Biomedical subjects

David A Jones

Publications and source records attributed to David A Jones.

At least 55 records · Page 3Linked to original sources

PubMed2004

Reproducibility of maximal quadriceps strength and its relationship to maximal voluntary activation in postpoliomyelitis syndrome.

OBJECTIVES: To determine what changes in maximal isometric strength can be detected in a symptomatic quadriceps muscle in patients with postpoliomyelitis syndrome (PPS) and to investigate the association between the variability in maximal strength and maximal voluntary activation (MVA). DESIGN: Repeated-measures over a 3-week interval. SETTING: University hospital. PATIENTS: Convenience sample of 65 patients with PPS. INTERVENTION: Dynamometer testing. MAIN OUTCOME MEASURES: Maximal voluntary contraction (MVC) torque of the quadriceps was measured with a Kin-Com dynamometer and MVA was determined by twitch interpolation. RESULTS: The mean difference between the 2 consecutive measurements was -0.7+/-12.8 Nm (95% confidence interval [CI], -3.9 to 2.5). The test-retest reliability was excellent for MVC torque (intraclass correlation coefficient [ICC]=.96; 95% CI,.93-.98) and moderate for MVA (ICC=.73; 95% CI,.56-.85). The smallest detectable change in MVC torque was 25% for an individual. The variability in MVA explained 18% of the variability in maximal strength. CONCLUSIONS: Variability in maximal quadriceps strength, measured with a fixed dynamometer, was large and partly related to variability in MVA. This implies that even with optimally standardized strength testing, a follow-up of many years is required to objectify progression of quadriceps weakness in an individual patient with PPS. To demonstrate changes in strength in groups of patients in follow-up or intervention studies, feasible sample sizes are required.

Adult↗

PubMed2004

Plant innate immunity - direct and indirect recognition of general and specific pathogen-associated molecules.

Plants have the capacity to recognise and reject pathogens at various stages of their attempted colonisation of the plant. Non-specific rejection often arises as a consequence of the potential pathogen's attempt to breach the first lines of plant defence. Pathogens able to penetrate beyond this barrier of non-host resistance may seek a subtle and persuasive relationship with the plant. For some, this may be limited to molecular signals released outside the plant cell wall, but for others it includes penetration of the cell wall and the delivery of signal molecules to the plant cytosol. Direct or indirect recognition of these signals triggers host-specific resistance. Our understanding of host-specific resistance and its possible links to non-host-specific resistance has advanced significantly as more is discovered about the nature and function of the molecules underpinning both kinds of resistance.

Carrier Proteins↗

PubMed2004

Identification of autoantigens in psoriatic plaques using expression cloning.

To search for autoantigens in psoriatic plaques, we screened cDNA libraries of plaque epidermis with psoriatic serum samples. This approach has been highly successful in identifying tumor antigens, but has not been widely applied to autoimmune disease. We identified 11 autoantigens including three with prominent reactivity and plausible disease relevance. These are keratin 13 (K13), heterogeneous nuclear ribonucleoprotein-A1 (hnRNP-A1), and a previously uncharacterized protein, FLJ00294. Serum antibody screening for these demonstrated reactivity in 40%, 38%, and 27% of psoriasis patients, respectively. Most positive samples reacted with all three, and we found that this was due to cross-reactivity among them. Enzyme-linked immunospot assay (ELISPOT) analysis of psoriatic peripheral blood T cells confirmed that these autoantigens are also recognized by T cells. This demonstrates that this is a feasible method to identify autoantigens in an autoimmune target tissue, and suggests that these antigens warrant further study in psoriasis. Furthermore, but peripheral blood of normal controls reacted to these autoantigens with essentially the same frequencies as patients, suggesting that psoriatics may have not only an immune system which is capable of reacting to certain autoantigens, but also to a skin immunoregulatory alteration which allows this normal reactivity to develop into abnormal inflammation.

Autoantigens↗

PubMed2004

Limited gene activation in tumor and normal epithelial cells treated with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine.

It remains unclear to what extent drugs targeting transcriptional repressor complexes affect global gene expression in cells derived from target and nontarget human tissues. To address this question, we used genome-wide expression analysis using microarrays to analyze the response of three tumor and one normal epithelial cell line to treatment with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (5-aza-CdR). Notably, we found that 5-aza-CdR treatment induced a limited number of genes (mean, 0.67%; range, 0.17-1.8% of 25,940 genes screened) in each cell line tested. The majority of the gene expression changes that followed 5-aza-CdR treatment were conserved in tumor and normal cells, including genes that function in cell proliferation, differentiation, immune presentation, and cytokine signaling. In contrast, 5-aza-CdR treatment induced the expression of cancer-testis class tumor antigens only in tumor cell lines. To explain this tissue-specific response, we analyzed the mechanism of transcriptional regulation of the prototype member of this tumor antigen gene family, MAGE-1. Taken from our analysis of MAGE-1 gene regulation, we propose that 5-aza-CdR-mediated gene activation has two distinct requirements: 1) the reversal of promoter hypermethylation, and 2) the presence of transcriptional activators competent for the activation of hypomethylated target promoters. This latter requirement for gene activation by 5-aza-CdR is probably mediated by sequence-specific transcription factors and may account for the limited number of human genes induced by 5-aza-CdR treatment. This revised model for gene activation by 5-aza-CdR has important implications for the use of DNA methyltransferase inhibitors in clinical settings.

Antigens, Neoplasm↗

PubMed2004

Deficiency in the nuclease activity of xeroderma pigmentosum G in mice leads to hypersensitivity to UV irradiation.

Xeroderma pigmentosum (XP) is a human disorder which is characterized by hypersensitivity to sunlight and elevated incidence of skin cancer. The disease is caused by mutations in genes that encode components of the nucleotide excision repair pathway. The gene product of XP complementation group G (XPG) is a structure-specific endonuclease which makes an incision 3' to DNA photoproducts and other helix-distorting DNA adducts. In addition, the XPG protein has been implicated in transcription and repair of oxidative DNA damage. Moreover, XPG is capable of cleaving R loops in vitro, a potential intermediate during immunoglobulin heavy-chain class switch recombination. Due to its multiple functions, complete elimination of XPG in mice results in severe postnatal growth defects and premature death. To understand the contribution of the XPG nuclease activity to its function in vivo, we introduced a point mutation into the mouse XPG gene which inactivates the nuclease catalytic site but leaves the remainder of the protein intact. The XPG nuclease-deficient animals develop normally and exhibit no obvious defect in class switch recombination. However, the mutant mice are hypersensitive to UV irradiation. This phenotype suggests that the nuclease activity of XPG is required only for nucleotide excision repair and that other regions of the protein perform independent functions.

Animals↗

PubMed2004

The effect of glucose infusion on glucose kinetics during a 1-h time trial.

PURPOSE AND METHODS: To investigate the effect of glucose infusion on glucose kinetics and performance, six endurance cyclists (VO2max = 61.7 +/- 2.0 (mean +/- SE) mL x kg(-1) x min(-1)) completed two performance trials in which they had to accomplish a set amount of work as quickly as possible (991 +/- 41 kJ). Subjects were infused with either glucose (20% in saline; carbohydrate (CHO)) at a rate of 1 g x min(-1) or saline (0.9% saline; placebo (PLA)). It was hypothesized that time trial performance would be unaffected by the infusion of glucose, as endogenous stores of CHO would not be limiting in the PLA trial. RESULTS: Plasma glucose concentration increased from 4.8 +/- 0.1 mmol x L(-1) to 5.9 +/- 0.3 mmol x L(-1) during the PLA trial and from 4.9 +/- 0.1 mmol x L(-1) at rest to 12.4 +/- 1.1 mmol x L(-1) during the CHO trial. These values were significantly higher at all time points during the CHO trial compared with PLA (P < 0.001). In the final stages of the time trial, Rd in the PLA trial was 49 +/- 5 micromol x kg(-1) x min(-1) compared with 88 +/- 7 micromol x kg(-1) x min(-1) in the CHO trial (P < 0.05). Despite these differences, there was no difference in performance time between PLA and CHO (60.04 +/- 1.47 min, PLA, vs 59.90 +/- 1.49 min, CHO, respectively). Infused carbohydrate oxidation in the last 25% of the CHO trial was at least 675 +/- 120 micromol x kg(-1) and contributed 17 +/- 4% to total carbohydrate oxidation. CONCLUSION: The results demonstrate that glucose infusion had no effect on 1-h cycle time-trial performance, despite an increased availability of plasma glucose for oxidation and evidence of increased glucose uptake into the tissues.

Adult↗

PubMed2004

The effect of carbohydrate mouth rinse on 1-h cycle time trial performance.

PURPOSE AND METHOD: To investigate the possible role of carbohydrate (CHO) receptors in the mouth in influencing exercise performance, seven male and two female endurance cyclists (VO(2max) 63.2 +/- 2.7 (mean +/- SE) mL.kg*(-1).min(-1)) completed two performance trials in which they had to accomplish a set amount of work as quickly as possible (914 +/- 40 kJ). On one occasion a 6.4% maltodextrin solution (CHO) was rinsed around the mouth for every 12.5% of the trial completed. On the other occasion, water (PLA) was rinsed. Subjects were not allowed to swallow either the CHO solution or water, and each mouthful was spat out after a 5-s rinse. RESULTS: Performance time was significantly improved with CHO compared with PLA (59.57 +/- 1.50 min vs 61.37 +/- 1.56 min, respectively, P = 0.011). This improvement resulted in a significantly higher average power output during the CHO compared with the PLA trial (259 +/- 16 W and 252 +/- 16 W, respectively, P = 0.003). There were no differences in heart rate or rating of perceived exertion (RPE) between the two trials (P > 0.05). CONCLUSION: The results demonstrate that carbohydrate mouth rinse has a positive effect on 1-h time trial performance. The mechanism responsible for the improvement in high-intensity exercise performance with exogenous carbohydrate appears to involve an increase in central drive or motivation rather than having any metabolic cause. The nature and role of putative CHO receptors in the mouth warrants further investigation.

Adult↗

PubMed2004

Training diagnosis for a load carriage task.

To explore the possibility of training diagnosis for a 3.2-km loaded march with a 25 kg load, 50 men trained for 10 weeks using either running, marching, and endurance-based circuit training (Circuits), or running, marching, and resistance training (Resistance). The march was performed before and after training, and other measurements related to loaded marching were conducted before training only. Each group was ranked by improvement in the loaded march, and divided into significantly different subgroups of 'good' and 'poor' responders (improvements of approximately 20% vs. 10%). For Circuits, there were significant differences between good and poor responders to training in the pretraining ratios of shuttle run: isometric lift strength (p = 0.031) and shuttle run: isometric back extension strength (p = 0.033). Stronger subjects with lower endurance responded better to Circuits. Resistance tended to show the opposite effect (p < 0.2). These are the first objective data on which to prescribe training for load carriage on an individual basis.

Adolescent↗

PubMed2003

Influence of environmental temperature on exercise-induced inspiratory muscle fatigue.

Exercise in the heat has detrimental effects on circulation that might negatively influence endurance performance. If blood is diverted away from the inspiratory muscles to the skin during exercise in the heat, exercise-induced inspiratory muscle fatigue might be exacerbated. Thus, we hypothesised that prolonged heavy endurance exercise in the heat would impair exercise performance and exacerbate inspiratory muscle fatigue compared to exercise in a thermo-neutral environment. Using a crossover design, seven male endurance trained subjects [mean (SEM) maximum oxygen uptake = 62.2 (1.5) ml x kg(-1) x min(-1)] were assigned at random to either a group that exercised in the heat at an ambient temperature of 35 degrees C (H) or a group that exercised in the cool at 15 degrees C (C). Maximum inspiratory mouth pressure at zero flow (P(0)), pressure normalised maximum relaxation rate (MRR/ P(0)), time constant for the pressure decay (tau), and maximum inspiratory flow at 30% P(0) (V(30)) were assessed immediately before and reassessed within 2, 30, and 60 min of completing a pre-loaded time trial [40 min at 65% peak power, plus approximately 30 min time trial] on a cycle ergometer. Group H completed the time trial 432 (135) s slower than group C [2285 (180) vs 1852 (122) s, respectively; Delta=24 (8)%, P=0.0094]. Repeat measurements within 2 min post-exercise revealed significant declines in P(0), MRR/ P(0), tau, and V(30) from baseline values, but no between-group differences were observed. In conclusion, heavy sustained exercise in the heat impaired subsequent time-trial performance but did not exacerbate inspiratory muscle fatigue in endurance-trained subjects.

Adult↗

PubMed2003

The Kindler syndrome protein is regulated by transforming growth factor-beta and involved in integrin-mediated adhesion.

Transforming growth factor-beta1 (TGF-beta1) contributes to tumor invasion and cancer progression by increasing the motility of tumor cells. To identify genes involved in TGF-beta-mediated cell migration, the transcriptional profiles of human mammary epithelial cells (HMEC) treated with TGF-beta were compared with untreated cells by cDNA microarray analysis. One gene up-regulated by TGF-beta was recently named kindlerin (Jobard, F., Bouadjar, B., Caux, F., Hadj-Rabia, S., Has, C., Matsuda, F., Weissenbach, J., Lathrop, M., Prud'homme, J. F., and Fischer, J. (2003) Hum. Mol. Genet. 12, 925-935). This gene is significantly overexpressed in some cancers (Weinstein, E. J., Bourner, M., Head, R., Zakeri, H., Bauer, C., and Mazzarella, R. (2003) Biochim. Biophys. Acta 1637, 207-216), and mutations in this gene lead to Kindler syndrome, an autosomal-recessive genodermatosis. TGF-beta stimulation of HMEC resulted in a marked induction of kindlerin RNA, and Western blotting demonstrated a corresponding increase in protein abundance. Kindlerin displays a putative FERM (four point one ezrin radixin moesin) domain that is closely related to the sequences in talin that interact with integrin beta subunit cytoplasmic domains. The critical residues in the talin FERM domain that mediate integrin binding show a high degree of conservation in kindlerin. Furthermore, kindlerin is recruited into a molecular complex with the beta1A and beta3 integrin cytoplasmic domains. Consistent with these biochemical findings, kindlerin is present at focal adhesions, sites of integrin-rich, membrane-substratum adhesion. Additionally, kindlerin is required for normal cell spreading. Taken together, these data suggest a role for kindlerin in mediating cell processes that depend on integrins.

Actins↗

PubMed2003

Identification of a gadd45beta 3' enhancer that mediates SMAD3- and SMAD4-dependent transcriptional induction by transforming growth factor beta.

GADD45beta regulates cell growth, differentiation, and cell death following cellular exposure to diverse stimuli, including DNA damage and transforming growth factor-beta (TGFbeta). We examined how cells transduce the TGFbeta signal from the cell surface to the gadd45beta genomic locus and describe how GADD45beta contributes to TGFbeta biology. Following an alignment of gadd45beta genomic sequences from multiple organisms, we discovered a novel TGFbeta-responsive enhancer encompassing the third intron of the gadd45beta gene. Using three different experimental approaches, we found that SMAD3 and SMAD4, but not SMAD2, mediate transcription from this enhancer. Three lines of evidence support our conclusions. First, overexpression of SMAD3 and SMAD4 activated the transcriptional activity from this enhancer. Second, silencing of SMAD protein levels using short interfering RNAs revealed that TGFbeta-induced activation of the endogenous gadd45beta gene required SMAD3 and SMAD4 but not SMAD2. In contrast, we found that the regulation of plasminogen activator inhibitor type I depended upon all three SMAD proteins. Last, SMAD3 and SMAD4 reconstitution in SMAD-deficient cancer cells restored TGFbeta induction of gadd45beta. Finally, we assessed the function of GADD45beta within the TGFbeta response and found that GADD45beta-deficient cells arrested in G2 following TGFbeta treatment. These data support a role for SMAD3 and SMAD4 in activating gadd45beta through its third intron to facilitate G2 progression following TGFbeta treatment.

Animals↗

PubMed2003

Knee and ankle range of motion during stepping down in elderly compared to young men.

A major factor limiting mobility in elderly subjects is their difficulty with descending steps but the physiological and biomechanical basis of this problem is not well understood. To address this question we have compared the kinematics of stepping down in six elderly male subjects and six weight- and height-matched younger subjects. Five reflective markers were positioned on the lower limbs and subjects were filmed stepping down from four heights (200, 250, 300, and 335 mm). Maximum angular displacements for the knee and ankle of the supporting limb were expressed as a percentage of each subject's passive range of motion (ROM). Time spent in 'foot flat' during single support was also compared. The results show the elderly subjects sustained dorsiflexion and a 'foot flat' position of the support limb for a significantly ( P<0.05) longer period than the young (approximately 20%). Consequently, elderly subjects utilised a greater percentage of their passive ankle ROM compared to the young (elderly approximately 200%; young approximately 125%). We conclude that the elderly maintained a 'foot flat' position for a longer period possibly to increase the time spent on a larger base of support. These results suggest that exercise prescription in the elderly should include stretching in order to increase the ROM at the ankle joint.

Adult↗

PubMed2003

Profound loss of T-cell receptor repertoire complexity in cutaneous T-cell lymphoma.

Cutaneous T-cell lymphoma (CTCL) is a malignancy of skin-homing T cells. A major feature of CTCL is profound immunosuppression, such that patients with advanced mycosis fungoides or Sézary syndrome have been compared with patients with advanced HIV disease and are susceptible to opportunistic infection. The etiology of this immunosuppression is unclear. We analyzed peripheral blood T cells of patients with CTCL with stage I to IV disease, using a sensitive beta-variable complementarity-determining region 3 spectratyping approach. Our data revealed a profound disruption of the complexity of the T-cell repertoire, which was universally observed in patients with advanced disease (stages III and IV), and present in up to 50% of patients with early-stage disease (stages I and II). In most patients, multiple monoclonal and oligoclonal complementarity-determining region 3 (CDR3) spectratype patterns in many different beta-variable families were seen. Equally striking was a reduction of normal T cells (as judged by absolute CD4 counts) across multiple beta-variable families. In general, CTCL spectratypes were reminiscent of advanced HIV spectratypes published elsewhere. Taken together, these data are most consistent with a global assault on the T-cell repertoire in patients with CTCL, a process that can be observed even in early-stage disease.

Adult↗

PubMed2003

Responses to exercise in the heat related to measures of hypothalamic serotonergic and dopaminergic function.

We have studied 12 recreationally active men to measure their responses to exercise in the heat and relate these to measures of hypothalamic function explored with a buspirone [5-hydroxytryptamine 1A (5-HT(1A)) agonist, dopaminergic D(2) antagonist] neuroendocrine challenge, with and without pretreatment with pindolol (5-HT(1A) antagonist). Pindolol treatment allowed the serotonergic and non-serotonergic components of prolactin release to be distinguished. Subjects exercised at 73 (5)% maximal rate of oxygen uptake (VO(2max)) until volitional fatigue at 35 degrees C (relative humidity, 30%). On another two occasions they underwent a buspirone challenge [0.5 mg (kg body mass)(-1)], once with, and once without, pindolol [0.5 mg (kg body mass)(-1)] pretreatment and the circulating plasma concentrations of prolactin were measured for the next 2.5 h. Rectal temperature increased throughout exercise, whilst mean skin temperature remained constant. There was a wide inter-subject variation in prolactin response to the neuroendocrine challenges. The proportion of the prolactin response to buspirone attributable to a non-serotonergic component (most likely dopaminergic) correlated both with exercise duration (r=0.657, P=0.028), rectal temperature at fatigue (r=0.623, P=0.041) and the rate of temperature rise (r=-0.669, P=0.024). Our results suggest that high activity of the dopaminergic pathways in the hypothalamus is a predictor of exercise tolerance in the heat.

Adaptation, Physiological↗

PubMed2003

Carbohydrate supplementation improves moderate and high-intensity exercise in the heat.

The aim of the present study was to clarify the effect of carbohydrate (CHO) supplementation on moderate and high-intensity endurance exercise in the heat. Eight endurance-trained men [maximal oxygen uptake ( VO(2max)) 59.5+/-1.6 ml kg(-1) bw(-1), mean+/-SE] cycled to exhaustion twice at 60% VO(2max) and twice at 73% VO(2max) at an ambient temperature of 35 degrees C. Subjects ingested either a 6.4% maltodextrin solution (CHO) or an artificially flavoured and coloured placebo (PLA). Time to fatigue was significantly greater with CHO in both the 60% and 73% VO(2max) trials (14.5% and 13.5% improvement, respectively). Heart rate and oxygen uptake ( VO(2)) did not differ at any point between PLA and CHO. Hypoglycaemia was not seen in any condition but plasma glucose concentrations tended to be higher at both intensities when CHO was fed. CHO oxidation rates were similar at 60% VO(2max) between CHO and PLA. There were no differences between PLA and CHO in the rate of rise of rectal temperatures ( T(rec)) at either intensity but there was a trend for subjects to fatigue at a high temperature when taking CHO. Ratings of perceived exertion (RPE) tended to be lower throughout both CHO trials; this was significant at 80 min and at fatigue at 60% VO(2max). It is concluded that supplementation with CHO improves exercise performance in the heat at both moderate and high endurance intensities. In the absence of a clear metabolic explanation, a central effect involving an increased tolerance of rising deep body temperature merits further investigation.

Adult↗

PubMed2003

The relationship between cognitive appraisal, affect, and catastrophizing in patients with chronic pain.

A study was conducted to clarify the nature of catastrophizing, a construct that is frequently referred to in the chronic pain literature. Information regarding 3 affective experience and 3 affect regulation dimensions was gathered from a heterogeneous sample of 104 chronic pain patients by using a semistructured clinical interview and the Affect Regulation and Experience Q-Sort (AREQ). Self-report questionnaires included visual analog pain scales, the Coping Strategies Questionnaire (CSQ), Multidimensional Pain Inventory (MPI), McGill Pain Questionnaire (MPQ), and Center for Epidemiological Studies Depression scale (CES-D). Hierarchical multiple regression was used to demonstrate the relative contributions of affective and cognitive appraisal components of catastrophizing. Thirty-one percent of the variance in CSQ-Catastrophizing scores was explained by a combination of cognitive appraisal variables (perceived ability to control pain; MPI Life Control) and AREQ scores, even after adjusting for pain severity and chronicity, age, and sex of participants. Results of the study strongly suggest that, rather than thinking of catastrophizing primarily as a cognitive coping construct, it should be described as an elaborate construct made up of both cognitive appraisal and affective components. Implications for tailoring interventions to match individual styles of affect regulation are discussed.

Adaptation, Psychological↗

PubMed2003

GFP-tagging of cell components reveals the dynamics of subcellular re-organization in response to infection of Arabidopsis by oomycete pathogens.

Cytoplasmic aggregation, the rapid translocation of cytoplasm and subcellular components to the site of pathogen penetration, is one of the earliest reactions of plant cells against attack by microorganisms. We have investigated cytoplasmic aggregation during Arabidopsis-oomycete interactions. Infection by non-pathogenic Phytophthora sojae was prevented in the plant epidermal cell layer, whereas Peronospora parasitica isolates Cala2 (avirulent) and Noks1 (virulent) could both penetrate into the mesophyll cell layer. Epidermal cell responses to penetration by these oomycetes were examined cytologically with a range of transgenic Arabidopsis plants expressing Green Fluorescent Protein (GFP)-tagged cell components. These included plants containing GFP-TUA6 for visualizing microtubules, GFP-hTalin for actin microfilaments, GFP-tm-KKXX for endoplasmic reticulum (ER), and STtmd-GFP for the Golgi apparatus. In all interactions, actin microfilaments were actively re-arranged and formed large bundles in cytoplasmic strands focused on the penetration site. Aggregation of ER membrane and accumulation of Golgi bodies at the infection site were observed, suggesting that production and secretion of plant materials were activated around the penetration site. Microtubules did not become focused on the penetration site. No difference was evident between the responses of epidermal cells in the non-host, incompatible and compatible interactions. This result indicates that the induction of cytoplasmic aggregation in Arabidopsis epidermal cells was neither suppressed by the virulent strain of Peronospora, nor effective in stopping infection.

Actin Cytoskeleton↗

PubMed2003

Venous obstruction in healthy limbs: a model for chronic compartment syndrome?

PURPOSE: Chronic exertional compartment syndrome (CECS) in the anterior tibial (AT) compartment is generally believed to be the result of reduced venous blood flow caused by restrictive compartments and increased intramuscular pressures. If this is so, then restricting venous flow in the muscles of healthy subjects during exercise should mimic CECS. METHODS: This hypothesis was tested in 10 control subjects (aged 19-41 yr, five males) with and without external venous occlusion induced by a sphygmomanometer cuff fitted just below the knee and inflated to 80 mm Hg. Twenty CECS patients (20-39 yr, 16 males) were studied without external occlusion. Subjects performed intermittent, isometric maximal voluntary contractions (MVC) of the AT for 20 min (1.6-s contractions, 0.5 duty cycle). MVC, tetanic force (2 s at 50 Hz), muscle thickness (ultrasound imaging), and pain were measured during exercise and 10 min of recovery. RESULTS: Venous occlusion in the controls induced greater pain, fatigue, and increase in muscle thickness (P < 0.01). Initially the patients fatigued more slowly than the occluded controls, but at the end of exercise, the fatigue and pain were similar in these two groups. The controls showed a greater increase in muscle size (P = 0.01). Recovery was similar in all three groups, although the size of the patients' muscles recovered rather more slowly. CONCLUSION: External venous occlusion of the AT muscles in control subjects induces changes very similar to those of CECS patients, although the different time courses indicate that different processes are involved. The AT compartment of CECS patients is capable of distension.

Adult↗