The present study aimed to compare quadriceps femoris muscle strength and fatigue between obese (grade II and III) and nonobese adults. Ten obese (mean age: 25 years; mean BMI: 41 kg/m(2)) and ten lean (mean age: 27 years; mean BMI: 23 kg/m(2)) men were tested. Quadriceps muscle fatigue was quantified as the (percent) torque loss during a voluntary isokinetic (50 maximal contractions at 180 degrees /s) and an electrostimulated (40 Hz) isometric protocol (5 min, 10% of the maximal torque). Maximal voluntary isometric and isokinetic torque and power were also measured. Voluntary torque loss was significantly higher (P < 0.05) in obese (-63.5%) than in lean subjects (-50.6%). Stimulated torque decreased significantly (P < 0.05) but equally in the two subject groups. Obese subjects displayed higher absolute (+20%; P < 0.01) but lower relative (i.e., normalized to body mass) (-32%; P < 0.001) muscle torque and power than their lean counterparts. Obese individuals demonstrated lower fatigue resistance during voluntary but not during stimulated knee extensions compared to their nonobese counterparts. Peripheral mechanisms of muscle fatigue -- at least those associated to the present stimulated test -- were not influenced by obesity. The observed quadriceps muscle function impairments (voluntary fatigue and relative strength) probably contribute to the reduced functional capacity of obese subjects during daily living activities.

NA.Comparison between voluntary and stimulated contractions of the quadriceps femoris for growth hormone response and muscle damage. J Appl Physiol 104: 75-81, 2008. First published November 1, 2007 doi:10.1152/japplphysiol.00335.2007.-This study aimed to compare voluntary and stimulated exercise for changes in muscle strength, growth hormone (GH), blood lactate, and markers of muscle damage. Nine healthy men had two leg press exercise bouts separated by 2 wk. In the first bout, the quadriceps muscles were stimulated by biphasic rectangular pulses (75 Hz, duration 400 s, on-off ratio 6.25-20 s) with current amplitude being consistently increased throughout 40 contractions at maximal tolerable level. In the second bout, 40 voluntary isometric contractions were performed at the same leg press force output as the first bout. Maximal voluntary isometric strength was measured before and after the bouts, and serum GH and blood lactate concentrations were measured before, during, and after exercise. Serum creatine kinase (CK) activity and muscle soreness were assessed before, immediately after, and 24, 48, and 72 h after exercise. Maximal voluntary strength decreased significantly (P Ͻ 0.05) after both bouts, but the magnitude of the decrease was significantly (P Ͻ 0.05) greater for the stimulated contractions (Ϫ22%) compared with the voluntary contractions (Ϫ9%). Increases in serum GH and lactate concentrations were significantly (P Ͻ 0.05) larger after the stimulation compared with the voluntary exercise. Increases in serum CK activity and muscle soreness were also significantly (P Ͻ 0.05) greater for the stimulation than voluntary exercise. It was concluded that a single bout of electrical stimulation exercise resulted in greater GH response and muscle damage than voluntary exercise. neuromuscular electrical stimulation; isometric strength; blood lactate; creatine kinase; muscle soreness IN RECENT YEARS, THE ACUTE effects of neuromuscular electrical stimulation (NMES) on neuromuscular and metabolic responses have received attention (16,28,33,37,39). It has been reported in several studies that electrically evoked contractions result in greater strength loss and greater increases in oxygen consumption and blood lactate compared with voluntary contractions at the same intensity (16,28,33,37,39). It has been speculated that the specific recruitment pattern of motor units during NMES is mainly attributed to the phenomena (16,28,37,39). Indeed, it is documented that the recruitment of motor units during stimulated contractions is different from voluntary contraction such that fast-twitch fibers could be activated at relatively low force levels (i.e., random/nonselective motor unit recruitment) (10,17,20,30).It is known that acute voluntary resistance exercise increases growth hormone (GH) secretion (for review see 22); however, limited information is available for acute GH responses to NMES. To the best of our knowledge, only two studies have reported GH responses to NMES. Greisen et al. (11) showed a significant increa...

BACKGROUND:Motor capabilities are reduced in obese (OB) individuals, and this impairment may result also from quantitative variation of muscle mass due to alterations in body composition. OBJECTIVE: This study aims to evaluate the differences in body mass (BM) and composition, as well as in muscle strength (ST) and power output (Ẇ ) between OB and NW males and females, and to test the hypothesis that variations in body composition affect muscle performance in OB subjects. DESIGN AND METHODS: Body composition (determined by BIA with a two-compartment model), upper and lower limb maximum ST (evaluated with isotonic machines) and lower limb maximum anaerobic Ẇ (measured with a jumping test) were studied in a group of 95 extremely OB subjects (OB: 28 males, 67 females; mean age7s.d.: 29.377.0 y; BMI: 41.274.4 kg/m 2 ) and in a control group of 18 NW voluntary subjects (NW: eight males, 10 females; age: 30.375.3 y; BMI: 22.672.1 kg/m 2 ). RESULTS: OB male and female subjects differed significantly with increases in BM being attained by a similar contribution of fat mass (FM) and fat-free mass (FFM) in male subjects, but mainly contributed by FM in female subjects. Compared with NW, both OB men and women had a greater amount of FFM (Po0.001) and, since a general linear correlation was found between ST and FFM (ST (N) ¼ 64.4 FFM (kg)À190.0, R 2 ¼ 0.612, Po0.001), they developed higher values of ST (Po0.05) than their respective NW counterparts. For the same reason, both OB and NW male subjects had higher ST (Po0.001) than their female counterparts. Correction for FFM eliminated all gender-and obesity-related ST differences. On the contrary, in spite of their higher absolute muscle strength, both OB men and women could develop absolute Ẇ similar to that of NW subjects, and were notably less powerful per unit BM than NW subjects (Po0.001), women being most affected among the OB. CONCLUSIONS: Obesity-related variation in body composition differs considerably by gender, and is responsible for differences in muscle performance: the higher muscle strength observed in OB subjects (both men and women) and in male subjects (both OB and NW) is accounted for by a greater amount of FFM. Nonetheless, biomechanical limitations appear to impair muscle power development during jumping in OB individuals.

Objective: To evaluate predictors of non-alcoholic fatty liver disease (NAFLD) in obese children. Design: Cross-sectional study. Subjects: Two hundred and sixty-eight obese children not consuming alcohol and without hepatitis B or C were consecutively studied at an auxology clinic. Measurements: Alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl-transferase (GGT), cholesterol, high-density lipoprotein (HDL)-cholesterol, low-density lipoprotein (LDL)-cholesterol, triglycerides, uric acid, glucose, glucose during oral glucose tolerance testing (OGTT), insulin, insulin during OGTT, insulin resistance as estimated by homeostasis model assessment (HOMA), C-reactive protein (CRP), and systolic and diastolic blood pressure were measured. Fatty liver was diagnosed by ultrasonography using standard criteria. Univariable and multivariable logistic regression was used to evaluate predictors of NAFLD. All predictors except gender and pubertal status were modeled as continuous variables. Results: NAFLD was detected in 44% of obese children. At univariable analysis, male gender, Z-score of body mass index (BMI) (Z-BMI), ALT, AST, GGT, triglycerides, uric acid, glucose, glucose during OGTT, insulin, insulin during OGTT, HOMA, CRP and systolic blood pressure were predictors of NAFLD, whereas HDL-cholesterol and late-pubertal status were predictors of the normal liver. At multivariable analysis, however, only Z-BMI, ALT, uric acid, glucose during OGTT and insulin during OGTT were independent predictors of NAFLD. Conclusion: Z-BMI, ALT, uric acid, glucose during OGTT and insulin during OGTT are independent predictors of NAFLD in Italian obese children, with most of the prediction explained by ALT and Z-BMI. Sponsorship: Centro Studi Fegato and Progetti di Ricerca Corrente, Istituto Auxologico Italiano.

IntroductIonThe increasing prevalence of obesity during the last decades (1) is ascribed mainly to a mismatch between energy intake and energy expenditure (EE) (2,3). The factors that influence this balance are numerous and complex, involving genes, environment, and their interaction. However, the rationale of weight management strategies is to identify and modify the amount of energy introduced and expended in order to regain normal body weight (BW) (1). EE is a major determinant of energy balance and body composition. According to an usually accepted scheme in human nutrition, daily EE (DEE) can be partitioned between basal metabolic rate (BMR) extrapolated to 24 h, which corresponds to the energy needed to sustain the body functions at rest and which accounts for ~65% of DEE in sedentary subjects (4); EE associated with physical activity (often referred to as the thermic effect of activity), which accounts for ~25% of DEE (5); and the thermic effect of food, which includes EE due to digestion, absorption, and metabolism of nutrients and which accounts for ~10% of DEE (5). Because of its large contribution to DEE, especially in obese subjects, BMR has frequently been the main focus of attention in the studies on the development and treatment of obesity.BMR can be considered as the sum of the EEs of tissues and organs in a fasting and resting state and in thermoneutral conditions. It depends on the mass and metabolic rate of tissues and organs (6). For instance, EE is ~10, 15, 20, 35, and 35 times higher in the digestive tract, liver, brain, heart, and kidney than in resting muscle, whereas it is only ~1/3 of resting muscle in white adipose tissues (7). Thus, although organs only account for ~7% of BW, they contribute ~60% of BMR. In comparison, skeletal and adipose tissues account for 35-40% of BW but only 18-22% and 3-4% of BMR, respectively (8). Generally, BMR depends on body composition as expressed by fat-free mass (FFM) and fat mass (FM) and on gender, age, physical activity, and nutritional status. The main determinant of BMR is FFM (6), whereas FM is significant only in obese subjects (9). Gender is also a significant determinant of BMR, with men having a greater BMR than females after adjustment for body composition (9,10). In addition, BMR markedly decreases with advancing age in sedentary populations (11) The objective of the present study was to explore the relationship between basal metabolic rate (BMR), gender, age, anthropometric characteristics, and body composition in severely obese white subjects. In total, 1,412 obese white children and adolescents (BMI > 97° percentile for gender and age) and 7,368 obese adults (BMI > 30 kg/m 2 ) from 7 to 74 years were enrolled in this study. BMR was measured using an indirect calorimeter equipped with a canopy and fat-free mass (FFM) were obtained using tetrapolar bioelectrical impedance analysis (BIA). Using analysis of covariance, we tested the effect of gender on the relationship between BMR, age, anthropometry, and body composition. In children and ad...

The purposes of this study were to compare postural stability between obese and lean subjects and to investigate the effect of a 3-week body weight reduction (BWR) program entailing specific balance training on postural stability of extremely obese patients. Time of balance maintenance and mean error on the medial-lateral direction at the trunk and lower limb level were assessed during a single limb stance on a movable platform in 19 non-obese and in 20 extremely obese individuals (age range: 20-40 yr). Time of balance maintenance was shorter (obese: 21.1+/-7.7 vs lean: 27.3+/-3.1 sec) and medial-lateral sway of the trunk was larger in obese (5.4+/-3.2 degrees) than in lean (3.2+/-1.1 degrees) subjects (p<0.05). Two subgroups of obese subjects were also tested after a BWR program (energy-restricted diet, moderate physical exercise, nutritional education and psychological counselling) combined with or without 6 sessions of specific balance training on a movable platform. BWR plus specific balance training enhanced time of balance maintenance (pre: 23.8+/-7.2 vs post: 30.0+/-0.0 sec) and reduced the trunk sway (5.2+/-2.8 degrees vs 2.6+/-0.9 degrees ) more than BWR alone (p<0.05). The present findings indicate that extremely obese individuals have inadequate postural stability (compared to their lean counterparts) that could however be improved by few sessions of specific balance training incorporated into a multidisciplinary BWR program. It was concluded that balance improvement is an important goal of rehabilitation, that would probably reduce the propensity of overweight individuals to fall while performing everyday activities.

Objective: To measure body water distribution and to evaluate the accuracy of eight-polar bioelectrical impedance analysis (BIA) for the assessment of total body water (TBW) and extracellular water (ECW) in severe obesity. Design: Cross-sectional study. Setting: Obesity clinic. Subjects: In all, 75 women aged 18-66 y, 25 with body mass index (BMI) between 19.1 and 29.9 kg/m 2 (ie not obese), 25 with BMI between 30.0 and 39.9 kg/m 2 (ie class I and II obese), and 25 with BMI between 40.0 and 48.2 kg/m 2 (ie class III obese). Methods: TBW and ECW were measured by 2 H 2 O and Br dilution. Body resistance (R) was obtained by summing the resistances of arms, trunk and legs as measured by eight-polar BIA (InBody 3.0, Biospace, Seoul, Korea). The resistance index at a frequency of x kHz (RI x ) was calculated as height 2 /R x . Results: ECW : TBW was similar in women with class III (4673%, mean7s.d.) and class I-II obesity (4573%) but higher than in nonobese women (3973%, Po0.05). In a random subsample of 37 subjects, RI 500 explained 82% of TBW variance (Po0.0001) and cross-validation of the obtained algorithm in the remaining 38 subjects gave a percent root mean square error (RMSE%) of 5% and a pure error (PE) of 2.1 l. In the same subjects, RI 5 explained 87% of ECW variance (Po0.0001) and cross-validation of the obtained algorithm gave a RMSE% of 8% and a PE of 1.4 l. The contribution of weight and BMI to the prediction of TBW and ECW was nil or negligible on practical grounds. Conclusions: ECW : TBW is similar in women with class I-II and class III obesity up to BMI values of 48.2 kg/m 2 . Eight-polar BIA offers accurate estimates of TBW and ECW in women with a wide range of BMI (19.1-48.2 kg/m 2 ) without the need of population-specific formulae. Sponsorship: Progetti di Ricerca Corrente, Istituto Auxologico Italiano.

Physical activity is essential in obesity management, but exercise capacity is compromised in obese individuals due to the excessive body mass, impacting on body movement's energetics, and to the dysfunctions of regulatory mechanisms, affecting cardiovascular responses. This study aims to compare the energetics and cardiovascular responses of walking and cycling in obese women, and to formulate recommendations regarding the most suitable type of exercise for obesity. Fifteen obese (OB) and six normal weight (NW) women exercised on treadmill (TM) and cycle ergometer (CE). During both exercise modalities, metabolic rate was higher in OB than in NW and correlated with measures of body mass. Leg movement metabolic rate during cycling depended upon individual adiposity, and when accounted for, mechanical efficiency was similar in the two groups. When accounting for extra mass, differences in metabolic rate among groups are abolished for CE, indicating no obesity impairment of muscle efficiency, but not for TM, suggesting that differences in biomechanics may explain the higher net cost of transport of OB. In both groups, HR was higher during CE than TM at the same oxygen uptake (VO(2)), but in OB the HR increment over VO(2) was greater for CE than for TM. Therefore, due to different cardiovascular responses to TM and CE in OB, walking is more convenient, enabling OB to attain target energy expenditure at lower HR or in a shorter time.