Original Research: Central and peripheral quadriceps fatigue in young and middle-aged untrained and endurance-trained men: A comparative study.

This study aimed to compare quadriceps function (i.e. strength, endurance, central, and peripheral fatigue) of young (Young-UnTr) and middle-aged (MidAge-UnTr) untrained men and young endurance-trained men (Young-Tr).

Skeletal muscle contractility and fatigability in adults with cystic fibrosis.

Background: Recent discovery of cystic fibrosis transmembrane conductance regulator expression in human skeletal muscle suggests that CF patients may have intrinsic skeletal muscle abnormalities potentially leading to functional impairments. The aim of the present study was to determine whether CF patients with mild to moderate lung disease have altered skeletal muscle contractility and greater muscle fatigability compared to healthy controls.

Methods: Thirty adults (15 CF and 15 controls) performed a quadriceps neuromuscular evaluation using single and paired femoral nerve magnetic stimulations.

Noninvasive estimation of oxygen consumption in human calf muscle through combined NMR measurements of ASL perfusion and T₂ oxymetry.

The objective of this work was to demonstrate the feasibility of measuring muscle O2 consumption (V˙O2) noninvasively with a combination of functional nuclear magnetic resonance (NMR) imaging methods, and to verify that changes in muscle V˙O2 can be detected with a temporal resolution compatible with physiological investigation and patient ease. T2-based oxymetry of arterial and venous blood was combined with the arterial-spin labeling (ASL)-based determination of muscle perfusion. These measurements were performed on 8 healthy volunteers under normoxic and hypoxic conditions in order to assess the sensitivity of measurements over a range of saturation values.

Effect of salbutamol on neuromuscular function in endurance athletes.

Purpose: The potential ergogenic effects of therapeutic inhaled salbutamol doses in endurance athletes have been controversially discussed for decades. We hypothesized that salbutamol inhalation may increase peripheral muscle contractility, reduce fatigability, and improve force recovery after a localized exercise in endurance athletes.

Methods: Eleven healthy, nonasthmatic male athletes with high aerobic capacities were recruited to be compared in a double-blinded, randomized crossover study of two dose levels of salbutamol (200 and 800 μg) and a placebo administered by inhalation before a quadriceps fatigue test.

Quadriceps function assessment using an incremental test and magnetic neurostimulation: a reliability study.

We investigated the reliability of a test assessing quadriceps strength, endurance and fatigability in a single session. We used femoral nerve magnetic stimulation (FMNS) to distinguish central and peripheral factors of neuromuscular fatigue. We used a progressive incremental loading with multiple assessments to limit the influence of subject's cooperation and motivation.

Benefits of neuromuscular electrical stimulation prior to endurance training in patients with cystic fibrosis and severe pulmonary dysfunction.

Background: We investigated the effect of neuromuscular electrical stimulation (NMES) training prior to endurance training in patients with cystic fibrosis (CF) and severe pulmonary obstruction.

Methods: Fourteen patients with CF (FEV(1) = 35% ± 11% predicted) were prospectively randomized to either a 6-week NMES training program (n = 7) or a 6-week control period (n = 7) both followed by ergocycle (ERGO) training (8 weeks) (NMES + ERGO and control + ERGO groups). Measurements were pulmonary function, mid-thigh circumference, quadriceps strength, 6-min walk distance, maximal exercise capacity on a cycloergometer, plasma biomarkers, insulin resistance (homeostasis model assessment indexes), and quality of life (CF questionnaire for adults and teenagers > 14 years of age [CFQ14 + ], Baseline Dyspnea Index-Transition Dyspnea Index).

Fat tissue alters quadriceps response to femoral nerve magnetic stimulation.

Objective: We investigate the influence that inguinal fat has on maximal quadriceps response to femoral nerve magnetic stimulation.

Methods: Vastus lateralis M-wave amplitude and quadriceps twitch peak torque were measured (i) in lean and overweight subjects and (ii) when slices of pig fat ranging from 2 to 18 mm in thickness were placed between the coil and the nerve.

Results: In overweight group, the maximal response could not be elicited when intensity was ≤90% and ≤85% of maximal power for twitch torque and M-wave amplitude, respectively.

Effects of coil characteristics for femoral nerve magnetic stimulation.

The aim of this study was to compare the efficiency of two coils used for femoral nerve magnetic stimulation and to compare them with electrical stimulation in inducing maximal response of the quadriceps. The mechanical and electromyographic (EMG) responses were dependent on the coil used. The 45-mm double coil showed greater efficiency to elicit a maximal quadriceps response, which was similar to electrical stimulation.

Comparison of electrical and magnetic stimulations to assess quadriceps muscle function.

This study aimed to 1) compare electrical and magnetic stimulations for quadriceps muscle function assessment, and 2) ascertain whether the ratios of the second twitch elicited by supramaximal electrical and magnetic femoral nerve stimulation at 10 and 100 Hz (T2(10:100)) and the total twitch force elicited by the same types of stimulations (Fpaired(10:100)) are equivalent to the standard low- to high-frequency force ratio associated with submaximal electrical tetanic stimulations (Ftet(10:100)). Quadriceps force and vastus lateralis EMG were recorded at rest (n = 21 subjects), immediately after, and 30 min after a 30-min downhill run (n = 10) when 1) supramaximal electrical nerve stimulation (ENS), 2) magnetic nerve stimulation (MNS) and 3) submaximal electrical muscle stimulation (EMS) were delivered in random order at 1 (single stimulation), 10, and 100 Hz (paired stimulations). Ten- and 100-Hz 500-ms tetani were also evoked with EMS to determine Ftet(10:100).

Effects of acute salbutamol inhalation on quadriceps force and fatigability.

Introduction: Oral beta2-agonist administration improves muscle function in persons without asthma. We performed a double-blind, randomized, controlled crossover study to assess whether acute inhaled salbutamol administration improves muscle strength and fatigability in healthy moderately trained subjects.

Methods: Quadriceps muscle strength was measured during maximal voluntary contraction (MVC) and femoral nerve magnetic stimulation (potentiated single twitch, TwQpeak) before and after (i) a maximal incremental cycling test (n = 10) and (ii) 50 maximal isometric one-leg extensions (n = 9).