Quadriceps Maximal Voluntary Contraction Research Articles

Relationship of pectoralis muscle area and skeletal muscle strength with exercise tolerance and dyspnea in interstitial lung disease.

Background: Pectoralis muscle area (PMA) is an easily derived computed tomography-based assessment that can provide insight into clinical features of other skeletal muscles. Respiratory and locomotor muscle dysfunction has been increasingly recognized in patients with interstitial lung disease (ILD). Its contribution to exercise performance has been controversial. Objective: We aimed to investigate if PMA is related with respiratory and locomotor skeletal muscle strength in ILD patients, and if skeletal muscle function is compromised and independently related with exercise capacity and dyspnea. Methods: Cross-sectional study where subjects performed incremental cycling cardiopulmonary exercise testing with maximal inspiratory (MIP) and expiratory (MEP) pressure measurements, and quadriceps maximal voluntary contraction (MVC) before and after exercise. Results: Thirty ILD patients (forced vital capacity [FVC] and lung diffusing capacity [DLCO] of 60±15% and 38±10% of predicted, respectively) and 15 healthy control subjects were studied. Patients presented significantly lower MIP and qMVC compared to controls. PMA was significantly associated with qMVC only (r=0.506; p<0.01). Only expiratory muscles showed a significant strength decline after exercise, both in patients and controls. In multivariate regression analysis, only FVC remained as independent predictor of peak aerobic capacity and MEP post exercise remained as independent predictor of peak exercise dyspnea even adjusting for FVC. Conclusion: ILD patients exhibited reduced inspiratory and quadriceps strength, but PMA was associated with the later only. Muscle strength was not associated with exercise capacity while expiratory muscle fatigue might underlie exertional dyspnea. (Sarcoidosis Vasc Diffuse Lung Dis 2017; 34: 200-208)

Effects of Kinesio taping in patients with quadriceps inhibition: A randomized, single-blinded study

ObjectiveTo determine effects of Kinesio taping (KT) on quadriceps activation and maximal voluntary isometric contraction (MVIC) in patients with quadriceps inhibition. DesignRandomized, single-blinded. SettingLaboratory. PatientsSixteen participants (9 males, 7 females) with quadriceps inhibition, as determined by 90% or lower in central activation ratio (CAR), participated. Main outcome measuresHoffmann reflex (H-reflex) of the vastus medialis and quadriceps CAR and MVIC were measured before taping, and participants were randomly allocated to either KT (KT application with tension) or sham (non-elastic tape application without tension) group. H-reflexes were assessed immediately and 20 min after tape was applied over the rectus femoris. All outcomes were measured again after tape was removed when participants returned the laboratory 24–48 h after taping. ResultsTwo-way repeated ANOVA found no group-by-time interaction for: H-reflex (F3,42 = 1.94, P = 0.14), CAR (F1,14 = 0.03, P = 0.86), or MVIC (F1,14 = 0.007, P = 0.93). None of the outcome measures differed between groups or over time (P > 0.05). ConclusionsKT applied to the rectus femoris did not change H-reflex of the vastus medialis and quadriceps CAR and MVIC in patients with quadriceps inhibition.

Static and Functional Balance in Individuals With COPD: Comparison With Healthy Controls and Differences According to Sex and Disease Severity

Studies have shown that individuals with COPD have impaired body balance, probably caused by the disease's multisystemic manifestations plus age-related decline in balance, potentially increasing the risk of falling and its consequences. However, little is known about the profile of individuals with COPD who present balance impairments, especially related to sex and disease severity stages. The aim of this work was to compare static and functional balance between subjects with COPD and healthy controls and to check possible differences according to sex and degrees of disease severity. Forty-seven subjects with COPD and 25 healthy controls were included in this study. Their static balance was assessed in one-legged stance using a force platform and functional balance with the Timed Up and Go test. Additionally, participants performed spirometry, the 6-min walk test and isometric quadriceps maximal voluntary contraction assessment. Disease severity was classified according to the Global Initiative for Obstructive Lung Disease stages and BODE (body mass index, air-flow obstruction, dyspnea, and exercise capacity) scores. In comparison with healthy controls, subjects with COPD had worse static (center of pressure displacement area: 9.3 ± 1.9 cm2 vs 11.6 ± 4.0 cm2, respectively, P = .01) and functional balance (Timed Up and Go test: 8.5 ± 1.3 s vs 10.3 ± 1.8 s, respectively, P < .001). In the COPD group, men performed better in the Timed Up and Go test than women (9.8 ± 1.2 s vs 10.9 ± 2.2 s, respectively, P = .03), whereas women presented a better static balance in comparison with men for all parameters related to center of pressure (P < .005 for all). Disease severity did not affect any balance results. Individuals with COPD had worse static and functional balance in comparison with healthy controls. Sex can mediate these results, depending on the type of balance evaluation (force platform or functional test). Balance performance was similar among the groups classified according to disease severity.

Immediate Effects Of Verbal Encouragement On Fatigued Quadriceps Strength, Activation, And Knee Joint Position Sense

PURPOSE: To examine the effects of verbal encouragement on quadriceps maximal voluntary isometric contraction (MVIC), central activation ratio (CAR), and knee joint position sense (KJPS). METHODS: Sixty eight active healthy male adults (age: 23.3±2.6) randomly underwent either condition (verbal: “kick, kick, harder, harder” or control: non-verbal encouragement during MVIC). Measurements were assessed at time-0 (baseline), -1, -2, and -3. Superimposed burst was delivered to the quadriceps during MVIC assessments (knee locked at 90°) for CAR calculations. For KJPS, subjects flexed their knees and stopped when they thought that their knee flexion angle was 15° or 45° (in a randomised order), then absolute error scores were calculated. Each assessment was performed on a dynamometer and assessed three times at time-0 and twice for other time intervals. Between assessments, muscular fatigue protocols (continuous knee extensions at 60°/s until three consecutive torque values dropped below 50% of the averaged MVIC value recorded during the previous assessments) were implemented. To test effects of verbal encouragement on quadriceps muscle and knee joint function over time, we performed mixed model ANOVAs and Tukey-Kramer post hoc tests (p<0.05) and calculated between-time effect sizes (ES). RESULTS: Our fatigue protocol immediately decreased both group’s MVIC (F3,198=4.42, p=0.005; verbal: a 24% reduction, ES: 1.13; control: a 27% reduction, ES: 1.44) and CAR (F3,198=10.91, p<0.0001; verbal: a 2.1% reduction, ES: 0.33; control: a 3.2% reduction, ES: 0.73) at time-1. While subjects in the control group showed a 6.8% and a 3.3% further decrease in MVIC (p=0.03, ES=0.30) and CAR (p<0.0001, ES=0.49), respectively, subjects in the verbal group did not change both values at time-2. Regardless of the conditions, absolute error scores in KJPS at 15° were began to alter at time-2 (F3,198=7.74, p<0.0001, a 17% reduction, ES=0.28) while those in KJPS at 45° were immediately altered at time-1 (F3,198=11.76, p<0.0001, a 29% reduction, ES=0.49), from the baseline values. CONCLUSIONS: (1) verbal encouragement may delay reduction of force output and activation, (2) fatigued muscle may affect adjacent joint position sense, and (3) less knee flexion, 15° appears to be more fatigue resistance.

Insulin resistance is associated with skeletal muscle weakness in COPD

Quadriceps weakness is seen across all GOLD stages of COPD and is associated with increased morbidity and mortality. As quadriceps weakness is only weakly associated with FEV1 , mechanisms other than airflow obstruction are implicated. We tested the hypothesis that insulin resistance contributes to skeletal muscle weakness in people with stable COPD. Fifty-one COPD patients (no exacerbations preceding 6 weeks, no rehabilitation preceding 3 months) without known diabetes mellitus underwent assessment of skeletal muscle, including measurement of quadriceps maximal voluntary contraction (QMVC). Physical activity was measured for 7 days using a multisensory biaxial accelerometer armband. Insulin resistance (HOMA2 IR) was calculated from fasting blood glucose and insulin concentrations. QMVC was 30 ± 13 kg (74 ± 25% predicted) and 16 (31%) participants had quadriceps weakness. There was a negative univariate correlation between HOMA2 IR and QMVC (r = -0.446, P = 0.002). HOMA2 IR was greater in people with quadriceps weakness (1.59 ± 0.99) than in those without (1.11 ± 0.55, P = 0.032). On multivariate analysis, with age, sex, weight, BODE index and step count per day included in the model, a one-unit increase in insulin resistance was associated with a 5.9 (2.0-9.8)-kg decrease in QMVC (P = 0.004) and a 4.2 (1.3-14.3)-fold increased risk of quadriceps weakness (P = 0.02). Insulin resistance is associated with skeletal muscle weakness in COPD, independent of potential confounders. Further studies are required to explore underlying mechanisms and determine whether insulin-sensitizing drugs could augment pulmonary rehabilitation in building skeletal muscle strength in COPD.

P213 The Impact Of Sleep Disordered Breathing On Peripheral Muscle

Introduction Chronic obstructive pulmonary disease is characterised by peripheral muscle wasting with consequent reduction in muscle strength and function. In this cohort of patients a reduction in muscle strength correlates with morbidity and mortality. Less well known are the characteristics of muscle in patients with sleep disordered breathing (SDB), a disease state that can also be dominated by inflammation, breathlessness and hypoxia. We sought to examine the impact of sleep disordered breathing on peripheral muscle size and strength. Method 51 subjects were recruited: 15 healthy controls (HC) with a normal body mass index (BMI, 2 ), 16 overweight and obese individuals with no SDB controls (SO), and 20 obese subjects with obstructive sleep apnoea (OSA). Subjects underwent measurements of Rectus Femoris Cross Sectional Area (RF CSA ) and quadriceps maximal voluntary contraction (QMVC). Handgrip strength and six minute walk distance (SMWD) were also recorded. Results As expected there were differences in BMI between the groups. There were also significant differences in muscle strength and RF CSA when corrected for body weight between HC and OSA groups and between SO and OSA groups, but no differences between HC and SO groups (Table 1). The SO group demonstrated higher measurements of strength and RF CSA than the HC group, however, the OSA group had lower measurements than both the HC and SO group. This translated to a functional difference as measured by the SMWD, again demonstrating the longest distance in the SO group and shortest in the OSA group. Discussion This study has demonstrated that in those with a BMI ≥25 kg/m 2 there appears to be a beneficial effect of excess weight on peripheral muscle size, strength and function; this may be due to the extra load carried by these individuals exerting a training effect on the muscles. However, in those who are obese with SDB, the SDB seems to exert a negative effect on muscle size, strength and function which may be a result of the inflammation and hypoxia SDB can cause.

P65 Static Balance Deficit In Chronic Obstructive Pulmonary Disease: Prevalence, Clinical Characteristics And Risk Of Significant Falls

Background Balance deficits are associated with increased risk of falls. The tandem stand (maintaining heel to toe stance for 10 seconds or more) is an established practical measure of static balance, and is associated with increased risk of falls and disability in community dwelling adults. The aim of the study was to establish the prevalence of static balance deficit in outpatients with stable COPD and any association with exercise capacity, lower limb muscle function and health related quality of life. Furthermore, it is not known whether the tandem stand predicts future risk of significant falls in patients with COPD. Method 174 outpatients with stable COPD (mean (SD) age 70 (9) years, FEV1 50 (21)% predicted) were stratified according to their ability to successfully complete the tandem stand. The incremental shuttle walk (ISW) test, habitual gait speed over 4 metres (4MGS), quadriceps maximal voluntary contraction (QMVC), the COPD assessment test (CAT), physical activity levels (defined as time spent in >3 METS according to the modified Minnesota Leisure-time Physical Activity Questionnaire) were also recorded. Self-reported falls and significant falls (defined as fall resulting in fracture or cerebral injury), corroborated by primary care records, were recorded over the following 12 months. Results 24% could not complete the tandem stand. Compared to those able to complete a tandem stand, these patients were significantly older, had lower maximal exercise capacity, weaker quadriceps muscle force and reduced daily physical activity (Table 1). No significant falls were reported within the whole cohort, but 20 patients (11%) reported non-injury falls after 12 months of follow-up (failed tandem: 19% versus successful tandem: 9%; p = 0.10). Conclusion Static balance deficit is common in patients with COPD, and is associated with reduced exercise capacity, quadriceps weakness and reduced daily physical activity. The tandem stand does not predict future risk of falls. Significant falls were not observed in this cohort.

Evaluating the Role of Inflammation in Chronic Airways Disease: The ERICA Study

Extrapulmonary manifestations are recognized to be of increasing clinical importance in Chronic Obstructive Pulmonary disease. To investigate cardiovascular and skeletal muscle manifestations of COPD, we developed a unique UK consortium funded by the Technology Strategy Board and Medical Research Council comprising industry in partnership with 5 academic centres. ERICA (Evaluating the Role of Inflammation in Chronic Airways disease) is a prospective, longitudinal, observational study investigating the prevalence and significance of cardiovascular and skeletal muscle manifestations of COPD in 800 subjects. Six monthly follow up will assess the predictive value of plasma fibrinogen, cardiovascular abnormalities and skeletal muscle weakness for death or hospitalization.As ERICA is a multicentre study, to ensure data quality we sought to minimise systematic observer error due to variations in investigator skill, or adherence to operating procedures, by staff training followed by assessment of inter- and intra-observer reliability of the four key measurements used in the study: pulse wave velocity (PWV), carotid intima media thickness (CIMT), quadriceps maximal voluntary contraction force (QMVC) and 6-minute walk distance (6MWT). This report describes the objectives and methods of the ERICA trial, as well as the inter- and intra-observer reliability of these measurements.

Proprioception in Subjects with Patellofemoral Pain Syndrome: Using the Sense of Force Accuracy

AbstractObjective: Comparison of the ability of reproducing isometric quadriceps force in patients with patellofemoral pain syndrome [PFPS] and healthy normal control subjects.Methods: The Ipsilateral Limb Matching method was utilized to assess the acuity of the sense of isometric force in the quadriceps muscle. At first, participants produced 20 and 60% of quadriceps maximal voluntary isometric contraction using an isokinetic dynamometer and visual feedback, and then they attempted to reproduce the target forces without visual feedback. They were asked to estimate and reproduce the target forces based on their own perception of the quadriceps force used earlier during the isometric contraction with feedback. This test was performed in 20° and 60° of knee flexion. The absolute error, constant error and variable error were used to measure the subjects' errors in their perception of sense of force.Results: Seventeen patients with PFPS [19 to 39 years old] and 17 matched healthy controls participated. The re...

P129 Skeletal muscle weakness, not arterial stiffness, differs according to GOLD group in COPD

IntroductionIn the GOLD 2011 COPD classification, patients in Group D are considered to be at highest risk of mortality, due to airflow limitation and exacerbations and also to be most...

Effects of Supplemental Carbohydrate Ingestion During Superimposed Electromyostimulation Exercise in Elite Weightlifters

The purpose of this investigation was to test the effects of carbohydrate supplementation on blood parameters and force output during superimposed electromyostimulation (SEMS) single-leg isometric contractions. We hypothesized that carbohydrate ingestion before and during muscle contractions would lead to greater glucose availability and greater total force output for the session. Six elite resistance trained male subjects participated in a randomized, counterbalanced, double-blind study. The subjects were randomly assigned to placebo (PL) or carbohydrate (CHO). The subjects in CHO consumed 1 g of carbohydrate per kilogram of body mass loading dose and 0.17 g of carbohydrate · per kilogram of body mass every 6 minutes during the exercise protocol. The PL received an equal volume of a solution made of saccharin and aspartame. The exercise protocol consisted of repeated 20-second isometric contractions of quadriceps muscle at 50% maximal voluntary contraction followed by 40 seconds of rest until failure occurred. Importantly, quadriceps maximal voluntary contraction with SEMS was performed in the beginning and then every 5 minutes during the last 3 seconds of isometric contractions throughout the exercise protocol. Venous blood samples were taken preexercise, immediately postexercise, and at 5 minutes postexercise and analyzed for glucose, nonesterified fatty acids, and glycerol. Our results indicate that CHO ingestion increased (p < 0.05) plasma glucose, but no significant differences (p > 0.05) were detected for nonesterified fatty acids or glycerol. Importantly, total force output during exercise protocol was higher (p < 0.05) in CHO compared with that in PL. Therefore, our data suggest that CHO supplementation before and during exercise may be beneficial for individuals performing high-volume resistance training.

Twitch and M‐wave potentiation induced by intermittent maximal voluntary quadriceps contractions: Differences between direct quadriceps and femoral nerve stimulation

The aim of this study was to investigate differences in twitch and M-wave potentiation in the quadriceps femoris when electrical stimulation is applied over the quadriceps muscle belly versus the femoral nerve trunk. M-waves and mechanical twitches were evoked using direct quadriceps muscle and femoral nerve stimulation between 48 successive isometric maximal voluntary contractions (MVC) from 10 young, healthy subjects. Potentiation was investigated by analyzing the changes in M-wave amplitude recorded from the vastus medialis (VM) and vastus lateralis (VL) muscles and in quadriceps peak twitch force. Potentiation of twitch, VM M-wave, and VL M-wave were greater for femoral nerve than for direct quadriceps stimulation (P < 0.05). Despite a 50% decrease in MVC force, the amplitude of the M-waves increased significantly during exercise. In addition to enhanced electrogenic Na(+) -K(+) pumping, other factors (such as synchronization in activation of muscle fibers and muscle architectural properties) may significantly influence the magnitude of M-wave enlargement.

Age-Specific Normal Values for the Incremental Shuttle Walk Test in a Healthy British Population

The Incremental Shuttle Walk Test (ISWT) is an important functional and prognostic marker in chronic disease. Aging has a detrimental effect on exercise performance. The objective of this study was to produce normal age-specific values for the ISWT in a healthy British population and to explore whether additional variables improve the accuracy of a predictive equation. Healthy subjects (N = 152), aged 40 to 90 years, were recruited. Data collection occurred over 2 study visits. Anthropometric and demographic data were collected, and lung function and quadriceps maximal voluntary contraction were measured. An accelerometer was worn for 2 consecutive days at home. The Duke Activity Status Index was completed, and the greatest distance from 2 ISWTs was recorded. One hundred forty subjects (56 men) with mean age (SD) of 59.4 (11.0) years completed 2 ISWTs. Forced expiratory volume in 1 second (FEV(1)) was 109.1% (14.56%) predicted and ISWT distance was 737 m (183 m). Age-specific normal values for the ISWT were observed: mean (lower limit of normal)--40 to 49 years, 824 m (765 m); 50 to 59 years, 788 m (730 m); 60 to 69 years, 699 m (649 m); and 70 years and older, 633 m (562 m). A predictive equation was developed from 114 subjects. Age, body mass index, FEV(1), quadriceps maximal voluntary contraction, and Duke Activity Status Index contributed to ISWT distance predicting 50.4% of the variation in performance. We have developed age-specific normal values for performance on the ISWT in a healthy British population. However, even using practical, clinically relevant variables, it is not possible to accurately predict exercise capacity from a regression equation.

Quadriceps bulk and strength and effect of its training in patients with moderate to severe chronic obstructive pulmonary disease

BackgroundSkeletal muscle dysfunction is one of the important systemic manifestations of chronic obstructive pulmonary disease (COPD) and is associated with mortality in those patients thus quantifying its bulk and strength is of great clinical interest and of particular value. ObjectiveEvaluation of quadriceps muscle bulk & strength in patients with moderate to severe stable COPD compared with normal healthy subjects and the effect of progressive resistant exercise program for 12weeks on quadriceps muscle strength and exercise capacity. Subjects and methodsForty patients with moderate to severe stable COPD they were 26 males and 14 females. Ten healthy subjects with the same age and sex were also included as controls. All patients and controls were evaluated at baseline for quadriceps maximal voluntary contraction (QMVC), exercise capacity, the mid – thigh cross sectional area (MTCSA) and spirometric pulmonary functions then patients were classified into 2 groups only group one performed the progressive resistant exercise program for 12weeks then reassessment of both group were done. ResultsPatients and controls were matched as regard age, weight, height and body mass index. There was significant difference between patients and control in QMVC, MTCSA, and FFM after training for 12weeks only group one had significant difference in QMVC, MTCSA and FFM/Kg in comparison to the baseline, while there was no significant difference as regard the pulmonary functions. Also there was significant difference between group 1 and 2 after 12weeks in QQMVC, MTCSA and FFM/kg. ConclusionWe have collected evidence indicating that both bulk and strength of quadriceps muscles in particular were reduced in patients with COPD compared with normal controls and these changes can be improved with progressive training without change in pulmonary functions.

The Effects of Knee Pain on the Quadriceps Strength, Proprioception and Balance in Patients with Knee Osteoarthritis

The purpose of this study was to assess the effects of knee pain on the quadriceps strength, proprioception and balance in subjects with bilateral knee osteoarthritis and the correlation between muscle strength, proprioception, and balance in knee osteoarthritis patients with knee pain. The inclusion criteria were symptomatic and radiographic bilateral knee osteoarthritis (Kellgren-Lawrence grade ≥2), visual analogue scale difference of the both knees ≥2. Thirty three participants (32 women, 1 men: mean age, 59.18 years) underwent assessment of maximal voluntary contraction of quadriceps and hamstring muscles, knee proprioceptive acuity (measure passive joint reposition sense) and balance index using Biodex System 3 isokinetic dynamometer and Biodex balance System. In this study, the more pain knee had weaker quadriceps strength than less pain knee (p 0.05). Poor proprioception was associated with low quadriceps strength and poor Medio-lateral Stability Index (p<0.05). Future studies needed to account the influence of pain on neuromuscular factors as well as attempt to further clarify the relationships between these factors.

Functional muscle impairment in facioscapulohumeral muscular dystrophy is correlated with oxidative stress and mitochondrial dysfunction

Facioscapulohumeral muscular dystrophy (FSHD), the most frequent muscular dystrophy, is an autosomal dominant disease. In most individuals with FSHD, symptoms are restricted to muscles of the face, arms, legs, and trunk. FSHD is genetically linked to contractions of the D4Z4 repeat array causing activation of several genes. One of these maps in the repeat itself and expresses the DUX4 (the double homeobox 4) transcription factor causing a gene deregulation cascade. In addition, analyses of the RNA or protein expression profiles in muscle have indicated deregulations in the oxidative stress response. Since oxidative stress affects peripheral muscle function, we investigated mitochondrial function and oxidative stress in skeletal muscle biopsies and blood samples from patients with FSHD and age-matched healthy controls, and evaluated their association with physical performances. We show that specifically, oxidative stress (lipid peroxidation and protein carbonylation), oxidative damage (lipofuscin accumulation), and antioxidant enzymes (catalase, copper–zinc-dependent superoxide dismutase, and glutathione reductase) were higher in FSHD than in control muscles. FSHD muscles also presented abnormal mitochondrial function (decreased cytochrome c oxidase activity and reduced ATP synthesis). In addition, the ratio between reduced (GSH) and oxidized glutathione (GSSG) was strongly decreased in all FSHD blood samples as a consequence of GSSG accumulation. Patients with FSHD also had reduced systemic antioxidative response molecules, such as low levels of zinc (a SOD cofactor), selenium (a GPx cofactor involved in the elimination of lipid peroxides), and vitamin C. Half of them had a low ratio of gamma/alpha tocopherol and higher ferritin concentrations. Both systemic oxidative stress and mitochondrial dysfunction were correlated with functional muscle impairment. Mitochondrial ATP production was significantly correlated with both quadriceps endurance (TLimQ) and maximal voluntary contraction (MVCQ) values (rho=0.79, P=0.003; rho=0.62, P=0.05, respectively). The plasma concentration of oxidized glutathione was negatively correlated with the TLimQ, MVCQ values, and the 2-min walk distance (MWT) values (rho=−0.60, P=0.03; rho=−0.56, P=0.04; rho=−0.93, P<0.0001, respectively). Our data characterized oxidative stress in patients with FSHD and demonstrated a correlation with their peripheral skeletal muscle dysfunction. They suggest that antioxidants that might modulate or delay oxidative insult may be useful in maintaining FSHD muscle functions.

Neuromuscular electrical stimulation prevents muscle function deterioration in exacerbated COPD: A pilot study

COPD is a condition with systemic effects of which peripheral muscle dysfunction is a prominent contributor to exercise limitation, health related quality of life (HRQoL) impairment, and is an independent predictor of morbidity and mortality. Pulmonary rehabilitation (PR) is a successful strategy to improve exercise tolerance and HRQoL through the improvement of muscle function in patients with stable COPD or early after severe exacerbations of COPD (SECOPD). However, muscle function further deteriorates during SECOPD before early PR programmes commence. We aimed to investigate the feasibility and efficacy of quadriceps neuromuscular electrical stimulation (NMES) applied during a SECOPD to prevent muscle function deterioration. We have conducted a pilot study in eleven COPD patients (FEV(1) 41.3 ± 5.6 % pred) admitted to hospital with a SECOPD. We randomly allocated one leg to receive NMES (once a day for 14 days) with the other leg as a control (non-stimulated leg). We measured the change in quadriceps maximal voluntary contraction (ΔQMVC) as the main outcome. Mean quadriceps muscle strength decreased in control legs (ΔQMVC -2.9 ± 5.3 N, p = ns) but increased in the stimulated legs (ΔQMVC 19.2 ± 6.1 N, p < 0.01). The difference in ΔQMVC between groups was statistically significant (p < 0.05). The effect of NMES was directly related to the stimulation intensity (∑mA) applied throughout the 14 sessions (r = 0.76, p < 0.01). All patients tolerated NMES without any side effects. NMES is a feasible and effective treatment to prevent quadriceps muscle strength derangement during severe exacerbations of COPD and may be used to compliment early post-exacerbation pulmonary rehabilitation.

Effects of Carbohydrate Supplementation on Force Output and Time to Exhaustion During Static Leg Contractions Superimposed with Electromyostimulation

The purpose of this study was to investigate the effects of carbohydrate ingestion on force output and time to exhaustion using single leg static contractions superimposed with brief periods of electromyostimulation. Six trained male subjects participated in a randomized, counterbalanced, double-blind study. The subjects were randomly assigned to placebo (PL) or carbohydrate (CHO). The subjects in CHO consumed 1 g of carbohydrate per kilogram of body mass loading dose and 0.17 g of carbohydrate per kilogram of body mass every 6 minutes during the exercise protocol. The PL received an equal volume of a solution made of saccharin and aspartame. The exercise protocol consisted of repeated 20-second static contractions of quadriceps muscle at 50% maximal voluntary contraction followed by 40-second rest until failure occurred. Importantly, the force output during quadriceps maximal voluntary contraction strength with superimposed electromyostimulation was measured in the beginning and every 5 minutes during the last 3 seconds of static contractions throughout the exercise protocol. Venous blood samples were taken preexercise, immediately postexercise, and at 5 minutes postexercise and analyzed for blood lactate. Our results indicate that time to exhaustion (PL = 16.0 ± 8.1 minutes; CHO = 29.0 ± 13.1 minutes) and force output (PL = 3,638.7 ± 524.5 N; CHO = 5,540.1 ± 726.1 N) were significantly higher (p < 0.05) in CHO compared with that in PL. Data suggest that carbohydrate ingestion before and during static muscle contractions can increase force output and increase time to exhaustion. Therefore, our data suggest that carbohydrate supplementation before and during resistance exercise might help increase the training volume of athletes.

Quadriceps neuromuscular function and self-reported functional ability in knee osteoarthritis

The purposes of this study were to determine 1) the relationships of self-reported function scores in patients with knee osteoarthritis (OA) to both maximal isometric torque and to isotonic power at a variety of loads, and 2) the degree to which muscle volume (MV) or voluntary activation (VA) are associated with torque and power measures in this population. Isometric maximal voluntary contraction (MVC) torque and isotonic power [performed at loads corresponding to 10, 20, 30, 40, and 50% MVC, and a minimal load ("Zero Load")] were measured in 40 participants with knee OA. Functional ability was measured with the Western Ontario and McMaster Osteoarthritis Index (WOMAC) function subscale. MV was determined with magnetic resonance imaging, and VA was measured with the interpolated twitch technique. In general, power measured at lower loads (Zero Load and 10-30% MVC, r(2) = 0.21-0.28, P < 0.05) predicted a greater proportion of the variance in function than MVC torque (r(2) = 0.18, P < 0.05), with power measured at Zero Load showing the strongest association (r(2) = 0. 28, P < 0.05). MV was the strongest predictor of MVC torque and power measures in multiple regression models (r(2) = 0.42-0.72). VA explained only 6% of the variance in MVC torque and was not significantly associated with power at any load (P > 0.05). Quadriceps MVC torque and power are associated with self-reported function in knee OA, but muscle power at lower loads is more predictive of function than MVC torque. The variance in MVC torque and power between participants is due predominantly to differences in MV and has little to do with deficits in VA.

S120 Reference values for the incremental shuttle walking test in a healthy population

<h3>Introduction</h3> The assessment of functional exercise capacity is important in the evaluation of patients with chronic conditions and field walking tests are often used to assess functional exercise capacity. The ISWT is one field exercise test which is often employed in the assessment of pulmonary and cardiac rehabilitation (PR, CR) patients and also to prescribe a walking speed. In PR and CR programmes the ISWT is employed to calculate walking speed set at a desired training threshold. The aim of the study was to establish reference values for the ISWT and an equation for its prediction in a healthy population. This will allow comparison between patients from PR and CR programmes and healthy age-matched controls. <h3>Methods</h3> Subjects were aged between 40 and 90 years, had normal spirometry defined as FEV₁ % pred &gt;80% and/or a FEV₁/FVC &gt;70% and had no known co-morbidities affecting mobility. The best distance from two ISWT was recorded along with body mass index (BMI) and leg length. Quadriceps maximal voluntary contraction (QMVC: Kg) was measured using a strain gauge (Kern). Physical activity was assessed using the DUKE physical activity questionnaire and an activity monitor (SenseWear PRO² Armband). The number of steps and energy expenditure achieved over 2 days was recorded. Subjects also completed the Hospital Anxiety and Depression Scale. <h3>Results</h3> 114 patients completed the study [mean (SD) age 60.48 (10.99) years, FEV₁ 108.82% (15.13) predicted, 37 male]. Mean ISWT distance was 690 m (152.68). There were no significant differences in walking distance between males and females (p&gt;0.05). ISWT distance showed significant correlations with age, BMI, FEV₁, QMVC, DUKE physical activity score and height (p&lt;0.01). Stepwise multiple regression analysis showed that age, BMI, FEV₁, QMVC and DUKE physical activity score were independent contributors to the ISWT distance achieved by healthy subjects, explaining 50.4% of the variance. (Abstract S120 figure 1). <h3>Conclusions</h3> Variance in the ISWT can be measured using a composite score, comprising of: age, BMI, FEV₁, QMVC and DUKE physical activity score. These findings would allow clinicians to express results of the ISWT as a percentage of the predicted values making results more meaningful for patients with chronic conditions.