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*

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

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

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

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*

Human locomotion involves a complex interplay among multiple brain regions and depends on constant feedback from the visual system. We summarize here the current understanding of the relationship among fixations, saccades, and gait as observed in studies sampling eye movements during locomotion, through a review of the literature and a synthesis of the relevant knowledge on the topic. A significant overlap in locomotor and saccadic neural circuitry exists that may support this relationship. Several animal studies have identified potential integration nodes between these overlapping circuitries. Behavioral studies that explored the relationship of saccadic and gait-related impairments in normal conditions and in various disease states are also discussed. Eye movements and locomotion share many underlying neural circuits, and further studies can leverage this interplay for diagnostic and therapeutic purposes.
Animals ; Brain ; Eye Movements ; Gait ; Humans ; Locomotion ; Posture ; Saccades

OBJECTIVE: To investigate the association of the muscle contraction with gating of the sensory input at central and peripheral levels according to the intensity of muscle contraction and location of the muscles, somatosensory evoked potentials (SSEPs) studies were evaluated at different levels of isometric contraction in the different muscles. METHOD: Median nerve SSEPs were recorded at Erb's point and scalp in the ten healthy adult subjects with isometric contraction of ipsilateral abductor pollicis brevis (APB), ipsilateral abductor digiti minimi (ADM) and contralateral APB. Median nerve SSEPs were recorded in each of these conditions during precontraction, weak contraction, strong contraction and 4 minutes after contraction. RESULTS: 1) N9 amplitudes of median SSEPs recorded at Erb's point were augumented during weak contraction and these amplitude augumentations were statistically significant in the ipsilateral APB contraction (p<0.05). 2) N20 amplitudes recorded at scalp were inhibited during strong isometric contraction and these amplitude inhibitions were statistically significant in the ipsilateral APB contraction (p<0.05). 3) The latencies of N9 and N20 potentials were not significantly changed during isometric contraction. CONCLUSION: Therefore peripheral nervous system as well as central nervous system is responsible for gating, so the subject should be asked for the best relaxation possible for higher reliability of SSEPs.
Adult ; Central Nervous System ; Evoked Potentials, Somatosensory* ; Humans ; Isometric Contraction ; Median Nerve ; Muscle Contraction* ; Muscles ; Peripheral Nervous System ; Relaxation ; Scalp

OBJECTIVE: To provide the off-loading knee brace was designed relief for the pain associated with osteoarthritis by reduce loads on the degenerative compartment of the knee. This study examined the effects of the off-loading knee brace on activation of femoral muscles during squatting, slow and fast walking exercise in healthy young individuals. METHOD: Ten healthy male subjects without a history of knee pain were recruited. Each subject was asked to do squatting, slow and fast walking exercises with a brace secured to the dominant leg. The same exercises were repeated without the brace. Surface electromyographic (sEMG) data was collected from the vastus medialis oblique (VMO), vastus lateralis (VL) and biceps femoris (BF) muscles from the dominant side of the leg. All dynamic root mean squre (RMS) values of sEMG were standardized to static RMS values of the maximal isometric contraction and expressed as a percentage of maximal activity. RESULTS: We found that VMO activity was significantly decreased with application of the off-loading knee brace during squatting and fast walking exercise. However there were no significant differences in VMO activity with application of the off-loading knee brace during slow walking exercise. CONCLUSION: These results suggest that the external moment of the brace which effectively stabilized the patella in the movement in which the knee joints become relatively unstable. The brace could be useful in the short term, but for long-term use, weakening of the VMO is predicted. Therefore the program of selective muscular strength strengthening for the VMO should be emphasized.
Braces ; Electromyography ; Exercise ; Humans ; Isometric Contraction ; Knee ; Knee Joint ; Leg ; Male ; Muscles ; Osteoarthritis ; Patella ; Quadriceps Muscle ; Walking

Myometrial relaxation of mouse via expression of two-pore domain acid sensitive (TASK) channels was studied. In our previous report, we suggested that two-pore domain acid-sensing K⁺ channels (TASK-2) might be one of the candidates for the regulation of uterine circular smooth muscles in mice. In this study, we tried to show the mechanisms of relaxation via TASK-2 channels in marine myometrium. Isometric contraction measurements and patch clamp technique were used to verify TASK conductance in murine myometrium. Western blot and immunehistochemical study under confocal microscopy were used to investigate molecular identity of TASK channel. In this study, we showed that TEA and 4-AP insensitive non-inactivating outward K⁺ current (NIOK) may be responsible for the quiescence of murine pregnant longitudinal myometrium. The characteristics of NIOK coincided with two-pore domain acid-sensing K⁺ channels (TASK-2). NIOK in the presence of K⁺ channel blockers was inhibited further by TASK inhibitors such as quinidine, bupivacaine, lidocaine, and extracellular acidosis. Furthermore, oxytocin and estrogen inhibited NIOK in pregnant myometrium. When compared to non-pregnant myometrium, pregnant myometrium showed stronger inhibition of NIOK by quinidine and increased immunohistochemical expression of TASK-2. Finally, TASK-2 inhibitors induced strong myometrial contraction even in the presence of L-methionine, a known inhibitor of stretch-activated channels in the longitudinal myometrium of mouse. Activation of TASK-2 channels seems to play an essential role for relaxing uterus during pregnancy and it might be one of the alternatives for preventing preterm delivery.
Acidosis ; Animals ; Blotting, Western ; Bupivacaine ; Estrogens ; Female ; Isometric Contraction ; Lidocaine ; Methionine ; Mice* ; Microscopy, Confocal ; Muscle, Smooth ; Myometrium ; Oxytocin ; Pregnancy ; Quinidine ; Relaxation* ; Tea ; Uterine Contraction ; Uterus

Shikonin, a natural flavonoid found in the roots of Lithospermum erythrorhizon, has been shown to possess many biological functions. The present study was undertaken to investigate the influence of shikonin on vascular smooth muscle contractility and to determine the mechanism involved. Denuded aortic rings from male rats were used and isometric contractions were recorded and combined with molecular experiments. Shikonin significantly relaxed fluoride-, thromboxane A2- or phorbol ester-induced vascular contraction suggesting as a possible anti-hypertensive on the agonist-induced vascular contraction regardless of endothelial nitric oxide synthesis. Furthermore, shikonin significantly inhibited fluoride-induced increases in pMYPT1 levels and phorbol ester-induced increases in pERK1/2 levels suggesting the mechanism involving the inhibition of Rho-kinase activity and the subsequent phosphorylation of MYPT1 and the inhibition of MEK activity and the subsequent phosphorylation of ERK1/2. This study provides evidence regarding the mechanism underlying the relaxation effect of shikonin on agonist-induced vascular contraction regardless of endothelial function.
Animals ; Fluorides ; Humans ; Isometric Contraction ; Lithospermum ; Male ; Muscle, Smooth, Vascular ; Nitric Oxide ; Phosphorylation ; Rats ; Relaxation ; rho-Associated Kinases