influence of exercise adherence level on modifiable coronary heart

Br J Sp Med 1993; 27(2)

Influence of exercise adherence level on modifiablecoronary heart disease risk factors andfunctional-fitness levels in middle-aged men

E. S. Wallace PhD, J. A. White PhD*, A. Downie FFOMt, G. Dalzell MDt and D. DoranBA§Department of Sport and Leisure Studies and NIBEC, University of Ulster, County Antrim, Northern Ireland,UK, *Department of Public Health Medicine and Epidemiology, University Hospital, Queen's Medical Centre,Nottingham, UK, tOccupational Health, Safety, and Environmental Services, Northern Telecom EuropeLimited, London, UK, tRegional Medical Cardiology Centre, Royal Victoria Hospital, Belfast, Northern Ireland,UK and §Physical Education Centre, Queen's University, Belfast, Northern Ireland, UK

The study investigated the potential health benefits of twolevels of short-term exercise intervention, compared withnon-intervention, on selected modifiable coronary heartdisease (CHD) risk factors and functional fitness states inmiddle-aged men. All subjects underwent medical screen-ing and signed informed consent before carrying out astandardized graded treadmill walk which requiredexercise up to 85% of age-predicted maximal heart rate.The results of the test were used together with musculo-skeletal fitness assessments, for the prescription of apersonalized exercise programme lasting 14 weeks. In all,55 subjects were classified by adherence into high (HA, n= 20), low (LA, n = 19), or non-adherence (NA, n = 16)groups according to the degree of documented participa-tion in the programme based on standard criteria(American College of Sports Medicine 1978, 1990). Inaddition, the respective groups of subjects were classifiedaccording to other modifiable and non-modifiable CHDrisk factors and compared by self-reported levels ofactivity and sport involvement as well as perceived bodyweight classification. The results indicated that there weremore comprehensive improvements in functional fitnessincluding significant gains in aerobic endurance capacity,muscular endurance and flexibility in the HA groupcompared with the LA and NA groups. However, therewas little or no change in the modifiable CHD risk factorsin any of the respective groups, although anthropometricindices of weight, body mass index (BMI), skinfolds andwaist:hips ratio tended to decrease in the HA and LAgroups but increased marginally in the NA group. Restingsystolic blood pressures declined slightly in all groups,but serum total cholesterol remained unchanged irrespec-tive of adherence level. The findings suggest that whilefunctional fitness status gains may arise from optimaladherence level to short-term exercise conditioning, theseare not matched by health gains in terms of ameliorationof modifiable CHD risk factors. However, the level ofadherence may be related to the recognized presence ofother known CHD risk factors.Keywords: Exercise adherence, CHD risk factors, fitness,middle-aged men

Address for correspondence: Dr E. S. Wallace, Department ofSport and Leisure Studies and NIBEC, University of Ulster,County Antrim BT37 OQB, Northern Ireland, UK

(E) 1993 Butterworth-Heinemann Ltd0306-3674/93/020101-06

The benefits of regular physical activity in thepromotion of health-related fitness and the ameliora-tion of coronary heart disease (CHD) risk factors hasreceived much attention recently with a consensus ofagreement among investigators concerning its im-portance. A meta-analysis of studies concerning CHDand physical activity' suggested that the literaturesupported the inference that physical activity isinversely and causally related to the incidence ofCHD. Furthermore, the study concluded that therelative risk of inactivity as a factor in the develop-ment of CHD appears to be of similar magnitude tothat of hypertension, hypercholesterolaemia andsmoking. Therefore it was suggested that in preven-tive health programmes designed to ameliorate CHDrisk, regular physical activity should receive the sameattention as other modifiable risk factor managementtechniques, such as the control of blood pressure,reduction of serum cholesterol and the elimination ofsmoking.The benefits of exercise amelioration of modifiable

CHD risk factors such as reductions in blood pressureand cholesterol levels have been widely reported inthe literature2. The reduction of resting bloodpressure after a single bout of exercise in both normaland hypertensive patients3, together with the reduc-tion in submaximal exercise systolic blood pressureafter exercise training4'5 suggest that exercise-induced effects of blood pressure regulation maycontribute towards a reduction in CHD risk bylowering of blood pressure levels2. Thus, exercisemay serve as a preventive modality in the ameliora-tion of the age-dependent rise in blood pressure aswell as exerting its effects through a reducedfrequency of arterial hypertension development6'7.The influence of physical activity in the modifica-

tion of blood lipid profiles as a potential for CHD riskfactor reduction has also been acknowledged8.Various types of exercise regimens including long-term, low-level activity9, as well as shorter-termaerobic programmes'0 and resistive exercise/circuitweight training routines1' have been reported toinfluence blood lipid levels favourably. However, theinfluence of body weight loss and dietary changes is

Br J Sp Med 1993; 27(2) 101

Exercise adherence, CHD risk factors and fitness in men: E. S. Wallace et al.

thought likely to contribute to the beneficial effectsobserved in lipid profile modification and subsequentimprovement in CHD risk status2.The population of Northern Ireland has not shared

the recent successes of North America, Australia andseveral European countries in the reduction of theincidence of CHD over the last t'wo decades12. One ofthe reasons postulated to account for this significantdecrease in the levels of CHD in these countries is theconcomitant increase in habitual levels of physicalactivity and associated positive health behaviour. Atleast part of this increased participation in regularphysical activity may be attributed to the enhancedpublic awareness of the relationship between healthand fitness and the provision for fitness programmesin the workplace 316. However, when the presentstudy was conducted there were no such operationalworkplace programmes in Northern Ireland. Further-more, there appeared to be a distinctly different socialattitude towards health and well-being, as well ascurrent practice, in terms of workplace provision ofcorporate health and wellness programmes byNorthern Ireland's employers"7, which together maylimit the potential effectiveness of such programmescompared with the other countries. Therefore, thepresent investigation was designed to determine theeffects of adherence levels to a supervised short-term,workplace exercise programme on selected modifi-able CHD risk factors and functional fitness levels in agroup of middle-aged men volunteers.

MethodsSubjectsIn all, 55 middle-aged men volunteers participated inthe study. The subjects were self-selected from themiddle and upper management levels of a multi-national telecommunications company located on theoutskirts of Belfast, Northern Ireland. The groupcomprised men of different socioeconomic status -social classes I and II professional and intermediate(OPCS). All subjects were screened initially byobtaining a medical history, a series of pulmonaryfunction tests and an examination by the companymedical officer. Written informed consent wasobtained from each subject before participation in theinvestigation.

ProceduresOn arrival at the laboratory, the subjects completed adetailed exercise history and current physical activityquestionnaire. A 32 RI fasting blood sample wasdrawn from the subject's finger to determine totalcholesterol level (Reflotron system, BoehringerMannheim, Lewes, UK), and resting blood pressurewas obtained by a trained nurse using standardauscultatory techniques. A range of anthropometricmeasurements was then taken, including height andweight, skinfold thicknesses and estimated body fatpercentage18, and body girth dimensions for determi-nation of waist to hips ratio. The subject then satwhile a standard V-5 electrocardiogram recordingwas obtained and blood pressures were subsequently

obtained before the start of the exercise test, whichwas conducted by an exercise physiologist with acardiologist in attendance. The usual range ofresuscitation equipment was available, including adefibrillator.The exercise test consisted of a walk on a treadmill

(P. K. Morgan, Chatham, UK) at a freely chosenspeed at zero grade for an appropriate period of timeto familiarize the subjects with the test requirements.This was followed by a modified Bruce protocol19which required the subject to walk at a fixed speed of5.65 km hr-1 at zero grade followed by an initialgradient increase of 5% with subsequent increases of2.5% with each incremental period of 3 min duration.The chosen endpoint of the test was 85% ofage-related maximal heart rate which was predeter-mined using a standardized method20. Exceptions tothis criterion were cases where subjects displayedirregular electrocardiogram (ECG) patterns, abnormalblood pressure responses, or chose voluntarily toterminate the test prematurely. ECG recordings(Cardiokinetics Life Trace 18, Cardiokinetics, Salford,UK) and blood pressure measurements (auscultatorytechniques) were obtained during the last 30 s of eachincremental exercise period. Total time for walking aswell as the incremental stage of the test terminationwere recorded as measures of endurance. Threeadditional specific physical fitness tests were thencompleted which were directed at musculoskeletalfunction, including grip strength, hip flexibility andabdominal endurance as outlined in the Eurofit testbattery2l. All subjects subsequently received a com-prehensive confidential personal report detailing thefindings from the various tests, along with aconsultation with the programme director, and thecompany's medical officer where necessary.

InterventionAfter initial assessment each subject was issued witha voluntary, individualized exercise prescriptionbased on their performance during the initial exercisetest. Unless otherwise contraindicated, each pro-gramme was designed to meet the criteria of theguidelines for aerobic conditioning22 and the subse-quent revision of these criteria23. A wide range ofactivities was offered including walking, running,bicycling, cycle-ergometry, rowing, simulated cross-country skiing and resistance training using amultigym fixed weight system. The subjects weresupervised closely during the 14-week period of theconditioning programme and were instructed torecord their exercise activities accurately in terms ofexercise mode, intensity, duration and frequency ofeach session.The data collected on activity participation permit-

ted subjects to be classified into groups depending ontheir level of adherence to the exercise programme.Adherence levels were determined using an equationdeveloped for determination of a total activitymetabolic index (AMI)24 where the overall AMI is:Total AMI = (Ix M x F xT)where I represents intensity coded in METS (restingmetabolic equivalent), M the number of months, F

102 Br J Sp Med 1993; 27(2)


the frequency per month, and T the duration of eachactivity or exercise session. The total AMI score isbelieved to be closely associated with total kilocalor-ies expended on leisure-time physical activity, a valueof particular relevance in weight control24, and thusexercise for health.Three discrete levels of physical activity were then

obtained, in terms of light, moderate, and heavy AMIwhich were equated with non-adherence (NA), lowadherence (LA), and high adherence (HA) levels inthe present study. The HA group demonstrated anactivity index which satisfied the American College ofSports Medicine (ACSM) criteria22 for aerobic condi-tioning. However, since the time of completion of thepresent study the ACSM revised and updated thecriteria for aerobic conditioning23. The implications ofthese revisions now indicate that the LA classificationconformed to the necessary levels prescribed tomaintain cardiorespiratory fitness22, while the HAgroup conformed to the level necessary both tomaintain and advance cardiorespiratory fitness23.After the 14-week conditioning period, subjectsunderwent the same battery of tests completed beforethe intervention programme. Thus data were avail-able for both pre- and post-intervention, whichpermitted an evaluation of the effects of participationin each adherence level category.

Data analysisAfter detailed analysis of the activity records thesubjects were divided among the three exerciseadherence level groups of NA, LA and HA for bothpre- and post-intervention analyses. The data ob-tained from the pre-intervention tests were analysedusing a one-way analysis of variance to determine ifany significant differences existed between the threecombinations of paired groupings before the in-tervention was applied. Similarly, this procedure was

Table 1. Physical characteristics of subjects within each exerciseadherence level group

Exercise Age Height Weight BMIadherence level (years) (cm) (kg) (kg m-2)

NA (n = 16) 42.7(8.9) 174.8(7.4) 79.0(14.8) 25.6(4.3)LA (n = 19) 37.6(9.7) 175.6(5.9) 76.5(8.8) 24.8(2.2)HA (n = 20) 41.3(10.7) 174.8(8.8) 80.1(9.4) 26.2(2.3)Total (n = 55) 40.4(7.0) 175.1(6.9) 78.5(11.43) 25.5(3.4)

Values are mean(s.d.)

applied to the post-intervention data to evaluateeffects of adherence level upon the variables underinvestigation. Each adherence level group data werefurther analysed using a repeated measures analysisof variance to determine within group differencesbefore and after the intervention period, with a posthoc Scheffe test applied to determine specific meandifferences contributing to significant F ratios identi-fied by the analysis of variance procedures.

ResultsThere were no significant differences in mean age,height and weight at the initiation of the exerciseprogramme in the respective exercise adherence levelgroups (Table 1). However, the LA group tended to beslightly younger and taller but lower in body weightand body mass index (BMI), compared with the NAand HA groups.The coronary risk profile of each adherence level

group indicated that there was a relatively evenmatch among groups in terms of CHD risk factors,with the notable exceptions of history of heart diseasein the family and elevated total serum cholesterol,both of which were seen to be more frequent in theHA group (Table 2). Nevertheless, there were nocontraindications to exercise programming displayedby individual members of the respective adherencelevel groups.The initial subjective estimates by each exercise

adherence level group in terms of reported exerciseand physical activity (EPA) profiles, present physicalfitness levels, and perceived versus actual bodyweight classifications revealed several interestinganomalies (Table 3). While the respective groups werereasonably well matched in terms of 'sedentary' and'moderately active' representations, few subjectsconsidered themselves to be 'active' or 'highly active'- categories commensurate with minimal levelsnecessary for maintaining22 or enhancing23 aerobicfitness status. Furthermore, in the NA group physicalfitness perceptions were at variance with the reportedEPA profiles, whereby the majority of subjectsconsidered themselves to be 'moderately active',while the distribution between 'very unfit' and'moderately fit' was even. In the HA and LA groupsthere was a sequential rise in the 'moderately fit' to'unfit' ratio, respectively, and the self-reportedfitness level profiles closely matched the EPAperceptions. However, none of the subjects in anygroup regarded themselves as 'trained', although the

Table 2. Coronary risk profiles of the respective exercise adherence level groups

Exercise adherence CHD diag CHD family CHD death Rheum fever Abn ECG Hypertensive Hypercholes Smoke >35 yearslevel (n) (n) (n) (n) (n) (n) (n) (n) (n)

NA(n =16) 1 6 3 1 0 2 9 3 10LA(n =19) 1 4 5 1 0 0 6 2 9HA (n =20) 1 13 6 1 1 3 13 2 13Total(n = 55) 3 23 14 3 1 5 28 7 32

n, number; CHD diag, coronary heart disease previously diagnosed; CHD family, history of coronary heart disease in immediate family;CHD death, premature death in immediate family due to coronary heart disease; Rheum fever, previously had rheumatic fever; Abn ECG,abnormal electrocardiogram previously diagnosed; Hypercholes, hypercholesterolaemia; smoke, regular cigarette smoker

Br J Sp Med 1993; 27(2) 103


Table 3. Reported levels of physical activity, physical fitness and body weight perceptions of the respective exercise adherence level groups

Exercise adherence Present level activity Present level fitnesslevel

Sedentary Moderately Active Highly Very Moderately Trained Highlyactive active unfit fit trained

NA (n =16) 5 11 0 0 8 8 0 0LA(n= 19) 4 14 1 0 4 15 0 0HA (n= 20) 5 12 3 0 7 13 0 0

Total 14 37 4 0 19 36 0 0

Exercise adherence Exercise habits Perceived body weight Classification25level overweight

Involved Involved Under Ideal Slightly Very (actual)in exercise in regular weight weight overweight overweightprogramme sport

NA (n =16) 1 6 1 5 8 2 8LA (n =19) 6 12 0 7 10 2 13HA (n =20) 2 7 1 3 14 2 15

Total 9 25 2 15 32 6 36

LA group indicated involvement in exercise andregular sports participation more frequently thaneither the NA or HA groups. Finally, in terms ofperceived body weight classifications, few consideredthemselves 'underweight', while the distribution of'overweight' was similar and the numbers consideredto be 'ideal weight' formed a minority across therespective groups. However, a majority of subjectswithin each respective group considered themselvesto be 'slightly overweight', which correspondedclosely with those classified over 10% ideal bodyweight".

In general the results observed among the threelevels of adherence to the 14-week aerobic condition-ing programme indicated selective improvements insome functional fitness variables with little or nochange in the modifiable CHD risk factors (Table 4). Inthe respective LA and HA groups there weresignificant increases of 13% and 43% in treadmillexercise times (both P < 0.001) and concomitantly,7% and 13% in the number of treadmill stagescompleted (both P < 0.05), but no significant changein either measure in the NA group. Furthermore, atthe pre-programme test the LA group had significantly

Table 4. The influence of exercise adherence level to aerobic conditioning on modifiable CHD risk factors and functional fitness levels

Variables Groups

NA (n =16) LA (n =19) HA n =20)Pre Post Pre Post Pre Post

TM time (min) 13.6(2.4) 14.0(2.7) 14.6(4.3) 16.5(4.3) 10.9(3.4) 15.9(3.3)

TM stage (No.) 4.6(0.7) 4.5(1.6) 4.6(1.0) 5.1(1.1) 3.7(1.1) 5.0(1.0)

HR (beats min-) 165.0(6.0) 166.0(8.0) 165.0(10.0) 166.0(12.0) 162.0(13.0) 164.0(13.0)Syst BP (mmHg) 129.0(14.7) 123.0(16.3) 120.0(10.9) 118.0(11.6) 125.0(18.6) 123.0(12.2)Diast BP (mmHg) 76.2(9.7) 78.3(9.5) 71.7(7.8) 72.5(8.1) 76.7(12.0) 77.2(8.6)Weight (kg) 79.0(14.8) 79.4(14.4) 76.5(8.8) 75.8(8.5) 80.2(9.4) 79.0(9.5)BMI (kgm2) 25.6(4.3) 25.7(4.3) 24.8(2.2) 24.4(1.9) 26.2(2.3) 25.9(2.0)X4 Skinfolds (mm) 49.6(16.4) 52.1(16.7) 44.6(15.0) 43.0(10.7) 45.7(12.4) 43.9(9.2)Estimated body fat (%) 22.9(4.7) 23.2(4.6) 20.7(4.5) 20.6(4.2) 21.3(4.2) 20.9(4.2)Waist: hips ratio 90.1(5.8) 91.5(5.7) 91.1(5.0) 90.6(4.4) 92.1(4.7) 90.7(4.3)Cholesterol (mmol 1-1) 5.86(1.51) 5.89(1.68) 5.03(1.36) 5.15(1.04) 5.58(1.31) 5.51(1.33)Grip strength (kg) 52.9(6.8) 52.8(6.3) 52.7(8.5) 52.6(7.10) 54.3(6.70) 52.7(6.10)

Abdominal endurance * t *(No. per 30s) 16.7(4.9) 21.2(5.3) 18.7(4.0) 22.9(4.70) 17.3(3.5) 22.7(6.0)

Flexibility (cm) 7.7(4.8) 7.2(5.4) 5.7(6.8) 5.6(6.9) 6.9(4.8) 8.6(6.1)

Syst BP, systolic blood pressure; Diast BP, diastolic blood pressureSignificance levels: *P < 0.05; tP < 0.01; tP < 0.001Values are mean(s.d.)

104 Br J Sp Med 1993; 27(2)


longer treadmill exercise times and number oftreadmill stages completed (both P < 0.005) than theHA group. However, while there were marginalpost-programme decreases in end exercise heart ratesand resting systolic and diastolic blood pressures inall three adherence level groups, these were notsignificant.

Similarly there were no significant anthropometricchanges among the three levels of exercise adherenceafter the conditioning programme, although therewas a trend towards a slight decrease in body weight,body mass index, sum of four skinfolds, estimatedbody fat percentage and waist:hips ratio in the LAand HA groups, which contrasted with the marginalincrease in these measures in the NA group.However, serum total cholesterol levels remainedunchanged over the duration of the study. Finally,significant improvements in abdominal endurancewere observed in the NA group (22%, P < 0.05) andin the respective LA and HA groups (22% and 31%,both P < 0.01) as well as an increase in flexibility inthe HA group (24%, P < 0.05), but no significantchange in grip strength in any group after theintervention programme.

DiscussionThe present study investigated the responses ofselected modifiable CHD risk factors, and functionalfitness levels to a short-term (14-week) aerobicconditioning programme in relation to three levels ofadherence by middle-aged men. The results sug-gested that in comparison with non-adherence (NA)and low adherence (LA), high adherence (HA) to astandard set of physical activity guidelines23 led to amore comprehensive improvement in a range offunctional abilities including aerobic endurance,muscular endurance and flexibility. However, interms of modifiable CHD risk factor status, whilethere were trends towards systolic blood pressureand body weight reductions associated with LA andHA, there was no evidence to suggest changes inserum total cholesterol levels regardless of the level ofadherence.Enhanced aerobic endurance capacity was evi-

denced by significant increases in treadmill exercisetimes and the number of exercise stages completed bythe LA and HA groups with the latter recording thelargest improvement in both parameters after theconditioning programme. These findings are inagreement with increased endurance capacity ob-served in a similar population group who partici-pated in an exercise programme using similarguidelines14. Furthermore, the increases in treadmillexercise performances by the LA and HA groupswere accompanied by marginal but non-significantincreases in end exercise heart rates which suggestedan improvement in exercise tolerance of the respec-tive groups of subjects.The changes in anthropometric dimensions in

general reflected the levels of adherence to theconditioning programme. Body weight changesshowed a significant reduction in the HA group, a

non-significant trend towards a reduction in the LAgroup, but little or no change in the NA groups overthe 14-week period. These relatively modest bodyweight decreases of 2.4% and 2.0% in the HA and LAgroups, respectively, were similar to those docu-mented in previous studies14'26. However, eventhough body weight decreased most profoundly inthe HA group, which exercised above the minimalstandard guidelines23, the weight reduction observedmay have been assisted by other factors such asdietary modification which was not assessed. Fur-thermore, the small but non-significant reduction inBMI noted in all groups was not accompanied by anydiscernible changes in the estimated percentage ofbody fat, which suggested that no change occurred inbody composition in the respective groups.

In each of the three adherence level groups restingsystolic blood pressure showed a tendency toward asmall but non-significant reduction after the condi-tioning programme, while resting diastolic bloodpressure remained relatively unchanged. However, itwas considered unlikely that normotensive subjectssuch as those in the present study would benefit fromexercise conditioning related blood pressure reduc-tions observed in subjects with mild or borderlinehypertension2728. Serum total cholesterol levelsremained relatively unaffected by the conditioningprogramme regardless of the level of exerciseadherence. This suggested that, unlike other studiesof longer duration, which have demonstrated signifi-cant reductions in cholesterol24'29 the duration of 14weeks used in the present study was insufficient tomodify total cholesterol levels. This conclusion issupported by the findings of other studies usingexercise programmes of similar duration which failedto demonstrate significant changes in cholesterollevel26'30 31. It has been suggested, therefore, thatexercise alone has little effect on total cholesterollevel31, although significant changes in other CHDrisk factor lipid fractions e.g. high density lipoprotein(HDL): low density lipoprotein (LDL) cholesterolratio may occur after exercise training withoutalteration in total cholesterol level".An evaluation of the initial coronary risk profile of

the respective exercise adherence level groups (Table2) indicated that the HA group had a relatively higherincidence of family CHD along with elevated serumtotal cholesterol level than the NA and LA groups.The presence of these factors therefore may haveinfluenced the exercise participation level by the HAgroup given the recent publicity concerning theprevalance of CHD risk factors in Northern Irelandand its status as world leader in premature mortalityfrom CHD12. Indeed, it has been suggested thatwillingness to take part in, along with type andamount of exercise performed, as well as adherencelevel to such programmes may be related to thepresence of one or more CHD risk factors29.However, the level of adherence to the conditioningprogramme in the present study did not appear to berelated to the subjective perceptions of level ofactivity, fitness status or personal body weightcharacteristics (Table 3), but may have been influ-enced by the involvement in similar programmes,other sport activities and the relatively overweight

Br J Sp Med 1993; 27(2) 105


levels demonstrated by the LA and HA groups (Table3).

In conclusion, the findings of the present investiga-tion suggested that differences in exercise adherencelevel to a short-term (14-week) conditioning pro-gramme may selectively influence specific functionlevels of fitness and modifiable CHD risk factors.Furthermore, the results indicated that adherence tothe minimum level of exercise suggested by standardguidelines23 produced fewer positive improvementsin low adherence compared with high adherence,while the isolated change noted in non-adherence,for example improved muscular endurance, mayhave been attributable to habituation effects alone.Nevertheless, it was evident that the relatively shortduration of the conditioning programme utilized bythe present study produced relatively fewer benefi-cial effects when compared with similar programmesof longer duration. However, the reduced benefits ofshort-duration conditioning programmes must be setagainst the problems of adherence, maintenance, anddrop-out rate associated with more prolonged time-scales.

AcknowledgementsA special thanks is extended to all the subjects from NorthernTelecom Europe, Monkstoun, Northern Ireland who volunteeredto participate in this study.

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