The clinical efficacy of functional electrical stimulation (FES) is limited by the rapid onset of fatigue. Functional electrical stimulation applications typically stimulate skeletal muscles with constant-frequency trains (CFTs). Our laboratory has identified trains that we call doublet-frequency trains (DFTs) and that produce greater forces than CFTs, but more fatigue during repetitive activat...

PURPOSE To determine the effects of high-speed eccentric training of rat plantar flexor muscles on: 1) maximum (120 Hz) force at 90 degrees ankle position; 2) fatigue (40 concentric muscle actions, ROM 50 degrees) and recovery (6 concentric muscle actions) tested at short or long muscle lengths; and 3) low-frequency fatigue. METHODS Training consisted of eccentric muscle actions from ankle po...

BACKGROUND Frequent or chronic tension-type headache in children is a prevalent and debilitating condition for the child, often leading to medication overuse. To explore the relationship between physical factors and tension-type headache in children, the quality of repeated measures was examined. The aim of the present study was to determine the test-retest repeatability of parameters determini...

BACKGROUND The control of force and its between-trial variability are often taken as critical determinants of motor performance. Subjects performed isometric trunk flexion and extension forces without and with experiment pain to examine if pain yields changes in the control of trunk forces. The objective of this study is to determine if experimental low back pain modifies trunk isometric force ...

We recorded the activity of 75 proximal-arm-related cells in caudal primary motor cortex (MI) while a monkey generated either isometric forces or limb movements against an inertial load. The forces and movements were in eight directions in a horizontal plane. The isometric force generated at the hand increased monotonically in the direction of the target force level. The force exerted against t...

The nonuniformity of dynamic mechanical responses along the length of stimulated frog sartorius muscle was examined by recording the length changes of muscle segments by means of streak photography. During isometric force development, the central or the pelvic end segment tended to shorten due to the stretching of the other segments. In muscles showing a marked nonuniformity in the segmental le...

Elevated levels of phosphate (Pi) reduce isometric force, providing support for the notion that the release of Pi from myosin is closely associated with the generation of muscular force. Pi is thought to rebind to actomyosin in an ADP-bound state and reverse the force-generating steps, including the rotation of the lever arm (i.e., the powerstroke). Despite extensive study, this mechanism remai...

UNLABELLED Limitations of current methods: The assessment of human variability in various compartments of daily energy expenditure (EE) under standardized conditions is well defined at rest [as basal metabolic rate (BMR) and thermic effect of feeding (TEF)], and currently under validation for assessing the energy cost of low-intensity dynamic work. However, because physical activities of daily ...

To expose cortical involvement in age-related changes in motor performance, we compared steadiness (force fluctuations) and fatigability of submaximal isometric contractions with the ankle dorsiflexor muscles in older and young adults and with varying levels of cognitive demand imposed. Sixteen young (20.4 ± 2.1 year: 8 men, 9 women) and 17 older adults (68.8 ± 4.4 years: 9 men, 8 women) attend...

CONTEXT Insufficient hip and thigh strength may increase an athlete's susceptibility to injury. However, screening for strength deficits using isometric and isokinetic instrumentation may not be practical in all clinical scenarios. OBJECTIVE To determine if functional performance tests are valid indicators of hip and thigh strength. DESIGN Descriptive laboratory study. SETTING Research la...