Caffeine has known ergogenic effects, some of which have been observed during submaximal isometric contractions. We used 15 subjects in a randomized, double-blind, repeated-measures experiment to determine caffeine's ergogenic effects on neuromuscular variables that would contribute to increased endurance capacity. Subjects performed repeated submaximal (50% maximal voluntary contraction) isome...

BACKGROUND Based on previously reported changes in muscle metabolism that could increase susceptibility to fatigue, we speculated that patients with chronic obstructive pulmonary disease (COPD) have reduced quadriceps endurance and that this will be correlated with the proportion of type I muscle fibres and with the activity of oxidative enzymes. METHODS The endurance of the quadriceps was ev...

The present study was designed to determine whether fatigue alters the ability to estimate an index of individual muscle force from shear elastic modulus measurements (experiment I), and to test the ability of this technique to highlight changes in load sharing within a redundant muscle group during an isometric fatiguing task (experiment II). Twelve subjects participated in experiment I, which...

When an active muscle is stretched, the resulting posteccentric steady-state force is known to be greater than the isometric force at the corresponding muscle length. The aim of our research was to clarify if residual force enhancement (RFE) is relevant for voluntary human muscle action in everyday like scenarios. Therefore 13 healthy subjects participated in our study and had to perform bilate...

The authors modeled variability of force during continuous isometric contractions of the quadriceps femoris. Twenty adults (aged 25 +/- 6 years old) performed isometric leg extensions. Target forces were 11 percentages of maximum voluntary contraction (%MVC), ranging from 2 to 95%, and 5 absolute levels, from 25 to 225 N. The authors used standard deviation of absolute force, coefficient of var...

INTRODUCTION This study evaluates the complexity of force and surface electromyography (sEMG) during knee extension and flexion at low-level isometric contractions in individuals with different degrees of diabetic peripheral neuropathy (DPN). METHODS Ten control and 38 diabetic participants performed isometric contractions at 10%, 20%, and 30% of maximal voluntary contraction. Knee force and ...

The purpose of our investigation was to determine if the near infrared spectroscopy technique was sensitive to changes in tissue oxygenation at low levels of isometric contraction in the extensor carpi radialis brevis muscle. Nine subjects were seated with the right arm abducted to 45 degrees, elbow flexed to 85 degrees, forearm pronated 45 degrees, and wrist and forearm supported on an armrest...

To test the hypothesis that a lower mean arterial pressure (MAP) response during voluntary isometric exercise in multiple sclerosis (MS) is related to a dampened muscle metabolic signal, 9 MS and 11 control subjects performed an isometric dorsiflexor contraction at 30% maximal voluntary contraction until target failure (endurance time). We made continuous and noninvasive measurements of heart r...