Maximal Graded Exercise Test Protocol Preferences of Relatively Fit ...

MEASUREMENT IN PHYSICAL EDUCATION AND EXERCISE SCIENCE, 5(1), 1–12 Copyright © 2001, Lawrence Erlbaum Associates, Inc.

Maximal Graded Exercise Test Protocol Preferences of Relatively Fit College Students Michael B. Spackman, James D. George, Todd R. Pennington, and Gilbert W. Fellingham Departments of Physical Education Department of Statistics Brigham Young University

This study was designed to compare the standardized Bruce protocol (Bruce, Kusumi, & Hosmer, 1973) with the Arizona State University (ASU; George, 1996) protocol to determine whether or not the ASU protocol is preferred while providing a relatively accurate, valid, and individualized format for maximal exercise testing in college stu& dents. Using indirect calorimetry, maximum oxygen consumption (VO 2 max ) was measured in 32 physically active college students (16 men, 16 women; age 21.1 ± 2.5 years) using the Bruce and ASU protocols in a random order. After completing both protocols in 3 to 6 days, participants were asked to rate their experience or satisfaction with each protocol, and also whether or not the grade and speed of the protocol were & tailored to their individual abilities. VO 2 max predictions were generated from the –1 · min–1) and ASU (45.33 ± 7.26 ml · kg–1 · min–1) regresBruce (43.12 ± 7.56 ml · kg sion models, respectively. No significant difference was found between the measured & and predicted VO 2 max means for both the Bruce and ASU protocols. Cross-validation & analyses comparing measured versus predicted VO 2 max values yielded similar results –1 · min–1, total error = 3.72 ml · kg–1 · min–1; ASU: r = (Bruce: r = .91, SEE = 3.61 ml · kg .91, SEE = 3.13 ml · kg–1 · min–1, total error = 3.15 ml · kg–1 · min–1). In terms of overall satisfaction, 93.8% of participants preferred taking the ASU protocol over the Bruce protocol. Our results suggest that the ASU protocol provides a maximal treadmill graded exercise test for college students that is individualized, time efficient, and rela& tively accurate in estimating VO 2 max . Key words: aerobic power, cardiorespiratory fitness evaluation

Requests for reprints should be sent to James D. George, Department of Physical Education, 105 Richards Building, Brigham Young University, Provo, UT 84602. E-mail: [email protected]

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The most accepted measurement of cardiorespiratory fitness (CRF) is the direct & measurement of maximum oxygen uptake (VO 2 max ) or aerobic power (American College of Sport Medicine [ACSM], 2000). Although direct measurement of & VO 2 max is the most accurate method to assess aerobic capacity, in the majority of clinical or laboratory settings the protocol is inconvenient. Consequently, CRF is usually estimated by prediction equations derived from various nondirect measure& ment protocols. A variety of VO 2 max prediction protocols are available, involving both maximal or submaximal exercise. To date, commonly employed protocols include bench stepping (Jette, Campbell, Mongeon, & Routhier, 1976; Johnson & Seigel, 1981; Metz & Alexander, 1971), cycle ergometry (Astrand & Ryhming, 1954; Fox, 1973; Kasch, 1984; Mastropaolo, 1970; Siconolfi, Cullinane, Carleton, & Thompson, 1982), treadmill walking or jogging (Bonen, Heyward, Cureton, Boileau, & Massey, 1979; Ebbeling, Ward, Duleo, Widrick, & Rippe, 1991; George, Vehrs, Allsen, Fellingham, & Fisher, 1993a; Hermiston & Faulkner, 1971; Kasch, 1984; Metz & Alexander, 1971), and track walking or running (Cooper, 1968; Doolittle & Bigbee, 1968; George, Vehrs, Allsen, Fellingham, & Fisher, 1993b; Heil, Freedson, Ahlquist, Price, & Rippe, 1995; Kline et al., 1987; Ribisl & Kacadorian, 1969). Other predictions of aerobic capacity include regression equations utilizing nonexercise models (Ainsworth, Richardson, Jacobs, & Leon, 1992; Fenster, Kennedy, Dematos, Smith, & Dalsky, 1993; George, Stone, & Burkett, 1997; Heil et al., 1995; Jackson et al., 1990; Williford et al., 1996). Although submaximal testing and nonexercise models are convenient, models that provide maximal exercise data are the most accurate predictors of aerobic power (Bruce, Kusumi, & Hosmer, 1973; Geroge, 1996; Storer, Davis, & Caiozzo, 1990). The Bruce et al. (1973) maximal treadmill graded exercise test (GXT) is popular in clinical or laboratory settings (ACSM, 2000; McInnis & Balady, 1994). The Bruce protocol, also demonstrates high predictive accuracy (R = .92, standard error of estimation [SEE] = 3.1 ml · kg–1 · min–1), is time efficient, uses walking or jogging, which is common and familiar to many people, and permits evaluation across a broad population ranging in fitness from active and athletic to sedentary, and ranging in health from cardiac patients to healthy participants. Despite the advantages, some participants may find the Bruce protocol not individualized to their own capabilities. Often, the initial workload is too high and the stages too abrupt to provide a protocol that is individually tailored or participant-friendly. Researchers have found (Foster et al., 1996; George, 1996; Myers et al., 1992) that smaller changes in speed and grade make maximal GXTs less abrupt for participants. Guidelines by the ACSM (2000) indicated the need for an individualized protocol where the treadmill speed is based on the capabilities of the participant. To provide a more participant-friendly protocol, yet still require maximal exercise output, recent attempts have been made to create alternatives to the Bruce protocol (Foster et al., 1996; George, 1996). As a follow-up to the George (1996) & study and in an attempt to improve VO 2 max prediction protocols that utilize maxi-

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mal treadmill exercise, in this study the maximal treadmill protocol developed at Arizona State University (ASU protocol) was compared with the Bruce protocol. Preferences for the ASU protocol or the Bruce protocol were examined for maximal exercise testing in college students.

METHODS Participants Physically active college students (N = 34; 17 men, 17 women) between 18 and 29 years of age were recruited primarily from physical education classes at Brigham Young University. Participants with previous experience with a maximal GXT were not included in the study. Most participants (n = 32) were White undergraduates, who were reportedly nonsmokers (100%).

Procedures Prior to any testing, all participants signed an informed consent document approved by Brigham Young University’s Institutional Review Board and also completed a Physical Activity Readiness Questionnaire (PAR–Q) to screen for cardiovascular contraindications. Participants were also instructed to (a) wear comfortable, loose-fitting clothing consistent with testing; (b) drink plenty of fluids over the 24-hr period preceding the test; (c) avoid food, tobacco, alcohol, and caffeine for at least 3 hr before testing; (d) avoid exercise and strenuous physical activity the day of the tests; and (e) get an adequate amount of sleep (6 to 8 hr) the night before the tests (ACSM, 2000). At the beginning of each test, participants reported to the lab dressed in light running clothes and shoes. Body mass and height were measured using a physician’s scale and stadiometer, with the participants’ shoes removed. Participants were informed of all exercise procedures and practiced walking or jogging on the treadmill using the one-way breathing apparatus. All participants performed the ASU protocol (Protocol A) and the Bruce protocol (Protocol B). The order of the maximal GXTs was randomized and participants took the tests 3 to 6 days apart. The Bruce protocol was performed according to Bruce et al. (1973) while the ASU protocol was performed according to the following procedures outlined in George (1996). For the initial 3-min stage of the GXT, participants walked up a 5% grade at a self-selected brisk pace. For the second 3-min stage, participants either continued walking at the same speed and 5% grade or self-selected a jogging pace and level grade. Participants indicated with hand signals when acceptable walking or jogging speeds were achieved. All participants (N = 34) elected to jog (range = 4.1

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miles · hr–1 to 6.7 miles · hr–1) after Stage 1. These two stages served as a 6-min warm-up. Following the first two stages, the treadmill grade was raised 1.5 % every minute with constant speed until the participant could no longer continue. Exercise heart rates [HRs] were constantly monitored using an electronic monitoring system (Polar CIC, Port Washington, NY). Expired gas volumes were quantified using a computerized metabolic machine (Marquette, St. Louis, MO). CO2 and VO2, as well as the respiratory exchange ratio (RER), were computed and printed every four breaths (Consentius Technologies, Salt Lake City, UT). The highest average full-minute oxygen uptake & measured during the test was accepted as the VO 2 max . VO2 values were considered maximal when two of the three following criteria were met (Kline et al., 1987): (a) RER equal to or greater than 1.1; (b) HR no less than 15 beats below the age predicted HRmax (220 – age); and (c) a leveling off of VO2 despite an increase in power output. Most participants (n = 32) met this standard; however, one female participant did not meet the standard and one male participant who was injured between tests was dropped from the study. Immediately after the completion of each protocol, participants were asked to declare their reason for termination, either whole body fatigue or leg fatigue. Ratings of perceived exertion (RPE; Borg, 1982) were recorded after every stage of the GXT. Three to six days after completing both protocols, participants completed a brief questionnaire indicating their preferred protocol. This questionnaire was administered by the physical education department secretary in a private nonlaboratory setting. Participants were asked to rate their experience or satisfaction with each protocol (labeled only as protocol A or B), and also whether or not the grade and speed of the protocols were tailored to their abilities and whether they experienced any posttest delayed-onset muscular soreness (DOMS). The questionnaire was completed several days posttesting so that the acute physical effects of either maximal GXT would not systematically bias the overall preference of the participant. Each question included a Likert response scale from 1 (low) to 7 (high). Participants were also asked to indicate which protocol of the two they would choose if they had to perform another maximal exercise test in 2 days. Data Analysis Comparison and cross-validation was made between the Bruce regression model & (VO 2 max = 6.70 – 2.82 [1 = male, 2 = female] + 0.056 [duration in sec]), and the & ASU regression model (VO 2 max = 4.702 + 2.674 [0 = female, 1 = male] – 0.0924 [body mass in kg] + 6.191 [speed in mph] + 1.311 [grade as fractional percent]). The cross-validation analyses included: repeated measures analysis of variance, paired t tests, Pearson product–moment correlation values (r), and the & –1 · min–1 of predicted percentage of measured VO 2 max values within ±4.5 ml· kg

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& –1 · min–1 is an arbitrary predetermined VO 2 max values. The value of ±4.5 ml · kg & range that represents acceptable VO predictions (Dolgener, Hensley, Marsh, 2 max & Fjelstul, 1994; Fenstermaker, Plowman, & Looney, 1992). Additionally, the SEE and total error were also determined for the cross-validation analyses. Questionnaire analyses included Likert scale mean comparisons using paired t tests. Statistical significance was set at p < .05. RESULTS The mean age, height, and body mass of the participants equaled 21.09 ± 2.52 years, 1.74 ± 0.10 m, and 71.58 ± 13.04 kg, respectively. Maximal exercise data for the total sample (N = 32) are presented in Table 1. No significant difference was found & between the measured and predicted VO 2 max means for both the Bruce and ASU protocols (Table 2). However, there was a significant difference (p < .04) between & –1 –1 the measured VO 2 max means of the Bruce (44.07 ± 8.9 ml · kg · min ) and ASU (45.02 ± 7.3 ml · kg–1 · min–1) protocols. Additionally, there was a significant difference in HRmax (192.2 ± 10.6 bpm vs. 194.7 ± 7.0 bpm; p = .0412), RPEmax (18.4 ± 0.8 vs. 19.4 ± 0.5; p < .0001), and RERmax (1.24 ± 0.08 vs. 1.17 ± 0.06; p < .0001). & When comparing measured versus predicted VO 2 max values (Table 2), the correlation for the Bruce protocol equaled .91, with SEE and total error values equaling 3.61 ml · kg–1 · min–1 and 3.72 ml · kg–1 · min–1, respectively. On the other hand, the correlation for the ASU protocol equaled .91, with SEE and total error values equaling 3.13 ml · kg–1 · min–1 and 3.15 ml · kg–1 · min–1, respectively. Presented in & Figure 1 and 2 are plots of predicted versus measured VO 2 max values using the Bruce and ASU regression models. In comparing preference data (Table 3), 53.1% of participants reported terminating the Bruce GXT because of leg fatigue, as opposed to whole body fatigue, TABLE 1 Maximal Exercise Data for the Bruce and Arizona State University (ASU) Protocols (N = 32) Variable Elapsed treadmill time (s) Elapsed treadmill time (min) Maximal treadmill speed (mph) Maximal treadmill grade (%) –1 · min–1) & Measured VO 2 max (ml · kg HRmax (beats · min–1) RPEmax (15-point scale) RERmax (VCO2/VO2)

Bruce Protocol

ASU Protocol

725.94 ± 117.50 12.09 ± 1.96 4.55 ± 0.55 16.94 ± 1.52 44.07 ± 8.91 192.22 ± 10.66 18.47 ± 0.88 1.24 ± 0.08

753.60 ± 106.20* 12.56 ± 1.77* 5.34 ± 0.70* 9.78 ± 2.64* 45.02 ± 7.37* 194.78 ± 7.05* 19.41 ± 0.50* 1.17 ± 0.06*

& Note. VO 2 max = maximum oxygen consumption; HR = exercise heart rate; RPE = rating of perceived exertion; RER = respiratory exchange ratio. *p < .05.

TABLE 2 & Cross-Validation of VO 2 max Regression Equations (N = 32) Variable

Bruce Model

ASU Model

–1 · min–1) & Measured VO 2 max (ml · kg & Predicted VO (ml · kg–1 · min–1)

44.07 ± 8.91

45.02 ± 7.37a

43.12 ± 7.56b .91 3.61 3.72 75.00

45.33 ± 7.26b .91 3.13 3.15 84.38

2 max

r SEE (ml · kg–1 · min–1) Total error (ml · kg–1 · min–1) Percentagec

& Note. ASU = Arizona State University; VO 2 max = maximum oxygen consumption; SEE = standard error of estimation. aSignificant difference between measured & VO2 max for Bruce and ASU protocols. bNo significant & & difference between measured and predicted VO . cPercentage of values within acceptable VO 2 max

range of ± 4.5 ml · kg–1 · min–1.

–1 · min–1) using the & FIGURE 1 Scattergram of observed versus predicted VO 2 max (ml · kg Bruce et al. (1973) prediction equation (line: y = x).

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2 max

–1 · min–1) using the & FIGURE 2 Scattergram of observed versus predicted VO 2 max (ml · kg George et al. (1996) prediction equation (line: y = x).

TABLE 3 Test Preference Data (N = 32) Question

Bruce Protocol

ASU Protocol

Grade

3.41 ± 1.74

5.16 ± 1.58*

Speed

3.71 ± 1.80

6.16 ± 0.92*

3.87 ± 1.45

5.66 ± 0.87*

2.66 ± 1.47

2.06 ± 1.13*

Rate how the protocol’s progression of grade and speed matched your current abilitiesa

Rate your overall satisfaction of the protocola Rate your delayed-onset muscle soreness after the

testa

Note. ASU = Arizona State University. aAll values are on a Likert scale of 1 (low) to 7 (high). *p < .05.

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whereas 28.1% of participants reported leg fatigue as the primary reason for terminating the ASU protocol. As far as the individualization of the grade and speed (1 [low] to 7 [high]), participants rated the ASU protocol significantly better than the Bruce protocol (p < .0001). For example, the Likert ratings for speed and grade for the Bruce protocol equaled 3.41 ± 1.74 and 3.71 ± 1.80, whereas the ASU protocol yielded scores of 5.16 ± 1.58 and 6.16 ± 0.92, respectively. For overall satisfaction, again there was a significant difference (p < .0001) between the Bruce and ASU protocols with ratings equaling 3.87 ± 1.45 and 5.66 ± 0.87, respectively. In terms of DOMS, there was significant difference (p < .02) between the Bruce (2.66 ± 1.47) and ASU (2.06 ± 1.13) protocols. Finally, 93.8% of participants, when asked if they had to perform one of these protocols again in 2 days, preferred the ASU protocol over the Bruce protocol. DISCUSSION This study is the first to compare the standardized Bruce protocol to an individualized, self-selected protocol (ASU protocol). Based on the results, the predictive accuracy of the ASU protocol is comparable to the Bruce protocol for relatively fit college students. Although both protocols appear to reach similar endpoints, they do so utilizing entirely different procedures. This study also documents what is commonly known, that participants prefer an individualized format over a standardized format. When participants responded to which protocol they would prefer to take again in 2 days, following participation in both protocols, 93.8% chose the ASU protocol. The ASU maximal treadmill GXT provides a test protocol for college students that is preferred over the Bruce protocol, as well as being individual& ized, time efficient, and relatively accurate in estimating VO 2 max (see Table 2). & Of all the maximal protocols that predict VO , the Bruce protocol appears to 2 max be the most commonly used (ACSM, 2000; Foster et al., 1984). The Bruce protocol (Bruce et al., 1973) is applicable to every settings, from clinical to laboratory. It also tests every subgroup of the population, from the sedentary to the elite athlete, as well as the healthy to the cardiac patient. This standard protocol is time efficient, yet broad enough to fit all age, health, and activity categories, necessitating large, abrupt stages. Consequently, in this case, a generalized “one type fits all” approach has been used. When examining the results from the Bruce protocol, the final RER was higher & than the ASU protocol, while the HRmax, RPEmax, and measured VO 2 max were lower. The preference data denoted that more than half of participants terminated the Bruce protocol because of leg fatigue. These results may suggest that some participants prematurely terminated the Bruce protocol because of local muscle fatigue instead of general, whole body fatigue. This may partially explain why the & & measured VO 2 max of the Bruce protocol was lower than the measured VO 2 max of

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the ASU protocol. This, together with the uncertainty of whether to walk or run during either Stage 3 or Stage 4, helps to create a less participant-friendly format. The question that naturally arises is, why is the Bruce protocol the most popular & protocol to predict CRF? Clearly, it accurately predicts VO 2 max as found in this study and in other studies (Bruce et al., 1973; McInnis & Balady, 1994; Pollock et al., 1976). In the clinical setting it could be used for time efficiency, where time is proportional to cost, or perhaps to impose the same exercise intensity across each stage for a potentially better comparative diagnosis. Longitudinal and epidemiological researchers who originally used the Bruce protocol need to continue doing so to maintain the test–retest continuity across participants. Other researchers may see these highly reputable studies as examples that they must follow and, therefore, use the Bruce protocol. With the variety of maximal GXTs available, it is necessary to find those that are individualized to the specific participant, as well as preferred, yet maintain relative accuracy and validity. Logic dictates that the greater the focus on individualistic orientation, the greater the enjoyment or satisfaction and motivation (Lloyd & Fox, 1992). The ACSM (2000) guidelines state that whichever exercise protocol is chosen, it should be individualized; for example, treadmill speed should be established based on the capabilities of the individual. Maximal ramp-type treadmill protocols are available that have small increments in speed and grade (Balke & Ware, 1959), but such protocols are not as individualized as they could be and may require a high time commitment depending on the fitness level of the participant. On the other hand, when allowing participants to self-select an intensity tailored to their physical abilities, an individualized maximal GXT may be more valuable in terms of the exercise prescription process. This would allow assessment of RPE, HR, perceptions or other variables at the self-selected intensity so that individualized exercise intensity adjustments and recommendations could be made. Additionally, the freedom to self-select an exercise intensity based on personal choice will not only increase the enjoyment of the exercise test, but may also promote exercise adherence as one begins an exercise program (Thompson & Wankel, 1980). Evidence has been provided that the ASU protocol can generate accurate & VO 2 max estimations while providing an individualized, self-selected, realistic testing format for college students. The result is a participant-friendly and administra& tor-friendly format that has realistic increases across stages (ASU protocol: VO 2 & cost per stage = 2 ml · kg–1 · min–1, Bruce protocol: VO cost per stage = 8–12 ml · 2 kg–1 · min–1) (Foster et al., 1996; George, 1996). Another advantage of the ASU & protocol is that VO 2 max predictions can be determined from the first two stages. The first stage is a 3-min walking stage, the second is a 3-min jogging stage. In the event that the individual does not reach maximal exertion, either of the initial & stages may be used as a submaximal test to predict VO 2 max . Although the average total elapsed time for the Bruce protocol was 12.09 ± 1.77 min, and the ASU proto-

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col was 12.56 ± 1.77 min (Table 1), the 6-min warm-up period of the ASU protocol could be easily shortened to reduce its overall testing time. In conclusion, the ASU maximal GXT provides a self-selected and individualized format for college-aged participants that is preferred over the standardized Bruce protocol. Although the Bruce protocol may offer diagnostic value in the clinical setting or may be needed to maintain the test–retest continuity in longitudinal studies, it is questionable whether it should be used in fitness or wellness centers as well as in the college or research setting. In terms of predictive accuracy, & both the ASU and Bruce regression models yield relatively accurate VO 2 max estimations in fit college aged individuals. Further research is now warranted to evaluate the generalizability of the results with a variety of samples. Moreover, it would be instructive to compare the Bruce protocol with an individualized maximal GXT such as the ASU protocol in the clinical or other settings.

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