***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: The purpose of this study was to develop a new two-regression model relating Actigraph activity counts to energy expenditure over a wide range of physical activities . Forty-eight participants [ age 35 yr ( 11.4 ) ] performed various activities chosen to represent sedentary , light , moderate , and vigorous intensities . Eighteen activities were split into three routines with each routine being performed by 20 individuals , for a total of 60 tests . Forty-five tests were r and omly selected for the development of the new equation , and 15 tests were used to cross-vali date the new equation and compare it against already existing equations . During each routine , the participant wore an Actigraph accelerometer on the hip , and oxygen consumption was simultaneously measured by a portable metabolic system . For each activity , the coefficient of variation ( CV ) for the counts per 10 s was calculated to determine whether the activity was walking/running or some other activity . If the CV was < or=10 , then a walk/run regression equation was used , whereas if the CV was > 10 , a lifestyle/leisure time physical activity regression was used . In the cross-validation group , the mean estimates using the new algorithm ( 2-regression model with an inactivity threshold ) were within 0.75 metabolic equivalents ( METs ) of measured METs for each of the activities performed ( P > or= 0.05 ) , which was a substantial improvement over the single-regression models . The new algorithm is more accurate for the prediction of energy expenditure than currently published regression equations using the Actigraph accelerometer BACKGROUND Risk stratification of patients with end-stage congestive heart failure is a critical component of the transplant c and i date selection process . Accurate identification of individuals most likely to survive without a transplant would facilitate more efficient use of scarce donor organs . METHODS AND RESULTS Multivariable proportional hazards survival models were developed with the use of data on 80 clinical characteristics from 268 ambulatory patients with advanced heart failure ( derivation sample ) .  Invasive and noninvasive models ( with and without catheterization-derived data ) were constructed . A prognostic score was determined for each patient from each model . Stratum-specific likelihood ratios were used to develop three prognostic-score risk groups . The models were prospect ively vali date d on 199 similar patients ( validation sample ) by calculation of the area under the receiver operating characteristic curve for 1-year event-free survival , the censored c-index for event-free survival , and comparison of event-free survival curves for prognostic-score risk strata . Outcome events were defined as urgent transplant or death without transplant . The noninvasive model performed well in both sample s , and increased performance was not attained by the addition of catheterization-derived variables . Prognostic-score risk groups derived from the noninvasive model in the derivation sample effectively stratified the risk of an outcome event in both sample s ( 1-year event-free survival for derivation and validation sample s , respectively : low risk , 93 % and 88 % ; medium risk , 72 % and 60 % ; high risk , 43 % and 35 % ) . CONCLUSIONS Selection of c and i date s for cardiac transplantation may be improved by use of this noninvasive risk-stratification model PURPOSE The purpose of this study was to use an accelerometer to measure daily walking  performance in patients with chronic heart failure ( CHF ) to investigate if this parameter is a determinant of New York Heart Association class and indicative of maximal and functional exercise capacity . METHODS Fifty patients with CHF were instructed to wear an accelerometer for 7 consecutive days while going about their daily business . Maximal and functional exercise capacity was assessed by cardiopulmonary ( VO(2peak ) ) and 6-minute walk testing , respectively . RESULTS Patients in New York Heart Association I , II , and III reached an average total walking time ( TWT ) of 160.6 + /- 35.8 minutes , 133.9 + /- 59.0 minutes , and 76.1 + /- 22.5 minutes per day of which 19 % , 19 % , and 9 % where spent in the fast walking mode ( > 83 m/minute ) , respectively . The TWT correlated strongly with VO(2peak ) ( r = 0.72 ; P < .001 ) and 6-minute walk testing distance ( r = 0.68 ; P < .001 ) . The TWT and time spent in fast walking mode were the strongest determinants in discriminating moderate CHF . CONCLUSION Daily walking performance is a clear determinant of maximal and functional exercise capacities in patients with CHF .  Walking intensity in particular is an independent predictor in discriminating patients with advanced heart failure . Monitoring of daily walking performance might aid in detecting disease progression and improve clinical outcome Background Physical activity has not been objective ly measured in prospect i ve cohorts with sufficiently large numbers to reliably detect associations with multiple health outcomes . Technological advances now make this possible . We describe the methods used to collect and analyse accelerometer measured physical activity  in over 100,000 participants of the UK Biobank study , and report variation by age , sex , day , time of day , and season . Methods Participants were approached by email to wear a wrist-worn accelerometer for seven days that was posted to them . Physical activity information was extracted from 100Hz raw triaxial acceleration data after calibration , removal of gravity and sensor noise , and identification of wear / non-wear episodes . We report age- and sex-specific wear-time compliance and accelerometer measured physical activity , overall and by hour-of-day , week-weekend day and season . Results 103,712 data sets were received ( 44.8 % response ) , with a median wear-time of 6.9 days ( IQR:6.5–7.0 ) . 96,600 participants ( 93.3 % ) provided valid data for physical activity analyses . Vector magnitude , a proxy for overall physical activity , was 7.5 % ( 2.35 mg ) lower per decade of age ( Cohen ’s d = 0.9 ) . Women had a higher vector magnitude than men , apart from those aged 45 - 54yrs . There were major differences in vector magnitude by time of day ( d = 0.66 ) . Vector magnitude differences between week and weekend days ( d = 0.12 for men , d = 0.09 for women ) and between seasons ( d = 0.27 for men , d = 0.15 for women ) were small . Conclusions It is feasible to collect and analyse objective physical activity data in large studies . The summary measure of overall physical activity is lower in older participants and age-related differences in activity are most prominent in the afternoon and evening . This work lays the foundation for studies of physical activity and its health consequences . Our summary variables are part of the UK Biobank data set and can be used by research ers as exposures , confounding factors or outcome variables in future analyses Reports of studies relating physical activity to stroke and cancer sub-types indicate inconsistent findings . Some are hampered by low statistical power , owing to a low number of events , and a failure to adjust for potential confounding variables . The purpose of this study was to relate physical activity to 12 mortality endpoints in a prospect i ve cohort study of 11,663 men aged 40–64 years who responded to an enquiry about travel activity during a baseline medical examination conducted between 1967 and 1969 . During 25 years of follow-up there were 4672  deaths .  Travel activity  was inversely related to mortality attributable to all-causes , coronary heart disease , respiratory disease and lung cancer , whereas the association with stroke was positive . There was evidence for attenuation of some of these associations on adjustment for potentially confounding variables . Our simplistic measure of physical activity may , in part , explain the weak associations seen BACKGROUND Previous research demonstrates that participation in light-intensity physical activity ( LIPA ) and moderate-to-vigorous physical activity ( MVPA ) are favorably associated with health-related quality of life ( HRQOL ) . Emerging work demonstrates that  sedentary behavior  ( SB ) is detrimentally associated with various cardiometabolic biomarkers , with few studies exploring the association of SB on HRQOL , and no studies examining this among congestive heart failure patients . Therefore , the purpose of this study was to examine the potential independent associations of SB on HRQOL among congestive heart failure patients . METHODS Data from the 2003 - 2006 National Health and Nutrition Examination Survey were used .  Physical activity was assessed over 7days during all waking hours using the ActiGraph 7164 accelerometer .  HRQOL was assessed using the Centers for Disease Control HRQOL index survey . RESULTS 190 participants self-reported a physician-diagnosis of congestive heart failure . After adjustments , SB behavior ( 1-min/day increase ) was associated with worse HRQOL ( β=0.004 ; 95 % CI : 0.0004 - 0.007 ; P=0.03 ) . When MVPA was added as a covariate to this model , SB remained significantly associated with worse HRQOL ( β=0.003 ; 95 % CI : 0.0001 - 0.007 ; P=0.04 ) . However , when adding LIPA to this model that also included MVPA as a covariate , SB was no longer associated with HRQOL ( β=0.0001 ; 95 % CI : -0.003 - 0.004 ; P=0.92 ) . CONCLUSIONS If confirmed by prospect ive/experimental work , this suggests that SB may not have detrimental HRQOL effects among congestive heart failure patients Background Given high rates of obesity , hypertension , and diabetes mellitus , black persons are at risk to develop heart failure . The association of moderate to vigorous physical activity ( MVPA ) and heart failure  in black adults is under research ed . The purpose of this study was to explore whether greater MVPA was associated with lower risk of heart failure hospitalizations ( HFHs ) among black adults with normal ejection fractions . Methods and Results We performed a prospect i ve analysis of 4066 black adults who participated in the Jackson Heart Study and who had physical activity measured , had normal ejection fraction on 2‐dimensional echocardiograms , and were followed for 7 years for incident HFH . We used Cox proportional regression analyses adjusted for age , sex , body mass index , smoking status , hypertension , diabetes mellitus , chronic obstructive pulmonary disease , coronary heart disease , atrial fibrillation , and chronic kidney disease and examined effect modification by sex and body mass index . Of the eligible population , 1925 participants , according to the duration of MVPA , had poor health ( 0 minutes/week ) , 1332 had intermediate health ( 1–149 minutes/week ) , and 809 had ideal health ( ≥150 minutes/week ) . There were 168 incident HFHs .  MVPA for intermediate and ideal health was associated with decreasing risk of incident HFH ( hazard ratio : 0.70 [ 95 % confidence interval , 49–1.00 ] and 0.35 [ 95 % confidence interval , 0.19–0.64 ] , respectively ; P trend=0.003 ) . The full model revealed hazard ratios of 0.74 [ 95 % confidence interval , 0.52–1.07 ] and 0.41 [ 95 % confidence interval , 0.22–0.74 ] , respectively . There was no effect modification  between MVPA and body mass index or sex on incident HFH . Conclusions A dose‐response relationship between increasing levels of MVPA and protection from incident HFH was found in black men and women with normal ejection fractions Purpose : Regular physical activity ( PA ) is recommended for patients with heart failure ( HF ) . However , the clinical and social characteristics of older HF patients with low-level PA  and the impact of light-intensity PA on 6-mo postdischarge adverse cardiovascular events are still unclear . Methods : Forty-one older patients who had been admitted because of decompensated HF ( American College of Cardiology [ACC]/American Heart Association [ AHA ] HF classification stage C/D : 76 ± 5 y ) were prospect ively enrolled . Light-intensity ( 1.5 - 2.9 metabolic equivalents [ METs ] ) and moderate-intensity ( ≥3 METs ) PAs were determined by triaxial accelerometry for at least 7 d postdischarge .  Six-min walk distance and 36-item Short Form question naire ( SF-36 ) score were evaluated at discharge . HF patients were stratified into either the HFPA-high or HFPA-low group according to median daily PA . Twenty-nine older ACC/AHA stage A/B out patients ( HF-risk ) , who were at risk for HF but no symptoms of HF had developed , also completed these assessment s. Clinical predictors for 6-mo postdischarge HF rehospitalization were assessed . Results : HF patients were anemic and less active . HFPA-low patients were less likely to engage in household work , took fewer steps , and had less light and moderate-intensity PA than HFPA-high patients . There were no differences in 6-min walk distance , SF-36 score , or left ventricular ejection fraction between HFPA-low and HFPA-high patients . Postdischarge PA , especially light-intensity PA  , was independently associated with HF rehospitalization . Conclusion : Low volume of PA postdischarge , especially at 1.5 to 2.9 METs , predicts 6-mo postdischarge HF rehospitalization in older HF patients CONTEXT The lifetime risk of  heart failure at age 40 years is approximately 1 in 5 in the general population ; however , little is known about the association 
    Output:
    
Overall ,  AQPA  showed a strong inverse relationship with mortality and predictive utility when combined with established risk scores , and prognostic roles in morbidity , predicting cognitive function , New York Heart Association functional class and intercurrent events ( e.g. hospitalisation ) , but weak relationships with health-related quality of life scores .
AQPA  has a strong prognostic role in CHF .
Big data and machine learning strategies will potentially yield better predictive value of AQPA  in CHF patients