OBJECTIVETo characterize the isometric contractility of Bufo gastrocnemius ex vivo in light of the rest tension.

METHODSBufo gastrocnemius treated with SOD inhibitor and ascorbate was stimulated electrically (12 V DC, 2 ms duration with a 2 s interval) to record the tension within 10 min. Weighted fitting to the relaxation curve of the tension below 90% of the peak tension with a mono-exponential model yielded the rest tension and relaxation rate.

RESULTSThe control gastrocnemius showed monotonic decrease of the rest tension, but treatment with SOD inhibitor and ascorbate resulted in a decrease of the rest tension followed by a fast increase within a 1.0 min contraction. The increase of the rest tension at 7.0 min of contraction of the treated muscle was significantly greater than that of the control muscle. The control muscle showed a monotonic decrease of the relaxation rate in 10 min, whereas treatment with SOD inhibitor and ascorbate produced increased relaxation rate followed by monotonic decrease till a plateau was reached. In the course of the 10 min recording, the relaxation rate of the treated muscle was lower than that of the control after the same duration of contraction.

CONCLUSIONRest tension is a characteristic index to represent the skeletal muscle contractility.

Animals ; Bufonidae ; Electric Stimulation ; In Vitro Techniques ; Isometric Contraction ; physiology ; Muscle Tonus ; physiology ; Muscle, Skeletal ; physiology

OBJECTIVETo explore the response of electroencephalography (EEG) signal to biceps brachii fatiguing induced by sustained isometric (non-maximal) voluntary contraction (non-MVC) and to lay a foundation for effective and reliable fatigue evaluation system and for understanding fatigue mechanisms.

METHODSTen male undergraduates performed two different isometric fatiguing tasks with the elbow flexion muscles under a load of 5 and 10 kg respectively, and synchronously EEG signals were collected from scalp. Then amplitude, spectral and Lempel-Ziv complexity C(n) of EEG were calculated.

RESULTSThe average EEG(AEEG) increased while the average mean power frequency (MPF) and complexity of EEG decreased in muscle fatigue. Furthermore, this phenomenon was distributed evenly across the entire scalp, but load only influenced AEEG, MPF and C(n) at Fz.

CONCLUSIONAEEG of EEG increases generally while MPF and C(n) increase generally during local muscle fatigue. This pattern of EEG reflects the central mechanism of muscle fatigue. AEEG, MPF and C(n) at prefrontal area show load dependence.

Adult ; Electroencephalography ; Exercise ; physiology ; Humans ; Isometric Contraction ; physiology ; Male ; Muscle Fatigue ; physiology

Evaluation of limbs muscle function is one of the difficult tasks in forensic clinical medicine. Recently, there are more and more cases needed to be evaluated on the limbs muscle function in forensic clinical appraisal. Thus the assessment methods for muscle function have been concerned increasingly. This paper introduces the classification of muscle function and the type of muscle contraction, reviews the assessment methods for muscle function and their application value, such as manual muscle test, simple instrumental muscle test, isokinetic muscle test and electrophysiological test. It has also proposed to evaluate the muscle function with multiple methods comprehensively.
Biomechanical Phenomena ; Electromyography/methods* ; Exercise Test/methods* ; Extremities/physiology* ; Forensic Medicine ; Humans ; Isometric Contraction/physiology* ; Muscle Contraction/physiology* ; Muscle Strength/physiology* ; Muscle Tonus ; Muscle, Skeletal/physiology* ; Muscles/physiology*

AIMTo explore the factors affect the change of sEMG signal by investigating the relationship between power spectral changes of sEMG signal and H+ in muscle during the short period of recovery after muscular fatigue.

METHODSAfter a fatiguing constriction of the muscle, its pH value would not be featured any apparent changes in a short period of time. However, we were able to observe the movement rule of the sEMG power spectrum within 30 s of its reversion duration. Surface EMGs of biceps brachii muscle were recorded from 8 healthy human volunteers during tasks. Muscle fatigue induced by isometric loading that included 60% of maximal voluntary contraction. Restitution of sEMG by recording 2 s, 4 s, 6 s, 8 s, 10 s, 20 s and 30 s by the same load after the end of the fatigue experiments of 60% MVC.

RESULTSThere was a significant monotonous decline in MPF during isometric fatigue contraction of 60% MVC. MPF was restituted rapidly in the short recovery period after muscular fatigue. It was recovered 26.5% of its whole declining scope only 2 s by the end of muscle movement, and has been reached 87.7% of its total decreasing value till 30 s after the exercise.

CONCLUSIONOur results suggested that the accumulation of H+ in muscle was not the only factor that affected "spectrum shift" during muscle fatigue. The change of CNS drive strategy might be the important mechanisms that attributed to the change of SEMG signal during isometric contractions.

Adult ; Electromyography ; Exercise ; Humans ; Isometric Contraction ; physiology ; Male ; Muscle Fatigue ; physiology ; Muscle, Skeletal ; physiology ; Physical Endurance ; physiology ; Young Adult

A hybrid method based on optimization and force-EMG relationships for predicting muscle force was presented and applied to the flexion movement of upper limb. The results were compared with those from classical optimization and from the method based on force-EMG relationships. The classical optimization can not predict the force of antagonistic muscles. The method based on force-EMG relationships can not satisfy the mechanical equilibrium. The hybrid method overcomes the two disadvantages, but the forces predicted by it fluctuate excessively. Now the hybrid method is just appropriate for use in predicting isometric and isokinetic movements.
Algorithms ; Electromyography ; methods ; Forecasting ; Humans ; Isometric Contraction ; physiology ; Models, Biological ; Muscle Contraction ; physiology ; Muscle, Skeletal ; physiology ; Physical Exertion ; physiology ; Stress, Mechanical

AIMIn order to elucidate the underlying mechanism of depressed maximal isometric twitch tension normalized by cross sectional area of muscle strip in unloaded soleus.

METHODSThe soleus and extensor digitorum longus (EDL) muscle strips were perfused in vitro and treated by 2,3-Butanedione monoxime (BDM).

RESULTSThe BDM decreased Pt of soleus and EDL in a concentration-dependent manner. The Pt could restored completely to normal level after washing out BDM. The isometric twitch duration was not altered during 1 mmol/L BDM of perfusion, but was shortened at 10 mmol/L dose. The time from maximal to half Pt in EDL was shorter than that in soleus during 10 mmol/L BDM of perfusion. The inhibitory effects of BDM on myosin ATPase activity were higher in EDL than in soleus. The inhibitory extent of BDM on myosin ATPase activity of soleus and EDL was lower than that on Pt.

CONCLUSIONThese results suggest that reduction in cross-bridge function of skeletal muscle may be one of reasons induced a decrease in its Pt. BDM is not a specific inhibitor on myosin ATPase activity and can affect multiple parts of excitation-contraction coupling in skeletal muscle.

Animals ; Diacetyl ; analogs & derivatives ; pharmacology ; Isometric Contraction ; drug effects ; physiology ; Male ; Muscle Contraction ; drug effects ; physiology ; Muscle, Skeletal ; drug effects ; physiology ; Myosins ; antagonists & inhibitors ; Rats ; Rats, Sprague-Dawley

Strength training is one of the most common exercises practiced in the field of physical therapy or sports training. However, limited methodology is available to evaluate its effect on the target muscle. This study aimed to test the hypothesis that surface electromyographic (EMG) data from both isometric and isotonic exercise can express changes within the muscle during a 12-week strength training program. Ten healthy male volunteer students (5 for training, 5 for controls) from Yonsei University were recruited for evaluation in this study. DeLorme's axiom was practiced for 12 weeks in the dominant elbow flexors and knee extensors of the training group. Tension for 1 repetition maximum and maximal voluntary isometric contraction, and surface EMG information such as the integrated EMG and three variables from the regression line of median frequency (MDF) data were measured at weeks 0, 3, 6, 9, and 12. The limb circumference was measured at weeks 0 and 12. During the strength training, which was enough for the increment of muscle strength and limb circumference, the rectified-integrated EMG and initial MDF increased with a significant linear pattern in both types of contraction. The two surface EMG variables were able to monitor the physiologic muscle changes during the training. Based on these results, we propose that these two surface EMG variables can be used for monitoring electrophysiological changes in the specific muscle that is undergoing the training program, under conditions where the contraction mode for EMG data collection is either static or dynamic.
Quadriceps Muscle/anatomy & histology/physiology ; Muscle, Skeletal/anatomy & histology/physiology ; Male ; Isotonic Contraction/physiology ; Isometric Contraction/physiology ; Humans ; Fourier Analysis ; Exercise Therapy/*methods ; Electromyography/*methods ; Body Weights and Measures ; Adult

OBJECTIVETo investigate the effect of ascorbic acid (VC) on relaxation of ex vivo Bufo gastrocnemius during sustained isometric contraction.

METHODSDynamic tension of the muscle was recorded under constant voltage stimulation within 7.0 min at 2 s intervals. The rest tension and relaxation rate of the muscle was obtained by weighted fitting to the relaxation process of tension <90% of its peak with a mono-exponential model to characterize the muscular relaxation.

RESULTSVC at 2.0 mmol/L alone or in combination with the inhibitors of the antixoidation enzymes (surperoxide dismutase, glutathione peroxidase and catalase) resulted in negligible alterations in the muscular relaxation kinetics. VC combined with the inhibitor of surperoxide dismutase resulted in significantly lowered relaxation rate while increased rest tension, but VC with the inhibitor of either catalase or glutathione peroxidase showed negligible action. VC combined with the inhibitors of all the 3 enzymes also caused significant effect on the muscular relaxation kinetics, which was similar the effect of VC with superoxide dismutase inhibitor.

CONCLUSIONVC at high concentration may result in oxidative toxicity to the biological system rich in transitional metal ion complexes but with low antioxidation capacity by causing superoxide-mediated oxidative damages.

Animals ; Ascorbic Acid ; pharmacology ; Bufonidae ; Electric Stimulation ; In Vitro Techniques ; Isometric Contraction ; drug effects ; Muscle Relaxation ; drug effects ; Muscle, Skeletal ; drug effects ; physiology

PURPOSE: This study investigated the correlation between isometric muscle strength, gross motor function, and gait parameters in patients with spastic cerebral palsy and to find which muscle groups play an important role for gait pattern in a flexed knee gait. MATERIALS AND METHODS: Twenty-four ambulatory patients (mean age, 10.0 years) with spastic cerebral palsy who were scheduled for single event multilevel surgery, including distal hamstring lengthening, were included. Preoperatively, peak isometric muscle strength was measured for the hip flexor, hip extensor, knee flexor, and knee extensor muscle groups using a handheld dynamometer, and three-dimensional (3D) gait analysis and gross motor function measure (GMFM) scoring were also performed. Correlations between peak isometric strength and GMFM, gait kinematics, and gait kinetics were analyzed. RESULTS: Peak isometric muscle strength of all muscle groups was not related to the GMFM score and the gross motor function classification system level. Peak isometric strength of the hip extensor and knee extensor was significantly correlated with the mean pelvic tilt (r=-0.588, p=0.003 and r=-0.436, p=0.033) and maximum pelvic obliquity (r=-0.450, p=0.031 and r=-0.419, p=0.041). There were significant correlations between peak isometric strength of the knee extensor and peak knee extensor moment in early stance (r=0.467, p=0.021) and in terminal stance (r=0.416, p=0.043). CONCLUSION: There is no correlation between muscle strength and gross motor function. However, this study showed that muscle strength, especially of the extensor muscle group of the hip and knee joints, might play a critical role in gait by stabilizing pelvic motion and decreasing energy consumption in a flexed knee gait.
Biomechanical Phenomena ; Cerebral Palsy/*physiopathology/surgery ; Female ; Gait/*physiology ; Humans ; Isometric Contraction/physiology ; Knee/physiopathology ; Knee Joint/surgery ; Male ; Muscle Spasticity/etiology/physiopathology ; Muscle Strength/*physiology ; Muscle Strength Dynamometer ; Muscle, Skeletal/*physiopathology ; Pelvis ; Postural Balance/physiology ; Tenotomy

Isokinetic technology in testing and training is the most advanced practical technique in the evaluation of muscle function. This method is a continuous dynamic test in the full range of the joint motion which has strong pertinence at the aspect of assessing muscle strength, and is an objective and quantitative method for reflecting each point's muscle strength in the range of the joint motion. This article reviews the key concepts, brief history of development and influencing factors of isokinetic technology in testing and training, introduces the progress in the field of rehabilitation medicine and sport science, etc., and discusses the future exploration in forensic science.
Biomechanical Phenomena ; Forensic Medicine/methods* ; Humans ; Isometric Contraction/physiology* ; Joints/physiopathology* ; Muscle Contraction/physiology* ; Muscle Strength/physiology* ; Muscle Strength Dynamometer ; Muscle, Skeletal/physiopathology* ; Physical Education and Training/methods* ; Physical Exertion ; Physical and Rehabilitation Medicine ; Posture ; Range of Motion, Articular/physiology* ; Sports Medicine ; Wounds and Injuries/rehabilitation*