patient health questionnaire −2(PHQ-2), mini-Social Phobia Inventory (mini-SPIN), and Epworth Sleepiness Scale (ESS) were obtained.ResultsThis 3-factor model had enough fitness (χ2 = 60.25, df = 51, p = 0.18, TLI = 0.99, CFI = 0.99, RMSEA = 0.03), Cronbach's α coefficient being 0.90. The intraclass correlation coefficient was 0.76. Also, the area under the receiver operating characteristic curve (AUC = 0.88) confirmed good discrimination ability. A cut-off score of 38 resulted in a sensitivity of 90% and a specificity of 75%. Multiple linear regression analyses showed that these scales were independently associated with the HSB score; the PHQ-2 (β = 0.24, p = 0.002), mini-SPIN (β = 0.29, p < 0.001) and ESS (β = 0.15, p = 0.048).ConclusionsOur data suggest that the HSB scale measured beliefs in NT1 and IHS patients with good validity, reliability, and discrimination ability. The HSB scale assesses the negative beliefs specific to patents with NT1 and IHS. This scale could be applied to the development of novel psychotherapeutic approach to patients with NT1 and IHS.