The effects of optical isomers of ephedrine (EPH) and methylephedrine (MEP) on the twitch response to electrical stimulation (1 msec, 1 Hz) in the isolated rat vas deferens were investigated to clarify the action on alpha 2-adrenoceptors. l-EPH (10(-7) 3 x 10(-5) M) and d-EPH (10(-6)-10(-4) M) markedly inhibited the twitch response in the presence of prazosin (10(-6) M). l-MEP also inhibited th...

An electrical stimulus delivered to a muscle nerve during a maximal voluntary contraction usually produces a twitchlike increment in force. The amplitude of this "interpolated twitch" is widely used to measure voluntary "activation" of muscles. In the present study, a computer model of the human adductor pollicis motoneuron pool was used to investigate factors that affect the interpolated twitc...

The network Twitch hosts a novel form of collective viewing audiovisual products, whose audience is centennials. We analyse the case Watch Parties, which allow users to watch films in real time with streamer. Taking three Parties streamer Lynx_Reviewer as study, methodological triangulation carried out: virtual ethnography, content analysis and semi-structured interview. By exploring phenomenon...

A study has been made of the isometric twitches of single motor units in the extensor hallucis brevis (EHB) muscle in man. The twitch contraction times ranged from 35 to 98 msec and the pooled results indicated the presence of at least two types of unit. The recorded twitch tensions also varied considerably (from 2 to 14 g) but were not related to the twitch speeds. The twitch tension developed...

Functional properties of in situ mitochondria and of mitochondrial creatine kinase were studied in saponin-skinned fibers taken from normal and M-creatine kinase-deficient mice. In control animals, apparent Km values of mitochondrial respiration for ADP in cardiac (ventricular) and slow-twitch (soleus) muscles (137 +/- 16 microM and 209 +/- 10 microM, respectively) were manyfold higher than tha...

Muscle fiber composition correlates with insulin resistance, and exercise training can increase slow-twitch (type I) fibers and, thereby, mitigate diabetes risk. Human skeletal muscle is made up of three distinct fiber types, but muscle contains many more isoforms of myosin heavy and light chains, which are coded by 15 and 11 different genes, respectively. Laser capture microdissection techniqu...

The superimposed twitch technique is frequently used to study the degree of motor unit activation during voluntary effort. This technique is one of the preferred methods to determine the activation deficit (AD) in normal, athletic, and patient populations. One of the limitations of the superimposed twitch technique is its variability under given contractile conditions. The objective of this res...

The resting membrane potential and intracellular potassium and sodium concentration of three guinea pig hind limb muscles were studied. These properties are related to the gross color, the speed of contraction, and the biochemically defined fiber type composing the muscle. The resting membrane potential and intracellular content were: white vastus (grossly white, fast-twitch glycolytic) -85.3 m...

We analyzed the twitch and summated torque (tetanus) during repetitive activation and recovery of the human soleus muscle in individuals with spinal cord injury. Thirteen individuals with complete paralysis (9 chronic, 4 acute) had the tibial nerve activated every 1,500 ms with a 20-Hz train (7 stimuli) for 300 ms and a single pulse at 1,100 ms. The stimulation protocol lasted 3 min and include...