Short-term beetroot juice supplementation improves muscle speed and power but does not reduce blood pressure or oxidative stress in 65-79 y old men and women.

We have previously demonstrated that acute ingestion of inorganic nitrate (NO)-rich beetroot juice (BRJ), a source of nitric oxide (NO) via the NO → nitrite (NO) → NO pathway, can improve muscle speed and power in older individuals. It is not known, however, whether this effect is maintained or perhaps even enhanced with repeated ingestion, or if tolerance develops as with organic nitrates, e.g.

The influence of acute dietary nitrate supplementation on skeletal muscle fatigue and recovery in older women.

Older individuals fatigue more rapidly during, and recover more slowly from, dynamic exercise. Women are particularly vulnerable to these deleterious effects of aging, which increases their risk of falling. We have shown that dietary nitrate (NO ), a source of nitric oxide (NO) via the NO  → nitrite (NO ) → NO pathway, enhances muscle speed and power in older individuals in the non-fatigued state; however, it is unclear if it reduces fatigability and/or improves recoverability in this population.

The influence of acute dietary nitrate supplementation on skeletal muscle fatigue and recovery in older women.

Older individuals fatigue more rapidly during, and recover more slowly from, dynamic exercise. Women are particularly vulnerable to these deleterious effects of aging, which increases their risk of falling. We have shown that dietary nitrate (NO ), a source of nitric oxide (NO) via the NO → nitrite (NO ) → NO pathway, enhances muscle speed and power in older individuals in the non-fatigued state; however, it is unclear if it reduces fatigability and/or improves recoverability in this population.

Dose-Response Effect of Dietary Nitrate on Muscle Contractility and Blood Pressure in Older Subjects: A Pilot Study.

We have recently demonstrated that dietary nitrate, a source of nitric oxide (NO) via the nitrate → nitrite → NO enterosalivary pathway, can improve muscle contractility in healthy older men and women. Nitrate ingestion has also been shown to reduce blood pressure in some, but not all, studies of older individuals. However, the optimal dose for eliciting these beneficial effects is unknown.

A Single Dose of Dietary Nitrate Increases Maximal Knee Extensor Angular Velocity and Power in Healthy Older Men and Women.

Background: Aging results in reductions in maximal muscular strength, speed, and power, which often lead to functional limitations highly predictive of disability, institutionalization, and mortality in elderly adults. This may be partially due to reduced nitric oxide (NO) bioavailability. We, therefore, hypothesized that dietary nitrate (NO3-), a source of NO via the NO3- → nitrite (NO2-) → NO enterosalivary pathway, could increase muscle contractile function in older subjects.

Cortical and spinal mechanisms of task failure of sustained submaximal fatiguing contractions.

In this and the subsequent companion paper, results are presented that collectively seek to delineate the contribution that supraspinal circuits have in determining the time to task failure (TTF) of sustained submaximal contractions. The purpose of this study was to compare adjustments in supraspinal and spinal excitability taken concurrently throughout the performance of two different fatigue tasks with identical mechanical demands but different TTF (i.e.

Preliminary evidence that anodal transcranial direct current stimulation enhances time to task failure of a sustained submaximal contraction.

The purpose of this study was to determine whether anodal transcranial direct current stimulation (tDCS) delivered while performing a sustained submaximal contraction would increase time to task failure (TTF) compared to sham stimulation. Healthy volunteers (n = 18) performed two fatiguing contractions at 20% of maximum strength with the elbow flexors on separate occasions. During fatigue task performance, either anodal or sham stimulation was delivered to the motor cortex for up to 20 minutes.

Reliability of a modified motor unit number index (MUNIX) technique.

Introduction: The purpose of this study was to examine the relative and absolute between-day reliability of the motor unit number index (MUNIX).

Methods: Young, healthy adults (n=19) attended two testing sessions separated by 4-weeks where their maximal pinch-grip strength, MUNIX, and motor unit size index (MUSIX) were assessed in the abductor pollicis brevis muscle. Reliability was assessed by intraclass correlation coefficients (ICC), coefficient of variation (CV) and limits of agreement (LOA).

Interrelationship between muscle strength, motor units, and aging.

The interrelationship between muscle strength, motor unit (MU) number, and age is poorly understood, and in this study we sought to determine whether age-related differences in muscle strength are moderated by estimates of functioning MU number and size. Eighteen older adults (OA; 67 ± 1.20 years) and 24 young adults (YA; 22 ± 0.

Effects of persistent Mal de debarquement syndrome on balance, psychological traits, and motor cortex exctiability.

Mal de debarquement syndrome (MdDS) is a poorly characterized and understood disorder of perceived motion. We sought to characterize postural control and the psychological impact of MdDS. Additionally, we explored whether patients with MdDS exhibit altered corticospinal and intracortical excitability.

Utilizing transcranial magnetic stimulation to study the human neuromuscular system.

Transcranial magnetic stimulation (TMS) has been in use for more than 20 years, and has grown exponentially in popularity over the past decade. While the use of TMS has expanded to the study of many systems and processes during this time, the original application and perhaps one of the most common uses of TMS involves studying the physiology, plasticity and function of the human neuromuscular system. Single pulse TMS applied to the motor cortex excites pyramidal neurons transsynaptically (Figure 1) and results in a measurable electromyographic response that can be used to study and evaluate the integrity and excitability of the corticospinal tract in humans.

Neurophysiologic effects of spinal manipulation in patients with chronic low back pain.

Background: While there is growing evidence for the efficacy of SM to treat LBP, little is known on the mechanisms and physiologic effects of these treatments. Accordingly, the purpose of this study was to determine whether SM alters the amplitude of the motor evoked potential (MEP) or the short-latency stretch reflex of the erector spinae muscles, and whether these physiologic responses depend on whether SM causes an audible joint sound.

Methods: We used transcranial magnetic stimulation to elicit MEPs and electromechanical tapping to elicit short-latency stretch reflexes in 10 patients with chronic LBP and 10 asymptomatic controls.

Cast immobilization increases long-interval intracortical inhibition.

Immobilization reduces muscle performance, and despite these performance losses being associated with neural impairments little is known regarding adaptations in cortical properties. We utilized transcranial magnetic stimulation to assess changes in flexor carpi radialis (FCR) intracortical facilitation (ICF), and short- and long-interval intracortical inhibition (SICI and LICI) in healthy humans undergoing 3 weeks of immobilization. Measurements were obtained at rest and during contraction (15% intensity).

Older adults exhibit more intracortical inhibition and less intracortical facilitation than young adults.

Background: Aging results in decreased neuromuscular function, which is likely associated with neurologic alterations. At present little is known regarding age-related changes in intracortical properties.

Methods: In this study we used transcranial magnetic stimulation (TMS) to measure intracortical facilitation (ICF), short- and long-interval intracortical inhibition (SICI and LICI), motor evoked potential amplitude, and silent period duration in young and older adults (21.

Men and women exhibit a similar time to task failure for a sustained, submaximal elbow extensor contraction.

Sex differences in muscle fatigue-resistance have been observed in a variety of muscles and under several conditions. This study compared the time to task failure (TTF) of a sustained isometric elbow extensor (intensity 15% of maximal strength) contraction in young men (n = 12) and women (n = 11), and examined if their neurophysiologic adjustments to fatigue differed. Motor-evoked potential amplitude (MEP), silent period duration, interference electromyogram (EMG) amplitude, maximal muscle action potential (M (max)), heart rate, and mean arterial pressure were measured at baseline, during the task, and during a 2-min ischemia period.

Delayed-onset muscle soreness induced by low-load blood flow-restricted exercise.

We performed two experiments to describe the magnitude of delayed-onset muscle soreness (DOMS) associated with blood flow restriction (BFR) exercise and to determine the contribution of the concentric (CON) versus eccentric (ECC) actions of BFR exercise on DOMS. In experiment 1, nine subjects performed three sets of unilateral knee extension BFR exercise at 35% of maximal voluntary contraction (MVC) to failure with a thigh cuff inflated 30% above brachial systolic pressure. Subjects repeated the protocol with the contralateral limb without flow restriction.

Restoration of voluntary muscle strength after 3 weeks of cast immobilization is suppressed in women compared with men.

Objective: To investigate sex-related differences in the loss and recovery of voluntary muscle strength after immobilization.

Design: Longitudinal, repeated measures.

Setting: Research laboratory.

Immobilization-induced increase in fatigue resistance is not explained by changes in the muscle metaboreflex.

Immobilization has been reported to enhance fatigability, which is paradoxical in light of the metabolic and molecular alterations that occur in atrophied muscles. We examined whether the immobilization-induced enhancement in fatigability was associated with attenuation in the muscle metaboreflex response. Ten subjects were examined after 3 weeks of hand-forearm immobilization.

Neuromuscular plasticity during and following 3 wk of human forearm cast immobilization.

Prolonged reductions in muscle activity results in alterations in neuromuscular properties; however, the time course of adaptations is not fully understood, and many of the specific adaptations have not been identified. This study evaluated the temporal evolution of adaptations in neuromuscular properties during and following 3 wk of immobilization. We utilized a combination of techniques involving nerve stimulation and transcranial magnetic stimulation to assess changes in central activation of muscle, along with spinal (H reflex) and corticospinal excitability [i.

Quantification of the corticospinal silent period evoked via transcranial magnetic stimulation.

A magnetic pulse to the cortex during a muscle contraction produces a motor evoked potential (MEP) followed by electrical quiescence before activity resumes that is indicative of corticospinal inhibition and commonly referred to as the corticospinal slient period (SP). The purpose of the present study was to determine the effect of stimulus intensity and quantification method on the between-visit variability of the SP in healthy individuals. On two occasions we recorded the SP from 9 humans at 3 stimulus intensities (10, 20 and 30% above active motor threshold [AMT]) and quantified the SP based on 8 common criteria.

Cloning the Schizosaccharomyces pombe lys2+ gene and construction of new molecular genetic tools.

Molecular genetic analyses in Schizosaccharomyces pombe rely on selectable markers that are used in cloning vectors or to mark targeted gene deletions and other integrated constructs. In this study, we used genetic mapping data and genomic sequence information to predict the identity of the S. pombe lys2(+) gene, which is homologous to Saccharomyces cerevisiae LYS4(+).