Quadriceps Endurance Research Articles

Quadriceps femoris muscle fatigue in patients with knee osteoarthritis

The purpose of this study was to characterize quadriceps femoris muscle fatigue of both lower extremities in patients with knee osteoarthritis (OA). Sixty-two subjects (mean age 68.2 years, standard deviation [SD] ± 7.9 years) with knee OA participated in the study. Significantly higher knee pain was reported in the involved knee than in the contralateral knee, as determined by a visual analog scale. Significant differences were demonstrated between the lower extremities in terms of maximal voluntary isometric contraction, in favor of the less involved leg (P = 0.0001). In contrast, the degree of fatigue of the quadriceps femoris muscle, as measured by the decrement in force production following ten repeated contractions, was significantly higher in the contralateral leg (P = 0.0002). Furthermore, normalization of the fatigue results to the first contraction yielded a similar result (P < 0.0001). Similar results were noted when analysis was performed separately for subjects whose involvement was unilateral or bilateral. The results indicate that, irrespective of the initial strength of contraction, the rate of muscle fatigue in the contralateral leg is significantly higher than in the involved leg. Hypotheses for these unexpected results are suggested. Rehabilitation of patients with knee OA should focus on increasing quadriceps muscle strength and endurance for both lower extremities.

Pathways associated with reduced quadriceps oxidative fibres and endurance in COPD

Reduced quadriceps endurance in chronic obstructive pulmonary disease (COPD) is associated with a predominance of type II glycolytic fibres over type I oxidative fibres (fibre shift) and reduced muscle energy stores. The molecular mechanisms responsible for this remain unknown. We hypothesised that expression of known regulators of type I fibres and energy production in quadriceps muscle would differ in COPD patients with and without fibre shift. We measured lung function, physical activity, exercise performance, quadriceps strength and endurance (nonvolitionally) in 38 Global Initiative for Chronic Obstructive Lung Disease stage I-IV COPD patients and 23 healthy age-matched controls. Participants underwent a quadriceps biopsy: type I and II fibre proportions were determined using immunohistochemistry and fibre shift defined using published reference ranges. Calcineurin A, phosphorylated AMP kinase (phospho-AMPK)-α, protein kinase A-α catalytic subunits, modulators of calcineurin activity and calmodulin, 14-3-3 proteins were measured by Western blotting, and myocyte-enriched calcineurin-interacting protein-1 mRNA measured by quantitative PCR. Downstream, nuclear myocyte enhancer factor-2 capable of DNA binding was quantified by transcription factor ELISA. Unexpectedly, calcineurin expression was higher, while phospho-AMPK was lower, in COPD patients with fibre shift compared to COPD patients without fibre shift. Phospho-AMPK levels correlated with quadriceps endurance in patients. Reduced phospho-AMPK may contribute to reduced quadriceps oxidative capacity and endurance in COPD.

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.Twenty healthy subjects (10 men and 10 women) performed the test on two different days. Maximal voluntary strength and evoked quadriceps responses via FMNS were measured before, after each set of 10 submaximal isometric contractions (5-s on/5-s off; starting at 10% of maximal voluntary strength with 10% increments), immediately and 30min after task failure.The test induced progressive peripheral (41±13% reduction in single twitch at task failure) and central fatigue (3±7% reduction in voluntary activation at task failure). Good inter-day reliability was found for the total number of submaximal contractions achieved (i.e. endurance index: ICC=0.83), for reductions in maximal voluntary strength (ICC>0.81) and evoked muscular responses (i.e. fatigue index: ICC>0.85). Significant sex-differences were also detected.This test shows good reliability for strength, endurance and fatigability assessments. Further studies should be conducted to evaluate its feasibility and reliability in patients.

Neuromuscular electrical stimulation appears to be useful in people with severe chronic obstructive pulmonary disease

In patients with chronic obstructive pulmonary disease (COPD), what effect does neuromuscular electrical stimulation (NMES) have on muscle function and walking endurance? Randomised, controlled trial in which the patients and those who collected outcome measures were blinded to group allocation. Home-based intervention with outcomes collected at a hospital in Quebec City, Canada. Patients who were clinically stable, sedentary and able to travel to the hospital with: (a) a smoking history >20 pack-years, (b) severe airflow obstruction, and (c) a 6-minute walk distance <400m. Exclusion criteria comprised any co-morbid condition associated with muscle wasting. Randomisation of 22 patients allocated 13 to the intervention group and 9 to the control group. Both groups received electrical stimulation 5 times a week for 6 weeks. Each session comprised 35min of bilateral stimulation for the quadriceps and 25min of bilateral stimulation for the calf. Stimulation was applied with the patient in sitting. They were encouraged to increase the intensity to the maximum they could tolerate. Patients were visited weekly at home by a research nurse to monitor progress. Parameters used by the intervention group were 50Hz frequency, 400μs pulse duration, and 6sec/16sec duty cycle. Parameters used by the control/sham group were 5Hz frequency, 100μs pulse duration, applied continuously. The primary outcome was quadriceps strength. The secondary outcomes included quadriceps endurance and performance during the endurance shuttle walk test. Data were available on 12 and 8 patients in the intervention and control groups, respectively. Current intensity increased over the training period in the intervention group from 20±4mA to 31±10mA (p <0.001). Compared with the control group, the intervention group conferred greater gains in quadriceps force (difference in mean percent change from baseline 14%, 95% CI 1% to 26%) and endurance (42%, 95% CI 4% to 80%), but not walking endurance. In patients with severe COPD, NMES delivered at home enhanced muscle function but not walking endurance.

S48 The Effect of Angiotensin-Converting Enzyme Inhibition on Skeletal Muscle Dysfunction in Chronic Obstructive Pulmonary Disease: A Randomised Controlled Trial

IntroductionSkeletal muscle impairment is a well recognised complication of COPD, predicting mortality in severe disease.1 Evidence from animal models, genetic studies and observational cohorts suggest a role for the renin-angiotensin...

Neuromuscular Stimulation of Quadriceps in Patients Hospitalised during an Exacerbation of COPD: A Comparison of Low (35 Hz) and High (50 Hz) Frequencies

Neuromuscular electrical stimulation (NMES) has shown to improve skeletal muscle strength and exercise capacity in stable patients with chronic obstructive pulmonary disease (COPD). Variations in NMES protocols are considerable. We aimed to compare changes in muscle strength after high-frequency and low-frequency NMES in patients admitted to hospital with an acute exacerbation of COPD. Patients were referred for inpatient (IP) rehabilitation during hospitalisation for an acute worsening of their COPD. They received 30-minute daily NMES to both quadriceps at a frequency of 35 or 50 Hz. NMES intensity was titrated to patients' tolerance. Isometric quadriceps muscle strength and endurance walking (ESWT) time were measured at baseline and on hospital discharge. A total of 10 patients in each treatment group underwent NMES during hospitalisation (mean [SD] age 68.0 [±7.4] years, FEV1 0.99 L [±0.58], FEV1/FVC 47% [± 27%], MRC 5 [IQR ±1]). There were no significant differences in baseline characteristics between groups. Muscle strength (legs combined) increased in both groups regardless of the NMES frequency used (35 Hz--3.8 ± 4.9; 50 Hz--3.4 ± 5.5 kg). This was only significant within the 35 Hz group. The change in ESWT also showed a trend to increase in both groups (35 Hz--109 ± 92.7; 50 Hz--145.6 ± 94.7). There was no significant difference between groups for either outcome. NMES is a feasible intervention to improve muscle strength in a cohort of patients admitted with an exacerbation of COPD. The response appears to be independent of the frequency used and both were well-tolerated.

Loss of quadriceps muscle oxidative phenotype and decreased endurance in patients with mild-to-moderate COPD

Being well-established in advanced chronic obstructive pulmonary disease (COPD), skeletal muscle dysfunction and its underlying pathology have been scarcely investigated in patients with mild-to-moderate airflow obstruction. We hypothesized that a loss of oxidative phenotype (oxphen) associated with decreased endurance is present in the skeletal muscle of patients with mild-to-moderate COPD. In quadriceps muscle biopsies from 29 patients with COPD (forced expiratory volume in 1 s [FEV1] 58 ± 16%pred, body mass index [BMI] 26 ± 4 kg/m(2)) and 15 controls (BMI 25 ± 3 kg/m(2)) we assessed fiber type distribution, fiber cross-sectional areas (CSA), oxidative and glycolytic gene expression, OXPHOS protein levels, metabolic enzyme activity, and levels of oxidative stress markers. Quadriceps function was assessed by isokinetic dynamometry, body composition by dual-energy X-ray absorptiometry, exercise capacity by an incremental load test, and physical activity level by accelerometry. Compared with controls, patients had comparable fat-free mass index, quadriceps strength, and fiber CSA, but quadriceps endurance was decreased by 29% (P = 0.002). Patients with COPD had a clear loss of muscle oxphen: a fiber type I-to-II shift, decreased levels of OXPHOS complexes IV and V subunits (47% and 31%, respectively; P < 0.05), a decreased ratio of 3-hydroxyacyl-CoA dehydrogenase/phosphofructokinase (PFK) enzyme activities (38%, P < 0.05), and decreased peroxisome proliferator-activated receptor-γ coactivator-1α (40%; P < 0.001) vs. increased PFK (67%; P < 0.001) gene expression levels. Within the patient group, markers of oxphen were significantly positively correlated with quadriceps endurance and inversely with the increase in plasma lactate relative to work rate during the incremental test. Levels of protein carbonylation, tyrosine nitration, and malondialdehyde protein adducts were comparable between patients and controls. However, among patients, oxidative stress levels were significantly inversely correlated with markers of oxphen and quadriceps endurance. Reduced muscle endurance associated with underlying loss of muscle oxphen is already present in patients with mild-to-moderate COPD without muscle wasting.

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.

Longitudinal assessment of muscle function and oxygen cost during isometric testing in children with cerebral palsy

The aim of the study was to document the longitudinal changes from one year to the next in knee extensor muscle strength and function and in cardiorespiratory demand during an isometric test in children with cerebral palsy (CP). Ten children with CP (GMFC I and II) and ten able-bodied children underwent a quadriceps strength and endurance assessment on an isokinetic dynamometer. Maximal voluntary isometric torque in the children with CP in the initial test was significantly lower than in controls (p = 0.0007) and did not change significantly over the year. No significant difference was found between the two groups for the initial static endurance measure (p = 0.93); it did not change significantly after one year in the children with CP (p = 0.74). Oxygen cost was significantly greater in the group with CP than in the control group (p < 0.01) and there was a further significant increase in the oxygen cost for the CP group 12 months later (p < 0.01). Ventilation and heart rate at exhaustion were also significantly lower in children with CP than controls in the initial test (p = 0.0001 and p = 0.009, respectively). The persisting muscle weakness and the increase in oxygen cost over time may in part have resulted from inactivity and misuse of muscle. Secondary adaptive soft tissue changes affecting the development of muscle may prevent the increases in strength and endurance normally associated with growth and development.

Benefits of combined aerobic/resistance/inspiratory training in patients with chronic heart failure. A complete exercise model? A prospective randomised study

BackgroundWe hypothesised that combined aerobic training (AT) with resistance training (RT) and inspiratory muscle training (IMT) could result in additional benefits over AT alone in patients with chronic heart failure (CHF). MethodsTwenty-seven patients, age 58±9years, NYHA II/III and LVEF 29±7% were randomly assigned to a 12-week AT (n=14) or a combined AT/RT/IMT (ARIS) (n=13) exercise program. AT consisted of bike exercise at 70–80% of max heart rate. ARIS training consisted of AT with RT of the quadriceps at 50% of 1 repetition maximum (1RM) and upper limb exercises using dumbbells of 1–2kg as well as IMT at 60% of sustained maximal inspiratory pressure (SPImax). At baseline and after intervention patients underwent cardiopulmonary exercise testing, echocardiography, evaluation of dyspnea, muscle function and quality of life (QoL) scores. ResultsThe ARIS program as compared to AT alone, resulted in additional improvement in quadriceps muscle strength (1RM, p=0.005) and endurance (50%1RM×number of max repetitions, p=0.01), SPImax (p<0.001), exercise time (p=0.01), circulatory power (peak oxygen consumption×peak systolic blood pressure, p=0.05), dyspnea (p=0.03) and QoL (p=0.03). ConclusionsARIS training was safe and resulted in incremental benefits in both peripheral and respiratory muscle weakness, cardiopulmonary function and QoL compared to that of AT. The present findings may add a new prospective to cardiac rehabilitation programs of heart failure patients whilst the clinical significance of these outcomes need to be addressed in larger randomised studies.

Vitamin D and skeletal muscle strength and endurance in COPD

It is not known whether vitamin D levels make a significant contribution to muscle dysfunction in chronic obstructive pulmonary disease (COPD). In 104 COPD patients (mean±sd forced expiratory volume in 1 s 44±22 % predicted) and 100 age- and sex-matched controls, serum 25-hydroxyvitamin D (25(OH)D), 1,25-dihydroxyvitamin D (1,25(OH)(2)D) and parathyroid hormone (PTH) levels were measured and related to quadriceps strength and endurance. In a subset of 26 patients and 13 controls, quadriceps biopsy was performed and mRNA expression of myogenic regulatory factors (mrf) and fibre-specific myosin heavy chains (MHC) was determined. COPD patients were weaker and less physically active than controls. 25(OH)D levels were similar in both groups (48.5±25.5 nmol·L(-1) COPD versus 55.4±28.3 nmol·L(-1) control, p=0.07) but PTH levels were significantly higher in patients (5.2±2.3 pmol·mL(-1) versus 4.4±2.0 pmol·L(-1), p=0.01). 1,25(OH)D was significantly correlated with strength in controls, but not in COPD patients and not with quadriceps endurance assessed using repetitive magnetic stimulation in COPD (n=35) or control (n=35) subjects. In controls, but not COPD patients, muscle biopsy analysis showed a negative relationship between 25(OH)D and MHCIIa expression (r(2)=0.5, p=0.01) and a positive relationship between mrf4 and MHCIIa expression (r(2)=0.5, p=0.009), and myogenic regulatory factor myf5 and MHCI expression (r(2)=0.72, p=0.004). In contrast with healthy controls, muscle strength is not associated with vitamin D levels in COPD, which may represent vitamin D resistance.

Functional Outcome After Repair of Proximal Hamstring Avulsions

Rupture of the proximal origin of the hamstrings leads to pain, weakness, and a debilitating decrease in physical activity. Repair of these injuries should be based on the expectation that these deficits can be addressed. The goal of this study was to objectively evaluate the efficacy of repair of proximal hamstring avulsions. Thirty-four patients were identified retrospectively to have a complete rupture of the proximal origin of the hamstrings based on the presence of a bowstring sign and the results of magnetic resonance imaging (MRI).Patients were contacted for follow-up evaluation to fill out a subjective questionnaire, to undergo functional testing, and to undergo isokinetic testing on a Cybex dynamometer. Twenty-three patients were evaluated. There were nine acute and fourteen chronic repairs, and the average period of follow-up was 43.3 months. Twenty-one of twenty-three patients reported returning to activity at an average of 95% of their pre-injury activity level at an average of 9.8 months. Eighteen patients reported excellent results; four, good results; and one, fair results. Hamstring strength was an average of 93% and 90% of that in the uninvolved limb at 240° per second and 180° per second, respectively. The hamstrings-to-quadriceps ratio was 56% for 240° per second and 48% at 180° per second. Hamstring endurance was an average of 81% and 91% of the nonoperative limb at 240° per second and 180° per second, respectively. Postoperative quadriceps strength and endurance were positively correlated with return to pre-injury level of activity (r = 0.6, p < 0.05; and r = 0.6, p < 0.05) and negatively correlated with time to return to sport (r = -0.5, p < 0.05; and r = -0.5, p < 0.05). There was no significant effect associated with age or time from injury. Repair of a symptomatic and displaced ruptured proximal hamstring tendon yields good subjective and objective functional results with minimal complications. Overall, patients are satisfied with surgical repair and experience return of functional activity with minimal postoperative weakness.

Evidence of an Early Physical Activity Reduction in Chronic Obstructive Pulmonary Disease Patients

Gouzi F, Préfaut C, Abdellaoui A, Vuillemin A, Molinari N, Ninot G, Caris G, Hayot M. Evidence of an early physical activity reduction in patients with chronic obstructive pulmonary disease. Objective To compare the lifetime pattern of physical activity (PA) in chronic obstructive pulmonary disease (COPD) patients and sedentary healthy subjects (SHS) using a PA questionnaire with a lifetime period of recall (Quantification de l'Activité Physique [QUANTAP] system), and to compare the pattern of PA reduction in COPD patients with the onset of breathlessness and other relevant clinical events in this disease (diagnosis, first rehabilitation, onset of smoking). Design Cross-sectional comparative study. Settings Outpatient university hospital and inpatient pulmonary rehabilitation center. Participants COPD patients (n=129; mean age ± SD, 61±10y; forced expiratory volume in 1s, 57±23%) and SHS (n=29; mean age ± SD, 61±5y; <150min·wk −1 of moderate-vigorous PA). Interventions Not applicable. Main Outcome Measures Lifetime PA was compared in COPD patients and SHS using the QUANTAP system. The patients with COPD and SHS underwent pulmonary function, exercise, and quadriceps endurance testing. The current PA level was assessed with a triaxial accelerometer and the Voorrips questionnaire. The age at the onset of breathlessness was also recorded. Results Accelerometry showed no significant difference between patients and SHS (in vector magnitude units, 136±56 vs 135±47; P=.95). Within the past 15 years, the cumulated PA level was not different for each 5-year period. Then, from the period of 16 to 40 years ago, it was systematically higher in patients compared with SHS (in metabolic equivalent/y −1; median [interquartile range], 6973 [5400–12,207] vs 4248 [3545–5919]; P<.05). The COPD patients reduced their PA earlier than the SHS (45y vs 55y; P<.01), and the PA was dropped before the onset of breathlessness (45y vs 49y; P<.001). Conclusions The observation of an early PA reduction, preceding the onset of breathlessness, suggests the implication of prior pathologic mechanisms in the PA reduction of COPD patients.

Aerobic capacity and skeletal muscle function in children with asthma

BackgroundPeripheral muscle strength and endurance are decreased in patients with chronic pulmonary diseases and seem to contribute to patients' exercise intolerance. However, the authors are not aware of any studies...

Muscle training with repetitive magnetic stimulation of the quadriceps in severe COPD patients

Previous studies have used electrical neuromuscular stimulation as a physical training method in patients with severe COPD. We introduce the use of the more tolerable magnetic stimulation for the same purpose, investigating the effectiveness of an eight-week protocol. Eighteen patients with severe COPD were randomly assigned to a magnetic stimulation training protocol, n=10, FEV(1)=30% (SD: 7) or to parallel clinical monitoring, control group, n=8, FEV(1)=35% (SD: 8). During eight weeks, patients were stimulated for 15min on each quadriceps femoris, three times per week. Quadriceps muscle strength and endurance measurements, quality-of-life questionnaires (SF36, SGRQ) and a six-minute walking test were all carried out before and after the training period in the stimulated and control subjects. All patients completed the training with increasing intensity of stimulation, displaying a significant improvement in voluntary quadriceps strength (17.5% of the baseline value) and exercise capacity, with a mean increase of 23m in the six-minute walking test. The questionnaire scores showed greater increases in quality-of-life scores in the trained subjects compared to the controls, particularly in the physical function areas: mean increments in SF36 in "physical function": +26, "role limitations due to physical problems": +40 and "vitality": +17.5, while +13, -4 and +1, respectively in controls. Saint George's "Activity" score improved by 19.6 points, for 11.5 in controls. In COPD patients who are limited due to dyspnoea, magnetic neuromuscular stimulation of the quadriceps constitutes a feasible training method for the lower limbs, with positive effects on the muscle function, effort capacity and perception areas.

Effects of exercise training in patients with idiopathic pulmonary arterial hypertension

We determined the physiological effects of exercise training on exercise capacity and quadriceps muscle function in patients with idiopathic pulmonary arterial hypertension (iPAH). In total, 19 clinically stable iPAH patients (New York Heart Association II-III) underwent a supervised exercise training programme for the duration of 12 weeks. Maximal capacity, endurance capacity and quadriceps function were assessed at baseline and after 12 weeks. In 12 patients, serial quadriceps muscle biopsies were obtained. 6-min walk distance and peak exercise capacity did not change after training. However, endurance capacity improved significantly after training, demonstrated by a shift of the anaerobic threshold to a higher workload (from 32+/-5 to 46+/-6 W; p = 0.003) together with an increase in exercise endurance time (p<0.001). Moreover, exercise training increased quadriceps strength by 13% (p = 0.005) and quadriceps endurance by 34% (p = 0.001). Training enhanced aerobic capacity of the quadriceps, by increasing capillarisation (1.36+/-0.10 to 1.78+/-0.13 capillaries per muscle fibre; p<0.001) and oxidative enzyme activity, especially of the type-I (slow) muscle fibres. No changes were found in cross-sectional area and fibre type distribution. Exercise training in iPAH improves exercise endurance and quadriceps muscle function, which is also reflected by structural changes of the quadriceps.

Effects of functional exercise training on performance and muscle strength after meniscectomy: a randomized trial

Muscular deficits and functional limitations have been found years after meniscectomy of the knee. The purpose of this randomized controlled trial was to examine the effect of functional exercise training on functional performance and isokinetic thigh muscle strength in middle-aged patients subsequent to meniscectomy for a degenerative tear. Four years after meniscectomy, 45 patients (29 men, 16 women) were randomized to functional exercise training, supervised by a physical therapist, three times weekly for 4 months or to no intervention. The exercise program comprised of postural stability training and functional strength and endurance exercises for leg and trunk muscles. Outcomes were three functional performance tests and isokinetic muscle strength. Thirty patients (16 exercisers/14 controls) completed the study. Compared with control patients, the exercise group showed significant improvement in one-leg hop (change 8 vs 2 cm; P=0.040), hamstrings strength 60 degrees /s (P=0.033), and quadriceps endurance 180 degrees /s (P=0.001). Functional exercise training was well tolerated and improved functional performance and thigh muscle strength in this group of middle-aged subjects with a previous degenerative meniscal injury and partial meniscectomy.

Cardiopulmonary exercise data during quadriceps isometric contraction sustained to fatigue in children with cerebral palsy

The aims of this study were to: 1) study the cardiopulmonary responses during exhaustive isometric contraction in cerebral palsy (CP) children vs. apparently normal (AN) children 2) to study the relationship between muscle endurance and maximal O 2 uptake (peak VO 2 ) in CP children. Eight CP children (GMFC 1 to 2) and 8 AN children underwent a graded cycle exercise test and a quadriceps force and endurance assessment with cardiopulmonary measurement on an isokinetic dynamometer. During isometric contraction, muscle endurance did not differ between the groups but a higher O 2 uptake was shown in the CP group. Moreover in this group, peak VO 2 was correlated with muscle strength (R = 0.77, P < 0.05) and endurance (R = 0.68, P < 0.05). Cerebral palsy children have a higher O 2 uptake during isometric endurance testing despite a lower absolute isometric force but their quadriceps endurance is not impaired after normalization with muscle mass and time. Additionally, quadriceps strength and endurance in CP children were in relationship with their peak VO 2 . This higher O 2 uptake is probably due to coactivation and/or cocontraction during exhaustive quadriceps isometric contraction.

Skeletal Muscle Strength and Endurance in Recipients of Lung Transplants

Exercise limitation in recipients of lung transplant may be a result of abnormalities in the skeletal muscle. However, it is not clear whether these abnormalities are merely a reflection of the changes observed in the pretransplant condition. The purpose of this paper was to compare thigh muscle volume and composition, strength, and endurance in lung transplant recipients to people with chronic obstructive pulmonary disease (COPD). Single lung transplant recipients (n=6) and people with COPD (n=6), matched for age, sex, and BMI participated in the study. Subjects underwent MRI to determine muscle size and composition, lower extremity strength testing and an isometric endurance test of the quadriceps. Lung transplant recipients had similar muscle volumes and intramuscular fat infiltration of their thigh muscles and similar strength of the quadriceps and hamstrings to people with COPD who had not undergone transplant. However, quadriceps endurance tended to be lower in transplant recipients compared to people with COPD (15 +/- 7 seconds in transplant versus 31 +/- 12 seconds in COPD, p = 0.08). Recipients of lung transplant showed similar changes in muscle size and strength as people with COPD, however muscle endurance tended to be lower in people with lung transplants. Impairments in muscle endurance may reflect the effects of immunosuppressant medications on skeletal muscle in people with lung transplant.

Muscle assessment in healthy teenagers: Comparison with teenagers with low back pain

ObjectivesTo describe muscle parameters in healthy teenagers and compare them to teenagers with chronic low back pain. MethodsA comparative study of 276 control teenagers and 51 teenagers with chronic low back pain (CLBP), benefiting from a specific treatment, 14.5 years average age. The control group is made up of teenagers without back pain and teenagers who reported some back pain when we asked them, but without specific treatment. The results to four static tests assessing trunk flexors, trunk extensors, hip extensors and quadriceps endurance are statistically compared. In the control group, associations between different clinical measures and possible back pain are looked for. ResultsThe two groups are homogeneous, concerning age, weight, standing height, sitting height and BMI (p>0,05). Low back pain is more common in girls, either in the control group (n=48; 69% of girls) or in the group with CLBP (n=51; 78%). CLBP is associated with a poor endurance strength of the trunk extensors (median: 2min 31s in the control group to 1min 45s in the CLBP), with hip extensors weakness (median: 2min 20s in the control group to 1min 24s in the CLBP), and with quadriceps weakness (median: 2min 39s in the control group to 1min 20s in the CLBP), (p=0.000). No significant difference was found between trunk flexors endurance in the two groups (median: 2min 11s in the control group to 2min 13s in the CLBP). In the control group, 48 teenagers reported back pain “often”, “very often” or “all the time”; no links were found between pain and muscle flexibility, measured with finger-floor distance, heel-cheek distance, and popliteal angle. Only the sitting height was found statistically higher (p=0.003) in the control teenagers who reported back pain (87cm) related to the ones who have no pain (85cm). Sport influences global strength in lower limbs and changes the ratio of quadriceps to hip extensors, in favour of quadriceps. Neither pain nor the ratio of trunk flexors to trunk extensors are modified by sport. There is a linear relation between Shirado's and Sorensen's logarithmic values: it is consequently possible to predict the Shirado value when we have the Sorensen one. Trunk extensors, hip extensors and quadriceps endurance is lower in the CLBP group, 14.5 years of age.