Effects of capsaicin on the circular muscle motility of the isolated guinea-pig ileum were investigated. Capsaicin produced a contraction followed by a relaxation of the circular muscle. Both responses were easily desensitized. As the late relaxation response was not sufficiently intense to be analyzed, the inhibitory effect of capsaicin on substance P-induced contractions was explored. Capsaic...

LOCOMOTION IS ARGUABLY one of the most ubiquitous and important manifestations of life, equally important to feeding as to escape predators. Evolution came up with three molecular motors to power motion: the actomyosin system Levitsky (11); the microtubule, dynein-based flagellar motors of eukaryotes (13); and the flagellar rotary motors of bacteria (15). All three systems serve propulsion, i.e...

Your muscles can contract in different ways: when you walk upstairs, the at fronts of your thighs shorten (concentric contraction), whereas downstairs, they lengthen (eccentric contraction). Concentric contractions require more oxygen and thus make burn calories. Eccentric are easier but break parts muscle feel sore for several days. If repeat eccentric exercises, however, will probably get big...

We developed a model to investigate the influence of the muscle force twitch on the simulated firing behavior of motoneurons and muscle force production during voluntary isometric contractions. The input consists of an excitatory signal common to all the motor units in the pool of a muscle, consistent with the "common drive" property. Motor units respond with a hierarchically structured firing ...

Botulinum toxin injection into the pylorus is reported to improve gastric emptying in gastroparesis. Classically, botulinum toxin inhibits ACh release from cholinergic nerves in skeletal muscle. The aim of this study was to determine the effects of botulinum toxin on pyloric smooth muscle. Guinea pig pyloric muscle strips were studied in vitro. Botulinum toxin type A was added; electric field s...

During prolonged submaximal muscle contractions, electromyographic (EMG) signals typically increase as a result of increasing motor unit activities to compensate for fatigue-induced force loss in the muscle. It is thought that cortical signals driving the muscle to higher activation levels also increases, but this has never been experimentally demonstrated. The purpose of this study was to quan...

Electromyostimulation (EMS) is often used in rehabilitation settings to evoke contractions in paralyzed muscle. Unfortunately, EMS inherently causes greater fatigue than voluntary activation. Muscles that are unloaded are susceptible to contractioninduced muscle injury. Therefore, the purpose of this study is to investigate factors that can influence torque production, such as variable-frequenc...

BACKGROUND Long-term piano training might induce some biochemical and structural adaptations in the intrinsic muscles of the hand or change the motor strategy of the nervous system. The main purpose of this study was to analyze whether the intrinsic muscles of the hands of pianists and sedentary controls differ in electromyographic characteristics at different strengths. METHODS Fifteen colle...

1. It is an old observation that non-volitional arm abduction movements accompanied by a sensation of arm lightness often occur as an after-effect following forceful voluntary arm abductor contractions against a restraint. In the present study we have tested the hypothesis that such non-volitional, so-called 'postural after-contractions' are tonic reflex responses to an enhanced resting dischar...

During effortful unilateral contractions, muscle activation is not limited to the target muscles but activity is also observed in contralateral muscles. The amount of this associated activity is depressed in a fatigued muscle, even after correction for fatigue-related changes in maximal force. In the present experiments, we aimed to compare fatigue-related changes in associated activity vs. par...