***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 
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    Input: OBJECTIVE To determine if physical activity was a risk factor for revision arthroplasty after primary total knee arthroplasty ( TKA ) due to osteoarthritis ( OA ) within the previous 15 years . METHODS This was a matched case-control study . The cases had primary TKA followed by revision arthroplasty . Controls had primary TKA and no revision arthroplasty .  Cases and controls were matched for age , sex , number of knees replaced , and date of primary TKA . St and ardized telephone interviews were conducted to assess historical leisure activity , occupational activity , and instrumental activities of daily living  after primary TKA in metabolic equivalent (MET)-hours per week . Conditional logistic regression was performed to identify the variables that predicted the need for revision arthroplasty . RESULTS Seventeen female and 9 male pairs , aged 47 to 85 years , participated . Most of the reported activity was of low impact and low or moderate intensity . Cases reported a median of 44.5 ( range 0 to 137 ) MET-hours of total historical physical activity  per week compared with controls ' 55.1 ( range 0 to 278 ) MET-hours . Total historical physical activity was not associated with the risk of revision arthroplasty ( OR 0.99 , 95 % CI 0.99 - 1.01 ) . Participants with primary TKA ( controls ) consistently reported more MET-hours of leisure and occupational activity than those with revision arthroplasty ( cases ) regardless of the number of knees replaced or whether or not walking was accounted for . CONCLUSION This study quantified and described patterns of physical activity in a population with TKA . Physical activity did not appear to be a risk factor for revision arthroplasty . Our results suggest that individuals undergoing primary TKA should be encouraged to remain active after surgery BACKGROUND Until now , the activity of the lower limb could only be exactly measured with expensive electronic pedometers . The aim of this study was to develop a feasible question naire to measure the activity of patients after arthroplasty . METHODS The " Daily Activity Question naire " ( DAQ ) was developed in several steps and the evaluation was carried out in three groups of patients with osteoarthritis of the hip ( 160 patients and 855 investigated days ) . The psychometric characteristics were verified . RESULTS The retest reliability ( ICC ) of the DAQ is in a range comparable to the electronic pedometer StepWatch . The testing of the criterion validity showed high correlations between the StepWatch and the DAQ ( r=0.743 ) . CONCLUSION Because of its high correlations to the load changes actually performed , the DAQ is especially suited to answer arthroplasty-related questions . In all patient groups , projected load changes between 1.8 and 2.4 million per year were found , which by far exceed the generally accepted test st and ards for endoprostheses CONTEXT Recent guidelines for treatment of overweight and obesity include recommendations for risk stratification by disease conditions and cardiovascular disease ( CVD ) risk factors , but the role of physical inactivity is not prominent in these recommendations . OBJECTIVE To quantify the influence of low cardiorespiratory fitness , an objective marker of physical inactivity , on CVD and all-cause mortality in normal-weight , overweight , and obese men and compare low fitness with other mortality predictors . DESIGN Prospect i ve observational data from the Aerobics Center Longitudinal Study . SETTING Preventive medicine clinic in Dallas , Tex . PARTICIPANTS A total of 25714 adult men ( average age , 43.8 years [ SD , 10.1 years ] ) who received a medical examination during 1970 to 1993 , with mortality follow-up to December 31 , 1994 . MAIN OUTCOME MEASURES Cardiovascular disease and all-cause mortality based on mortality predictors ( baseline CVD , type 2 diabetes mellitus , high serum cholesterol level , hypertension , current cigarette smoking , and low cardiorespiratory fitness ) stratified by body mass index . RESULTS During the study period , there were 1025 deaths ( 439 due to CVD ) during 258781 man-years of follow-up . Overweight and obese men with baseline CVD or CVD risk factors were at higher risk for all-cause and CVD mortality compared with normal-weight men without these predictors . Using normal-weight men without CVD as the referent , the strongest predictor of CVD death in obese men was baseline CVD ( age- and examination year-adjusted relative risk [ RR ] , 14.0 ; 95 % confidence interval [ CI ] , 9.4 - 20.8 ) ; RRs for obese men with diabetes mellitus , high cholesterol , hypertension , smoking , and low fitness were similar and ranged from 4.4 ( 95 % CI , 2.7 - 7.1 ) for smoking to 5.0 ( 95 % CI , 3.6 - 7.0 ) for low fitness . Relative risks for all-cause mortality in obese men ranged from 2.3 ( 95 % CI , 1.7 - 2.9 ) for men with hypertension to 4.7 ( 95 % CI , 3.6 - 6.1 ) for those with CVD at baseline . Relative risk for all-cause mortality in obese men with low fitness was 3.1 ( 95 % CI , 2.5 - 3.8 ) and in obese men with diabetes mellitus 3.1 ( 95 % CI , 2.3 - 4.2 ) and as slightly higher than the RRs for obese men who smoked or had high cholesterol levels . Low fitness was an independent predictor of mortality in all body mass index groups after adjustment for other mortality predictors . Approximately 50 % ( n = 1674 ) of obese men had low fitness , which led to a population -attributable risk of 39 % for CVD mortality and 44 % for all-cause mortality . Baseline CVD had population attributable risks of 51 % and 27 % for CVD and all-cause mortality , respectively . CONCLUSIONS In this analysis , low cardiorespiratory fitness was a strong and independent predictor of CVD and all-cause mortality and of comparable importance with that of diabetes mellitus and other CVD risk factors Introduction The health benefits of regular cardiovascular exercise are well-known . Such exercise , however , has traditionally been defined as vigorous physical activity , such as jogging , swimming , or aerobic dance . Exercise of moderate intensity also promotes health , and many U.S. adults may be experiencing the health benefits of exercise through lifestyle activities of moderate intensity , such as yard work , housework , or walking for transportation . Until recently , public health surveillance systems have not included assessment s of this type of physical activity , focusing on exercise of vigorous intensity . We used an enhanced surveillance tool to describe the prevalence and amount of both moderate-intensity and vigorous-intensity physical activity among U.S. adults . Methods We analyzed data from the 2001 Behavioral Risk Factor Surveillance System , a state-based , r and om-digit  – dialed telephone survey administered to U.S. adults aged 18 years and older ( n = 82,834 men and 120,286 women ) .  Physical activity behavior was assessed using questions design ed to quantify the frequency of participation in moderate- or vigorous-intensity physical activities performed during leisure time or for household chores and transportation . Results Overall , 45 % of adults ( 48 % of men and 43 % of women ) were active at recommended levels during nonworking hours ( at least 30 minutes five or more days per week in moderate-intensity activities , equivalent to brisk walking , or at least 20 minutes three or more days per week in vigorous activities , equivalent to running , heavy yard work , or aerobic dance ) . Less than 16 % of adults ( 15 % of men and 17 % of women ) reported no moderate or vigorous activity in a usual week . Conclusion Integrating surveillance of lifestyle activities into national systems is possible , and doing so may provide a more accurate representation of the prevalence of recommended levels of physical activity . These results , however , suggest that the majority of U.S. adults are not active at levels associated with the promotion and maintenance of health Abstract Limitation in daily physical activity is one of the reasons for total hip arthroplasty ( THA ) or total knee arthroplasty ( TKA ) . However , studies of the effects of THA or TKA generally do not determine actual daily activity as part of physical functioning . We determined the effect of THA or TKA on patients ’ actual physical activity and body function ( pain , stiffness ) , capacity to perform tasks , and self-reported physical functioning . We also assessed whether there are differences in the effect of the surgery between patients undergoing THA or TKA  and whether the improvements vary between these different outcome measures . We recruited patients with long-st and ing end-stage osteoarthritis of the hip or knee awaiting THA or TKA .  Measurements were performed before surgery and 3 and 6 months after surgery . Actual physical activity improved by 0.7 % . Patients ’ body function , capacity , and self-reported physical functioning also improved . The effects of the surgery on these aspects of physical functioning were similar for THA and TKA . The effect on actual physical activity ( 8 % ) was smaller than on body function ( 80%–167 % ) , capacity ( 19%–36 % ) , and self-reported physical functioning ( 87%–112 % ) . Therefore , in contrast to the large effect on pain and stiffness , patients ’ capacity , and their self-reported physical functioning , the improvement in actual physical activity of our patients was less than expected 6 months after surgery . Level of Evidence : Level I , prospect i ve study . See the Guidelines for Authors for a complete description of levels of evidence This study examined the effect of the surgical approach used in  total hip arthroplasty ( THA )  on gait mechanics six months following surgery . Quantitative gait analysis was performed on 29 subjects : 10 anterolateral ( A-L ) and 10 posterolateral ( P-L ) THA patients and nine able-bodied , velocity-matched subjects . Discriminant function analysis was used to determine the distinction of the groups with respect to sagittal plane hip range of motion , index of symmetry , trunk inclination , pelvic drop , hip abduction , and foot progression angles . The A-L group had the largest trunk inclination ( 3.0+/-2.4 degrees ) and the smallest hip range of motion ( 34.0+/-7.4 degrees ) . Both THA groups demonstrated greater asymmetry as expressed by the smaller symmetry index ( 0.97+/-0.04 for A-L and 0.98+/-0.05 for the P-L ) than the able-bodied group ( 0.99+/-0.01 ) . The classification procedure correctly classified 89 % of the control group cases , 90 % of the A-L cases , and 50 % of the P-L cases . These results support the conclusion that six months following surgery , the gait of the majority ( 85 % ) of THA patients has not returned to normal . The A-L patients displayed distinct gait patterns , while a small percentage ( 30 % ) of the P-L patients demonstrated normal gait . While these differences are statistically significant , the clinical significance is unknown and linked to the duration that they persist Accumulating data suggest that the amount of use , and not simply the duration in situ , influences the wear and survival of total joint replacements . An electronic , digital pedometer was used to record the number of steps taken by 111 non-r and omized volunteers who had had at least one total hip or knee replacement . The patients averaged 4988 steps per day , which extrapolates to approximately 0.9 million cycles per year for each joint of the lower extremity . Average activity ranged widely from 395 to 17,718 steps per day , an approximately forty-five-fold difference . The most active patient walked more than 3.5 times the average number of steps per day . Age was significantly associated with activity ( p = 0.048 ) , but there was a high degree of variability ( st and ard deviation , 3040 steps per day ) . Patients who were less than sixty years old  walked 30 per cent more on average than those who were sixty years old or more ( p = 0.023 ) . Men  walked 28 per cent more on average than women ( p = 0.037 ) , and men who were less than sixty years old walked 40 per cent more on average than the rest of the patients ( p = 0.011 ) . These data indicate that individual differences in the activity of the patient can be a substantial source of variability in rates of polyethylene wear in vivo . The pedometer is an inexpensive investigational tool with many potential applications , including st and ardizing wear measurements of joint replacements on the basis of gait cycles rather than time . This quantitative approach may provide prognostic information regarding the survival of joint prostheses .  Pedometer data may also be useful for quantitative assessment of walking ability in outcome studies BACKGROUND Wear of the acetabular cup and implant loosening in total hip arthroplasty are thought to be affected by individual patient activity levels . METHODS Activity levels of 100 patients with unilateral primary hip replacements  were measured using a digital pedometer 10-years post-operatively . FINDINGS Activity rates of hip replacement patients 10 years post surgery were found to fall with increasing age strata , with the age group 70 - 74 years showing significantly reduced activity rates compared to the 55 - 64 years age group and the age group greater than 80 years showing significantly reduced activity rates compared 
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Conclusions These results suggest patients undergoing TJA are less active than recommended to achieve health-enhancing activity levels ( greater than 10,000 steps/day ) , but they appear more active than normally assumed in typical wear simulations .