the arthritis, diet and activity promotion trial (adapt): design, rationale, and baseline results

Controlled Clinical Trials 24 (2003) 462–480

Design paper

The Arthritis, Diet and Activity Promotion Trial(ADAPT): design, rationale, and baseline results

Gary D. Miller, Ph.D.a,*, W. Jack Rejeski, Ph.D.a,Jeff D. Williamson, M.D., M.P.H.b, Timothy Morgan, Ph.D.c,

Mary Ann Sevick, Ph.D.c, Richard F. Loeser, M.D.b,Walt H. Ettinger, M.D.b, Stephen P. Messier, Ph.D.a for

the ADAPT investigatorsaDepartment of Health and Exercise Science Wake Forest University, Winston-Salem, North Carolina, USA

bDepartment of Internal Medicine, Wake Forest University School of Medicine, Winston-Salem,North Carolina, USA

cDepartment of Public Health Sciences, Wake Forest University School of Medicine, Winston-Salem,North Carolina, USA

Manuscript received May 7, 2002; manuscript accepted March 19, 2003

Abstract

Osteoarthritis (OA) of the knee leads to restrictions of physical activity and ability to performactivities of daily living. Obesity is a risk factor for knee OA and it appears to exacerbate kneepain and disability. The Arthritis, Diet, and Activity Promotion Trial (ADAPT) was developed totest the efficacy of lifestyle behavioral changes on physical function, pain, and disability in obese,sedentary older adults with knee OA. This controlled trial randomized 316 sedentary overweight andobese older adults in a two-by-two factorial design into one of four 18-month duration interventiongroups: Healthy Lifestyle Control; Dietary Weight Loss; Structured Exercise; or Combined Exerciseand Dietary Weight Loss. The weight-loss goal for the diet groups was a 5% loss at 18 months.The intervention was modeled from principles derived from the group dynamics literature and socialcognitive theory. Exercise training consisted of aerobic and strength training for 60 minutes, threetimes per week in a group and home-based setting. The primary outcome measure was self-report ofphysical function using the Western Ontario and McMaster University Osteoarthritis Index. Othermeasurements included timed stair climb, distance walked in 6 minutes, strength, gait, knee pain,health-related quality of life, knee radiographs, body weight, dietary intake, and cost-effectivenessof the interventions. We report baseline data stratified by level of overweight and obesity focusing onself-reported physical function and physical performance tasks. The results from ADAPT will provide

* Corresponding author: Gary Miller, Box 7868 Reynolda Station, Wake Forest University, Winston-Salem,NC 27109. Tel.: �1-336-758-1901; fax: �1-336-758-4680.

E-mail address: [email protected]

0197-2456/03/$—see front matter � 2003 by Elsevier Inc. All rights reserved.doi:10.1016/S0197-2456(03)00063-1

mailto:[email protected]

G.D. Miller et al./Controlled Clinical Trials 24 (2003) 462–480 463

approaches clinicians should recommend for behavioral therapies that effectively reduce the incidence ofdisability associated with knee OA. � 2003 by Elsevier Inc. All rights reserved.

Keywords: Exercise; Physical function; Disability; Health-related quality of life

Introduction

Osteoarthritis (OA) is the most prevalent chronic joint condition and the leading causeof disability in the United States, with the majority of those afflicted being over the age of65 [1,2]. An estimated 43 million individuals had arthritis in 1997. By the year 2020, asmany as 60 million persons may be affected by this disease [3]. Symptomatic or radiographicevidence of knee OA is present in 10–33% of adults over the age of 65 [4,5]. Prevalencerates of self-reported arthritis increase dramatically with age [3]. The disease is more commonin women than men and more often observed in African-American than Caucasianwomen [3,6].

In 1997 arthritis was reported to be a cause of activity limitations in 8 million persons inthe United States [3]. Knee OA and its associated symptoms are a major cause of physicaldisability, leading to a loss of independence in older adults. Several studies have shown thatolder adults with knee OA are more likely to have restrictions with mobility and transferactivities and a reduced ability to perform instrumental activities of daily living whencompared to age-matched healthy controls [7–9].

Although the cause of knee OA is unknown, obesity is a primary risk factor [10–12]. Cross-sectional data indicate that individuals clinically defined as obese with a body mass index(BMI) � 30.0 kg·m�2 were four times more likely to have knee OA than those with a BMIin the desirable range of �25.0 kg·m�2 [5]. The degree of obesity at an early age also affectsthe risk of developing knee OA later in life. For example, men and women in the top quartileof BMI at age 40 have a three- and ninefold greater risk, respectively, for developing knee OAat age 50 compared to persons at the lowest BMI quartile at age 40 [13]. Observationalevidence from the Framingham Knee OA Study showed that a lower weight of 5.1 kgdecreased the risk of developing knee OA by over 50% in women with a baseline BMIabove 25 kg·m�2 [10]. Prior work from our group has shown that higher BMI levels are associatedwith increased pain and decline in both self-reported and performance-based measures offunction in older adults with knee OA [14]. However, there are no data from randomizedcontrolled clinical trials that relate weight loss to the prevention of incident knee OA orits progression.

The mechanism for obesity as a causative agent for knee OA is hypothesized to be mechan-ical [15]. The excessive forces on the joint produce changes in chondrocytes that alter thesynthesis and degradation of the constituents of hyaline cartilage [16]. Furthermore, anincrease in forces has been observed in the lower extremity of obese individuals with kneeOA [17]. Another proposed mechanism is that endocrine products from adipose tissue, suchas tumor necrosis factor-alpha, the interleukins, or leptin may play a role in the development andprogression of OA. This is based on the work by Toda and colleagues, which demonstratedthat the changes in radiographic knee OA were correlated with reductions in body fat butnot associated with changes in body weight from a weight-loss program [18].

G.D. Miller et al./Controlled Clinical Trials 24 (2003) 462–480464

Randomized controlled trials have shown that exercise therapy improves knee pain, physi-cal activity, physical function, and self-reported disability in individuals with knee OAcompared to sedentary controls [14,19–22]. These benefits have been observed with strengthtraining and a variety of aerobic exercise modalities, including fitness walking, aerobicexercise, and cycling [23,24]. We previously found in the Fitness Arthritis and Seniors Trial(FAST) that 18 months of aerobic exercise training for 1 hour per day, three times perweek, produced up to 12% improvement in self-reported physical disability, knee pain, andperformance on physical tasks as compared to a health education control group [14]. Inaddition, a resistance-trained group also showed beneficial effects on these measures ascompared to a health education control group [14]. Based on these and other findings, theAmerican College of Rheumatology guidelines for treating individuals with OA recommendthat exercise be a vital component of therapy [25].

The benefits obtained from the exercise intervention utilized in FAST has led us to examinethe effect of a lifestyle intervention to promote weight loss on disability from knee OA,radiographic progression of knee OA, health-related quality of life, and gait biomechanicsin older adults. Although obesity is a major risk factor for OA, no large randomized controlledtrials had previously been conducted that examined weight loss on physical disability inobese older adults. Similarly, no trials have evaluated the relative benefits of weight loss,alone or in combination with exercise, on these measures. The Arthritis, Diet, and ActivityPromotion Trial (ADAPT) tested the relative effectiveness of weight loss and exercise andtheir combination in reducing disability and pain in older, obese, sedentary adults with kneeOA. The specific aims of the study were:

1. To compare the effectiveness of a dietary weight-loss intervention, an exercise interven-tion, and their combination on self-reported disability and physical function in older,overweight and obese, sedentary adults with knee OA.

2. To determine the effectiveness of the interventions on radiographic progression of kneeOA, knee pain, performance measures of function, exercise capacity, and health-relatedquality of life in this population.

3. To determine the effectiveness of the interventions on gait biomechanics, with a specificemphasis on forces and moments at the knee joint.

4. To determine the incremental cost-effectiveness of the interventions in producing theoutcomes under investigation.

The purpose of this paper is to present the design for the trial, to describe the populationin ADAPT, and to report analysis of the baseline data focusing on self-reported physicalfunction and physical performance tasks. In addition, analysis on the baseline data wasperformed to examine the differences in physical function and physical performance tasks bydegree of overweight and obesity.

Research design and methods

ADAPT was a single-center, 18-month randomized controlled trial. A two-by-two factorialdesign was utilized for comparing the effects of dietary weight loss and exercise interventions


on physical function and disability in older adults with knee OA (see Fig. 1). There werefour arms to the study: Healthy Lifestyle Controls, Dietary Weight Loss, Structured Exercise, orCombined Exercise and Dietary Weight Loss. The data collectors in the study were blindedto the intervention assignment of the participants but the interventionists and participantswere not blinded. Participants were instructed and reminded at every visit to not provideany information to staff regarding their intervention.

Study population

Participant recruitment for the study was performed in six waves over an 18-month periodfrom November 1996 through June 1998. A total of 316 community-dwelling women and menwere randomized into the four arms of the study with each group having approximately 78participants. Older (�60 years), overweight, and obese (BMI � 28.0 kg·m�2) sedentary adultswith radiographic evidence of knee OA were recruited for the study. Potential participants wereasked a single question about their participation in physical activity. They were consideredsedentary for inclusion in this study if, in the past 6 months, they had not engaged in aformal exercise program defined by �1 sessions per week of formal exercise for 20minutes or more, or expending �200 calories per week in moderate- to high-intensityactivities. Examples of activities were suggested to the participant that would satisfy thisenergy expenditure. The inclusion and exclusion criteria (Table 1) were developed to givethe highest level of assurance that physical disability was due to knee OA and that the trialincluded persons who were likely to benefit from a weight-loss and physical activity interven-tion. In addition, current conditions that prevented individuals from beginning or completingthe interventions were a rationale for exclusion from the trial.

Fig. 1. Two-by-two design scheme.


Table 1. Inclusion and exclusion criteria

Inclusion• Age � 60 years old• Overweight or obese with BMI � 28.0 kg·m�2

• Sedentary activity pattern and not actively participating in a formal exercise program within the past 6 months(defined by 20 minutes or more of formal exercise �1 session per week or expending �200 calories per weekin moderate- to high-intensity activities)

• Symptomatic knee OA (radiographic grade II–III using Kellgren and Lawrence criteria) of one or both knees• Self-reported difficulty in at least one of the following activities attributed to knee pain: lifting and carrying

groceries, walking one-quarter mile, getting in and out of a chair, or going up and down stairs

Exclusion• Significant comorbid disease that would pose a safety threat or impair ability to participate, including: coronary

artery disease, severe hypertension, peripheral vascular disease, stroke, congestive heart failure, chronic obstruc-tive pulmonary disease, insulin-dependent diabetes, psychiatric disease, renal disease, liver disease, anemia,dementia, inability to walk without an assistive device or blindness

• Inability or unwillingness to modify dietary or exercise behaviors due to environment or to speak and read English• Excessive alcohol use with a cutoff of �14 drinks per week• Unable to finish the 18-month study or unlikely to be compliant, including living more than 50 miles from

the site or planning to leave the area for 3 months or more during the next 18 months

Interventions

The delivery of the intervention for each arm of the study was conducted independent ofthe other groups to eliminate cross-contamination of the treatments. The exercise programwas conducted 3 days per week for 60 minutes per session and was similar for the Exerciseand Exercise-Diet groups. The exercise interventionists were exercise physiologists withmore than 2 years of experience in working with the older adult population in the clinicalsetting. They were trained in behavioral techniques by the health psychologist. Participantsengaged in a structured, facility-based training program for the first 4 months of theintervention. Individuals in the exercise groups were instructed on techniques to promoteretention in the program. Subsequent to this initial period, participants had the option tochoose to continue exercising in the facility for the remaining 14 months of the intervention,or to transition to a home-based exercise program for the duration of the study, or tocombine both facility and home-based approaches. Before moving to a home-based program,participants were instructed on behavioral techniques to facilitate adherence and then weretransitioned during months 5 and 6 of the intervention, tapering the number of visits tothe facility and increasing the number of exercise sessions at home [26,27]. In the facil-ity, the exercise program consisted of a warm-up phase (5 minutes), an aerobic phase (15minutes), a strength phase (20 minutes), a second aerobic phase (15 minutes), and a cool-down phase (5 minutes). The primary mode of aerobic training consisted of walking andwas patterned after FAST [14]. Participants were allowed flexibility in choosing their modefor aerobic training. The exercise intensity for the aerobic exercise was 50–85% of the heartrate reserve using the symptom-limited maximum heart rate obtained from a graded exercisetest. Participants regularly monitored and recorded their heart rate during the exercise sessions.Strength training included four stations: leg extension, leg curl, heel raise, and step-ups usingankle cuff weights and a weighted vest. Two sets of 12 repetitions were performed at each


station. Resistance was progressively increased during the intervention as strength improved.Lower-body flexibility exercises were also performed at each session. Weights were providedto the participants if they chose to perform home-based exercises.

Both Diet and Exercise-Diet groups were prescribed similar dietary intervention strategies.The diet intervention was conducted by trained registered dietitians, holding master of sciencedegrees, with experience working with older adults and adult education. They worked withthe health psychologist in the development and delivery of the behavioral aspects of theintervention. The weight-loss goal for these two groups was a mean loss of �5% of initialbody weight. The dietary intervention was modeled on principles derived from the groupdynamics literature and social cognitive theory [28,29]. In the Trial of NonpharmacologicalTreatment in the Elderly (TONE), obese, hypertensive, older adults (60–80 years) were ableto maintain a 5.4% decrease in body weight over a 30-month period with monthly contactsduring the 22-month maintenance phase [30]. We anticipated achieving a similar weightloss since participants in the two studies were of similar age and ADAPT utilized many ofthe same weight-loss strategies and techniques used in TONE. We hypothesized that thislevel of weight loss would be efficacious in relieving symptoms of knee OA. Specifically,Toda et al. showed that a 5.6% decrease in body weight over a 6-week period produced asignificant decrease in symptoms of knee OA in women over the age of 45 years [18].

Both group and individual diet sessions were utilized throughout the duration of theinvestigation with one in every four sessions being an individual appointment. The firstsession was an introductory, individual meeting with the interventionist to establish weight-lossgoals and to orient the participant to the study and facilities. The first 4 months were termedthe intensive phase with weekly meetings conducted by a registered dietitian trained in theintervention strategy. The topics in the intensive phase focused on healthful food selectionwith portion and dietary fat control to decrease energy intake, emphasizing an increasedawareness in the consequence of, and the need to change, dietary habits. Participants wereindividually counseled on reducing energy intake by �500 calories per day in order toachieve the desired weight loss. Examples of group program topics included Healthy Eating,Reading Labels, Shopping, Food Preparation, Meal Ideas, Restaurants, Ethnic Eating, SpecialOccasions, and Old and New Routines. Self-regulatory skills were taught by the intervention-ists, including self-monitoring, goal setting, environmental management, stimulus control,and cognitive restructuring. Group sessions included problem solving, education on a specifictopic, and tasting of nutritious foods consistent with the intervention. Individual sessionsincluded a review of participant progress, problem solving, goal setting, and answeringspecific questions.

Biweekly meetings were held during months 5 and 6 of the transition period. The emphasisof this phase was to maintain and prevent relapse in participants who reached their weight-loss goals and to reestablish new goals for those who did not reach their goals. During themaintenance period of months 7–18, diet meetings were held monthly. In addition tothese meetings, phone contacts were alternated every 2 weeks to provide interventionist-participant contact on a biweekly basis. Further contact was facilitated through regularlydistributed newsletters that provided pertinent nutrition information and a schedule of eventsfor the intervention groups. The goals of the maintenance phase included assisting in weightmaintenance for those who had achieved their weight-loss goals and providing counsel for


participants who had a difficult time in losing weight and adhering to the intervention. Asin TONE, both individual and group sessions were tailored to consider the older adultlearner including sensory and motor changes, alterations in cognitive function, and cohort andsituational differences [30]. Intervention groups were approximately 12–14 participants insize.

Adherence to the exercise and dietary interventions was monitored based on attendanceto sessions and completion of routine exercise logs. Exercise interventionists routinelymonitored the logs for completeness and quality of data entry. If logs were incomplete, theinterventionists reminded participants that these records needed to be complete and, asappropriate, to recall and fill in missing records. Individuals transitioned to home-basedexercise also submitted regular exercise logs detailing the day of week, exercise duration,and heart rate achieved for each exercise session.

Participants randomized to the healthy lifestyle group met monthly for 1 hour over thefirst 3 months of the trial. Topics for these sessions included osteoarthritis, obesity, andexercise. In addition, phone contacts were established on a monthly (for months 4–6)and bimonthly (months 7–18) basis. Information on pain, medications, illnesses, and hospital-ization was obtained during the phone contacts.

Recruitment

Recruitment strategies combined advertising through media exposure and mass mailings.A commercially available computer-based mailing list of age-eligible households was usedto identify a target audience for mass mailings. The minority recruitment goal was 30%,with most of these expected to be African-Americans (26%), along with a representation ofHispanics (1%), Native Americans (1%), and Asian-Americans (0.5%). Strategies to targetrecruitment of minorities included: (1) oversampling in zip codes with a large minoritypopulation; (2) working for endorsements by leaders in the minority community and promot-ing the study in minority neighborhoods through churches and civic organizations; (3)performing screening in senior residential sites and shopping centers in minority neighbor-hoods; (4) developing culturally sensitive recruitment materials for each minority subgroup;(5) providing transportation for eligible subjects who otherwise would not be able to partici-pate in the intervention or data collection; and (6) advertising in ethnic-specific newspapersand radio stations. Recruitment for the study was conducted through a central core andsponsored by a Claude D. Pepper Older Americans Grant.

Screening and outcome measurement periods

ScreeningA total of 2209 persons contacted the recruitment core personnel and were screened via

phone for major eligibility criteria. Participants who passed the phone screen were scheduledfor an initial screening visit, which included obtaining the written informed consent followingrequirements of the Institutional Review Board at Wake Forest University School of Medicine,background demographics (occupation history, income, education, community involvement),medical history, medication use, physical examination, self-report of disability, knee pain,physical activity, body weight, and screening blood tests. If individuals met the initial


eligibility criteria, a knee X-ray was obtained. Based on these results a second screening visitwas scheduled and a physician-supervised treadmill graded exercise test was administered toassess the safety of engaging in an exercise intervention and to develop the exercise prescrip-tion for those subsequently randomized. An interventionist interviewed participants to assesstheir ability to comply with the intervention. Following eligibility confirmation, 316 individu-als were randomized to one of the four interventions. During the randomization visit, datawere collected on health-related quality of life, social support, and physical performance[31,32]. Approximately one-third and one-half of the participants were randomized intosubsets for measurements of dietary assessment and biomechanics/strength, respectively.

Follow-upAdditional measurements were obtained at follow-up visits scheduled for months 6 and

18 of the intervention. A complete list of measurements obtained and their scheduling isfound in Table 2.

Outcome measures

Study staff who administered questionnaires and conducted testing procedures were trainedin these procedures and followed standard operating protocols. These staff members werenot interventionists and were blinded to group assignments.

Physical functionThe measurement of physical function was assessed through self-report questionnaires

and physical performance tests.

Self-report

Self-reported physical function was measured using the Western Ontario and McMasterUniversity Osteoarthritis Index (WOMAC) and the FAST Functional Performance Inventory[14,33]. The WOMAC has been validated and is recommended by the Osteoarthritis ResearchSociety as the measure of choice [33]. The 24-item WOMAC instrument was developed foruse by individuals who have OA of the hip or knee and is a health status instrument thatassesses participant’s perception of pain, joint stiffness, and physical function. The primaryoutcome measurement for ADAPT is the mean response for the 17 questions in WOMACthat are directed toward physical function. Although the WOMAC is a self-report assessment,it is the most common primary measure in previous clinical trials of OA. The FAST FunctionalPerformance Inventory, developed for that study, utilizes 23 questions directed toward as-sessing self-reported difficulties in performing physical tasks required for daily living, whichwas a secondary outcome measure [14]. This instrument provides distinct dimensions inbasic activities of daily living (e.g., dressing one’s self), complex instrumental activities ofdaily living (e.g., doing light housework), ambulation and climbing (e.g., climbing stairs),transfer (e.g., getting into and out of a car), and upper extremities (e.g., lifting heavyobjects). The dimensions have good internal consistency (all Cronbach alphas �0.80) andhave statistically significant relationships with objective measures of function [34].


Performance

Laboratory tests used to assess physical performance included the 6-minute walk distanceand stair climb time. Briefly, for the first test, participants were instructed to walk as far aspossible in a 6-minute time period on an established course. They were not allowed to carrya watch and were not provided with feedback during the trial. Performance was measuredby the total distance covered. This test is significantly correlated to treadmill time and symptom-limited maximal oxygen consumption (r � 0.52 and r � 0.53, respectively) and has a3-month test-retest reliability of 0.86 [34]. The second performance test was a timed stairclimb that involved ascending and descending a flight of five stairs as quickly as possible.During the ascent, participants were told to hang on to the handrail with their left hand and,without hesitation, turn around on the platform at the top and climb down using the same

Table 2. List and timing of outcome measures

Measures Baseline at screening and randomization 6-month follow-up 18-month follow-up

Eligibility screen XInformed consent XDemographics XBlood draw X X XQuestionnaires

Medical history X X XMMSEa XMedications X X XSocial supportb X X XSF 36c X X XSleepd X X XWOMACe X X XSelf/body X X Ximage [38]Knee pain X X Xscale [34]Physical functionf X X X

Physical exam X XX-ray X XHeight/weight X X XStair climb X X X6-minute walk X X XGraded exercise test X XBiomechanics/strengthg X X XDietary intakeh X X XCost-effectiveness X X X

a Mini-Mental State Examination [36].b Medical Outcomes Social Support Survey [32].c Medical Outcomes Study 36-item Short Form Health Survey [31].d Sleep Disturbance Questionnaire.e Western Ontario McMaster University Osteoarthritis Index [33].f FAST Functional Performance Inventory [14].g Only performed on a randomized subset of one-fourth of the cohort.h Only performed on a randomized subset of one-third of the cohort.


hand to hold onto the rail. Performance was measured as the time required to complete the task.This test has a correlation value of r � �0.49 with maximal functional capacity and a test-retest reliability over a 3-month period of 0.75–0.87 [34].

Knee painKnee pain was assessed using the WOMAC and the knee pain scale (KPS). The WOMAC

has five questions that allow the participant to rate their pain from “none” to “extreme”while sitting, lying in bed, standing, walking, and ascending and descending stairs. The KPSinstrument was developed from FAST with a focus on measuring knee pain in persons withknee OA [34]. It assesses the frequency and intensity of knee pain in relation to the perfor-mance of daily activities that involve ambulation/climbing and transfer. Two-week test-retestreliability exceeds 0.84 for all subscales of the KPS.

Health-related quality of lifeParticipant’s overall health-related quality of life was determined by the Medical Outcomes

Study 36-item Short Form Health Survey (SF-36) [31]. This widely used scale is multidimen-sional. It has two summary sources for physical and mental health as well as eight subscalescores: physical functioning, role limitations due to physical and emotional problems, pain,general health perceptions, vitality, social functioning, emotional well-being, and healthtransition. It has been validated in patients with osteoarthritis [35].

Other psychological assessmentsThe Mini-Mental State Examination was administered to assess cognitive performance [36].

This instrumentwasadministeredby studystaffwith proper trainingandexperience.Depressivesymptoms were measured by the Centers for Epidemiologic Studies-Depression instrumentwith self/body image measured using a body satisfaction scale [37,38].

Radiographic disease severityAnteroposterior standing knee X-rays were obtained at baseline and 18 months to determine

the effects of the interventions on radiographic disease. A foot map was drawn at the firstX-ray to ensure identical positioning for comparing baseline and end-of-study measurements.Knee X-ray films were read by a single physician masked to assignment, treatment group,and timing of the X-ray (baseline or 18 months). Severity of OA was assessed using aclassification scheme adapted from Altman et al. [39]. Both the medial and lateral compart-ments were graded for osteophytes, subchondral cysts, and joint space narrowing on a 0 to3 Likert scale using an atlas. The scores for each feature were added to compute a summaryseverity score from 0 to 24 for the most affected knee.

Gait and strength analysisOne-half of the participants in the study were randomized to gait and strength testing.

These measurements were conducted and supervised by a staff member with a master ofscience degree in biomechanics with specific training in gait and strength analyses. Thesemeasurements were overseen by the principal investigator for the study (S. Messier). Priorto testing, subjects’ freely chosen walking speeds were assessed using a Lafayette Model


63501 photoelectric control system. Three-dimensional high-speed video analysis (60 Hz)was performed using a four-camera (60 Hz) Motion Analysis Corporation motion analysissystem. A low-pass Butterworth digital filter with a cutoff frequency of 6 Hz smoothed theraw coordinate data and Orthotrak software calculated the relevant kinematic and temporalvariables. Kinetic data were gathered in synchrony with the kinematic data using an AMTIforce platform set to sample data at 1000 Hz. Knee joint forces were calculated using aninverse dynamics model developed by DeVita and Hortobagyi [40].

Knee concentric/eccentric extension muscular strength was assessed using a Kin-Com125E isokinetic dynamometer. Prior to testing, a warm-up period was provided to habituatethe subjects to the testing equipment. The order of testing was concentric/eccentric extensionfollowed by concentric/eccentric flexion at a velocity of 30� second�1. Gravity effect torquewas calculated based on the subject’s leg weight at a 45� angle. The activation force foreach muscle group was set at 50% of maximal voluntary isometric contraction.

Knee extensors were tested through a joint arc from 90� to 30� (0� � full extension). Thefirst and last 10� were subsequently deleted to account for the acceleration and decelerationof the dynamometer at the ends of the range of motion, and also to account for possibleinconsistent effort [41]. Hence, average force was calculated as the average force betweenjoint angles of 40� and 80�. Two maximal reproducible trials were averaged and the maximumnumber of trials for each test was six. Subsequently, knee concentric/eccentric flexion testswere conducted through the same range of motion used for the extension tests.

Cost-effectiveness and cost-benefitA cost-effectiveness analysis was performed from a payer perspective (i.e., including those

cost and outcome elements that would be realized by an insurer). The cost variables consideredin this study included: (1) the economic value of the intervention, (2) the cost of any adverseevents resulting from intervention activities, (3) the cost associated with additional referralsfor medical care made by intervention staff, and (4) any cost savings from reduced utilizationof health-care services.

Process measures

Body weight and heightBody weight and height were measured at baseline, 6 months, and 18 months. Both were

obtained in comfortable clothes, with shoes and outer garments removed. The scale wascalibrated prior to baseline and at each follow-up testing assessment.

Dietary intakeA registered dietitian from the General Clinical Research Center at Wake Forest University

Baptist Medical Center, who was not involved with the delivery of the intervention, obtaineda 24-hour recall at baseline, 6 months, and 18 months on one-third of the cohort.

Data management

Dietary intake recalls were processed and summary nutrition measures were performedusing the Nutrient Data System (NDS) developed by the Nutrition Coordinating Center at


the University of Minnesota, Minneapolis (Nutrient Database, version 2.1). The NDS systemis used because it is accurate and standardized and has a comprehensive food and nutrientdatabase. NDS automatically prompts the interviewer to probe for complete food intake,food descriptions, variable recipe ingredients, and food preparation methods. Nutrient calcula-tions were performed using the NDS algorithms. Strength and gait measures were elec-tronically captured by the Kin-Com 125E isokinetic dynamometer and Motion AnalysisCorporation motion analysis system equipment, respectively. These data files were convertedto SAS datasets for processing and merging with other subjects research data. All otherresearch measures were recorded on study forms and entered into a FoxPro database withbuilt in data range checks. All files were converted to SAS data files for statistical analysis.

Statistical considerations

The primary objective of the trial was to test the effect of diet and exercise on self-reported physical function. The four groups comprised a two-by-two factorial design to allowthe comparison of the independent and joint effects of diet and exercise interventions. Anestimate of the mean and standard deviation of the WOMAC scale (32.2 � 13.8) was obtainedfrom Bellamy et al. [33]. An estimate of the mean and standard deviation of the gaitbiomechanics (medial force) (49.2 � 13.2) was obtained by repeated measures analysis ofvariance using SAS PROC MIXED, a program for possibly missing repeated observations,based on data on over 400 participants from the FAST clinical trial [14].

The sample size was chosen to provide adequate power to detect a 20% difference inWOMAC score between the main effects groups. The main effects of weight reduction andphysical activity interventions were felt to be additive or nearly additive. If the effect of onefactor is additive by a factor p then the joint effect of weight reduction and lifestyle physicalactivity intervention would have a joint effect of 10% × (1 � p). Sample size calculationswere made to allow for 75–100% additivity. The sample size calculations further assumedthat the retention rate would be 85%. Our experience with FAST and TONE resulted inretention rates of 84% and 94%, respectively [14,30]. In addition, participants who droppedout after the first or second follow-up visit provided some information; therefore, thesecalculations were conservative. Based on these assumptions, the total evaluable samplesize required to obtain 90% power to detect a 20% relative effect of each main effect in atwo-way repeated measures analysis of variance was 196 or 254 if assumed 100% or 75%additivity of effects.

We chose an effect size of 20% for a change in self-reported disability because we wouldconsider that clinically meaningful and it is in the range of effect sizes noted in other studies[14,42,43]. A sample size of 254 evaluable subjects at 18-month follow-up was the goal ofthe study. In order to allow for 15% loss to follow-up, a total sample size of 300 to berandomized was chosen in order to have 90% power for the primary and main secondaryoutcome measures. The sample size of 300 would provide 90% power if the additivity wasas low as 75%. Biomechanics data were obtained on one-half of the participants in thetrial as this provided more than 80% power to detect a 20% difference in medial force. Nutritiondata were obtained on one-third of participants in the trial as this provided more than 80%power to detect a 20% difference in nutrient intake.


Analysis of variance and the chi-square test were used to test for differences in baselinecharacteristics by treatment groups. The ADAPT population was stratified by BMI intooverweight (BMI � 28.0–29.9 kg·m�2), class I obesity (BMI � 30.0–34.9 kg·m�2), classII obesity (BMI � 35.0–39.9 kg·m�2), and class III obesity (BMI � 40.0 kg·m�2) [44].Means of physical function and pain scales of the WOMAC and the physical performancetasks were compared among the four BMI categories by analysis of variance.

Results

Study recruitment was fulfilled in July 1998 and final data collection for the study wascompleted in December 1999. The total number of persons prescreened via telephone duringthe 18-month recruitment period was 2209. Of these, 72% were ineligible (1596/2209) and13% declined to participate (297/2209), leaving 316 people who were randomized to oneof the four treatment groups. Data analyses for the primary outcomes of ADAPT are finalizedwith presentation of the results forthcoming.

Baseline demographics and comorbid illnesses for participants randomized into the studyare described below. The mean age of the randomized participants at baseline was 68.6years, ranging from 60–89. Nearly three-fourths of all participants were women (72.8%).Seventy-five percent were classified as white/Caucasian. Another 22% were African-Americanand there was representation from Native American, Asian/Pacific Islander, and Hispanicpopulations. Approximately 44% had an annual household income between $10,000 and$34,999, with an additional 44% earning more than $35,000 per year. The majority ofparticipants had some post-high school education, with 33% having at least a college degree.The most prevalent comorbid condition was hypertension with almost 50% of participantsbeing affected. Additionally, more than 28% had some form of heart disease, includingangina (11.5%), congestive heart failure (3.5%), history of heart attack (4.1%), or other heartdisease (21.1%).

Selected outcome variables at baseline for the entire randomized ADAPT cohort arepresented in Table 3. Values are presented as means (standard deviation). Prior to the initiationof the interventions, BMI was 34.5 (5.4) kg·m�2 with a range from 28.0 to 64.7 kg·m�2.The summary score for the 17 self-reported physical function items in the WOMAC scalewas 24.39 (11.72), with a score of 6.95 (3.52) for the pain items in the WOMAC scale. Forthe FAST Functional Performance Inventory, the mean rating for the 23 items was 2.00(0.60) (not shown in Table 3). In descriptive terms, this value coincides with “Usually did(specific activity) with a little difficulty.”

In addition to self-reported physical disability, physical performance of two separate taskswere used in ADAPT to assess physical function. The mean 6-minute walk distance for allparticipants at baseline was 423.1 (80.6) m with a distance ranging from 140.8 to 649.8 m.The second performance task, the timed stair climb, showed a range 3.3 to 53.4 secondswith a mean value of 10.3 (6.1) seconds.

Participants were stratified by class of overweight and obesity based on their BMI. TheBMI range for the overweight category was 28.0 to 30.0 kg·m�2. Class I obesity includedBMI from 30.0 to 35.0 kg·m�2; class II obesity was from 35.0 to 40.0 kg·m�2; and class


Table 3. Baseline measures of physical function, pain, physical and mental health, 6-minute walk distance, andstair climb time across all participants and for classes of overweight and obesity

BMI 28.0 BMI 30.0 BMI 35.0 BMI OverallOverall to 30.0 to 35.0 to 40.0 �40.0 p-valuemeana (SD) (kg·m�2) (kg·m�2) (kg·m�2) (kg·m�2) from[range] (n � 67) (n � 124) (n � 75) (n � 48) ANOVA

BMI (kg·m�2) 34.5 (5.4) 28.8 (0.8) 32.4 (1.5) 37.0 (1.2) 44.1 (5.0)[28.0–64.7]

WOMAC 24.39 (11.72) 23.80 (10.32)1,2 22.25 (12.79)1 26.36 (10.21)2 28.46 (11.44)3 0.0062functionb [1.0–68.0]

WOMAC 6.95 (3.52) 6.68 (2.94)1,2 6.42 (3.74)1 7.55 (3.26)2 8.00 (3.67)3 0.0211Painc [0.0–20.0]

6 minute walk 423.1 (80.6) 427.6 (86.0) 428.0 (84.4) 419.8 (64.3) 410.1 (81.6) 0.6396distance (m) [140.8–649.8]

Stair climb 10.3 (6.1) 10.9 (7.6)1,2 9.2 (4.6)1,d 10.3 (5.8)1,2 12.0 (5.6)2 0.0238time (secs) [3.3–53.4]a Means not sharing a common superscript within each row differ at the p 0.05 from one another.b WOMAC function is the summary score of 17 items on the WOMAC questionnaire.c WOMAC pain is the summary score of 5 items on the WOMAC questionnaire.d p � 0.052 for comparison between stair climb time for BMI 30–35 and 30 categories.

III obesity was �40.0 kg·m�2. Mean values of WOMAC scores for function and pain,distance walked in 6 minutes, and stair climb time for each BMI category are presentedin Table 3. The lowestWOMACscore for function (indicatinghigher function) wasobserved forclass I obesity, which was significantly less than the score reported in the class II and classIII obesity categories. Additionally, participants who were overweight had a significantlylower score than those with class III obesity. A similar pattern was observed for the WOMACpain scale with less pain reported by those with class I obesity than with class II or IIIobesity. In the timed stair climb, however, there were differences between groups with the30–35 BMI category having the fastest time (9.2 seconds) and the �40 BMI categoryshowing the slowest time (12.0 seconds). Statistical significance was not reached in othercategory comparisons, although there was a trend for class I obesity to have a faster stair climbtime than the overweight category (p � 0.052).

Discussion

ADAPT is the first randomized controlled trial to examine the effects of weight loss, withand without exercise, on physical functional decline and disability in older, overweight andobese adults with knee OA. Prior evidence on this population from FAST has shown thatboth aerobic exercise and weight training reduce the decline in physical function [14]. Therehas previously only been observational evidence to support the effectiveness of weight lossin reducing the decline in physical function in older adults with knee OA [10].

The final data collection occurred in December 1999, culminating a 4-year period ofrecruitment, intervention, and testing. Previous experience with this population in our commu-nity provided us with valuable knowledge for successful recruitment as we surpassed our


initial recruitment goal of 300 participants. Overall, recruitment went very well as the variousrecruitment techniques provided a strategy for recruiting minorities in the study. We foundthat the 18-month duration of the study was a tremendous time commitment. Becauseof this, there were a few occasions when a participant was randomized but the start ofthe intervention was postponed until a later wave. These participants were much more likelyto be noncompliant to their intervention.

This is one of only a few studies that has attempted to achieve sustained weight loss inobese older adults with impaired physical function [18,30]. The weight-loss goal establishedwas a 5% loss in weight from baseline. As reported, this level of weight loss is thought tobe achievable in this population with the designed intervention, and a 5% weight loss has beenshown to produce statistically significant alterations in knee pain in obese women. Modestweight loss of this level has also been shown to offer benefits for other metabolic comorbiditiesassociated with obesity, including reductions in blood pressure and blood cholesterol andimprovements in insulin sensitivity [45].

The recent publication of the Activity Counseling Trial showing the effectiveness ofphysical activity counseling in the primary care setting for improving cardiorespiratory fitnessin women illustrates that implementation of a lifestyle behavior can be successful in improvinghealth [46]. Likewise, the exercise intervention utilized in FAST provides evidence thatincreasing physical activity can reduce decline in physical function in participants with kneeOA [14]. ADAPT builds on the intervention design and outcome from these studies byadding a second behavioral strategy with an emphasis on dietary restriction to induce weightloss. Furthermore, the ADAPT target population was older, overweight and obese adultswith knee OA (BMI � 28.0 kg·m�2 as inclusion criteria).

The exercise intervention was developed to encompass both cardiovascular fitness andstrength. A unique feature of ADAPT is the combination of both of these exercise trainingmodes into a single exercise regime that can be implemented in a facility-based setting oradapted for a home-based program. The development of an exercise intervention that allowedmaximal flexibility and choices for the participants, yet still maintained a high degree of qualitycontrol for the study personnel, was also an important methodologic design advancement inADAPT. The intent was to formally test a new intervention that allowed the participant toexercise in an environment best suited for their continued participation, whether this choicewas in a facility, their home, or a combination of these two. In our earlier experience withFAST, the exercise intervention consisted of 3 months of facility-based activity followed by15 months of mandatory home-based exercise. The overall exercise compliance in thatstudy was nearly 70% in both aerobic and strength interventions. We anticipate that theflexibility afforded to participants in ADAPT will promote continued participation inthe exercise intervention as measured by attendance at facility-based sessions and by exerciselogs completed by participants exercising at home. Since time and access are the mostcommonly reported barriers to physical activity, we felt that the flexibility provided wouldreduce recidivism [47].

Comparison of the baseline data among the classes of overweight and obesity illustratethat higher classes of obesity are associated with lower levels of self-reported physicalfunction and higher levels of pain compared to the lowest class of obesity (BMI 30.0 kg·m�2

to 35.0). A reduction in self-reported physical function and physical performance tasks and


an increase in pain have previously been shown to be associated with obesity [48]. Additionally,other studies have demonstrated that functional limitations assessed via self-report andobjective evaluations are associated with high BMI values [48]. This is apparently indepen-dent of the presence of cardiovascular disease or other obesity-related disorders [49]. Further-more, obese individuals have been shown to have a lower perception of their health [50].These findings from the ADAPT cohort add to the previous literature and are unique in thatthe study focused on older, obese adults with knee OA. Furthermore, our results provideevidence that in the obese population, higher levels of obesity further exacerbate the impair-ments in physical function and pain as assessed by self-reported and objective measures. Itis interesting to note that the lower physical function found in the higher BMI categorieswas not accompanied by differences in the 6-minute walk distance. However, the timed stairclimb did show divergence among BMI levels in the same direction as the self-reportedoutcomes. For this population, the stair climb appears to be a more discriminating and chal-lenging task than the 6-minute walk. This may be due to the source of disability in thispopulation, namely knee OA. This is consistent with the reported greater difficulty in climbingstairs than walking on level ground in individuals with mild radiographic evidence of kneeOA [51].

It is noteworthy that the participants in the overweight category did not report higherphysical function or less pain than those in either class I or class II obesity. In fact, therewas a strong trend for those with a BMI of less than 30.0 kg·m�2 to have a slower stair-climb time than participants with class II obesity (p � 0.052). It might be inferred that thosein the overweight group would have the most progressive or advanced disease compared toclass I or II obesity. In an attempt to explain these findings, we examined the age and genderdistribution within the BMI groups, the hypothesis being that an increase in age andgreater female distribution in the overweight group might influence the findings. The meanage for the four distributions ranged from 70.1 years for the overweight category to 66.4years for class III obesity, with the mean age for class I and II obesity being 69.3 and67.5 years, respectively. The percent of females in the BMI groups ranged from 81.3% forclass III obesity to 68.6% for class I obesity. Overweight and class II obesity groups had77.6% and 69.3% females, respectively. Since there are only slight differences in the ageand gender distribution among the BMI groups, it is unlikely that these factors contributedto the reported observations. Although no mechanistic data have yet been analyzed, wespeculate that the etiology of the disease may be different between overweight and obese indi-viduals. The influence of the stress imposed on the knee joints and the levels of hormonesthat may contribute to the etiology and pathophysiology of knee OA would likely be less in theoverweight group. Therefore, the cause ofOAin the overweightpopulationmayarise fromotherfactors. These may cause the overweight group to have more physical restrictions anddisability than predicted based on their BMI. These findings, if replicated by others, maybecome valuable regarding the treatment of the disorder. It will be of interest to examinethe response of the behavioral treatment in ADAPT among the different BMI categories.

Knee OA is the leading cause of disability in older adults and obesity is a major riskfactor for this joint disease. The results from ADAPT will provide new and valuable insightsinto the behavioral approaches clinicians should recommend for behavioral therapies thateffectively reduce the incidence of disability associated with this prevalent disease.


The strengths of this trial include the full factorial design, the duration of the intervention,and the collection of both self-reported and physical performance measurements. The studyis limited in that there is little mechanistic data being collected. The lack of body compositiondoes not allow us to ascertain whether the weight loss was from changes in body fat,lean body mass (i.e., muscle), or a combination of both.

Acknowledgments

This project is being funded by the Claude D. Pepper Older Americans (Grant5P60AG10484-00) and the General Clinical Research Center (Grant M01-RR07122). Theinvestigators would also like to acknowledge the other investigators and personnel involvedin the development and operation of the study.

References

[1] Lawrence RC, Helmick CG, Arnett FC, et al. Estimates of the prevalence of arthritis and selectedmusculoskeletal disorders in the United States. Arthritis Rheum 1998;41:778–799.

[2] Centers for Disease Control and Prevention. Prevalence of disabilities and associated health conditionsamong adults—United States, 1999. Morbidity and Mortality Weekly Reports 2001;50:120–125.

[3] Centers for Disease Control and Prevention. Prevalence of arthritis—United States, 1997. Morbidity andMortality Weekly Reports 2001;50:334–336.

[4] Davis MA, Ettinger WH, Neuhaus JM. The role of metabolic factors and blood pressure in the associationof obesity with osteoarthritis of the knee. J Rheumatol 1988;15:1827–1832.

[5] Felson DT, Naimark A, Anderson J, et al. The prevalence of knee osteoarthritis in the elderly. TheFramingham Osteoarthritis Study. Arthritis Rheum 1987;30:914–918.

[6] Davis MA. Epidemiology of osteoarthritis. Clin Geriatr Med 1988;4:241–255.[7] Ettinger WH, Davis MA, Neuhaus JM, Mallon KP. Long-term physical functioning in persons with knee

osteoarthritis from NHANES.I: Effects of comorbid medical conditions. J Clin Epidemiol 1994;47:809–815.[8] Guccione AA, Felson DT, Anderson JJ. Defining arthritis and measuring functional status in elders:

methodological issues in the study of disease and physical disability. Am J Public Health 1990;80:945–949.[9] Verbrugge LM, Gates DM, Ike RW. Risk factors for disability among U.S. adults with arthritis. J Clin

Epidemiol 1991;44:167–182.[10] Felson DT, Zhang Y, Anthony JM, Naimark A, Anderson JJ. Weight loss reduces the risk for symptomatic

knee osteoarthritis in women. The Framingham Study. Ann Intern Med 1992;116:535–539.[11] Oliveria SA, Felson DT, Cirillo PA, Reed JI, Walker AM. Body weight, body mass index, and incident

symptomatic osteoarthritis of the hand, hip, and knee. Epidemiology 1999;10:161–166.[12] Sturmer T, Gunther KP, Brenner H. Obesity, overweight and patterns of osteoarthritis: the Ulm Osteo-

arthritis Study. J Clin Epidemiol 2000;53:307–313.[13] Gelber AC, Hochberg MC, Mead LA, et al. Body mass index in young men and the risk of subsequent

knee and hip osteoarthritis. Am J Med 1999;107:542–548.[14] Ettinger WH Jr, Burns R, Messier SP, et al. A randomized trial comparing aerobic exercise and resistance

exercise with a health education program in older adults with knee osteoarthritis. The Fitness Arthritisand Seniors Trial (FAST). JAMA 1997;277:25–31.

[15] Radin EL, Burr DB, Caterson B, et al. Mechanical determinants of osteoarthrosis. Semin ArthritisRheum 1991;21(Suppl 2):12–21.

[16] Howell DS, Treadwell BV, Troiano RP. Etiopathogenesis of osteoarthritis. In: Moskowitz RM, HowellDM, Goldberg VM, Mankin HJ, editors. Osteoarthritis: diagnosis and management. Philadelphia: W.B.Saunders Company, 1992. p. 233–254.


[17] Messier SP, Ettinger WH, Doyle TE. Obesity: effects of gait in an osteoarthritic population. Journal AppliedBiomechanics 1996;12:161–172.

[18] Toda Y, Toda T, Takemura S, et al. Change in body fat, but not body weight or metabolic correlates ofobesity, is related to symptomatic relief of obese patients with knee osteoarthritis after a weight controlprogram. J Rheumatol 1998;25:2181–2186.

[19] Deyle GD, Henderson NE, Matekel RL, et al. Effectiveness of manual physical therapy and exercise inosteoarthritis of the knee. A randomized, controlled trial. Ann Intern Med 2000;132:173–181.

[20] Peterson MG, Kovar-Toledano PA, Otis JC, et al. Effect of a walking program on gait characteristics inpatients with osteoarthritis. Arthritis Care Res 1993;6:11–16.

[21] Schilke JM, Johnson GO, Housh TJ, O’Dell JR. Effects of muscle-strength training on the functionalstatus of patients with osteoarthritis of the knee joint. Nurs Res 1996;45:68–72.

[22] van Baar ME, Dekker J, Oostendorp RA, et al. The effectiveness of exercise therapy in patients withosteoarthritis of the hip or knee: a randomized clinical trial. J Rheumatol 1998;25:2432–2439.

[23] Mangione KK, McCully K, Gloviak A, et al. The effects of high-intensity and low-intensity cycle ergometryin older adults with knee osteoarthritis. J Gerontol A Biol Sci Med Sci 1999;54:M184–M190.

[24] O’Reilly SC, Muir KR, Doherty M. Effectiveness of home exercise on pain and disability from osteoarthritisof the knee: a randomised controlled trial. Ann Rheum Dis 1999;58:15–19.

[25] Hochberg MC, Altman RD, Brandt KD, et al. Guidelines for the medical management of osteoarthritis. PartII. Osteoarthritis of the knee. American College of Rheumatology. Arthritis Rheum 1995;38:1541–1546.

[26] Meichenbaum D, Turk DC. Facilitating treatment adherence: a practitioner’s guidebook. New York: PlenumPress, 1987.

[27] Rejeski WJ, Brawley LR, Ettinger W, Morgan T, Thompson C. Compliance to exercise therapy in olderparticipants with knee osteoarthritis: implications for treating disability. Med Sci Sports Exerc1997;29:977–985.

[28] Cartwright DC, Zander A. Group dynamics: research and theory. New York: Harper & Row, 1953.[29] Bandura A. Social foundations of thought and action: a social cognitive theory. Englewood Cliffs, NJ:

Prentice Hall, 1986.[30] Whelton PK, Appel LJ, Espeland MA, et al. Sodium reduction and weight loss in the treatment of

hypertension in older persons: a randomized controlled trial of nonpharmacologic interventions in theelderly (TONE). TONE Collaborative Research Group. JAMA 1998;279:839–846.

[31] Coons SJ, Rao S, Keininger DL, Hays RD. A comparative review of generic quality-of-life instru-ments. Pharmacoeconomics 2000;17:13–35.

[32] Sherbourne CD, Stewart AL. The MOS social support survey. Soc Sci Med 1991;32:705–714.[33] Bellamy N, Buchanan WW, Goldsmith CH, Campbell J, Stitt LW. Validation study of WOMAC: a health

status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapyin patients with osteoarthritis of the hip or knee. J Rheumatol 1988;15:1833–1840.

[34] Rejeski WJ, Ettinger WH, Shumaker S, et al. The evaluation of pain in patients with knee osteoarthritis:the knee pain scale. J Rheumatol 1995;22:1124–1129.

[35] Kantz ME, Harris WJ, Levitsky K, Ware JE, Davies AR. Methods for assessing condition-specific andgeneric functional status outcomes after total knee replacement. Med Care 1992;30(Suppl):MS240–MS252.

[36] Folstein MF, Folstein SE, McHugh PR. “Mini-mental state.” A practical method for grading the cognitivestate of patients for the clinician. J Psychiatr Res 1975;12:189–198.

[37] Myers JK, Weissman MM. Use of a self-report symptom scale to detect depression in a communitysample. Am J Psychiatry 1980;137:1081–1084.

[38] Reboussin BA, Rejeski WJ, Martin KA, et al. Correlates of satisfaction with body function and bodyappearance in middle- and older aged adults: The Activity Counseling Trial (ACT). Psychology and Health2000;15:239–254.

[39] Altman RD, Fries JF, Bloch DA, et al. Radiographic assessment of progression in osteoarthritis. ArthritisRheum 1987;30:1214–1225.

[40] DeVita P, Hortobagyi T. Functional knee brace alters predicted knee muscle and joint forces in personswith ACL reconstruction during walking. Journal of Applied Biomechanics 2001;17:297–311.


[41] Kramer JF, Vaz MD, Hakansson D. Effect of activation force on knee extensor torques. Med Sci SportsExerc 1991;23:231–237.

[42] Ettinger WH Jr, Afable RF. Physical disability from knee osteoarthritis: the role of exercise as an interven-tion. Med Sci Sports Exerc 1994;26:1435–1440.

[43] Kovar PA, Allegrante JP, MacKenzie CR, et al. Supervised fitness walking in patients with osteoarthritisof the knee. A randomized, controlled trial. Ann Intern Med 1992;116:529–534.

[44] National Institute of Health NHLBI. Clinical guidelines on the identification, evaluation and treatment ofoverweight and obesity in adults—the evidence report. Obes Res 1998;6:51S–209S.

[45] Goldstein DJ. Beneficial health effects of modest weight loss. Int J Obes Relat Metab Disord 1992;16:397–415.

[46] The writing group for the Activity Counseling Trial research group. Effects of physical activity counselingin primary care: the Activity Counseling Trial: a randomized controlled trial. JAMA 2001;286:677–687.

[47] Sherwood NE, Jeffery RW. The behavioral determinants of exercise: implications for physical activityinterventions. Annu Rev Nutr 2000;20:21–44.

[48] Larsson UE, Mattsson E. Functional limitations linked to high body mass index, age and current pain inobese women. Int J Obes Relat Metab Disord 2001;25:893–899.

[49] Stafford M, Hemingway H, Marmot M. Current obesity, steady weight change and weight fluctuation aspredictors of physical functioning in middle aged office workers: the Whitehall II Study. Int J Obes RelatMetab Disord 1998;22:23–31.

[50] Wolk A, Rossner S. Obesity and self-perceived health in Sweden. Int J Obes Relat Metab Disord 1996;20:369–372.

[51] Jordan J, Luta G, Renner J, et al. Knee pain and knee osteoarthritis severity in self-reported task specificdisability: the Johnston County Osteoarthritis Project. J Rheumatol 1997;24:1344–1349.

the arthritis, diet and activity promotion trial (adapt): design, rationale, and baseline results

Documents