The phenomenon of posttetanic potentiation, in which a single submaximal contraction or series of submaximal contractions strengthens a subsequent contraction, has been observed in both skeletal and cardiac muscle. In this study, we describe a similar phenomenon in swine carotid arterial smooth muscle. We find that a submaximal K(+) depolarization increases the force generation of a subsequent ...

A computer-based model of the knee was used to study forces in the cruciate ligaments induced by co-contraction of the extensor and flexor muscles, in the absence of external loads. Ligament forces are required whenever the components of the muscle forces parallel to the tibial plateau do not balance. When the extending effect of quadriceps exactly balances the flexing effect of hamstrings, the...

The study compared changes in intramuscular and surface recordings of EMG amplitude with ultrasound measures of muscle architecture of the elbow flexors during a submaximal isometric contraction. Ten subjects performed a fatiguing contraction to task failure at 20% of maximal voluntary contraction force. EMG activity was recorded in biceps brachii, brachialis, and brachioradialis muscles using ...

Human-machine integration has been widely implemented in various fields, such as entertainment, human movement assistance, and rehabilitation. This study focuses on electrically-induced muscle contractions. In this technology, it is important to stimulate the optimal position, called motor point (MP), belly induce contraction with lowest current injection. Because positional relationship betwee...

Jet nozzle is a core component of the hydraulic perforating fracturing tool, and design structure directly affects effectiveness efficiency. In this paper, flow field characteristics nozzles are calculated by SST k- ω turbulence model. The results show that parameters significantly influence jet performance. Through orthogonal experiments, conical-cylindrical geometric preliminarily optimized a...

This study addresses the design of riprap aprons as a scour countermeasure near abutments under clear-water conditions. It deals with the lateral extent of riprap aprons and the geometry of the scour hole prevailing at the apron edge. The study applies to riprap aprons acting as granular filters. The scour depth appears to be independent for a sufficiently long relative abutment length. Scour h...

OBJECTIVE This study investigates the impact of isometric contraction of anterior cervical muscles on cervical lordosis. METHODS 29 volunteers were randomly assigned to an anterior head translation (n=15) or anterior head flexion (n=14) group. Resting neutral lateral cervical x-rays were compared to x-rays of sustained isometric contraction of the anterior cervical muscles producing anterior ...

We monitor the dissolution of arrayed picoliter-size sessile microdroplets of the aqueous phase in oil, generated using a recently developed fluidic device. Initial pinning of the microdroplet perimeter leads to a nearly constant contact diameter, thus contraction proceeds via microdroplet (micrometer-diameter) height and contact angle reductions. This confirms that picoliter microdroplets cont...