The effect of diet and strength training on obese children's physical self-concept.

AIM: The aim of this study was to examine the effects of a 6-week diet and exercise program, with emphasis on strength training, on the physical self-concept, body composition, and physical fitness of young overweight and obese children. METHODS: Eighty-two overweight and obese children aged 8-11 years were randomized into a diet-only or a diet-and-strength training group. Self-concept, body composition and physical fitness were measured before and after the 6-week study period using the Physical Self Description Questionnaires (PSDQ), dual-energy X-ray absorptiometry (DXA), and standard fitness tests. Dietary intake was assessed with a food frequency questionnaire. Total daily energy intake was significantly reduced in both groups with a trend of more reduction in the diet-only group. RESULTS: Both groups developed greater confidence in strength. Those in the diet-and-strength training group also improved their endurance self-concept. Body Mass Index (BMI) decreased significantly in both groups. Lean mass increased significantly in both groups but significantly more in the diet-and-strength training group (+0.8 kg vs +0.3 kg, P<0.05). Handgrip, shuttle run, sit-up, and push-up were significantly improved in both groups, to a significantly greater extent in the diet-and-strength training group. CONCLUSION: These findings confirm the 6-week program of either diet-only or diet-and-strength training improved overweight/obese children's self-perception of muscular strength and body composition. With the diet-and-strength training program, self-concept in endurance also improved and the gain in lean body mass was more than double that of the diet only group.

End-expiratory carbon monoxide levels in healthy subjects living in a densely populated urban environment.

Carbon monoxide (CO) has a high affinity for haemoglobin and is a common cause of poisoning in industry and the home. Exhaled CO levels in patients with respiratory disease have been reported but exhaled CO in a large cohort of healthy subjects grouped by age and gender has not been reported. Exhaled CO levels and spirometry lung function data were recorded from 1032 subjects at a university campus and two commercial plazas. Subjects were also asked to complete a respiratory symptom questionnaire. Ninety-eight subjects reported respiratory disease and were excluded from the study. Non-smoking male subjects (n=508) had higher exhaled CO levels (4.36+/-2.54 ppm) [range 0-21 ppm] compared with female (n=348) subjects (3.72+/-2.12 ppm) [range 0-14 ppm] (p<0.0005), and older subjects (>60 years) had lower exhaled CO levels compared with young subjects (<22 years) (p=0.018). Over 13% of non-smokers had an exhaled CO greater than 7 ppm. Smokers showed significantly higher exhaled CO levels compared with non-smokers (p<0.0005) and smokers who complained of frequent cough and sputum production had higher levels of exhaled CO compared with smokers without such complaints. Smoking history (pack-years) was directly related to age (r=0.59) but correlated inversely with forced expiratory flow in the 1st second (FEV1) (r=-0.29) and peak expiratory flow rate (PEFR) (r=-0.25) (p<0.05). If a city's micro environmental CO concentrations and human activity patterns is available, regular monitoring of exhaled CO in healthy subjects has the potential to be used as a functional index of air pollution.

Self-perception of physical competences in preadolescent overweight Chinese children.

OBJECTIVE: To compare self-perceptions of physical competences in overweight and in normal weight preadolescent Chinese children. DESIGN: Cross-sectional study. SETTING: Three primary schools and a university hospital in Hong Kong. SUBJECTS: A total of 634 children, comprising 558 (462 normal weight, 96 overweight) aged 8-12 y randomly sampled from three primary schools, and 76 similar age overweight children recruited from the community for a diet and exercise intervention programme. MEASUREMENTS: Height, weight and percentage body fat were measured. Self-perceptions of physical competences were determined by Physical Self-Descriptive Questionnaire (PSDQ). Corresponding actual physical competences were measured by physical fitness tests. RESULTS: Overweight children perceived themselves to have significantly more body fat than normal weight children, with poorer appearance, sports competence, endurance, coordination, flexibility, overall physical self-concept and self-esteem, but to be no less healthy, no less physically active and no less strong. Overweight children performed less well than normal weight children in measures of endurance, coordination and flexibility but better in strength. Poor self-perception of physical competences appeared only partly related to deficiencies in actual physical competences. CONCLUSION: Overweight children have poorer self-perception of their physical competences but do not perceive themselves to be less strong, healthy or physically active than normal weight children. Exercise programmes for overweight children could be more effective if designed with the knowledge of these self-perceptions.

Energy expenditure and physical activity of obese children: cross-sectional study.

OBJECTIVES: To investigate the total daily energy expenditure and physical activity pattern of a group of obese and non-obese Hong Kong children. DESIGN: Cross-sectional study. SETTINGS: University teaching hospital, Hong Kong. PARTICIPANTS: Eighteen obese children aged 6 to 17 years and 18 age- and sex-matched non-obese children in the local Hong Kong community. MAIN OUTCOME MEASURES: Total daily energy expenditure and physical activity pattern were estimated for 3 days using heart rate monitoring. Body composition was measured by dual-energy X-ray absorptiometry. RESULTS: In obese children, both total fat mass and fat-free mass were greater than in non-obese children. Total daily energy expenditure and its sleep and sedentary components were higher in absolute terms (by 42%, 43%, and 126%, respectively) for obese children. When normalised for body weight, the basal metabolic rate was no different between obese and non-obese children, while the total daily energy expenditure of the obese children was significantly lower (by 22%) than that of non-obese children. When normalised for fat-free mass, the basal metabolic rate and the sedentary component of total daily energy expenditure were significantly higher for obese children. Obese children spent 12% less time asleep, but 51% more time in sedentary activity and 30% less time physically active: a ratio of active-to-sedentary waking time of 0.6 for obese children and 1.9 for non-obese children. CONCLUSIONS: Although the basal metabolic rate may be influenced by body composition, the finding of a normal basal metabolic rate when normalised for body weight suggests that an intrinsic difference of metabolic rate is not a major contributory cause of obesity. The study pointed particularly to the potential benefit of increasing physical exercise time relative to sedentary activities to reduce the prevalence of childhood obesity. Obese and non-obese children had similar basal metabolic rates when adjusted by fat-free mass and fat mass. Obese children spent more time in sedentary activities.

Respiratory health of bus drivers in Hong Kong.

OBJECTIVE: We conducted a cross-sectional study to evaluate the lung function and respiratory symptoms of Hong Kong bus and tram drivers exposed to air pollutants. METHODS: Demographic information, vital signs, pulmonary function, respiratory symptoms and blood lead levels in 358 male drivers of air-conditioned buses (ACB) were compared with 129 male drivers of non-air-conditioned buses and trams (NACB). Particulate matter (PM10), carbon dioxide (CO2) and carbon monoxide (CO) levels were measured in 16 air-conditioned and 15 non-air-conditioned trams along the same route. RESULTS: Forced vital capacity, forced expiratory volume in 1 s and maximal voluntary ventilation were lower but blood lead levels were higher in the NACB drivers compared with ACB drivers. More NACB drivers compared to ACB drivers reported frequent productive cough, dry cough, as well as sore throat. The measured lung function parameters in the NACB drivers were lower than a cohort of personnel working in an academic environment. The work-year duration was longer and scheduled days off per month were shorter for NACB (13.4+/-8.8 years and 4.3+/-1.3 days) compared to ACB drivers (11.5+/-9 years and 5.4+/-0.8 days), respectively (P < 0.001). The PM10 and CO2 levels were higher in ACB (265+/-83 microg/m3 and 2,114+/-69.6 ppm) compared to non-air-conditioned trams (161+/-103 microg/m3 and 500 ppm, respectively) (P < 0.005). CONCLUSION: We hypothesise that prolonged exposure to air pollutants adversely affects lung function in our NACB drivers but air recirculation could result in higher blood lead levels in ACB drivers.