Six‐minute walking test and the assessment of cardiorespiratory responses during weight‐loss programmes in obese children

Purpose. We assessed the exercise tolerance and cardiorespiratory responses during 2‐month weight‐loss programmes using the 6‐minute walking test (6MWT) in obese children. Methods. Twenty‐eight male obese children were randomly assigned to either a control group (C), an energy restriction group (R), an exercise training at maximum lipid‐oxidation (LIPOXmax) group (E), or an energy restriction/training group (RE). The body composition, the submaximal incremental cycling exercise, and the 6MWT were performed before and after the 2‐month programme. Results. After the programme, RE group showed a significant improvement of body composition (body weight reduced by 6.3 ± 1.5 kg, p < 0.01), and an increase of 6‐minute walking distance (6MWD) (+13.7%, p < 0.01). Similarly, maximum oxygen uptake calculated according to the American College of Science Medicine guideline (VO_2maxACSM) and VO_2max predicted from 6MWD were respectively higher (+12.9% and +10.0%, p < 0.01) than the R or E groups. Bland‐Altman analysis highlighted an agreement of these two methods of VO_2max measurement. Moreover, in all participants the 6MWD was significantly correlated with VO_2maxACSM and LIPOXmax (r = 0.77, p < 0.001 and r = 0.67, p < 0.01; respectively) before the programme as well as their changes in percentage over the programme (r = 0.85 and r = 0.86, p < 0.0001; respectively). Conclusions. We concluded that a 2‐month weight‐loss programme including energy restriction and exercise training targeted at LIPOXmax improved body composition and cardiorespiratory tolerance in obese children. Furthermore, the 6MWT could be considered as a useful and reliable tool for the assessment and the follow‐up of cardiorespiratory responses during weight‐loss programme in obese children. Copyright © 2010 John Wiley & Sons, Ltd.     

The effect of L-arginine administration on muscle force and power in postmenopausal women

Previously published data (J Bone Miner Res (2005); 20: 471) did not give evidence that the administration of the nitric oxide precursor L-arginine increases bone formation and decreases bone resorption in postmenopausal women. Data of this trial were reanalysed for putative effects of L-arginine on muscle mass and muscular function. Therefore, 11 females of the former study group (n=15; age 54.5+/-4.1 years; daily oral administration of 18 g L-arginine hydrochloride (equivalent of 14.2 g L-arginine) over 6 months) and 12 females of the control group (n=15; age 55.3+/-4.4 years; daily administration of 18 g dextrose over 6 months) were analysed for biomechanical parameters (MIGF, maximal isometric grip force; PJF, peak jump force; PJP, peak jump power) and for the cross-sectional muscle area (MA) and fat area (FA) at forearm and leg (calf) measured by peripheral quantitative computed tomography. The study was performed in a double-blind design. The assessment of muscular and biomechanical parameters was undertaken before and after 6 months of L-arginine versus placebo administration. L-arginine-supplemented females had a significant increase of PJF/kg in comparison with the control group. PJP/kg, MIGF, MA and FA were not significantly influenced by the administration of L-arginine. In conclusion, the administration of L-arginine increased maximal force in mechanographic analyses and may prevent a decline of muscle force in postmenopausal women.     

Six‐minute walk test in obese children and adolescents: Reproducibility and validity

Background and Purpose . The six‐minute walk test (6MWT) is increasingly used in clinical practice. The aims of this study were to determine the reproducibility of the 6MWT in obese children and adolescents, to describe walking capacity in this population and compare the results with values from normal‐weight children (known group validity), and, finally, to describe the correlation between distance walked and estimated maximum oxygen uptake (VO₂max). Methods . Reproducibility was determined by a test–retest design and known group validity by a comparative design. The 6MWT was first test–retested in 49 obese children (30 boys, 19 girls, 8–16 years, body mass index [BMI] 24.9–52.1 kg?m^?2). Then, for validation, 250 obese children (126 boys, 124 girls, 8–16 years, BMI 23.2–57 kg/m²) and 97 normal‐weight children (48 boys, 49 girls, 8–16 years, BMI 13.3–23.2 kg·m^?2) performed the 6MWT. The obese children also performed a sub‐maximal bicycle ergometry test. Results . In the test–retest, the obese children walked 571 m the first test and 57 m the second (p = 0.578). The measurement error (S_w) was 24 m, coefficient of variation (CV): 4.3% and the intraclass correlation (ICC1:1): 0.84. Repeatability was 68 m, and limits of agreement were +71 and ?65 m. In comparison mean (standard deviation), six‐minute walk distance (6MWD) in the obese children was 571 m (65.5), and in the normal‐weight children, 663 m (61.1) (p < 0.001). The correlation between 6MWD and estimated VO₂max (r = 0.34) was low. Conclusions . The 6MWT showed good reproducibility and known group validity, and can be recommended for use in clinical practice in the studied population. To evaluate individual outcomes after intervention, the 6MWD needs to change by >68 m to be statistically significant. The 6MWD performed by obese children averaged 86% of the distance normal‐weight children walked. In obese children, the correlation between 6MWD and estimated VO₂max was low, hence the 6MWT cannot substitute a bicycle ergometry test. Copyright © 2008 John Wiley & Sons, Ltd.     

Cardiac power output and its response to exercise in athletes and non‐athletes

Cardiac power output (CPO) is an integrative measure of overall cardiac function as it accounts for both, flow‐ and pressure‐generating capacities of the heart. The purpose of the present study was twofold: (i) to assess cardiac power output and its response to exercise in athletes and non‐athletes and (ii) to determine the relationship between cardiac power output and reserve and selected measures of cardiac function and structure. Twenty male athletes and 32 age‐ and gender‐matched healthy sedentary controls participated in this study. CPO was calculated as the product of cardiac output and mean arterial pressure, expressed in watts. Measures of hemodynamic status, cardiac structure and pumping capability were assessed by echocardiography. CPO was assessed at rest and after peak bicycle exercise. At rest, the two groups had similar values of cardiac power output (1·08 ± 0·2 W versus 1·1 ± 0·24 W, P>0·05), but the athletes demonstrated lower systolic blood pressure (109·5 ± 6·2 mmHg versus 117·2 ± 8·2 mmHg, P<0·05) and thicker posterior wall of the left ventricle (9·8 ± 1 mm versus 9 ± 1·1 mm, P<0·05). Peak CPO was higher in athletes (5·87 ± 0·75 W versus 5·4 ± 0·69 W, P<0·05) as was cardiac reserve (4·92 ± 0·66 W versus 4·26 ± 0·61 W, P<0·05), respectively. Peak exercise CPO and reserve were only moderately correlated with end‐diastolic volume (r = 0·54; r = 0·46, P<0·05) and end‐diastolic left ventricular internal diameter (r = 0·48; r = 0·42, P<0·05), respectively. Athletes demonstrated greater maximal cardiac pumping capability and reserve than non‐athletes. The study provides new evidence that resting measures of cardiac structure and function need to be considered with caution in interpretation of maximal cardiac performance.     

Caught between conduct and free choice ‐ a field study of an empowering programme in lifestyle change for obese patients

Scand J Caring Sci; 2011; 25; 126–133
Caught between conduct and free choice ‐ a field study of an empowering programme in lifestyle change for obese patients The aim of this study was to investigate understandings and strategies of empowerment in Learning and Mastery Centres, in a course in lifestyle change for morbidly obese patients. A field study was conducted with nonparticipant observation, and data analysis was inspired by Foucauldian discourse analysis. The analysis revealed powerful discourses underlying the course, and the analysis showed how different discourses were set at play within the teaching strategies in the course. The course leaders balanced powerful aspects that involved directing the participants towards strategies promoting their autonomy. The analysis revealed how strategies to reduce the impression of direction and conduct are powerful actions. From a Foucauldian perspective of power, this analysis demonstrates how power is everywhere as a productive force. When creating programmes to empower patients to help them deal with their health, it seems vital that health professionals examine power. By accepting the presence of power, professionals can examine the truth motivation underlying an empowerment programme.     

Validation of a single‐stage fixed‐rate step test for the prediction of maximal oxygen uptake in healthy adults

Healthcare professionals with limited access to ergospirometry remain in need of valid and simple submaximal exercise tests to predict maximal oxygen uptake (VO_2max). Despite previous validation studies concerning fixed‐rate step tests, accurate equations for the estimation of VO_2max remain to be formulated from a large sample of healthy adults between age 18–75 years (n > 100). The aim of this study was to develop a valid equation to estimate VO_2max from a fixed‐rate step test in a larger sample of healthy adults. A maximal ergospirometry test, with assessment of cardiopulmonary parameters and VO_2max, and a 5‐min fixed‐rate single‐stage step test were executed in 112 healthy adults (age 18–75 years). During the step test and subsequent recovery, heart rate was monitored continuously. By linear regression analysis, an equation to predict VO_2max from the step test was formulated. This equation was assessed for level of agreement by displaying Bland–Altman plots and calculation of intraclass correlations with measured VO_2max. Validity further was assessed by employing a Jackknife procedure. The linear regression analysis generated the following equation to predict VO_2max (l min^?1) from the step test: 0·054(BMI)+0·612(gender)+3·359(body height in m)+0·019(fitness index)?0·012(HRmax)?0·011(age)?3·475. This equation explained 78% of the variance in measured VO_2max (F = 66·15, P<0·001). The level of agreement and intraclass correlation was high (ICC = 0·94, P<0·001) between measured and predicted VO_2max. From this study, a valid fixed‐rate single‐stage step test equation has been developed to estimate VO_2max in healthy adults. This tool could be employed by healthcare professionals with limited access to ergospirometry.     

单纯性肥胖儿童应付方式特点与心理状况研究

目的探讨单纯性肥胖儿童的应付方式特点与心理健康状况。方法采用症状自评量表、应付方式问卷对64例单纯性肥胖儿童和64例正常儿童进行评定。结果肥胖组症状自评量表的躯体化、人际关系、抑郁、焦虑、敌对性、恐怖因子分显著高于正常组(P<0.05)。应付方式问卷肥胖组自责、幻想、退避因子分显著高于正常组(P<0.05)。症状自评量表因子与应付方式问卷因子中自责与人际关系、抑郁、焦虑、恐怖呈正相关(r=0.32～0.61,P<0.05);幻想与躯体化、抑郁、敌对呈正相关(r=034～0.44,P<0.05);退避与人际关系、敌对呈正相关(r=035～0.46,P<0.05)。结论单纯性肥胖儿童存在较多的心理问题,且多使用自责、幻想、退避等不成熟应付方式,其心理问题与不成熟应付方式有关。     

Balance and muscle power of children with Charcot-Marie-Tooth

BACKGROUND:

In certain diseases, functional constraints establish a greater relationship with muscle power than muscle strength. However, in hereditary peripheral polyneuropathies, no such relationship was found in the literature.

OBJECTIVE:

In children with Charcot-Marie-Tooth (CMT), to identify the impact of muscle strength and range of movement on the static/dynamic balance and standing long jump based on quantitative and functional variables.

METHOD:

The study analyzed 19 participants aged between 6 and 16 years, of both genders and with clinical diagnoses of CMT of different subtypes. Anthropometric data, muscle strength of the lower limbs (hand-held dynamometer), ankle and knee range of movement, balance (Pediatric Balance Scale) and standing long jump distance were obtained by standardized procedures. For the statistical analysis, Pearson and Spearman correlation coefficients were used.

RESULTS:

There was a strong positive correlation between balance and the muscle strength of the right plantar flexors (r=0.61) and dorsiflexors (r=0.59) and a moderate correlation between balance and the muscle strength of inversion (r=0.41) and eversion of the right foot (r=0.44). For the long jump and range of movement, there was a weak positive correlation with right and left plantar flexion (r=0.20 and r=0.12, respectively) and left popliteal angle (r=0.25), and a poor negative correlation with left dorsiflexion (r=-0.15).

CONCLUSIONS:

The data on the patients analyzed suggests that the maintenance of distal muscle strength favors performance during balance tasks, while limitations in the range of movement of the legs seem not to be enough to influence the performance of the horizontal long jump.     

Effects of hypocaloric very‐low‐carbohydrate diet vs. Mediterranean diet on endothelial function in obese women*

Background Obesity is a cardiovascular risk factor associated with endothelial dysfunction, but the effect of different weight loss strategies on endothelial function is not known. The effect of diet on endothelial function in two hypocaloric diets, a very‐low‐carbohydrate diet (A) and a Mediterranean diet (M), was measured by brachial artery flow‐mediated dilation (FMD). Design Using a longitudinal, randomized, open study design, subjects were engaged in a 2‐month weight loss diet. FMD, inflammatory cytokines [interleukin‐6 (IL‐6) and tumour necrosis factor‐α] and a marker of oxidative stress [8‐iso‐prostaglandin F2α (8‐iso‐PGF2α)] were measured in subjects on three occasions: before initiating the diet (T0), after 5–7 days of dieting (T5) and after 2 months of dieting (T60). The very short‐ and medium‐term time points were established to discriminate respectively the effect of the diet itself (T5) from that of weight loss (T60). Twenty overweight/obese but otherwise healthy women (BMI: 27–34·9 kg m^?2; age 30–50 years) completed the study. Results Group A lost more weight (mean ± SEM; ?7·6 ± 0·8 kg) than group M (?4·9 ± 0·6 kg, P = 0·014) at T60. The FMD was not significantly different between the two groups at T0 (group A: 12·2 ± 2·9% vs. group B: 10·3 ± 2·3%, P = ns). In group A, FMD was significantly reduced at T5 and returned to baseline at T60; in group M, FMD increased at T5 and returned to baseline at T60 (P = 0·007 for diet × time interaction). Serum concentrations of IL‐6 and 8‐iso‐PGF2α were not significantly different between the two groups at T0 and increased significantly at T5 only in group A (P < 0·001 and P < 0·005 respectively). Conclusion As endothelial dysfunction is known to be associated with acute cardiovascular events, this study suggests that the cardiovascular risk might be increased in the first days of a very‐low‐carbohydrate diet.     

Effects of blood‐flow‐restricted resistance training on muscle function in a 74‐year‐old male with sporadic inclusion body myositis: a case report

Sporadic inclusion body myositis (sIBM) is a systemic disease that is characterized by substantial skeletal muscle weakness and muscle inflammation, leading to impaired physical function. The objective was to investigate the effect of low‐load resistance exercise with concurrent partial blood flow restriction to the working muscles (blood‐flow‐restricted (BFR) training) in a patient with sIBM. The training consisted of 12 weeks of lower extremity BFR training with low training loads (~25‐RM). The patient was tested for mechanical muscle function and functional capacity before and after 6 and 12 weeks of training. Maximal horizontal gait speed increased by 19%, which was accompanied by 38–92% improvements in mechanical muscle function (maximal isometric strength, rate of force development and muscle power). In conclusion, BFR training was well tolerated by the patient with sIBM and led to substantial improvements in mechanical muscle function and gait speed.     

Platelet rescue by macrophage depletion in obese ADAMTS‐13‐deficient mice at risk of thrombotic thrombocytopenic purpura

Essentials

• Obesity is a potential risk factor for development of thrombotic thrombocytopenic purpura (TTP).
• Obese ADAMTS‐13‐deficient mice were triggered with von Willebrand factor (VWF).
• Depletion of hepatic and splenic macrophages protects against thrombocytopenia in this model.
• VWF enhances phagocytosis of platelets by macrophages, dose‐dependently.

Summary

Background

Thrombotic thrombocytopenic purpura (TTP) is caused by the absence of ADAMTS‐13 activity. Thrombocytopenia is presumably related to the formation of microthrombi rich in von Willebrand factor (VWF) and platelets. Obesity may be a risk factor for TTP; it is associated with abundance of macrophages that may phagocytose platelets.

Objectives

To evaluate the role of obesity and ADAMTS‐13 deficiency in TTP, and to establish whether macrophages contribute to thrombocytopenia.

Methods

Lean or obese ADAMTS‐13‐deficient (Adamts‐13^?/?) and wild‐type (WT) mice were injected with 250 U kg^?1 of recombinant human VWF (rVWF), and TTP characteristics were evaluated 24 h later. In separate experiments, macrophages were depleted in the liver and spleen of lean and obese WT or Adamts‐13^?/? mice by injection of clodronate‐liposomes, 48 h before injection of rVWF.

Results

Obese Adamts‐13^?/? mice had a lower platelet count than their lean counterparts, suggesting that they might be more susceptible to TTP development. Lean Adamts‐13^?/? mice triggered with a threshold dose of rVWF did not develop TTP, whereas typical TTP symptoms developed in obese Adamts‐13^?/? mice, including severe thrombocytopenia and higher lactate dehydrogenase (LDH) levels. Removal of hepatic and splenic macrophages by clodronate injection in obese Adamts‐13^?/? mice before treatment with rVWF preserved the platelet counts measured 24 h after the trigger. In vitro experiments with cultured macrophages confirmed a VWF dose‐dependent increase of platelet phagocytosis.

Conclusions

Obese Adamts‐13^?/? mice are more susceptible to the induction of TTP‐related thrombocytopenia than lean mice. Phagocytosis of platelets by macrophages contributes to thrombocytopenia after rVWF injection in this model.