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J ClinEpidemtolVol. 46, No. 12,pp. 140%141, 1993 0895-4356/93 6.00+ 0.00Pruned in Great ritain Pergamon Press Ltd

ACCURACY OF THE COLLEGE ALUM NUS PHYSICALACTIVITY QUESTIONNAIRE*

BARBARAE INSWORTH,~ RTHUR S EON>~ MARKT.RICHARDSON ~DAVID R. JACOBS*and R. S. PAFFENBARGER JR

Applied Physiology Labo ratory, Department of Physical Education, Exercise and Sport Scienceand Department of Nutrition, School of Public Health, University of North Carolina at ChapelHill, NC 275 99, Division of Epidemiology, School of Public Health, University of Minnesota,Minneapolis, MN , 3Division of Kinesiology, School of Kinesiology and Leisure Studies, Universityof Minnesota, Minneapolis, MN 4Area of Health and Hum an Performance, University ofAlabam a, Tuscaloosa, AL and %chool of Medicine, Stanford University, Palo Alto, CA, U.S.A.

Recei ved i n revi sed orm 25 June 1993)

Abstract-The validity and reproducibility of the Physical Activity Index from the CollegeAlumnus Questionnaire (PAI-CAQ) were determined in 78 men and women (21 -59 yr)with a broad range of physical activity habits. The PAX-CAQ was computed as the sum ofenergy expende d in stair climbing, walking , and sports and recreational physical activityrecalled from the past week. Data were validated against measures of cardiorespiratoryfitness, body fatness, motion detection, and physical activity records. All physical activitywas record ed by participants for six 48-hou r pe riods. Each day of the week, includingweeke nds, were represented at least twice in the physical activity records. A ge-adjustedcorrelation coefficients between like activities on the College Alumnus Questionnaire andphysical activity records ranged from 0.2 5 to 0.65 in men and 0 .28 to 0.86 in women .Correlations between the PAI-CAQ and validation criteria that reflected total andheavy-intensity physical activities were higher (r = 0.34-0.69, p < 0.05) than for lighter-intensity ph ysical activities and motion detection e xpresse d in MET-mind-r and kcald(r < 0.35, p > 0.05). Test-retest reproducibility was higher over 1 month r = 0.72) thanover 8 and 9 months (I = 0.34 and 0.43) (p < 0.05 ). Energy expend ed in walking and stairclimbing was underestimated on the College Alumnus Questionnaire, resulting in lowerPAI-CAQ scores, as comp ared to the physical activity record s.Exercise Exertion Validity Reproducibility Leisure activities

INTRODUCTION comp lete, valid, reliable, an d assess physicalTo study the association between physical ac-tivity and health outco mes in population sur-veys, questionnaires are needed that are easy to

*Sections of this paper were presented at the 1988 and 1990Ameri can Col l ege of Sports Medici ne Annual Meeti ngs inDallas, Texas and Salt Lake City, Utah and publishedin abstract form [2].?A11 correspondence should be addressed to: Barbara E.Ainsworth, Ph.D., MPH, Applied Physiology Labora-tory, Department of Physical Education, Exercise &Sport Science, 25C Fetzer Gym nasium, University ofNorth Carolina at Chapel Hill, Chapel Hill, NC27599-8700, U.S.A.

activity habits equally well in men and women.Recent evaluations of commonly-used physicalactivity questionnaires indicate that many ofthese instruments focus primarily on partici-pation in sports, formal exercise and otherheavy-intensity physical activities [3,4].

One of the better known physical activityassessment tools is the College Alumnus Ques-tionnaire [5]. From the College Alumnus Ques-tionnaire, a Physical Activity Index (PAI-CAQ)is calculated, which is used to characteriz ephysical activity habits [6,7], and study theassociations between physical activity and

1403

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1404 BARBARA . AINSWORTH et a lchronic disease rates [5, S--13], longevity [14],cardiorespiratory fitness [15, 161, and energybalance in male alumni of Pennsylvania andHarvard University [5].The validity of the PAI-CAQ , using severalvalidation criteria concurrently, in a singlesample of subjects has not been previouslyreported. This study examines the test-retestreproducibility and the validity of the PAI-C AQagainst direct and indirect measures of physi-cal activity in 78 men and women with a broadrange of physical activity ha bits.

METHODSDat a are reported from the Survey of Activity,

Fitness, and Exercise study (SAFE). SAFE wasa NHLBI-funded study designed to examine thevalidity a nd reproducibility of a variety of physi-cal activity question naires common ly used inepidemiolog ic research projects. A detailed studyprotocol and subject eligibility requirem ents forSAFE were reported elsewhere [3,4, 171.Participants

Participants consisted of 28 men and 50women, ranging in age from 21 to 59 years(mean + D, 38 f 9 years). The study design wasapproved by the University of Min nesotas insti-tutional review board for studies involving hu-man subjects and written informed consent wasobtained. Subjec ts were recruited by advertise-ments placed on bulletin boards in the Univer-sitys academ ic and hospital facilities. Onehundred and three volunteers attended a pre-study orientation meeting and were stratified byphysical activity sta tus into low, modera te, orhigh activity groups using a modified scoringscheme for the Lipid Research Clinics physicalactivity questionna ire [4]. Seventy-eight of thesesubjects com pleted the study. Of the 25 non-finishers, 20 dropped-ou t prematurely, while 5were screened but never participated. Compari-son of the results indicate d no statistically signifi-cant differences in baseline physical fitness andphysical activity measurements between thosewho did and did not complete the study.Data collection

The SAFE study protocol included 14 clinicvisits, spaced approximately 26 days apart.*A MET is defined as the ratio of the associated metabolicrate for a specific activity divided by the resting meta-bolic rate. It is also defined as an energy expenditure ofI kcal.hr- per kg body m ass.

Forty eight-hou rs before each clinic visit, sub-jects recorded all physical activity at leastevery 4 hours in a diary designe d for thestudy. During the same 48 hour period, subjectswore a Caltrac accelerometer (Caltrac, H emoki-netics, Madison, WI) and recorded theirenergy expenditure reading s in kilocaloriesfrom the Caltrac on their physical activity recordform.During each clinic visit, participants com-pleted various questionnaires regarding theirphysical activity habits and reviewed theirphysical activity records with trained interview-ers. The Caltrac motion detectors also werechecked at each clinic visit to ensure properfunctioning. In addition , during three of theclinic visits, subjects performed max imal tread -mill graded exercise tests with gas analysis andbody composition studies to assess physicalfitness status. An average clinic visit lasted 50minutes.

College Alumnus Questionnaire. This ques-tionnaire was mailed to participants homes(similar to the manner of administration in theCollege Alum nus Study) [5] at the beginningand during the middle of the study (i.e., afterthe pre-study orientation visit 1 and beforevisits 8 and 9). Participants completed thequestionnaire at home and brought it withthem to the next clinic visit. The question-naire w as collected by the study staff withou tediting in order to duplicate the metho dsused by Paffenbarger et al. [5] for administer-ing this questionnaire in the College Alum nusStudy. Question naire results averaged over clinicvisits 1, 8, and 9 were used in this report totest the validity an d the short-and long-termreproducibility of the PAI-C AQ .Physical activity is assessed by three que stionsthat are used to comprise the PAI-CAQ.Respondents are asked to identify the numberof flights of stairs climbed per day and cityblocks walked per day, and the frequencyand duration of sports and recreationalactivities performed during the past week.Adjustm ent for variability in participationhabits for the sports and recreationalactivities listed is made by having subjectsidentify the weeks in the past year eac hactivity was performed. Intensity levelsin METS * for sports and recreational activitieswere obtained from the Compendium ofPhysical Activities developed for the SAF Estudy [18]. The PAI-CAQ was computed asMET-minewk- using the formula obtained from

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Physical Activity Questionnaires 1405Paffenbarger et al. [5]: (city blocks walked perday x 7 days per week x 8 METS perblock) + flights of sta irs climbed per day x 7days per week x 4 METS per flight) + [activityMET intensity x events per week x duration inminutes per event)/(weeks participated peryear/52 weeks per year)]. The term MET-minawk- was used in this study to express theenergy costs of physical activities independentof body weight. MET-minewk- is equivalent tothe kcalwk- term used by Paffenbarger et al.[5] who excluded body weight when computingthe PAI-CAQ scores in their 1978 paper.

Direct validation criteriaPhysical activity records. All physical activity

was recorded by participants on a physicalactivity record for 48-hour periods before eachclinic visit. Each day of the week, includingweekends, were represented at least twice duringthe course of the study year. For each physical

activity record entry, sub jects recorded a generaland specific description of physical ac tivity, anestimate of the intensity or pace of the effort, theduration of activity in minu tes, a nd noted ifthe activity wa s occupationa lly-related. Types ofphysical activity recorded included, but werenot limited to, sports and recreational activi-ties, househo ld ch ores, shopping, coo king, per-sonal care and hygiene, activities of daily living,child care, sleeping, transportation, lawn andgarden activities, and various occupationaltasks. Subjects made physical activity recordentries every 4 hours during the 48 hour timeperiod. At each visit, a trained intervieweredited the 48-hour record for clarity in thepresence of the participan t. Trained coderstransferred the data to data entry forms andassigne d each activity a MET intensity code.The MET levels for the recorded physicalactivities were obtained from the SAFE studysCompendium of Physical Activities [181.Energyexpenditure was computed as MET-mins for

Table 1. Mean MET-m inwk- + SD for the visit-specific physical activity indices (PAI) for theCollege Alumnus Q uestionnaire and the Physical Activity 48-hour records*College Alumnus PAI Physical Activity Record PA1

Clinic visits Clinic visitsVariables 1 8 9 Average 2 8 9 AveragePhvsical Activitv Index (Met-min wk -I)Men .033 1885 1618 1897 4562 4166 4671 4420(1583) (1467) (1371) (1192) (2577) (2580) (2884) (1875)Women 1570 1122 1063 1243 3953 3310 3455 3540(1186) (998) (824) (832) (2035) (1743) (1543)All 1736 1376 1270 1270 (Z 3630 3894 3856(1351) (1219) (1086) (1086) (2468) (2276) (2280) (1711)Sports recreation (MET-min .wkMen 1311 1094(1505) (1360)Women 829 547(1024) (842)All 505 729(363) (1065)

) 949(1289)1063(688)

1180(1138)$8)806(916)

1888(2510)1368(2233)1555(2333)

1616(2131)676(1329)1027(1722)

2511(2684)795(1116)1415(2004)

1964(1675)915(1176)1291(1456)City blocks walked (Met-min.wk-)Men 486 537 418 470 2225 2238 1705 2056(376) (348) (399) (303) (1138) (1887) (1176) (997)Women 515 380 380 433 2231 2151 2137 2173(358) (347) (341) (286) (1101) (1401) (1167) (845)All 505 432 394 416 2229 2182 1982 2131(362) (353) (361) (291) (1107) (1581) (1181) (898)Flights of stairs climbed (MET-m in.wk - ).Men 238 253 250 247 488 312 353Women (f ) (429) (321)195 187 (z? (410) (151)355 326 E) (232)330(172) (145) (158) (155) (303) (301) (235)All 230 215 212 222 (27;) 321 307 339(178) (272) (232) (192) (330) (258) (340) (233)*All: visits 1 & 2 (n = 78), visit 8 (n = 75), visit 9 (n = 74). W omen: visits 1 & 2 (n = 50), visit 8(n = 47), visit 9 (n = 46). Men: all visits (n = 28).

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1406 B-AU E. AINSWORTHt alTable 2. Age-adjusted correlations between direct and indirect validation criteria and the College Alumnus QuestionnairePhysical Activity Index (PAX-CAQ)

PI-CAQ and Component PartsMen?

Validation CriteriaFlightsstairs City sports PA%blocks & rec. Index

Physical activity record-PA1 specific (MET-m in.wk-)Flights stairs climbed 0.45* 0.19 0.03 0.12City blocks walked 0.32 0.64** 0.20 0.37Sports & recreation -0.08 -0.12 0.25 0.29Z fits, blks, & spts 0.07 0.14 0.51** 0.65**Physical activity record-intensity specific (MET-m inwk-)Total LTPA 0.17 0.17 0.46* 0.60**Heavy intensity LTPA 0.04 -0.01 0.56** 0.69**Moderate intensity LTPA 0.03 0.07 -0.38 -0.24Light intenstiy LTPA 0.20 0.27 0.30 0.35Caltrac (k&d-) 0.14 0.16 -0.19 -0.05Caltrac (METsd-) 0.38* 0.21 -0.02 0.19

-0.02 0.00 0.55** 0.5l?**0.21 -0.09 -0.40 -0.36PAI-CAQ and Component PartsALLt

Validation criteriaFlightsstairs City sports PASblocks & rec. Index

WomentFlights City sports PA%stairs blocks & rec. In&x

0.86** 0.06 -0.08 0.130.03 0.28 0.36* 0.32*-0.05 0.27 0.43** 0.54.0.13 0.30* 0.53** 0.54210.25 0.27 0.03 0.34**0.25 0.38. 0.42** 0.65**-0.08 0.16 0.12 0.150.24 0.11 -0.25 0.03-0.21 0.17 0.10 0.08-0.11 0.19 0.16 0.19

0.21 0.26 0.32 0.53**-0.26 -0.11 -0.26 -0.36

Physical activity record-PA1 specific (MET-m inwk-)Flights stairs climbed 0.79** 0.09 -0.02City blocks walked 0.06 0.34** 0.25*sports. & recreation -0.02 0.17 0.39**Z Flts, blks, & spts 0.13 0.26 0.53**Physical activity record-intensity specific (MET-m inwk-)Total LTPA 0.22 0.23* 0.21Heavy intensity LTPA 0.22 0.30 0.49,.Moderate intensity LTPA -0.03 0.12 -0.05Light intensity LTPA 0.18 0.14 -0.05Caltrac (k&d-) -0.00 0.17Caltrac (METsd-) 0.07 0.21 8%

0.170.24*0.48**0.60**0.42.0.69**0.040.080.170.29

0.17 0.16 0.43** 0.60**0.22 -0.12 -0.34** .0&l**< 0.05; p < 0.01.tSample sixes: direct va lidation criteria (men, II = 28; women, n = 50; all n = 78).Indirect validation criteria (men. n = 27: women. n = 49: all, n = 76).$PA =physical activity. \

each activity by multiplying the MET level xduration in minu tes per event. Forty-eight hourMET-mm scores also were summed for leisure-time physical activities according to intensitylevels (light, ~4 METS; moderate, 4.5-5.5METS; heavy, 26.0 METS) as well as by ac-tivity types listed on the PAI-CA Q (e.g. Sightsof stairs climbed, walking, and sports and rec-reational activities), m ultiplied by 3.5 (to obtainweekly MET-min scores) and were presentedin MET -rninwk- Physical activity recordsobtained at clinic visits 2, 3, 8, 9, 12, and 13were averaged to compu te leisure-time physical

activity scores by intensity and thus reflectseason al variability in physical activity habits.Physical activity records obtained at clinic visits2, 8, and 9 were averaged to compute PhysicalActivity Index scores (PAI-PAR) and thusreflected visit-specific validation criteria for theCollege Alumnu s Qu estionnaire scores. Sincethe physical activity records were not kept bysubjects at the pre-study orientation visit (visit1) when the first College Alumnu s Question-naire was completed , physical activity recordsfrom visit 2, completed 28 days later, were usedto compare the visit 1 PAI-CAQ scores.

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Physical Activity Questionnaires 1407Caltrac Accelerometer The Caltrac Ac-celerometer wa s used to provide a direct, objec-tive measu remen t of daily energy expenditure

[19]. Caltrac 24-hour scores were reported bothin kcal, which factors in the metabo lic data ofheight, weight, age, and sex (Caltrac,_,), andMETS, which is independent of metabolic data(CaltracM,). The Caltrac,,, score was com-puted by dividing each participants Caltrac,,score by their estimate d resting metabolic rateas described elsewhere [4]. Caltrac,,, and Cal-tracMETs cores were averaged over all 14 studyvisits to represent a measu re of daily physicalactivity during the study year and thereby reflectseason al variability in physical activity habits.Ind irect val idat ion cr i ter ia

Card iorespiratory f i tness Cardiorespiratoryfitness was assessed by direct measurementof peak or symptom -limited oxygen uptake(VoZpll;) using a Beckman Metabolic Measure-ment Cart during a treadmill g raded exercisetest developed for the SAFE study. The tread-mill test protocol begins at 3 m.p.h. and 0%grade and progressively increases in grade orspeed at an energy cost of approxima tely 1MET per stage. The test protocol and pro-cedures used to determine IoZ, are describedin detail elsewh ere [4]. vole,, values presentedhere are the average of three measurements(clinic visits 2, 3, 13).

Body composi t ion Body density wasmeasured by hydrostatic weighing [20] and con-verted to percent body fat by the Siri equation[21] at clinic visit 1. Residual lung volume usedin the determination was measured by the closedcircuit oxygen dilution method of Wilm ore [22 ].Data analyses

Means and standard deviations were calcu-lated for the validation realms and the PAI-CAQ data for men and women. Skewed datafrom the PAI-CAQ and physical activityrecords were normalized using decimal logarith-mic transforma tions. Before taking logarithm s,1.0 was added to each value to account for thechance of having zero values for some variables.Average PAI-CAQ results from the three clinicvisits previously described were used in thevalidation analyses. The average PAI-CAQscore also was compared with average physicalactivity records data from visits 2, 8, and 9 .Validity wa s investigated using sex-specific, age-adjusted linear regression analysis to identifythe amou nt of variability (r2) in the validation

realms explained by the log PAI-CA Q and itscompo nent parts (flights of stairs climbed, cityblocks walked, and sports and recreational ac-tivities). Correlation coefficients were compu tedby taking the square root of the r 2 obtainedfrom the regression an alyses. Short-term (clinicvisits 8 and 9) and long-term (clinic visits 1 and8 and clinic visits 1 and 9) reproducibility of thelog PAI-CA Q scores were determined usingPearson product-mo ment correlation analysisadjusted for age in men and women. Data wereanalyzed using SAS statistical software (SASInstitute, Cary, NC).

RESULT 3wea ns f standa rd deviations for the vali-dation realm measures were: cardiorespiratoryfitness (V,, pul; 35.6 &-9.6 mlkg-amin-),body fatness (%fat = 27.5 & 9.6), motion detec-tion (Caltrac,, = 2,225 f 449 kcald-; Cal-trac,, = 1.29 f 0.10); physical activity recordleisure-time physical activity scores (total =471 f 222 MET-mind; heavy intensity =113 f 122 MET-mind; moderate intensity =41 + 37 MET-mined-; light intensity = 75 &-43MET-mind). Non-occupational leisure-timephysical activity energy expenditure averagedacross 6 physical ac tivity records wa s1915 f 260 MET-mind- for the study sample.Age-and sex-adjusted data for the validationcriteria were presented elsewhere [3].

Analysis of the Physical Activity Index scorefrom physical activity records showed the PAI-PAR represented about 20% of the total dailynon-occ upational energy expenditure (379MET-mind/1915 + 260 MET-mined-). Sex-specific means and standard deviations for thePAI-CA Q and its component parts and thephysical activity records are presented inTable 1. PAI-CAQ scores were generally higherat the first clinic visit as comp ared to clinic visits8 and 9. Scores also were generally higher inmen as compared to women. In comparison tothe physical activity records at each clinic visit,walking and stair climbing appeared to be un-derestimated by the College Alumnus Question-naire in both m en and women. The sports andrecreation scores also were significantly low eron the College Alumnus Questionnaire as com-pared to the physical activity records. Thisresulted in significantly lower Physical ActivityIndex obtained from the College AlumnusQuestionnaire as compared to the physical ac-tivity records.

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1408 BARBARA NSWORTH et al.

Table 2 shows the correlations between thePAI-CA Q and its component parts and thedirect and indirect validation realm data. Stat-istically significant correlation coefficients wereobserved between like categories from theCollege Alumnu s Questionnaire and physicalactivity records for all categories except sportsand recreation in men, and city blocks w alk-ing in women. In men, the Physical ActivityIndex from the College Alumnus Question-naire also was significantly correlated withthe direct validation measu res of total-andheavy-intensity leisure-time physical activityand the indirect validation measu re of Vo,,. Inwom en, the Physical Activity Index from theCollege Alumnus Questionnaire also was sig-nificantly correlated with the direct validationmeasures of city blocks walked, sports andrecreation activities, total-and heavy-intensityleisure-time physical activity from the physi-cal activity records, and the indirect validationmeasures of Vozw and percent body fat scores.The sports and recreation scores from the Col-lege Alumnu s Questionnaire were significantlycorrelated with the physical activity recordsheavy-intensity physical activity and Vo2pal; nmen and women. The majority of other corre-lations between the PAI-CAQ and its com-ponent parts and the validation realms were loworder and non-significant.Table 3 presents the age-adjusted correlationcoefficients for the short-and long-term repro-ducibility of the PAI-CAQ and its componentparts. Short-term reproducibility ranged fromr 0.31 to 0.88. Long-term reproducibilityranged from r 0.01 to 0.63 for repeat admin-istrations of the questionnaire 8 and 9 monthsapart.

DISCUSSIONThe results presented here sugge st that theCollege Alumnu s Questionnaire Physical Ac-tivity Index is a moderately good instrum ent forclassifying people for habitual activity statusand that the instrument has acceptable short-term repeatability.These results are consistent with earlier vali-dation studies that showed statistically signifi-cant associations among the PAI-CAQ andmeasu res of cardiorespiratory fitness [163recorded body motion [23], and body fatness

[24]. Other studies also show ed a significantcorrelation between the PAI-CAQ and highdensity lipoprotein cholesterol l 1 251. ThePAI-CA Q correlated best with validation

measu res that reflected participation in bothheavy-intensity and total leisure-time physica lactivity. In addition, as would be expected,significant correlations were found between likeactivities on the College Alumnus Questionnaireand the physical activity records. This suggeststhat the PAI-CA Q questionnaire items are re-called reasonably well and that they contributeto the validity of the PAI-CAQ as a measure ofoverall leisure-time physical activity energy ex-penditure.

Howeve r, su bjects tended to underestim atethe amount of walking and stairclimbing theyreported on the College Alumnus Question-naire. Weekly energy cost estimates for walkingon the College Alumn us Q uestionnaire wereabout one fifth of those obtained from thephysical activity records. The underestimationof walking may be related to the wording on theCollege Alumnu s Questionnaire which queriessubjects on the number of city blocks walked ina usual day . This wording may cause subjectsto think only about walk ing in the context ofcity blocks an d does not reflect the majority ofwalking each day which occurs in and aroundthe house and for transportation . Thus, clarifi-cation of the questionnaire items to ensure thatall walking is recalled would most likely reducethis under-representation.The Physical Activity Index scores from theCollege Alumnu s Q uestionnaire also werenearly two thirds lower than those recorded onthe physical activity records. Based on thephysical activity records, only 8% of the studyparticipants had a PAI-PAR score of less than2000 MET-minwk - This is in contrast to 41%of the participants who reported expending lessthan 2000 MET-minw k- on the College Alum-nus Questionnaire. Paffenbarger et al. [5] ob-served that a Physical Activity Index of 2000MET-minw k- appeared to be the optimal forassociation with reduced incidence of fatal andnon-fatal myocardial infarctions in male collegealumni. It is unknown if the participants in theCollege Alumnus Study also underestimatedtheir total amount of weekly walking a s ob-served in our SAFE study. If so, it is possiblethat the 2000 MET& inwk- estimate for opti-mal reduction of heart attack risk may actuallybe an undere stimation of energy expenditure.Even though the PAI-CAQ appears to bea reasonably valid and reproducible physicalactivity assessment tool for the activities in-cluded, the relatively low amo untof total dailyleisure energy expenditure accounted for by the

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ysical ActivityQuestionnaires 1409physical activity records (20%) should benoted. This is probably because the PAI-CAQdoes not assess activities of daily living orother non-sport and non-recreational activities.The PAI-CA Q also does not assess for occu-pational physical activity. These limitations,therefore, appea r to result in a gross under-estimation of total daily physical activity. T hus,to account for a larger perce nt of habitu aldaily physical activity, addition al question-naire items would be required, particularly toidentify occupa tional, househo ld, child care,activities of daily living, inactivity, and othernon-structured physical activities, which con-tribute substantia lly to ones total daily energyexpenditure.The Physical Activity Index from the CollegeAlumn us Questionnaire yielded consistent re-sults when administered over one months time,however, recall over 8 and 9 months was lessaccurate. These findings are in agreement withprevious stu dies that show good repeatability ofthe PAI-CA Q over a l-month period [6], but arein disagreement with those that show goodrepeatability over a l-year period [6 ,23]. Therelatively low test-retest correlation over the 8and 9 month periods in our SAFE study (e.g.January to August an d September) may reflectseason al differences in physical activity for thiscohort residing in Minnesota as well as vari-ability in physical activity ha bits over time. Itis also possible tha t inaccu rate recall of physi-cal activity habits over time or that statisticalregression to the mean of the PAI-CA Q scoresfrom visit 1 to visits 8 and 9 may have biasedthe long-term test-retest correlation coefficientsobserved in this study toward the null.Although our SAFE Study provides the mostcomprehensive evaluation of the College Alum-nus Questionnaire to date, it has limitationsspecific to the methodology used and popu-lation studied. First, the College Alumnus Ques-tionnaire was mailed to each participants homeand returned by them to the clinic withouteditorial checking by the clinic staff. As pre-viously mentioned, this approach was used toreplicate the procedure used by Paffenbargeret al. [Sl. It is quite conceivable that errors in theway the subjects interpreted the College Alum-nus Questio nnaire or recorded the informationmay have introduced errors into the results inthis, as well as in the College A lumnus Study.However, if so, the error is probably minim alsince the results of the PAI-CA Q were fairlyconsistent from one adm inistration to the next.

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1410 B~ARA E. INSWORTHt al.Second, the weekly energy expenditure score forthe sports and recreation activities from thephysical activity records at each visit was esti-mated from the 48-hour MET-min score. Sincethe frequency of participation during the weekwhen the physical activity records were recordedand the weeks of participation for the activitiesduring the past year were unknown, the activi-ties were scored as if they were performed dailywithout adjustment for participation habits inthe past year. This may have resulted in a slightoverestimation of the energy expended in sportsand recreational activities on the physical ac-tivity records. Third, the samp le consisted of avolunteer cohort of participa nts who were Cau -casian, college educated, urban dwellers, non-smoke rs, and worked in professional, clinical, orother white-collar occupa tions. Furthermo re,two-thirds of the study subjects were women. Itis unknown how these demographic factors mayhave influenced the results of this study and thusour results require replication in other popu-lations.

In summary, the simultaneous evaluation ofthe College Alumnu s Questionnaire with direct-and indirect measu res of physical activity sho wsthis instrument to be a valid and reliable physi-cal activity assessm ent tool. However, energyexpenditure in walking and stair climbing activi-ties appears to be underestimated by the currentinstrument, resulting in a lower PAI-CAQ scorethan computed from similar activities on physi-cal activity records. Rew ording of some ques-tionnaire items may be useful to ensure ac curaterecall of all activities in future revisions of theCollege Alumnus Questionnaire.Acknowledgements-This project was supported y fundingby a National Heart, Lung, and Blood Institute grant,lROl-HL37354, awarded to Drs Leon and Jacobs. The datain this paper were used for a MPH thesis from the Divisionof Epidemiology, School of Public Health, University ofMinnesota by Dr Ainsworth. We would like to thank M.Carl McNally, Yvonne Guptil, and Terry1 Hartma n fortheir help in the data collection phase of this study.

REFERENCESAinsworth BE, McNa lly MC, Richardson M, RutlinM, Cook T, Jacobs DR Jr, Serfass RC, Leon AS.Validity of the Paffenbarger College Alumni PhysicalActivity Questionnaire. Med Sd Sparta Exert (Ab-stract) 1988 ; 20(2) Suppl.: S46.A&worth BE, Jacobs DR Jr, Leon AS. Validity ofAssessment of Physical Activity using the CollegeAlumnus Questionnaire.. Med Sd Sports Exer (Ab-stract) 1990, 22 2) Suppl.: S79.Jacobs DR Jr, Ainsworth BE, Hartmann TJ, LeonAS. Simultaneous evaluation of ten physical activityquestionnaires. Med d Sports Exert 1993 ; 25: 81-91.

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