When muscle fibres isolated from the frog's semitendinosus are placed in a calcium-free, bicarbonate buffered Ringer's solution the twitch declines in an irregular stepwise fashion and disappears usually within 1 to 9 min. There is often an initial period of twitch potentiation when the fibres are exposed to 0-Ca2+. Although considerably shorter than the time in 0-Ca2+ required to deplete intra...

The clinical application of transdiaphragmatic twitch pressure (Pdi,tw) response to phrenic nerve stimulation has been hindered by the requirement for placement of oesophageal and gastric balloons. Investigators have reported that mouth twitch pressure (Pmo,tw) estimates Pdi,tw accurately at lung volumes above and below functional residual capacity (FRC). However, it is not known whether Pmo,tw...

UNLABELLED We have recently described that local contractions can be triggered by a preceding twitch in rat cardiac trabeculae in or near damaged ends of the muscle. These local contractions appeared to propagate along the trabeculae with a constant velocity; hence, they can be denoted as triggered propagated contractions (TPCs). These studies have also shown that stretch and/or subsequent shor...

The accumulation of covalently modified proteins is an important hallmark of biological aging, but relatively few studies have addressed the detailed molecular-chemical changes and processes responsible for the modification of specific protein targets. Recently, Narayanan et al. [Narayanan, Jones, Xu and Yu (1996) Am. J. Physiol. 271, C1032-C1040] reported that the effects of aging on skeletal-...

Tissue vascularization is tightly coupled to its oxidative capacity. This phenomenon is especially well characterized in skeletal muscle, which can be enriched in either oxidative slow-twitch or glycolytic fast-twitch myofibers.1,2 Slow-twitch muscles are characterized by high-oxidativecapacity fatigue-resistant (type I) fibers and dense vascularity. Conversely, fast-twitch (type II) muscles ha...

In This Issue In This Issue Saying NO to muscular dystrophy ccording to the prevailing model for Duchenne muscular dystrophy (DMD) pathogenesis, a lack of dystrophin protein makes muscle cells susceptible to mechanical damage, leading to muscle breakdown. On page 123, Wehling et al. suggest that the major damage in DMD may actually be caused by a secondary consequence of dystrophin loss: destru...

Based on new advancements in digital technology, we developed a PC- and DSP-based measurement and control system for isolated papillary muscle experiments. High flexibility was obtained through a three level control. Length or force was controlled real-time with a sample frequency of 5000 Hz. Muscle length and up to three segment lengths were measured simultaneously and each of these lengths co...

The purpose of the study was to quantify the effect of motor-unit synchronization on the spike-triggered average forces of a population of motor units. Muscle force was simulated by defining mechanical and activation characteristics of the motor units, specifying motor neuron discharge times, and imposing various levels of motor-unit synchronization. The model comprised 120 motor units. Simulat...

The effect of carbohydrate supplementation on skeletal muscle glucose transporter GLUT-4 protein expression was studied in fast-twitch red and white gastrocnemius muscle of Sprague-Dawley rats before and after glycogen depletion by swimming. Exercise significantly reduced fast-twitch red muscle glycogen by 50%. During a 16-h exercise recovery period, muscle glycogen returned to control levels (...

INTRODUCTION Autonomous twitch elicitation at myofascial trigger points from spondylotic radiculopathies-induced denervation supersensitivity can provide favourable pain relief using electrical twitch-obtaining intramuscular stimulation (ETOIMS). AIM To provide objective evidence that ETOIMS is safe and efficacious in migraine and persistent pain management due to decades-old injuries to head...