Resting heart rate as a predictor of metabolic dysfunctions in obese children and adolescents

Background: Recent studies have identified that a higher resting heart rate (RHR) is associated with elevated blood pressure, independent of body fatness, age and ethnicity. However, it is still unclear whether RHR can also be applied as a screening for other risk factors, such as hyperglycemia and dyslipidemia. Thus, the purpose of the presented study was to analyze the association between RHR, lipid profile and fasting glucose in obese children and adolescents.Methods: The sample was composed of 180 obese children and adolescents, aged between 7-16 years. Whole-body and segmental body composition were estimated by Dual-energy X-ray absorptiometry. Resting heart rate (RHR) was measured by heart rate monitors. The fasting blood samples were analyzed for serum triglycerides, total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and glucose, using the colorimetric method.Results: Fasting glucose, TC, triglycerides, HDL-C, LDL-C and RHR were similar in both genders. The group of obese subjects with a higher RHR presented, at a lower age, higher triglycerides and TC. There was a significant relationship between RHR, triglycerides and TC. In the multivariate model, triglycerides and TC maintained a significant relationship with RHR independent of age, gender, general and trunk adiposity. The ROC curve indicated that RHR has a high potential for screening elevated total cholesterol and triglycerides as well as dyslipidemia.Conclusion: Elevated RHR has the potential to identify subjects at an increased risk of atherosclerosis development.

Correlates of session-rate of perceived exertion (RPE) in a karate training session

Objective. The aim of this study was to analyze the relationships between the rate of perceived exertion (RPE) of a whole exercise session (RPE-S) and objective measures of exercise intensity during a karate training session.Methods. Eight well-trained karate athletes performed a single training session involving basic karate techniques and sparring. Heart rate (HR) was continuously monitored, while blood lactate ([lac]13) and rating of perceived exertion using the Borg's 6-20 scale were taken each 10-min during exercise. Athletes were also asked to rate their RPE-S using a modified CR-10 scale 30-min after exercise.Results. Significant relationships (P<0.05) were found between RPE-S and mean values of %HRmax (r(p) = 0.91), %HR reserve (r(p) = 0.87), [lac]b(r(p) = 0.96), and RPE (r(p) = 0.78) during the session, but not between RPE-S and the duration of exercise bout (r(s) = 0.28; P > 0.05). RPE-S was also significantly related (P < 0.05) to percentage of time sustained under ventilatory thresold (VT) (r(p) = 0.96), between VT and respiratory compensation point (RCP) (r(p) = 0.93) and above RCP (r(p) = 0.96).Conclusion. These results suggest RPE-S to be a valid tool for assessing interindividual variations in global exercise intensity during karate training. (C) 2010 Elsevier Masson SAS. All rights reserved.

POSITIONING DURING RESISTANCE ELBOW FLEXOR EXERCISE AFFECTS ELECTROMYOGRAPHIC ACTIVITY, HEART RATE, and PERCEIVED EXERTION

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effect of Strength Training on Rate of Force Development in Older Women

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

ACUTE EFFECT of STATIC STRETCHING on RATE of FORCE DEVELOPMENT and MAXIMAL VOLUNTARY CONTRACTION IN OLDER WOMEN

Gurjao, ALD, Goncalves, R, de Moura, RF, and Gobbi, S. Acute effect of static stretching on rate of force development and maximal voluntary contraction in older women. J Strength Cond Res 23(7): 2149-2154, 2009-The purpose of this study was to investigate, in older women, the acute effect of static stretching (SS) on both muscle activation and force output. Twenty-three older women (64.6 +/- 7.1 yr) participated in the study. The maximal voluntary contraction (MVC), rate of force development (RFD) (50, 100, 150, and 200 ms relative to onset of muscular contraction), and peak RFD (PRFD) (the steepest slope of the curve during the first 200 ms) were tested under 2 randomly separate conditions: SS and control (C). Electromyographic (EMG) activity of the vastus medialis (VM), vastus lateralis (VL), and biceps femoris (BF) muscles also was assessed. The MVC was significantly lower (p < 0.05) in the 3 trials of SS when compared with the C condition (control: 925.0 +/- 50.9 N; trial 1 : 854.3 +/- 55.3 N; trial 2 : 863.1 +/- 52.2 N; and trial 3 : 877.5 +/- 49.9 N). PRFD showed a significant decrease only for the first 2 trials of SS when compared with the C condition (control: 2672.3 +/- 259.1 N/s; trial 1 : 2296.6 +/- 300.7 N/s; and trial 2 : 2197.9 +/- 246.3 N/s). However, no difference was found for RFD (50, 100, 150, and 200 ms relative to onset of muscular contraction). The EMG activity for VM, VL, and BF was not significantly different between the C and SS conditions. In conclusion, the older women's capacity to produce muscular force decreased after their performance of SS exercises. The mechanisms responsible for this effect do not appear to be related to muscle activation. Thus, if flexibility is to be trained, it is recommended that SS does not occur just before the performance of activities that require high levels of muscular force.

Muscle damage slows oxygen uptake kinetics during moderate-intensity exercise performed at high pedal rate

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

THE RATE of FORCE DEVELOPMENT OBTAINED AT EARLY CONTRACTION PHASE IS NOT INFLUENCED BY ACTIVE STATIC STRETCHING

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Autonomic control of heart rate during forced activity and digestion in the snake Boa constrictor

Reptiles, particularly snakes, exhibit large and quantitatively similar increments in metabolic rate during muscular exercise and following a meal, when they are apparently inactive. The cardiovascular responses are similar during these two states, but the underlying autonomic control of the heart remains unknown. We describe both adrenergic and cholinergic tonus on the heart during rest, during enforced activity and during digestion (24-36h after ingestion of 30% of their body mass) in the snake Boa constrictor. The snakes were equipped with an arterial catheter for measurements of blood pressure and heart rate, and autonomic tonus was determined following infusion of the beta -adrenergic antagonist propranolol (3mg kg(-1)) and the muscarinic cholinoceptor antagonist atropine (3 mg kg-1).The mean heart rate of fasting animals at rest was 26.4 +/- 1.4 min(-1), and this increased to 36.1 +/- 1.4 min(-1) (means +/- S.E.M.; N=8) following double autonomic block (atropine and propranolol). The calculated cholinergic and adrenergic tones were 60.1 +/- 0.3% and 19.8 +/- 2.2%, respectively. Heart rate increased to 61.4 +/- 1.5 min(-1) during enforced activity, and this response was significantly reduced by propranolol (maximum values of 35.8 +/-1.6 min(-1)), but unaffected by atropine. The cholinergic and adrenergic tones were 2.6 +/- 2.2 and 41.3 +/- 1.9 % during activity, respectively. Double autonomic block virtually abolished tachycardia associated with enforced activity (heart rate increased significantly from 36.1 +/- 1.4 to 37.6 +/- 1.3 min(-1)), indicating that non-adrenergic, non-cholinergic effectors are not involved in regulating heart rate during activity. Blood pressure also increased during activity.Digestion was accompanied by an increase in heart rate from 25.6 +/- 1.3 to 47.7 +/- 2.2 min(-1) (N=8). In these animals, heart rate decreased to 44.2 +/- 2.7 min-1 following propranolol infusion and increased to 53.9 +/- 1.8 min-1 after infusion of atropine, resulting in small cholinergic and adrenergic tones (6.0 +/- 3.5 and 11.1 +/- 1.1 %, respectively). The heart rate of digesting snakes was 47.0 +/- 1.0 min(-1) after double autonomic blockade, which is significantly higher than the value of 36.1 1.4 min-1 in double-blocked fasting animals at rest. Therefore, it appears that some other factor exerts a positive chronotropic effect during digestion, and we propose that this factor may be a circulating regulatory peptide, possibly liberated from the gastrointestinal system in response to the presence of food.

Demographic aspects of Chrysomya megracephala (Diptera, Calliphoridae) adults maintained under experimental conditions: Reproductive rate estimates

The objective of this work was to evaluate some aspects of the populational ecology of Chrysomya megacephala, analyzing demographic aspects of adults kept under experimental conditions. Cages of C. megacephala adults were prepared with four different larval densities (100, 200, 400 and 800). For each cage, two tables were made: one with demographic parameters for the life expectancy estimate at the initial age (eo), and another with the reproductive rate and average reproduction age estimates. Populational parameters such as the intrinsic growth rate (i) and thefinite growth rate (lambda) were calculated as well.

Toxin jararhagin in low doses induces interstitial edema and increases the metabolic rate and red blood cells in mice

Jararhagin is a metalloproteinase from Bothrops jararaca responsible for hemorrhage, inflammation, necrosis and edema. Effects of low doses of the toxin were analyzed on the energy metabolism of mice as well as its physiological implications. Measures of O-2 consumption (VO2) were quantified after 4 and 24 h of the jarathagin administration during four weeks. Hematocrit and histology of the lungs were also analyzed after the end of the treatment. Results showed that animals that received subcutaneous doses of jararhagin had significant increase in VO2 from second (120 ng) and third weeks (60 ng) after 4 and 24 h, comparing to control, as well as in the number of erythrocytes after four weeks. Histology of the lungs showed interstitial edema within the alveolar septum. Results suggest that the jararhagin toxin caused an increase in VO2 and edema of intra-alveolar septum. The increase of the erythrocytes could be a physiological response to adjust the higher necessity of oxygen, due to diffusional abnormalities caused by the edema. Thus, low doses of jararhagin promote endothelial edema which lead to changes in several physiological conditions. (c) 2006 Elsevier Ltd. All rights reserved.

Effects of season, temperature, and body mass on the standard metabolic rate of tegu lizards (Tupinambis merianae)

This study examined how the standard metabolic rate of tegu lizards, a species that undergoes large ontogenetic changes in body weight with associated changes in life-history traits, is affected by changes in body mass, body temperature, season, and life-history traits. We measured rates of oxygen consumption ((V) over dot o(2)) in 90 individuals ranging in body mass from 10.4. g to 3.75 kg at three experimental temperatures ( 17 degrees, 25 degrees, and 30 degrees C) over the four seasons. We found that standard metabolic rate scaled to the power of 0.84 of body mass at all experimental temperatures in all seasons and that thermal sensitivity of metabolism was relatively low (Q(10) approximate to 2.0-2.5) over the range from 17 degrees to 30 degrees C regardless of body size or season. Metabolic rates did vary seasonally, being higher in spring and summer than in autumn and winter at the same temperatures, and this was true regardless of animal size. Finally, in this study, the changes in life-history traits that occurred ontogenetically were not accompanied by significant changes in metabolic rate.

Baroreflex control of heart rate in the broad-nosed caiman Caiman latirostris is temperature dependent

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)