Submaximal Treadmill Exercise Test to Predict VO 2 max in Fit Adults

Measurement in Physical Education and Exercise Science ISSN: 1091-367X (Print) 1532-7841 (Online) Journal homepage: http://www.tandfonline.com/loi/hmpe20 Submaximal Treadmill Exercise Test to Predict VO 2 max in Fit Adults Pat R. Vehrs, James D. George, Gilbert W. Fellingham, Sharon A. Plowman & Kymberli Dustman-Allen To cite this article: Pat R. Vehrs, James D. George, Gilbert W. Fellingham, Sharon A. Plowman & Kymberli Dustman-Allen (2007) Submaximal Treadmill Exercise Test to Predict VO 2 max in Fit Adults, Measurement in Physical Education and Exercise Science, 11:2, 61-72, DOI: 10.1080/10913670701294047 To link to this article: https://doi.org/10.1080/10913670701294047 Published online: 05 Dec 2007. Submit your article to this journal Article views: 18406 View related articles Citing articles: 14 View citing articles Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalinformation?journalcode=hmpe20 Download by: [37.44.202.246] Date: 16 December 2017, At: 11:25

MEASUREMENT IN PHYSICAL EDUCATION AND EXERCISE SCIENCE, 11(2), 61 72 Copyright 2007, Lawrence Erlbaum Associates, Inc. Submaximal Treadmill Exercise Test to Predict VO 2 max in Fit Adults Pat R. Vehrs and James D. George Department of Exercise Sciences Brigham Young University Gilbert W. Fellingham Department of Statistics Brigham Young University Sharon A. Plowman and Kymberli Dustman-Allen Department of Kinesiology and Physical Education Northern Illinois University This study was designed to develop a single-stage submaximal treadmill jogging (TMJ) test to predict VO 2 max in fit adults. Participants (N = 400; men = 250 and women = 150), ages 18 to 40 years, successfully completed a maximal graded exercise test (GXT) at 1 of 3 laboratories to determine VO 2 max. The TMJ test was completed during the first 2 stages of the GXT. Following 3 min of walking (Stage 1), participants achieved a steady-state heart rate (HR) while exercising at a comfortable self-selected submaximal jogging speed at level grade (Stage 2). Gender, age, body mass, steady-state HR, and jogging speed (mph) were included as independent variables in the following multiple linear regression model to predict VO 2 max (R = 0.91, standard error of estimate [SEE] = 2.52 ml kg 1 min 1 ): VO 2 max (ml kg 1 min 1 ) = 58.687 + (7.520 Gender; 0 = woman and 1 = man) + (4.334 mph) (0.211 kg) (0.148 HR) (0.107 Age). Based on the predicted residual sum of squares (PRESS) statistics (R PRESS = 0.91, SEE PRESS = 2.54 ml kg 1 min 1 ) and small total error (TE; 2.50 ml kg 1 min 1 ; 5.3% of VO 2 max) and constant error (CE; 0.008 ml kg 1 min 1 ) terms, this new prediction equation displays minimal shrinkage. It should also demonstrate similar accuracy when it is applied to other samples that include participants of comparable age, body mass, and aerobic fitness level. Correspondence should be sent to Pat R. Vehrs, Brigham Young University, Department of Exercise Sciences, PO Box 22081 Provo, UT 84602. E-mail: pat_vehrs@byu.edu

62 VEHRS ET AL. This simple TMJ test and its corresponding regression model provides a relatively safe, convenient, and accurate way to predict VO 2 max in fit adults, ages 18 to 40 years. Key words: physical fitness, oxygen consumption, aerobic capacity, exercise testing The most accurate way to assess aerobic capacity is the direct measurement of maximal oxygen uptake (VO 2 max) during a graded exercise test (GXT); however, the direct measurement of VO 2 max is often limited to laboratory, clinical, and research settings. The need to assess aerobic capacity in the general public has led to the development of various exercise and nonexercise prediction models. Previous investigators (Ainsworth, Richardson, Jacobs, & Leon, 1992; George, Stone, & Burkett, 1997; Heil, Freedson, Ahlquist, Price, & Rippe, 1995; Jackson et al., 1990; Malek, Housh, Berger, Coburn, & Beck, 2004, 2005) reported valid estimates of aerobic capacity using nonexercise test variables. Such models are effective for use in large epidemiological cohorts in which an exercise test to predict or measure VO 2 max would be impractical. VO 2 max can also be predicted using exercise tests that require maximal exertion on a treadmill (Bruce, Kusumi, & Hosmer, 1973; Foster et al., 1996; George, 1996) or track (Cooper, 1963, 1968). Although it may be efficacious to use an exercise test requiring maximal effort in young, fit, and willing participants, submaximal exercise tests, which are relatively safer and require less time, are practical in a variety of settings. Submaximal exercise testing provides the administrator an opportunity to observe responses to exercise and to teach participants about selection of an appropriate intensity of exercise. Use of a treadmill as a mode of submaximal exercise testing is effective because (a) treadmills are readily available in laboratories and fitness facilities; (b) jogging is a popular form of exercise, and treadmills are often used as a training modality; (c) treadmill protocols are easy to administer and control; and (d) individualized jogging programs can be based on the results of the treadmill jogging (TMJ) test. The use of early developed multistage submaximal treadmill protocols to estimate VO 2 max is time consuming (Town & Golding, 1977) or requires cumbersome data collection (Hermiston & Faulkner, 1971). A more recently developed single-stage treadmill walking protocol (Ebbeling, Ward, Puleo, Widrick, & Rippe, 1991) is convenient and practical to use. To date, only one single-stage submaximal TMJ protocol has been developed (George, Vehrs, Allsen, Fellingham, & Fisher, 1993a). Following a 3-min walking warm-up stage, the TMJ test requires participants to jog at a self-selected submaximal jogging speed between 4.3 and 7.5 mph at level grade until a steady-state heart rate (HR) 180 bpm (beats per minute) is achieved (George et al., 1993a).

SUBMAXIMAL TREADMILL JOG 63 VO 2 max is predicted using a regression equation that includes gender, weight, self-selected jogging speed, and steady-state HR as independent variables. According to the American College of Sports Medicine (ACSM) guidelines, asymptomatic men and women who are under the ages of 45 and 55, respectively, and meet no more than one risk factor threshold may begin an exercise program without a pre-exercise physical exam or exercise test (ACSM, 2006). There is a potential for a large portion of these individuals to use jogging as their preferred mode of exercise. To date, the TMJ test has only been validated in 18- to 29- year-old men and women at a single location (George et al., 1993a). Validating the TMJ test in a heterogenous sample of participants with a broader age range would increase its generalizability and utility in a variety of settings. Therefore, this study was designed to (a) evaluate the predictive accuracy of an existing regression equation used to predict VO 2 max from the TMJ test in participants ages 18 to 40 years old from three different testing locations, and, if necessary; (b) develop a new VO 2 max prediction equation applicable to a broader and more heterogeneous age range. METHOD Participants Participants in this study include 250 men and 150 women, ages 18 to 40 years old from three university human performance laboratories in three different states. Data from 122 participants who participated in the original George et al. (1993a) study were included in this study. Prior to participation, all participants read and signed an informed consent form approved by the university s institutional review board for participants and completed a pre-exercise testing screening questionnaire. All participants were classified as low risk according to the ACSM (2006) risk stratification. Exercise Testing Procedures All participants completed a maximal GXT to determine VO 2 max. Participants were asked to refrain from strenuous exercise for 24 hr prior to testing and to arrive in the laboratory at least 3 hr after eating a meal. Height (cm) and body mass (kg) were measured prior to performing the GXT. All GXTs were performed on a calibrated motorized treadmill. Oxygen consumption was measured during the GXT using a standard laboratory metabolic cart. Participants were fitted with a mouthpiece, two-way nonrebreathing valve (Hans Rudolf model 2700B, Kansas City, MO), and a nose clip so that expired gases could be measured. HR was continuously measured and recorded using an electronic HR monitor (Polar, Inc.)

64 VEHRS ET AL. worn by the participant. During each stage of the GXT, participants reported a rating of perceived exertion using a 15-point scale (Noble, Borg, & Jacobs, 1983). Participants began the maximal GXT by walking at a self-selected brisk walking speed at level grade for 3 min. This was followed by jogging at a self-selected, submaximal jogging speed between 4.3 and 7.5 mph at level grade for 3 min or until a steady-state HR was achieved. Thereafter, the treadmill speed remained constant throughout the remaining stages of the exercise test; however, the grade was increased 1.5% each additional minute until the participant voluntarily terminated the test due to fatigue, despite verbal encouragement. The participant s effort was considered maximal if physical signs suggestive of exhaustion were apparent and at least two of the following three criteria were met: (a) maximal RER > 1.10, (b) maximal HR (HRmax) no less than 15 beats below age predicted maximal HR, and (c) leveling off of VO 2 despite an increase in workload (George, 1996; Larsen et al., 2002; Vehrs & Fellingham, 2006; Vehrs, George, & Fellingham, 1998). The metabolic carts were configured to calculate and print VO 2 values every 15 sec. Maximum VO 2 was defined as the highest 30-sec average value, whereas HRmax was defined as the highest single HR value recorded during the GXT. The leveling off of VO 2, despite an increase 1 in workload, was defined as a change in VO 2 of less than ± 2mL kg 1 min once VO 2 max was achieved. Exercise HR during the second stage of the GXT was considered steady state when consecutive HRs over a 30-sec period differed by 3 bpm. Steady-state HR and the jogging speed selected by each participant during the second stage of the GXT were recorded and used in the following regression equation to predict VO 2 max (R adj = 0.88, standard error of estimate [SEE] = 3.1 ml kg 1 min 1 ): VO2max (ml kg 1 min 1 ) = 54.07 + (7.062 Gender; 0 = female and 1 = male) (0.1938 kg) + (4.47 mph) (0.1453 HR), where kg = body mass, mph = self-selected jogging speed, and HR = steady-state heart rate (bpm) while jogging at level grade at the self-selected jogging speed (George et al., 1993a). Testing Locations Maximal GXTs were performed in the human performance laboratories at Brigham Young University (Provo, UT), Northern Illinois University (Dekalb, IL), and The University of Houston (Houston, TX). Each test site used the maximal GXT protocol described previously. VO 2 was measured using a TrueOne 2400 Metabolic Measurement System (ParvoMedics, Sandy, UT) at Brigham Young University and with a Vmax 229 (SensorMedics, Norma Linda, CA) metabolic cart at Northern Illinois University and The University of Houston. Prior to testing, the oxygen and carbon monoxide analyzers were calibrated using room air and medical-grade gases of known concentrations. The flow meters were calibrated using a 3.0 L syringe at various flow rates.

SUBMAXIMAL TREADMILL JOG 65 Statistical Analysis All data were analyzed using SAS. Statistical significance was set at p <.05. Because the TMJ test was utilized at three different locations, there was a concern that the results might differ across locations. This would be a possibility if the original prediction equation (George et al., 1993a) was missing a salient variable that might be different in the three locations. To test for the possibility of a location effect, Proc Mixed was utilized including the measured VO 2 max as the dependent variable, predicted VO 2 max from the original TMJ regression equation (George et al., 1993a) as the independent variable, age as a fixed effect, and location as a random effect in the model. The 122 participants from the original George et al. study were excluded from this analysis. The estimates of the variance components for the model were 0.184 for location and 6.11 for error. A likelihood ratio test for the significance of the location effect yielded a chi-square statistic of 2.5 with 1 degree of freedom. The effect of performing the TMJ test at three different locations was not significant (p >.05). Age was a significant (p =.0003) independent variable that was not included in the original prediction equation. Consequently, a new regression equation was needed to predict VO 2 max, which included participants from all three locations and age as one of the independent variables. Gender, age, body mass, self-selected jogging speed, and steady-state HR data from all 400 participants were evaluated as independent variables in stepwise multiple linear regression to predict measured VO 2 max. The ability of the new equation to predict VO 2 max was assessed by the Pearson product moment correlation coefficient and the SEE. The cross-validation analysis of the new VO 2 max equation was evaluated using the predicted residual sum of squares PRESS) method (Holiday, Ballard, & McKeown, 1995). PRESS statistics are based on the error in predicting when each case is deleted from the model one at a time. In SAS, this error is termed predicted residual SS. From the PRESS statistic, an adjusted R(R PRESS = 1 [PRESS/SS Total ]) 1 / 2 and SEE (SEE PRESS = [PRESS/N] 1 / 2 ) was calculated. The advantage of using the PRESS technique for cross validation is that data from all participants can be used to build the regression model. In traditional data-splitting methods, in which the data are partitioned into validation and cross-validation groups, the regression model is built on only a portion of the data. The R 2 PRESS and SEE PRESS were used to assess the extent of shrinkage when the new VO 2 max prediction equation is applied across independent samples of men and women within the same age range as those in this study. Based on previous recommendations (Malek, Berger, Housh, Coburn, & Beck, 2004; Malek, Housh, et al., 2004; Malek et al., 2005), further evaluation of the validity of the new VO 2 max equation was based on the calculation of the constant error (CE; mean difference of measured VO 2 max predicted VO 2 max) and total error (TE; [ measured VO 2 max predicted VO 2 max) 2 /N] 1 / 2 ) error terms.

66 VEHRS ET AL. RESULTS Table 1 includes descriptive information about the participants from each testing site. Data recorded while jogging at a self-selected speed during the second stage of the GXT are shown in Table 2. Multiple linear regression analysis yields the following equation (R = 0.91, SEE = 2.52 ml kg 1 min 1 ) for predicting VO 2 max (ml kg 1 min 1 ): VO 2 max (ml kg 1 min 1 ) = 58.687 + (7.520 Gender; 0 = woman and 1 = man) + (4.334 mph) (0.211 kg) (0.148 HR) (0.107 Age), where mph = self-selected jogging speed, HR = steadystate HR (bpm) while jogging at level grade at the self-selected jogging speed, kg = body mass, and age = age in years. The new regression equation results in an TABLE 1 Participant Characteristics BYU a NIU b UH c Characteristics M SD M SD M SD Age (years) 26.7 ± 6.6 23.3 ± 2.9 24.5 ± 4.9 Mass (kg) 70.0 ± 12.3 74.7 ± 13.5 73.3 ± 14.6 Height (cm) 174.3 ± 9.1 172.1 ± 7.6 175.1 ± 8.5 BMI (kg m 2 22.9 ± 2.9 25.1 ± 3.4 23.8 ± 3.7 VO 2 max (ml kg 1 min 1 47.5 ± 6.3 46.5 ± 5.9 46.4 ± 5.9 Maximal HR (beats per minute) 190.6 ± 7.6 194.8 ± 7.4 194.1 ± 7.5 % Age pred HRmax 98.6 ± 4.3 99.1 ± 3.6 99.3 ± 3.5 Maximal RER 1.17 ± 0.04 1.18 ± 0.05 1.18 ± 0.07 Maximal RPE 18.7 ± 0.8 18.8 ± 1.6 18.8 ± 2.6 Note. BYU = Brigham Young University; NIU = Northern Illinois University; UH =The University of Houston; BMI = Body Mass Index; HR = heart rate; RER =respiratory exchange ratio; Age pred HRmax = age predicted maximal heart rate (220 age). a n = 218. b n = 53. c n = 129. TABLE 2 Treadmill Jogging Test steady-state exercise date Speed (mph) Heart rate (beats per minute) VO 2 (ml kg 1 min 1 RER Participants M SD M SD M SD M SD Total a 5.7 ± 0.7 156.8 ± 13.5 32.1 ± 4.0 0.94 ± 0.08 Men b 5.9 ± 0.6 154.6 ± 13.8 33.2 ± 3.9 0.94 ± 0.08 Women c 5.3 ± 0.5 160.6 ± 11.9 30.4 ± 3.6 0.94 ± 0.08 Note. VO 2 = Oxygen consumption; RER = respiratory exchange ratio. a N = 400. b n = 250. c n = 150.

SUBMAXIMAL TREADMILL JOG 67 average predicted VO 2 max value (47.01 ± 5.61mL kg 1 min 1 ) that was similar to the average measured value (47.00 ± 6.14 ml kg 1 min 1 ). The unstandardized coefficients, t statistics, and beta coefficients for each independent variable are shown in Table 3. All five independent variables significantly contributed to the reduction in error (p <.05). CE and TE terms and the crossvalidation PRESS statistics are also shown in Table 3. The CE term was not significantly different from zero (t = 0.428, p =.669). The predicted VO 2 max is plotted against the measured VO 2 max in Figure 1. DISCUSSION Most, if not all, equations developed to estimate aerobic capacity from submaximal exercise tests were originally validated in participants from a single location. Most researchers agree that an equation to predict VO 2 max derived at one location can be used at other locations. This is as long as the exercise test is performed according to the described protocol, and the participants assessed match the age, gender, fitness level, and other characteristics of the participants from which the equation was derived. The disadvantage of single-site studies is Variable TABLE 3 Regression Equation and Statistics for a New Equation to Predict VO 2 max (N = 400) Unstandardized Regression Coefficients t value Beta Coefficient Constant 58.687 24 11 Gender 7.520 20 67 0 59 Speed (mph) 4.334 19 94 0 47 Body mass (kg) 0.211 17 86 0 46 HR (bpm) 0.148 14 40 0 32 Age 0.107 4 59 0 10 R 0 91 SEE (ml kg 1 min 1 2 52 5 3% SEE (ml kg 1 min 1 0 008 R PRESS 0 91 SEE PRESS (ml kg 1 min 1 2 54 5 4% TE (ml kg 1 min 1 2 50 5 3% Note. Gender codes are 0 = female, and 1 = male. Speed = self-selected treadmill jogging speed (4.3 7.5 mph); HR = steady-state heart rate during jogging onlevel grade at the self-selected jogging speed; CE = constant error; SEE = standard error of the estimate; TE = total error; (%) SEE and TE = SEE and TE as a percentage of measured VO 2 max. p values for all independent variables were <.0001.

68 VEHRS ET AL. Measured VO 2 max (ml kg 1 min 1 ) 65 60 55 50 45 40 35 30 30 Female Male 35 40 45 50 55 60 65 Predicted VO 2 max (ml kg 1 min 1 ) FIGURE 1 Plot of measured and predicted VO 2 max values. Note: that the dashed line represents the line of identity (X = Y). The solid line represents the line of best fit for the combined data. that they do not capture all of the variability inherent in any process. Accounting for multisite variability broadens the range of circumstances to which inferences may appropriately be applied. In this multisite study, differences in the measurement of gas exchange between metabolic carts may affect the agreement in VO 2 values measured at each location and the validity of a submaximal exercise test to predict measured VO 2 max. Thus, it could be argued that some or all of the participants in this study should have been tested at all locations. This was unreasonable considering the geographical location of the three testing sites. The inherent interlaboratory differences in participants and metabolic carts not usually apparent in single-site studies strengthen this study. The reliability of VO 2 max measurements at each location may also affect multisite studies such as this. The standardized protocol for the GXT (inclusive of the TMJ test) minimizes the likelihood of both intralaboratory and interlaboratory variability. In addition, although the intralaboratory reliability of VO 2 max measurements at all three locations was not evaluated, unpublished data from two of the three labs indicate that the TrueOne 2400 Metabolic Measurement System and Vmax 229 are highly reliable. This study increases the generalizability of the TMJ test by including participants from three different geographical locations, thereby accounting for some interinvestigator and laboratory-specific procedural differences that would otherwise not be included in a single-site study. The results of this study concur with previous researchers (Ebbeling et al., 1991; Kline et al., 1987) who indicated that age is an important variable in predicting cardio-respiratory fitness in a diverse sample of participants. Due to the homogeneous sample and the relatively narrow age range of participants in

SUBMAXIMAL TREADMILL JOG 69 the George et al. (1993a) study, age was originally not found to be a significant independent variable in the prediction of VO 2 max using the TMJ test. As such, the original TMJ test was appropriate for use in assessing the cardiorespiratory fitness of men and women between the ages of 18 and 29 years of age. Even though the predicted VO 2 max from the original TMJ regression equation (George et al., 1993a) demonstrates acceptable results in this study (SEE = 2.59 ml kg 1 min 1,CE= 0.26, TE = 2.60), age was found to be a significant variable missing from the original TMJ regression equation. The addition of age in the new TMJ regression equation improved the validity of the prediction as demonstrated by the reduced SEE, CE, and TE terms (see Table 3). The standardized beta weights indicate that compared to gender, treadmill speed (mph), body mass (kg), and steady state HR (bpm), age explained the least amount of variance in VO 2 max values. There are two explanations for this. First, it could be expected that gender and body mass would account for large portions of the variance in VO 2 max values. In an exercise test such as the TMJ test, it could also be expected that treadmill speed and HR response explain much of the variance in VO 2 max values. Second, the age range of the participants in this study may have limited the variability accounted for by the age variable. Nevertheless, age must be accounted for, and the new TMJ prediction equation reported in this study accurately predicts VO 2 max in fit 18- to 40-year-old men and women. George et al. (1993a) suggested that age-specific protocols might be necessary when the TMJ test is cross validated in individuals older than 29 years of age. The original speed and HR criteria established by George et al. were intended to restrict exercise intensity and provide guidelines for a realistic protocol for relatively fit individuals (VO 2 max > 35 ml kg 1 min 1 ). The participants in our study were also relatively fit, having fitness levels similar to those of the participants in the original study (George et al., 1993a). The lowest and average measured VO 2 max in the George et al. study (35.9 and 48.3 ml kg 1 min 1 ) and this study (33.4 and 46.6 ml kg 1 min 1 ), respectively, were comparable. All of the participants in this study, including the 4 participants with measured VO 2 max values = 35 ml kg 1 min 1 and the 108 participants 30 to 40 years of age, were able to self-select a comfortable jogging speed between 4.3 and 7.5 mph that also elicited a steady-state HR _180 bpm. The jogging pace selfselected by the participants in this study elicited responses (see Table 2) indicative of a submaximal effort. The average percentage of VO 2 max (69.9 ± 7.9) and percentage of HRmax (81.7 ± 6.9) during the steady-state jog were, in this study, nearly identical to those previously reported by George et al. It is reasonable to expect that some low-fit individuals would not be able to comfortably maintain a steady-state submaximal jogging pace within the TMJ test guidelines. It is possible that the 4 lower fit participants in this study were able to complete the TMJ test because they only had to maintain a steady-state pace for 3 to 4 min. The VO 2 max of some lower fit or older individuals may best be estimated using

70 VEHRS ET AL. a walking protocol on a treadmill (Ebbeling et al., 1991) or track (Kline et al., 1987). Because we have found no other single-stage submaximal TMJ protocols to compare our results with, the PRESS cross-validation statistics, CE, and TE reported in this study (see Table 3) for the TMJ test need to be compared to other treadmill walking or track jogging protocols. Ebbeling et al. (1991) developed a treadmill walking test that uses independent variables (age, gender, treadmill speed, and HR) at 5% grade in a generalized equation (R 2 = 0.86, SEE = 4.85 ml kg 1 min 1, TE = 3.59 ml kg 1 min 1 ) to predict VO 2 max in 139 participants 20 to 59 years old. George, Vehrs, Allsen, Fellingham, and Fisher (1993b) reported that a 1-mile steady-state track jog test at a self-selected pace accurately predicted VO 2 max (R adj = 0.87, SEE 3.0 ml kg 1 min 1 ). The cross-validation statistics reported by George et al. included an SEE that represented 6.6% of VO 2 max. Larsen et al. (2002) reported accurate predictions (R = 0.90, SEE = 2.87 ml kg 1 min 1 )ofvo 2 max when participants were given the option to walk, jog, or run a 1.5-mile distance at a steady-state pace. The cross-validation statistics reported by Larsen et al. included an R PRESS = 0.89 and a SEE PRESS = 3.04 ml kg 1 min 1 that represented 6.6% of VO 2 max. Compared to other track or treadmill walking or jogging protocols, the TMJ test and the new prediction equation reported in this study are practical alternatives to maximal exercise testing. The CE ( 0.008 ml kg 1 min 1 ), SEE PRESS (2.54 ml kg 1 min 1 ; 5.4% of VO 2 max), and TE (2.50 ml kg 1 min 1 ; 5.3% of VO 2 max) are lower than those previously reported for exercise (Ebbeling et al., 1991; George et al., 1993b; Larsen et al., 2002) and recently developed nonexercise models (George et al., 1997; Malek, Housh, et al., 2004; Malek et al., 2005). Ideally, there should be close agreement between SEE and TE. The TE represents the true difference between measured and predicted VO 2 max, whereas the SEE reflects only the error associated with the regression between the variables (Malek, Berger, et al., 2004). The TE is the best single criterion for determining the accuracy of a prediction equation because it combines the errors associated with the SEE and CE (Malek, Berger, et al., 2004). The SEE and TE will be equal if the CE is zero. The SEE and TE presented in this study (see Table 3) are similar due to the low CE ( 0.008 ml kg 1 min 1 ). This is illustrated by the fact that the line of identity and the line of best fit are nearly identical (see Figure 1). The SEE, SEE PRESS, and TE expressed as a percentage of measured VO 2 max presented in this study ( 5.4%; see Table 3) are less than one half of the values previously suggested (Malek, Berger, et al., 2004) as typical of submaximal exercise tests. Based on the low CE, SEE, TE, and SEE and TE as a percentage of VO 2 max, the TMJ test and the new regression equation developed in this study accurately predict VO 2 max and are viable alternatives to maximal exercise testing for fit adults who are 18 to 40 years of age. The single-stage, self-selected jogging pace

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