Short-term heart rate variability in asthmatic obese children: effect of exhaustive exercise and different humidity conditions.

AIM: Asthmatic obese children experience changes in functional capacity and autonomic control. Previous heart rate variability (HRV) studies were based on 24-hour recordings, little research has been conducted on the short-term HRV in asthmatic obese children, primarily during physical effort indifferent environmental humidity conditions. The aim of this study was to evaluate the effect of aerobic activity on short-term HRV in asthmatic obese children under two different environmental humidity conditions. METHODS: Ten obese boys with mild asthma as experimental group and 15 obese healthy boys with the same conditions were involved as a control group. Protocol included progressive and exhaustive aerobic activities on a calibrated ergometer pedal bicycle in two various environmental humidity 35±5% and 65±5%. HRV was measured by PADSY MEDSET Holter monitoring device during three phases; pre-test, mid-test and post-test. Then, short-term HRV was assessed from calculation of the mean R-R interval measured on HRV at each phases. RESULTS: HRV significantly decreased at mid-test and post-test among asthmatic and health children. However, the aforesaid changes were significantly higher in the asthmatic than health children following. Moreover, decrease of short-term HRV was significantly greater in the 35±5% than 65±5% environmental humidity. CONCLUSION: Our findings suggest from the autonomic standpoint, asthmatic and non-asthmatic children respond differently to exhaustive exercise induced stress. Aerobic exercise at an environment with high humidity compared with the low humidity appears to have additional benefits on short-term HRV in that it enhances the parasympathetic and autonomic modulation of the heart in asthmatic obese children.

The effect of creatine supplementation on muscle fatigue and physiological indices following intermittent swimming bouts.

We evaluated the effect of Creatine (Cr) supplementation on muscle fatigue and physiological indices after intermittent swimming bouts in trained swimmers. Sixteen healthy non-elite swimmers (19±4 years, 75±12 kg) were randomly assigned into two groups of either Cr supplementation or placebo and performed six repeated sprints swimming bouts of 50-m departing every 120 seconds. The Cr group was supplemented 4 times a day for 6 days. Blood lactate, Creatine Kinase (CK), creatinine, heart rate, best repeated sprint (RSb) and mean repeated sprint (RSm) times, and percentage of speed decrement (%Dec) were measured at the various phases of swimming bouts. Repeated measure ANOVA and independent t-student tests showed CK and blood lactate concentration increased gradually after the third and sixth swimming bouts. % Dec in Cr group was significantly lower after 3rd swimming bout, also heart rate in Cr group was associated with lower increase in HR mean (P<0.05) compared to placebo. These results suggest that Cr supplementation may improve swimming performance and reduce increased blood lactate levels following intermittent sprint swimming bouts. In conclusion Cr supplementation in trained swimmers may improve anaerobic performance and heart rate variations independent of the effect of intensive sprint swimming bouts.

The interactive effects of exercise type and environment temperature on HSP72 in active females.

The purpose of this study was to determine the effects of endurance and/ or weight training in normal and/ or moderate heat environments on heat shock protein (HSP72) response in active young females. Forty-five healthy active female (21±3 year, 61.4±10.2 kg, VO2max 37.2±5.3 mL/kg/min) were randomLy assigned into five groups; endurance training+normal heat (ET+NH), endurance training+moderate heat (ET+MH), weight training+normal heat (WT+NH), weight training+moderate heat (WT+MH) and heat group (HG). The training protocols include treadmill running to exhaustion on a treadmill at %65-75 V02max in the ET+NH and ET+MH groups and 4 sets of eccentric actions of elbow flexors (two sets with %50 and two sets with %60 1RM) in the WT+NH and WT+MH groups. Fasting blood samples were collected from non-dominant arm at three phases; consist of rest (baseline) and mid-test and 30 min after the training protocols. Endurance training and/ or weight training, in particularly, in the moderate heat ambient resulted in an increase in the HSP72, creatin kinase (CK) and cortisol values, as compared to ET+NH and WT+NH groups and the mid-test and baseline phases. However, the HSP72 and CK concentrations significantly increased in WT+ NH group, as compared to ET+NH group. Furthermore, WT+MH group showed significant increase in HSP72 levels, as compared to ET+ NH group. These findings suggest the muscle damage related to factors such as; exercise type, environment temperature and increase in exercise-induced body temperature.

Endurance exercise training and diferuloyl methane supplement: changes in neurotrophic factor and oxidative stress induced by lead in rat brain.

Lead is a highly neurotoxic agent that particularly affects the developing central nervous system. In the current study we investigated the neuroprotective effects of exercise training and/or diferuloyl methane (DM) supplement, which is known as curcumin, on lead acetate-induced neurotoxicity in the rat hippocampus. Sixty rats were randomly divided into six groups: 1) lead acetate, 2) DM supplement, 3) endurance training, 4) training+ DM supplement, 5) sham and 6) base. The rats in the training groups performed treadmill running consisting of 15 to 22 m · min(-1) for 25 to 64 min, 5 times a week for 8 weeks. All groups except sham received lead acetate (20 mg · kg(-1)), whereas the sham group received DM solvent. In addition, the DM and training + DM groups received DM solution (30 mg · kg(-1)) intraperitoneally. Chronic administration of lead acetate resulted in a significant increase in the malondialdehyde (MDA) in plasma, but not in the hippocampus. In addition, it led to significantly decreased brain-derived neurotrophic factor (BDNF) in the hippocampus and total antioxidant capacity (TAC) levels, as compared to the sham group. Treadmill running, DM supplementation, or both resulted in a significant decrease in MDA levels and significantly increased BDNF and TAC levels, as compared to the lead acetate group. These results provide a rationale for an inhibitory role of DM supplement and regular exercise in the attenuation of lead-induced neurotoxicity.