Evidence of fair method ological quality suggests that walking is associated with significant improvements in outcome compared with control interventions but longer-term effectiveness is uncertain .
With the use of the U.S. Preventive Services Task Force system , walking can be recommended as an effective form of exercise or activity for individuals with chronic musculoskeletal pain but should be supplemented with strategies aim ed at maintaining participation .
OBJECTIVE To systematic ally review the evidence examining effects of walking interventions on  pain and self-reported function in individuals with chronic musculoskeletal pain .
Update on the Methods of the U.S. Preventive Services Task Force: Estimating Certainty and Magnitude of Net Benefit
The major goal of the U.S. Preventive Services Task Force ( USPSTF ) is to provide clinicians and policymakers with a reliable and accurate source of evidence -based recommendations on a wide range of preventive services . To accomplish this goal , the USPSTF systematic ally review s the evidence concerning both the benefits and harms of widespread implementation of a preventive service . It then assesses the certainty of the evidence and the magnitude of the benefits and harms . On the basis of this assessment , the USPSTF assigns a letter grade to each preventive service signifying its recommendation about provision of the service ( Table 1 ) . Table 1 . U.S. Preventive Services Task Force Recommendation Grid * An important , but often challenging , step is determining the balance between benefits and harms to estimate net benefit ( that is , benefits minus harms ) . In this issue , the Task Force reports an up date to its recommendation for carotid artery stenosis screening ( 1 , 2 ) . Because carotid artery stenosis screening has both known benefits and harms , estimating net benefit was critical in the final USPSTF recommendation that clinicians not provide carotid artery stenosis screening in asymptomatic people ( recommendation letter grade D ) . Release of this recommendation provides an opportunity for the Task Force to up date and explain to a clinical audience the process by which it evaluates evidence , determines the certainty and magnitude of net benefit , and gives a letter grade to the recommendation . We will do this by considering 3 questions : 1 ) What evidence does the Task Force consider to estimate net benefit ? 2 ) How does the Task Force estimate the certainty of net benefit ? and 3 ) How does the Task Force estimate the magnitude of net benefit ? What Evidence Does the Task Force Consider to Estimate Net Benefit ? The overarching question that the Task Force seeks to answer for every preventive service is whether evidence suggests that provision of the service would improve health outcomes if implemented in a general primary care population . For screening topics , this st and ard could be met by a large r and omized , controlled trial ( RCT ) in a representative asymptomatic population with follow-up of all members of both the group invited for screening and the group not invited for screening . For example , the Multicentre Aneurysm Screening Study ( 3 ) was a population -based RCT of screening for abdominal aortic aneurysm in which 67800 asymptomatic men age 65 to 74 years in the United Kingdom were r and omly assigned to be invited or not to be invited for screening . Both groups were followed for a mean of 4.1 years , and abdominal aortic aneurysmrelated mortality and all-cause mortality were compared . No RCTs of carotid artery stenosis screening have been published ; however , RCTs comparing carotid endarterectomy to medical management of asymptomatic carotid artery stenosis are available . The distinction between RCTs that r and omly assign people to undergo screening  versus RCTs that r and omly assign people known to have a condition to an intervention is important . In contrast to the latter , RCTs of screening take into account the false-positive and false-negative rates of the screening test , the possibility of adverse events from the test , the accuracy and potential for adverse events of any subsequent confirmatory diagnostic tests , and the inevitable failure to follow through on the test or any subsequent steps needed before the therapeutic intervention is delivered . In addition , conditions detected by screening may have different biological characteristics than those detected in other ways . The benefits of treating screened individuals , therefore , can not be assumed to be the same as those of treating symptomatic individuals . Screening trials directly answer a simple question important to the primary care setting : Does screening for a certain condition improve health outcomes ? Direct RCT evidence about screening is often unavailable , so the Task Force considers indirect evidence . To guide its selection of indirect evidence , the Task Force constructs a chain of evidence within an analytic framework . Figure 1 of the evidence up date ( 2 ) in this issue ( page 861 ) shows the analytic framework for the Task Force assessment of carotid artery stenosis screening . Each arrow in the framework defines a key question , and each key question represents a link in the chain of evidence . Rectangles in the framework represent the intermediate outcomes ( rounded corners ) or the health outcomes ( square corners ) ; ovals represent harms . To form an unbroken chain , evidence must support each link in the chain , thereby connecting the target population ( far left side of the framework ) to the improved health outcome ( far right side of the framework ) . For each key question , the body of pertinent literature is critically appraised , focusing on 6 questions ( Table 2 ) . The USPSTF will now describe its judgment about the evidence for each key question as convincing , adequate , or inadequate . Evidence may be considered convincing when derived from several high- quality studies with consistent , logical results that are generalizable to the U.S. primary care population and setting . Evidence may be deemed adequate when , on the basis of judgment , most but not all of these 6 questions are answered favorably . When evidence is conflicting or the studies are of poor quality individually or in aggregate , the evidence for a key question is considered inadequate . Inadequate evidence may create a critical gap in the evidence chain . Table 2 . Questions Considered by the U.S. Preventive Services Task Force for Evaluating Evidence Related Both to Key Questions and to the Overall Certainty of the Evidence of Net Benefit for the Preventive Service How Does the Task Force Estimate the Certainty of Net Benefit ? The next step in the Task Force process is to use the evidence from the key questions to assess whether there would be net benefit if the service were implemented . In 2001 , the USPSTF published an article that documented its systematic processes of evidence evaluation and recommendation development ( 4 ) . At that time , the Task Force 's overall assessment of evidence was described as good , fair , or poor . The Task Force realized that this rating seemed to apply only to how well studies were conducted and did not fully capture all of the issues that go into an overall assessment of the evidence about net benefit . To avoid confusion , the USPSTF has changed its terminology . Whereas individual study quality will continue to be characterized as good , fair , or poor , the term certainty will now be used to describe the Task Force 's assessment of the overall body of evidence about net benefit of a preventive service and the likelihood that the assessment is correct . Certainty will be determined by considering all 6 questions in Table 2 ; the judgment about certainty will be described as high , moderate , or low . In making its assessment of certainty about net benefit , the evaluation of the evidence from each key question plays a primary role . It is important to note that the Task Force makes recommendations for real-world medical practice in the United States and must determine to what extent the evidence for each key question even evidence from screening RCTs or treatment RCTs can be applied to the general primary care population . Frequently , studies are conducted in highly selected population s under special conditions . The Task Force must consider differences between the general primary care population and the population s studied in RCTs and make judgments about the likelihood of observing the same effect in actual practice . For carotid artery stenosis screening , the Task Force search ed for evidence about the true prevalence of high- grade carotid artery stenosis in the general population , the generalizability of treatment effectiveness estimates based on RCTs conducted in selected population s , and the complication rate from carotid endarterectomy in asymptomatic individuals if performed in nontrial setting s ( for example , community hospitals ) . It is also important to note that 1 of the key questions in the analytic framework refers to the potential harms of the preventive service . The Task Force considers the evidence about the benefits and harms of preventive services separately and equally . Data about harms are often obtained from observational studies because harms observed in RCTs may not be representative of those found in usual practice and because some harms are not completely measured and reported in RCTs . For example , the surgeons who enrolled patients in RCTs of carotid artery stenosis were selected on the basis of their low postoperative stroke and mortality rates . Widespread screening for carotid artery stenosis would invariably lead to surgical treatment provided in hospitals ( or by surgeons ) with higher rates of complications . The harms of screening for carotid artery stenosis , including the harms from carotid angiography to confirm the diagnosis of carotid artery stenosis in patients screening positive by carotid ultrasonography  , were not captured in some treatment RCTs . Putting the body of evidence for all key questions together as a chain , the Task Force assesses the certainty of net benefit of a preventive service by asking the 6 major questions in Table 2 . The Task Force would rate a body of convincing evidence about the benefits of a service that , for example , derives from several RCTs of screening in which the estimate of benefits can be generalized to the general primary care population as high certainty ( Table 3 ) . The Task Force would rate a body of evidence that was not clearly applicable to general practice or has other defects in quality , research design , or consistency of studies as moderate certainty . Certainty is low when , for example , there are gaps in the evidence linking parts of the analytic framework , when evidence to determine the harms of treatment is unavailable , or
Evidence of fair method ological quality suggests that walking is associated with significant improvements in outcome compared with control interventions but longer-term effectiveness is uncertain .
With the use of the U.S. Preventive Services Task Force system , walking can be recommended as an effective form of exercise or activity for individuals with chronic musculoskeletal pain but should be supplemented with strategies aim ed at maintaining participation .
OBJECTIVE To systematic ally review the evidence examining effects of walking interventions on  pain and self-reported function in individuals with chronic musculoskeletal pain .