Ambulatory Assessment of Skin Conductivity During First Thesis Presentation: Lower Self-Confidence Predicts Prolonged Stress Response

In this field study self-confidence was tested to predict the course of galvanic electrodermal stress response prior, during and after public speaking. Ten graduate students initially rated their self-confidence and afterwards presented their thesis proposals orally in a 10-min presentation to their supervisor and peers. Galvanic skin response level was measured throughout and analysed for 10 min prior to, during, and 10 min after the presentation. Two major galvanic electrodermal stress response types were observed. Five students showed a ‘healthy response’, i.e. an anticipatory increase in electrodermal conductance, followed by a decrease after termination of the presentation. The other five students showed a steady increase of skin conductance during and after their presentation (‘prolonged response’). In line with the allostatic load model the ‘prolonged response’ group reported significantly lower self-confidence before presentation than the ‘healthy response’ group (p < 0.01). Self-confidence is a resource in novices facing an unfamiliar stressor.     

Evaluation of interleukin 13 polymorphisms in systemic sclerosis

Systemic sclerosis (SSc) is a multisystem disease of unknown etiology. It is characterized by excessive cutaneous and visceral fibrosis, damage to small blood vessels, and production of autoantibodies. Interleukin-13 (IL-13) has been shown to be involved in abnormal fibrosis in other diseases. Therefore, we have evaluated its possible involvement in SSc. We analyzed four IL13 gene polymorphisms, rs1800925 (IL13-1055), rs20541 (Arg130Gln), rs847, and rs2243204 in 107 unrelated SSc patients (40 patients having diffuse cutaneous form and 67 patients having limited cutaneous form) and in 170 controls. All subjects were Caucasians. In the total patient population and in the diffuse cutaneous subset, we observed an association between two IL13 polymorphisms, IL13 rs1800925 (IL13-1055), and IL13 rs2243204, and disease (p=0.03–0.04). The IL13 rs2243204T allele was more common in SSc patients (p=0.01, OR=2.3 CI 1.21–4.38) and in the diffuse cutaneous form (p=0.01, OR=2.95, CI 1.35–6.49) than in control subjects. Our result supports the suggestion that polymorphisms in IL13 are associated to SSc and skin fibrosis process. However, further studies on larger and independent population and functional analyses are needed to confirm these findings.     

Effect of Lifestyle Modification on Adipokine Levels in Obese Subjects with Insulin Resistance

Objective: To study the effect of weight loss in response to a lifestyle modification program on the circulating levels of adipose tissue derived cytokines (adipokines) in obese individuals with insulin resistance. Research Methods and Procedures: Twenty‐four insulin‐resistant obese subjects with varying degrees of glucose tolerance completed a 6‐month program consisting of combined hypocaloric diet and moderate physical activity. Adipokines [leptin, adiponectin, resistin, tumor necrosis factor‐α (TNF‐α), interleukin‐6 (IL‐6)] and highly sensitive C‐reactive protein were measured before and after the intervention. Insulin sensitivity index was evaluated by the frequently sampled intravenous glucose tolerance test. Results: Participants had a 6.9 ± 0.1 kg average weight loss, with a significant improvement in sensitivity index and reduction in plasma leptin (27.8 ± 3 vs. 23.6 ± 3 ng/mL, p = 0.01) and IL‐6 (2.75 ± 1.51 vs. 2.3 ± 0.91 pg/mL, p = 0.012). TNF‐α levels tended to decrease (2.3 ± 0.2 vs. 1.9 ± 0.1 pg/mL, p = 0.059). Adiponectin increased significantly only among diabetic subjects. The reductions in leptin were correlated with the decreases in BMI (r = 0.464, p < 0.05) and with changes in highly sensitive C‐reactive protein (r = 0.466, p < 0.05). Discussion: Weight reduction in obese individuals with insulin resistance was associated with a significant decrease in leptin and IL‐6 and a tendency toward a decrease in circulating TNF‐α, whereas adiponectin was increased only in diabetic subjects. Further studies are needed to elucidate the relationship between changes of adipokines and the health benefits of weight loss.     

Larger anti-adipogenic effect of angiotensin II on omental preadipose cells of obese humans

Objective: The ability to form new adipose cells is important to adipose tissue physiology; however, the mechanisms controlling the recruitment of adipocyte progenitors are poorly understood. A role for locally generated angiotensin II in this process is currently proposed. Given that visceral adipose tissue reportedly expresses higher levels of angiotensinogen compared with other depots and the strong association of augmented visceral fat mass with the adverse consequences of obesity, we studied the role of angiotensin II in regulating adipogenic differentiation in omental fat of obese and non‐obese humans. Research Methods and Procedures: The angiotensin II effect on adipose cell formation was evaluated in human omental adipocyte progenitor cells that were stimulated to adipogenic differentiation in vitro. The adipogenic response was measured by the activity of the differentiation marker glycerol‐3‐phosphate dehydrogenase. Results: Angiotensin II reduced the adipogenic response of adipocyte progenitor cells, and the extent of the decrease correlated directly with the subjects’ BMI (p = 0.01, R² = 0.30). A 56.3 ± 3.4% and 44.5 ± 2.7% reduction of adipogenesis was found in obese and non‐obese donors’ cells, respectively (p < 0.01). The effect of angiotensin II was reversed by type 1 angiotensin receptor antagonist losartan. Discussion: A greater anti‐adipogenic response to angiotensin II in omental adipose progenitor cells from obese subjects opens a venue to understand the deregulation of visceral fat tissue cellularity that has been associated with severe functional abnormalities of the obese condition.     

Glucose Tolerance and Skeletal Muscle Gene Expression in Response to Alternate Day Fasting

Objective: Alternate day fasting may extend lifespan in rodents and is feasible for short periods in nonobese humans. The aim of this study was to examine the effects of 3 weeks of alternate day fasting on glucose tolerance and skeletal muscle expression of genes involved in fatty acid transport/oxidation, mitochondrial biogenesis, and stress response. Research Methods and Procedures: Glucose and insulin responses to a standard meal were tested in nonobese subjects (eight men and eight women; BMI, 20 to 30 kg/m²) at baseline and after 22 days of alternate day fasting (36 hour fast). Muscle biopsies were obtained from a subset of subjects (n = 11) at baseline and on day 21 (12‐hour fast). Results: Glucose response to a meal was slightly impaired in women after 3 weeks of treatment (p < 0.01), but insulin response was unchanged. However, men had no change in glucose response and a significant reduction in insulin response (p < 0.03). There were no significant changes in the expression of genes involved in mitochondrial biogenesis or fatty acid transport/oxidation, although a trend toward increased CPT1 expression was observed (p < 0.08). SIRT1 mRNA expression was increased after alternate day fasting (p = 0.01). Discussion: Alternate day fasting may adversely affect glucose tolerance in nonobese women but not in nonobese men. The gene expression results indicate that fatty acid oxidation and mitochondrial biogenesis are unaffected by alternate day fasting. However, the increased expression in SIRT1 suggests that alternate day fasting may improve stress resistance, a commonly observed feature of calorie‐restricted rodents.     

An increased carbon dioxide production in transient hypoxia in healthy subjects at rest

Indices of pulmonary gas exchange and heart rate (HR) have been measured in 24 healthy subjects not adapted to hypoxia after hypoxic aerial mixture (HAM) (17, 15, 13 vol % of oxygen) respiration for 15 min. Using group data analysis, it has been shown that hypoxia under the conditions of inhalation of 17 and 15 vol % of O₂ caused no significant changes. Hypoxia under the conditions of 13 vol % of O₂ inhalation is a threshold one, when ventilation (SpO₂) drops below 85%. A significant increase in the lung ventilation (Ve) (10–14%, p < 0.05) and HR (11–15%, p < 0.05) have been observed in this case. Hyperpnea was accompanied by an increase in the oxygen uptake rate by 10% and carbon dioxide release rate (10–18%, p < 0.05). On the contrary, individual data analysis showed changes in the pulmonary gas exchange indices in 90% of subjects in the case of inhalation of 17 vol % of O₂ HAM. Four response types have been found: ventilation (increase in lung ventilation), hypoxic hypometabolism (decrease in oxygen consumption rate), and mobilization response (increase in oxygen utilization in the lungs), and anaerobic response, which is expressed in an increase in the carbon dioxide release rate along with an increase in the respiratory quotient. All these responses are of an individual type, but the ventilation response is developed in response to hypoxia caused by inhalation of 13 vol % of O₂ HAM and a decrease in SpO₂ below 85% in more than 60% of cases.     

Physiological Effects of Slot Play in Women

The purpose of this study is to describe the physiological responses occurring during slot gambling in 23 females with problematic and non-problematic gambling backgrounds in two sites: at a casino using their own money and at a casino laboratory without wagering money. Using the National Opinion Research Center Diagnostic Screen (NODS), 12 women were not-at-risk gamblers and 11 were at-risk, problem, or pathological gamblers. Blood pressure (BP), heart rate (HR), respiratory rate (RR), skin conductance (SC), and skin temperature (ST) were measured for 5 min before gambling (baseline), 10 min while gambling, and 5 min after gambling (recovery). In the casino, SBP (p = .001), DBP (p = .031), HR (p = .030), and RR (p = 004) rose during gambling and fell during recovery; ST rose throughout the study (p = .006). There were no differences between subjects based on NODS score. A total of 12 subjects were also studied in the laboratory. SBP (p = .004), DBP (p = .000); HR (p = .023); RR (p = .000) and SC (p = .002) rose during gambling and fell during recovery; ST rose throughout the study (p = .006). There were no significant differences by location. The observed effects suggest that females find slot play physiologically arousing, with or without financial stakes, because physiological changes were consistent with an arousal response.     

Effects of Obesity and Weight Loss on Cardiac Function and Valvular Performance

KARASON, KRISTJAN, INGEMAR WALLENTIN, BO LARSSON, LARS SJOSTROM. Effects of obesity and weight loss on cardiac function and valvular performance. Obes Res. 1998;6:422–429. Objective : To study the consequences of long-standing obesity on myocardial function and valvular performance and to determine the effects of weight loss on these cardiovascular features. Research Methods and Procedures : We included 41 patients with obesity referred for weight-reducing gastroplasty, 31 patients with obesity who received dietary recommendations, and 43 lean subjects. Body weight and blood pressure were measured, and cardiac function and valvular performance were estimated echocardiographically. Left ventricular ejection fraction was used to assess systolic heart function, and the ratio of transmitral early to atrial (E/A) peak flow velocity was used as an estimate of diastolic filling. All three study groups were investigated at baseline, and the two groups with obesity were re-examined at 1-year follow-up. Results : Patients with obesity had higher blood pressure, greater cardiac output, lower ejection fraction, and reduced E/A ratio, compared with lean subjects (p<0.01). Surgical treatment of obesity led to significant decreases in body weight, whereas body weight remained unchanged in the group treated with dietary recommendations (p<0.001). In the weight loss group, blood pressure and cardiac output decreased and the E/A ratio increased (p<0.001). Left ventricular ejection fraction tended to increase in the weight loss group and decrease in the obese control group p<0.01). No significant valvular disease was observed in any of the subjects with obesity at baseline or after weight loss. Discussion : We conclude that weight reduction in subjects with obesity is associated with improvements in left ventricular diastolic filling and has favorable effects on left ventricular ejection fraction. Neither obesity nor weight loss seem to promote valvular heart disease.     

时间定价激活经济效用心理定势：来自电生理学的证据

目的:从电生理学角度探讨时间定价是否激活经济效用心理定势。方法:采用脑电α波、皮肤电、心率作为经济效用定势的指标,考察时间定价组被试与控制组被试的差异。结果:与控制组相比,时间定价使个体大脑α波功率值和功率百分比更低、皮肤电更大、心率更快,个体更不平静、更不耐烦(P0.05或P0.01)。结论:时间定价可能激活了经济效用心理定势。     

Desaturation of skeletal muscle structural and depot lipids in obese individuals during a very-low-calorie diet intervention

Objective: This study investigated whether a very‐lowcalorie dietary intervention (VLCD) may influence composition of skeletal muscle cell membrane phospholipid and composition and concentration of intramyocellular triglyceride (IMTG) in obese subjects. The working hypothesis proposed that a VLCD would decrease saturated fatty acids (FAs) and increase long‐chain polyunsaturated FAs (LCPUFAs) in muscular structural lipids, as such changes have been associated with improved insulin sensitivity. Research Methods and Procedures: Skeletal muscle biopsies (vastus lateralis) were obtained from 13 obese subjects (nine women) before and after 8 weeks on VLCD (～600 to 800 kcal/d). FA composition in muscle cell membrane phospholipid and concentration and FA composition of IMTG were determined by gas‐liquid chromatography. Results: Baseline BMI was 36.0 ± 3.4 kg/m². Weight loss was 9.3 ± 1.1 kg (8.8 ± 1.1%; p < 0.0001); loss of adipose tissue was 5.9 ± 0.9 kg (p < 0.0001). Insulin resistance (by homeostasis model assessment) decreased (?44 ± 7%; p < 0.001). Muscle cell membrane phospholipid saturated FAs decreased (?3.2 ± 1.3%; p < 0.05), whereas monounsaturated FAs (4.3 ± 1.7%; p < 0.05), LCPUFAs (11 ± 6%; p < 0.05), and the ratio of LCPUFAs to saturated FAs (12 ± 5%; p < 0.05) increased. IMTG decreased, but not significantly (?5%). IMTG‐saturated FAs decreased (?3.3 ± 1.5%; p < 0.05), whereas LCPUFAn‐3 (29 ± 9%; p < 0.01), LCPUFAn‐6 (33 ± 9%; p < 0.01), and the ratio of LCPUFAs to saturated FAs (34 ± 8%; p < 0.001) increased. Plasma total cholesterol (?15 ± 6%; p < 0.05), low‐density lipoprotein‐cholesterol (?16 ± 5%; p < 0.01), high‐density lipoprotein‐cholesterol (?8 ± 2%; p < 0.01), and plasma triglyceride (?19 ± 12%; p = 0.10) all decreased during the VLCD. Discussion: Desaturation of both muscle cell membrane phospholipid and IMTG was significant but modest during a VLCD in obese subjects. Further research must delineate whether such changes in skeletal muscle structural and depot lipid composition themselves are enough to promote the observed improvements in insulin action.     

Autonomic Nervous System Activity During Actual and Mentally Simulated Preparation for Movement

The aim of this study was to compare actual versus mentally simulated preparation for a complex motor skill. Two behavioral periods are observed during weightlifting: (i) an initial phase in which the subject standing behind the bar is thought to focus his attention on forthcoming execution and (ii) a second phase between hands/bar contact and execution during which the subject is thought to increase activation. Such mental processes accompanying behavioral sequences are correlated with autonomic nervous system activity, phasic responses corresponding to allocation of attentional resources, and tonic variations related to increasing general activation. To study mental processes during preparation for action, 12 subjects performed actual and imagined preparation phases of execution. Six autonomic variables were measured continuously. Skin potential (² = 0.16), skin temperature amplitude (Z = –0.66) and duration (Z = –1.78), skin blood flow amplitude (Z = –0.56) and duration (Z = –1.51), respiratory frequency amplitude (Z = –0.14) and duration (Z = –0.13), and duration of heart rate response (Z = –1.25) were shown to be comparable (p >.05), whatever the modality of preparation. However, during mentally simulated preparation, skin resistance response was shorter than in actual preparation (Z = –2.12, p <.05), thus attesting to a weaker load, whereas lower decrease in heart rate was elicited (Z = –1.96, p <.05). This may be explained by this particular experimental condition because mental preparation would not lead to actual action. Such autonomic variables could be used as feedback to improve performance.     

Dysregulation of the Autonomic Nervous System Can Be a Link between Visceral Adiposity and Insulin Resistance

Objective: To evaluate the interplay among abdominal adipose tissue distribution, the cortisol axis, the autonomic nervous system, and insulin resistance. Research Methods and Procedures: Two age‐, sex‐, and BMI‐matched groups were studied. Fifteen subjects were first‐degree relatives of patients with type 2 diabetes (R), and 15 had no family history of diabetes (controls, C). A hyperinsulinemic euglycemic clamp, cortisol measurements, and analysis of heart rate variability (HRV) were performed. Computed tomography was performed in a subgroup (n = 9 + 9) to determine abdominal adipose tissue distribution. Results: R tended to be less insulin‐sensitive than C (M value 9.2 ± 1.0 vs 10.3 ± 0.7 mg/kg per minute, not significant). Stimulation with tetracosactin or corticotropin releasing hormone yielded lower peak serum cortisol levels in R (p = 0.03 and p = 0.06, respectively). The amount of visceral abdominal fat (VAT) tended to be greater in R. In all subjects, VAT was negatively correlated to insulin sensitivity (r = ?0.93, p < 0.001). There was a positive association between VAT and resting heart rate (r = 0.70, p = 0.003) and sympathetic/parasympathetic ratio in HRV assessment after tilt (r = 0.53, p = 0.03). Subcutaneous abdominal tissue was not associated with insulin sensitivity or any of the hormonal or HRV assessments. Discussion: Subjects genetically predisposed for type 2 diabetes had a tendency toward a larger amount of VAT and to lower insulin sensitivity compared with control subjects. The amount of visceral fat was strongly associated with insulin resistance and signs of a high ratio of sympathetic vs. parasympathetic reactivity. A large amount of visceral fat may act in concert with sympathetic/parasympathetic imbalance to promote the development of insulin resistance, and this may be partly independent of genetic background.     

Reduction of Plasma Leptin Concentrations by Arginine but Not Lipid Infusion in Humans

Objective: We examined short-term effects of arginine infusion on plasma leptin in diabetic and healthy subjects. Research Methods and Procedures: Arginine stimulation tests were performed in C-peptide negative type 1 [DM1; hemoglobin A_1c; 7.3 ± 0.3%], hyperinsulinemic type 2 diabetic (DM2; 7.6 ± 0.7%), and nondiabetic subjects (CON; 5.4 ± 0.1%). Results: Fasting plasma leptin correlated linearly with body mass index among all groups (r = 0.61, p = 0.001). During arginine infusion, peak plasma insulin was lower in DM1 than in DM2 (p < 0.05) and CON (p < 0.01). Plasma leptin decreased within 30 minutes by ∼11% in DM1 (p < 0.001), DM2 (p < 0.01), and CON (p < 0.005), slowly returning to baseline thereafter. Plasma free fatty acids (FFAs) were higher in DM1 (0.6 ± 0.1 mM) and DM2 (0.6 ± 0.1 mM) than in CON (0.4 ± 0.1 mM, p < 0.05) and transiently declined by ∼50% (p < 0.05) at 45 minutes in all groups before rebounding toward baseline. To examine the direct effects of FFAs on plasma leptin, we infused healthy subjects with lipid/heparin and glycerol during fasting, and somatostatin-insulin (∼35 pM) -glucagon (∼90 ng/mL) clamps were performed. In both protocols, plasma leptin continuously declined by ∼25% (p < 0.05) during 540 minutes without any difference between the high and low FFA conditions. Discussion: Arginine infusion transiently decreased plasma leptin concentrations both in insulin-deficient and hyperinsulinemic diabetic patients, indicating a direct inhibitory effect of the amino acid but not of insulin or FFAs.     

The neurophysiological basis of the marijuana experience

Experiments were done with 75 healthy young adults to explore the neurophysiological basis of the acute marijuana intoxication state. Tests included recording the scalp EEG, visual and auditory cerebral evoked-potentials, the CNV, cerebral slow potentials related to certainty of response correctness in auditory discrimination tasks, heart rate, respiration and the galvanic skin response. All variables were recorded over 45 minutes before and 45 minutes after smoking a marijuana cigarette containing either 4.8, 9.1 or less than 0.01 mg. Δ⁹-THC.High doses of marijuana induced a significant decrease in the peak power of the alpha rhythm and an increase in auditory evoked-response latency. The CNV increased in ampiitude after smoking marijuana in low doses and sequential CNVs showed changes consistent with sustained attention but decreased certainty about performance following either low or high dose. Marijuana interfered significantly with performance of the discrimination task itself.     

Modulating effect of dopamine on amplitude of GABA-produced chemocontrolled currents in multipolar spinal cord neurons of ammocaete

By using the patch-clamp method in the whole cell configuration, modulating effect of dopamine on GABA-activated currents has been studied on isolated multipolar spinal cord neurons of the ammocaete (larva of the lamprey Lampetra planeri). At application of dopamine (5 μM), there was observed in some cases a decrease of the GABA-activated current, on average, by 33.3 ± 8.7% (n = 8, p < 0.01), in other cases—an increase of the amplitude, on average, by 37.3 ± 11.8% (n = 5, p < 0.01). Concentration of GABA amounted to 2 mM. Study of action of agonists of D1- and D2-receptors on amplitude of chemocontrolled currents has shown that agonist of D1-receptors (+)-SKF-38393 (5 μM) decreases the GABA-activated current amplitude, on average, by 63.1 ± 11.7% (n = 8, p s< 0.01); the agonist of D2-receptors (−)-quinpirole (5 μM) produces in various cells the dopamine-like effects: an increase of the GABA-activated current amplitude, on average, by 61.0 ± 13.8% (n = 8, p < 0.01) and a decrease of amplitude, on average, by 55.7 ± 2.0% (n = 6, p < 0.01). It has been shown that antagonist of D2-receptors sulpiride (5 μM) does not block effects produced by dopamine. The dopamine effects were partially blocked by antagonist of D1-receptors (+)-SCH-23390 (5 μM): a decrease of the GABA-activated amplitude current amounted, on average, to 11.7 ± 1.8% (n = 7, p < 0.01), while an increase of amplitude—8.3 ± 2.0% (n = 5, p < 0.01). At the same time, effects of agonist of D1-receptors quinpirole (5 μM) were partially blocked by antagonist of D1-receptors (+)-SCH-23390: a decrease of the GABA-activated current amplitude amounted, on average, to 9.2 ± 3.4% (n = 6, p < 0.01) and an increase of amplitude—6.3 ± 1.8% (n = 10, p < 0.01). The obtained data indicate differences of mechanisms of the receptor-mediated effect of agonists of dopamine receptors on GABA-activated and potential-activated currents of multipolar neurons of the ammocaete spinal cord.     

Evaluation of the functional state of operators with allowance for individual psychological characteristics

This article deals with the features of the evaluation of changes in the functional state during the professional activity of operators. We estimated the dynamics of the functional state and efficiency of operators under the effect of aircraft noise and individual psychophysiological characteristics. We also investigated changes in the functional state of operators depending on their psychological characteristics. It was found that changes in the functional state of the organism in operators with high levels of anxiety, low degrees of extraversion, and high emotional lability were more pronounced in the modeling of operator activity with exposure to aircraft noise, as evidenced by significant changes in psychophysiological parameters. After 60 minutes of noise stress, the latent period of a simple and a complex sensorimotor reaction in introverts increased by 9.1% (p < 0.05) and 8.1% (p < 0.05), respectively. In the group of subjects with high levels of anxiety, there was a decrease in the general state, activity, and mood by 18.9% (p < 0.01), 20.9%, and 14.9% (p < 0.05), respectively, and a decrease in the accuracy of reaction to a moving object by three times (p < 0.05). The latent period of simple sensorimotor reaction in emotionally labile subjects after the exercise was increased by 15% (p < 0.05), and the reaction time on a moving object was increased by 8.9% (p < 0.05) as compared with the group of emotionally stable subjects. Thus, the data suggest that changes in the functional state of operators depends on the level of extraversion, personal anxiety, and emotional lability, and does not depend on the level of behavioral regulation, which must be taken into consideration during the assessment of functional state.     

Effects of Weight Loss and Physical Activity on Muscle Lipid Content and Droplet Size

Objectives : To address the potential effects of weight loss and physical activity (WL + Ex) on intramyocellular lipid (IMCL) and lipid droplet size in overweight and obese previously sedentary individuals. Research Methods and Procedures : IMCL and lipid droplet size was determined in vastus lateralis, obtained by percutaneous biopsy, from 21 obese volunteers (9 men/12 women), using Oil Red O staining, along with succinate dehydrogenase histochemistry and mitochondrial immunohistochemistry as measures of skeletal muscle oxidative capacity. Insulin sensitivity (IS) was determined by glucose clamp. Results : A 4‐month WL + Ex intervention resulted in ～10% WL and ～15% increase in maximal oxygen uptake, leading to a 46% increase in IS (all p < 0.01). IMCL did not significantly change (p = 0.36). However, the size of lipid droplets decreased after WL + Ex (p < 0.01), and this decrease in lipid droplet size correlated with increased IS (p < 0.01) and the amount of physical activity (p < 0.05). Succinate dehydrogenase activity and mitochondrial labeling increased significantly (p < 0.01), without a significant shift in fiber type distribution. Discussion : In summary, IMCL does not decrease in response to WL + Ex in obese, previously sedentary individuals, yet the lipid within muscle is dispersed into smaller droplets. This change in the size of lipid droplets, likely coupled with a concomitant increase in oxidative enzyme capacity, is correlated to improved IS.     

Ten months of exercise improves general and visceral adiposity, bone, and fitness in black girls

Objective: The goal of this study was to evaluate the impact of a 10‐month after‐school physical activity (PA) program on body composition and cardiovascular (CV) fitness in young black girls. Research Methods and Procedures: Subjects were 8‐ to 12‐year‐olds recruited from elementary schools. Body composition was measured using anthropometrics {waist circumference and BMI, DXA [percentage body fat (%BF)] and bone mineral density (BMD)}, and magnetic resonance imaging [visceral adipose tissue (VAT)]. CV fitness was measured using a graded treadmill test. The intervention consisted of 30 minutes homework/healthy snack time and 80 minutes PA (i.e., 25 minutes skills instruction, 35 minutes aerobic PA, and 20 minutes strengthening/stretching). Analyses were adjusted for age, baseline value of the dependent variable, and sexual maturation (pediatrician observation). Results: Mean attendance was 54%. Compared with the control group, the intervention group had a relative decrease in %BF (p < 0.0001), BMI (p < 0.01), and VAT (p < 0.01) and a relative increase in BMD (p < 0.0001) and CV fitness (p < 0.05). Higher attendance was associated with greater increases in BMD (p < 0.05) and greater decreases in %BF (p < 0.01) and BMI (p < 0.05). Higher heart rate during PA was associated with greater increases in BMD (p < 0.05) and greater decreases in %BF (p < 0.005). Discussion: An after‐school PA program can lead to beneficial changes in body composition and CV fitness in young black girls. It is noteworthy that the control and intervention groups differed in change in VAT but not waist circumference. This suggests that changes in central adiposity can occur in response to PA, even in young children, but that waist circumference may not be a good indicator of central adiposity.     

Impact of Diet‐Induced Weight Loss on the Cardiac Autonomic Nervous System in Severe Obesity

Objective: To determine the impact of diet‐induced weight loss on cardiac autonomic nervous system modulation and arrhythmias in subjects with severe obesity and the influence of a high‐fat or a high‐carbohydrate diet regimen on heart rate variability in reduced‐obese individuals. Research Methods and Procedures: Eight severely obese subjects (BMI ≥ 40.0 kg/m²) underwent a 3‐month weight loss program followed by a 3‐month reduced‐weight maintenance regimen. Thereafter, each subject was admitted for an inpatient period of 17 days on two separate occasions. A high‐carbohydrate (60%) or high‐fat (55%) diet of appropriate energy content for weight maintenance was prescribed during each inpatient phase. Heart rate variability was derived from a 24‐hour Holter monitoring system in all subjects during their inpatient stay. Cardiac Holter monitoring was performed at three occasions (baseline, diet phase I, and diet phase II), including the second night of a two overnight calorimetry chamber stay. Results: After the diet regimen, there was a 10% decrease in weight. There were no significant changes in systolic and diastolic blood pressure, arrhythmias, glucose, insulin, total cholesterol, low‐density lipoprotein‐cholesterol, high‐density lipoprotein‐cholesterol, respiratory exchange ratio, and resting energy expenditure between experiments. Mean heart rate was lower after weight loss compared with baseline (p < 0.001). After weight loss, there was an increase in the parasympathetic indices of heart rate variability showing an increase in cardiac vagal modulation (all p < 0.05). Discussion: Weight loss is associated with significant improvement in autonomic cardiac modulation through enhancement of parasympathetic modulation, which clinically translates into a decrease in heart rate.