***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: ObjectOur objective was to investigate the effect of a long-term moderate exercise program on cardiac autonomic nervous system ( ANS ) activity in healthy children . Methods Three hundred and five children aged 6–11 years participated in a 12-month school-based exercise training program ( 130–140 bpm , 20 min/day , 5 days/week ) . Cardiac ANS activities were measured using heart rate variability ( HRV ) power spectral analysis in resting conditions . Following the first measurement , 100 children from the lowest total power ( TP ) HRV were chosen as experimental sample s and the same number of age- , height- , and weight-matched controls ( CG ) was r and omly selected from the remaining children . Results In the low group ( LG ) , all the frequency components of the HRV were significantly increased after the training period , whereas only low-frequency power was augmented in the control group ( CG ) . Conclusion Our data suggest that the 12-month moderate exercise training has a positive effect on cardiac ANS activity in the children who initially had low HRV Despite their extensive use , the reproducibility of cardiac autonomic measurements in children is not well-known . We investigated the reproducibility of short-term continuous measurements of heart rate ( HR ) , heart rate variability ( HRV , time and frequency domain ) , and spontaneous baroreflex sensitivity ( BRS , frequency domain ) in the supine and st and ing position in 57 children ( 11.2+/-0.7 years , 52.6 % boys ) . Reproducibility between two sessions within a two-week interval was evaluated by intraclass correlation coefficients ( ICCs ) , st and ard error of measurement , coefficients of variation ( CVs ) , limits of agreement , and Bl and -Altman plots . HR and HRV were moderately-to-highly ( ICC=.63-.79 ; CV=5.7%-9.7 % ) and BRS moderately ( ICC=.49-.63 ; CV=11.4%-14.0 % ) reproducible . While the BRS measurements were slightly less reproducible than the HR and HRV measurements , all can be reliably applied in research , thus implicating sufficient capacity to detect real differences between children . Still , clinical studies focusing on individual changes in cardiac autonomic functioning need to address the considerable r and om variations that may occur between test-retest measurements The aim of the present investigation was to compare the accuracy of the  heart-rate ( HR ) deflection point ( HRDP ) and the second HR variability threshold ( HRVTh2 ) to predict  anaerobic threshold in boys . HRDP was determined from slope trends of successive linear regressions . HRVTh2 was determined from the high frequency 's peak and power-density trends . The second ventilatory threshold ( VTh2 ) corresponding to the first decrease in PETCO2 , with an increase in VE /VCO2 , was used as the reference measure of AnT. Results show that VO2 and HR were similar at HRDP , HRVTh2 , and VTh2 . HRVTh2 and HRDP were highly correlated . It appears that HRVTh2 is a good alternative to HRDP for assessing anaerobic threshold . HRVTh2 and HRDP might rely on similar mechanisms Overwhelming evidence shows the quality of reporting of r and omised controlled trials ( RCTs ) is not optimal . Without transparent reporting , readers can not judge the reliability and validity of trial findings nor extract information for systematic review s. Recent method ological analyses indicate that inadequate reporting and design are associated with biased estimates of treatment effects . Such systematic error is seriously damaging to RCTs , which are considered the gold st and ard for evaluating interventions because of their ability to minimise or avoid bias . A group of scientists and editors developed the CONSORT ( Consoli date d St and ards of Reporting Trials ) statement to improve the quality of reporting of RCTs . It was first published in 1996 and up date d in 2001 . The statement consists of a checklist and flow diagram that authors can use for reporting an RCT . Many leading medical journals and major international editorial groups have endorsed the CONSORT statement . The statement facilitates critical appraisal and interpretation of RCTs . During the 2001 CONSORT revision , it became clear that explanation and elaboration of the principles underlying the CONSORT statement would help investigators and others to write or appraise trial reports . A CONSORT explanation and elaboration article was published in 2001 alongside the 2001 version of the CONSORT statement . After an expert meeting in January 2007 , the CONSORT statement has been further revised and is published as the CONSORT 2010 Statement . This up date improves the wording and clarity of the previous checklist and incorporates recommendations related to topics that have only recently received recognition , such as selective outcome reporting bias . This explanatory and elaboration document-intended to enhance the use , underst and ing , and dissemination of the CONSORT statement-has also been extensively revised . It presents the meaning and rationale for each new and up date d checklist item providing examples of good reporting and , where possible , references to relevant empirical studies . Several examples of flow diagrams are included . The CONSORT 2010 Statement , this revised explanatory and elaboration document , and the associated website ( www.consort-statement.org ) should be helpful re sources to improve reporting of r and omised trials Objectives : To investigate the reliability of heart rate variability ( HRV ) measures at rest and during light exercise  in children . Methods : Short term ( five minute ) HRV was assessed in 12 children ( 11–12 years of age ) .  HRV measures were collected at rest with the children supine , breathing at 12 breaths/min , and during exercise on a cycle ergometer while exercising at 25 % of peak oxygen uptake . Both resting and exercise data were collected twice from each child . Results : Intraclass correlation coefficients were low to moderate for most measures with wide confidence intervals for each variable in both resting and exercise conditions . R and om variation ( typical error ) within repeated measurements ranged from 31 % to 187 % . Conclusions : These preliminary findings suggest that HRV measures are unreliable at rest and during light exercise in children aged 11–12 years . Tighter control of extraneous influences is recommended Aging results in marked abnormalities of cardiovascular regulation .  Regular exercise can improve many of these age-related abnormalities . However , it remains unclear how much exercise is optimal to achieve this improvement or whether the elderly can ever improve autonomic control by exercise training to a degree similar to that observed in healthy young individuals . Ten healthy sedentary seniors [ 71 + /- 3 ( SD ) yr ] trained for 12 mo ; training involved progressive increases in volume and intensity . Static hemodynamics were measured , and R-wave-R-wave interval ( RRI ) , beat-to-beat blood pressure ( BP ) variability , and transfer function gain between systolic BP and RRI were calculated at baseline and every 3 mo during training . Data were compared with those obtained in 12 Masters athletes ( 68 + /- 3 yr ) and 11 healthy sedentary young individuals ( 29 + /- 6 yr ) at baseline . Additionally , the adaptation of these variables after completion of identical training loads was compared between the seniors and the young . Indexes of RRI variability and baroreflex gain were decreased in the sedentary seniors but preserved in the Masters athletes compared with the young at baseline . With training in the seniors , baroreflex gain and resting BP showed a peak adaptation after moderate doses of training following 3 - 6 mo . Indexes of RRI variability continued to improve with increasing doses of training and increased to the same magnitude as the young at baseline after heavy doses of training for 12 mo ; however , baroreflex gain never achieved values equivalent to the young at baseline , even after a year of training . The magnitude of the adaptation of these variables to identical training loads was similar ( no interaction effects of age x training ) between the seniors and the young . Thus RRI variability in seniors improves with increasing " dose " of exercise over 1 yr of training . In contrast , more moderate doses of training for 3 - 6 mo may optimally improve baroreflex sensitivity , associated with a modest hypotensive effect ; however , higher doses of training do not lead to greater enhancement of these changes . Seniors retain a similar degree of " trainability " as young subjects for cardiac autonomic function to dynamic exercise The risk of sudden death is increased in athletes with a male predominance .  Regular physical activity increases vagal tone , and may protect against exercise-induced ventricular arrhythmias . We investigated training-related modulations of the autonomic nervous system in female and male endurance athletes . Runners of a 10-mile race were invited . Of 873 applicants , 68 female and 70 male athletes were r and omly selected and stratified according to their average weekly training hours in a low ( ≤4 h ) and high ( > 4 h ) volume training group . Analysis of heart rate variability was performed over 24 h. Spectral components ( high frequency [ HF ] and low frequency [ LF ] power in normalized units ) were analyzed for hourly 5 min segments and averaged for day- and nighttime . One hundred and fourteen athletes ( 50 % female , mean age 42 ± 7 years ) were included . No significant gender difference was observed for training volume and 10-mile race time . Over the 24-h period , female athletes exhibited a higher HF and lower LF power for each hourly time-point . Female gender and endurance training hours were independent predictors of a higher HF and lower LF power . In female athletes , higher training hours were associated with a higher HF and lower LF power during nighttime . In male athletes , the same was true during daytime . In conclusion , female and male athletes showed a different circadian pattern of the training-related increase in markers of vagal tone . For a comparable amount of training volume , female athletes maintained their higher markers of vagal tone , possibly indicating a superior protection against exercise-induced ventricular arrhythmias OBJECTIVE The beat-to-beat variability in electrocardiogram intervals ( RR , i.e. , heart-period variability ) provides information on cardiac autonomic activity that predicts arrhythmias and mortality rate in animals and adults . We determined the effect of physical training on heart-period variability in obese children . METHODS Thirty-five subjects were r and omly assigned to physical training and control groups . The training involved 4 months of exercise , 5 days per week , 40 minutes per day . Cardiovascular fitness was measured with submaximal heart rate during supine cycling ; percentage of body fat was measured with dual-energy absorptiometry ; and resting heart-period variability  parameters were measured in a supine position . A pretraining to posttraining change score was computed for each variable . The effect of the training was determined by comparing the changes of the training and control groups . RESULTS Compared with the control group , the trained group ( 1 ) reduced submaximal heart rate and percentage of body fat ( p < 0.01 ) ; ( 2 ) increased in the root mean square of successive differences , a time-domain parameter reflective of vagal tone ( p < 0.05 ) ; ( 3 ) decreased in low-frequency power expressed as a percentage of total power , a frequency-domain index of combined sympathetic and vagal activity ( p < 0.03 ) ; and ( 4 ) decreased in the ratio of low- to high-frequency power , an index of sympathetic-parasympathetic balance ( p < 0.01 ) . CONCLUSIONS In obese children , physical training alters cardiac autonomic function favorably by reducing the ratio of sympathetic to parasympathetic activity OBJECTIVE Heart rate variability provides non-invasive information about cardiac parasympathetic activity ( PSA ) . We determined in obese children : ( 1 ) relations of baseline PSA to body composition and hemodynamics ; ( 2 ) effects of physical training ( PT ) and cessation of PT ; and ( 3 ) which factors explained individual differences in responsivity of PSA to the PT . RESEARCH METHODS AND PROCEDURES The root mean square of successive differences ( RMSSD ) was the index of PSA . Obese children ( n = 79 ) were r and omly assigned to groups that participated in PT during the first or second 4-month periods of the study . RESULTS Baseline RMSSD was significantly ( p<0.05 ) associated with lower levels of : fat mass , fat-free mass , subcutaneous abdominal adipose tissue , resting heart rate ( HR ) , resting systolic blood pressure , and exercise HR . Stepwise multiple regression produced a final model ( R2 = 0.36 ) that included only resting HR . The analysis of changes over the three time points of the study found a significant ( p = 0.026 ) time by group interaction , such that RMSSD increased during periods of PT and decreased following cessation of PT . Greater individual increases in response to the PT ( p<0.05 ) were seen in those who had lower pre-PT RMSSD levels , showed the greatest decreases in resting HR , and increased most in vigorous physical activity . The final regression model retained only the change in resting HR as a significant predictor of the changes in the RMSSD ( R2 = 0.23 ) . DISCUSSION Regular exercise that improved fitness and body composition had a favorable effect on PSA in obese children The aim of this study was to determine the influence of breathing frequency and tidal volume on resting heart rate variability in children aged 9 years ( n = 29 ) and 16 years ( n = 19 ) . Heart rate variability was measured in four conditions : ( 1 ) without the control of ventilation followed at r and om by ( 2 ) a fixed breathing frequency of 12 breaths · min -1 , ( 3 ) a breathing frequency of 12 breaths · min -1 but with a fixed tidal volume of 30 % vital capacity and ( 4 ) a fixed breathing frequency of 6 breaths·min -1 and a tidal volume of 30 % vital capacity . A total of 128 RR intervals ( the time between two spikes in the heart rate ) were detected and absolute high- and low-fre 
    Output:
    
In conclusion , the available results from r and omized controlled trials do not support the hypothesis that physical training improves HRV in healthy children[AUQ2 ]