A Modified Submaximal Cycle Ergometer Test Designed to Predict Treadmill VO 2max

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1 Measurement in Physical Education and Exercise Science ISSN: X (Print) (Online) Journal homepage: A Modified Subimal Cycle Ergometer Test Designed to Predict Treadmill VO James D. George, Pat R. Vehrs, Garth J. Babcock, Michael P. Etchie, Troy D. Chinevere & Gilbert W. Fellingham To cite this article: James D. George, Pat R. Vehrs, Garth J. Babcock, Michael P. Etchie, Troy D. Chinevere & Gilbert W. Fellingham (000) A Modified Subimal Cycle Ergometer Test Designed to Predict Treadmill VO, Measurement in Physical Education and Exercise Science, 4:4, 9-43, DOI: /S MPEE0404_3 To link to this article: Published online: 18 Nov 009. Submit your article to this journal Article views: 4341 View related articles Citing articles: 6 View citing articles Full Terms & Conditions of access and use can be found at Download by: [ ] Date: 07 January 018, At: 09:09

2 MEASUREMENT IN PHYSICAL EDUCATION AND EXERCISE SCIENCE, 4(4), 9 43 Copyright 000, Lawrence Erlbaum Associates, Inc. VO A Modified Subimal Cycle Ergometer Test Designed to Predict Treadmill VO James D. George, Pat R. Vehrs, Garth J. Babcock, Michael P. Etchie, Troy D. Chinevere, and Gilbert W. Fellingham Brigham Young University This study sought to develop a modified subimal cycle ergometer test designed to predict imal oxygen consumption ( VO ) obtained on a treadmill. Volunteers (N = 156; women = 80, men = 76) with ages from 18 to 39 years old successfully performed a subimal cycle protocol on a stationary cycle ergometer and a imal graded exercise test (GXT) on a treadmill. Open circuit calorimetry was used during the GXT to measure VO. Multiple linear regression resulted in the following prediction equation: VO = Sex (0 = women; 1 = men) Age (year) Body Mass (kg) Power Output (W) Heart Rate (bpm), which had acceptable validity (r =.88, standard error of estimate [SEE]= 3.1 ml kg 1 min 1 ). Selected participants (n = 34) performed the subimal cycle ergometer test twice (within a 5-day period), yielding a test retest intraclass reliability coefficient of r =.95 for VO estimations across days. The reliability of VO estimates for women (r =.93) was greater than that for men (r =.74). Cross-validation results were also acceptable using predicted residual sum of squares (PRESS; r PRESS =.87, SEE PRESS = 3.4 ml kg 1 min 1 ), which suggests that the new equation should yield acceptable accuracy when it is applied to a similar, but independent sample of adults. In summary, the modified cycle ergometer test developed in this study yields relatively accurate estimates of treadmill VO in young adults, requires only a moderate level of exertion, and appears to be a convenient and time-efficient means of estimating cardiorespiratory fitness. Key words: subimal field test, VO prediction, estimation of aerobic power Requests for reprints should be sent to James D. George, Department of Physical Education, Brigham Young University, 105 Richards Building, Provo, UT jim_george@byu.edu

3 30 GEORGE ET AL. Since the early work of Sjostrand (1947) and Astrand and Ryhming (1954), subimal cycle ergometry has remained a popular test mode for assessing cardiorespiratory fitness or imal oxygen consumption ( VO ). Such protocols are convenient because they provide a relatively inexpensive way to predict cardiorespiratory fitness, permit physiological measures such as blood pressure and electrocardiography to be easily monitored, and allow for the selection of precise work rates across a wide variety of individual fitness levels. In addition, the physical demands of cycle ergometry tests are usually well tolerated by those with orthopedic restrictions (Fox, 1973; Golding, Meyers, & Sinning, 1989; Kasch, 1984; Siconolfi, Cullinane, Carleton, & Thompson, 198). Subimal cycle ergometer tests, however, have several potential limitations. First, unlike other common field tests (Ebbeling, Ward, Duleo, Widrick, & Rippe, 1991; George, Vehrs, Allsen, Fellingham, & Fisher, 1993; Kline et al., 1987; McArdle, Katch, Pechar, Jacobsen, & Ruck, 197), there are no widely accepted VO regression equations in the literature for subimal cycle ergometer tests. Instead, either nomograms or charting and extrapolation methods are used to predict VO (Astrand & Ryhming, 1954; Golding et al., 1989). The classic Astrand and Ryhming nomogram, for example, provides a way to estimate VO (based on sex, exercise power output, and exercise heart rate) without requiring step-by-step mathematical calculations. Although nomograms were convenient at the time, current availability of computers and programmable calculators now make it relatively easy to compute VO predictions directly from regression equations. The extrapolation method of estimating VO following a subimal cycle ergometer test (American College of Sports Medicine [ACSM], 1995; Golding et al., 1989) requires drawing a line of best fit across subimal heart rate data points and extrapolating to a predicted or measured imum heart rate (HR ). The corresponding imal power output is then matched with a VO estimate from the YMCA prediction chart or used to calculate VO with the ACSM cycle ergometer metabolic equation (ACSM, 1995). Compared with using a single regression equation to predict VO, the extrapolation method seems to be unnecessarily cumbersome, especially when this method does not appear to significantly enhance predictive accuracy (Lockwood, Yoder, & Deuster, 1997; Zwiren, Feedson, Ward, Wilke, & Rippe, 1991). A second limitation is that researchers have regressed subimal cycle ergometry data (work rate, heart rate, etc.) on VO values obtained from a cycle ergometer, rather than from imal treadmill data (Fox, 1973; Siconolfi et al., 198; Zwiren et al., 1991). This is problematic because several researchers have indicated that imal cycle protocols generate VO scores that are 10% to 0% lower than imal treadmill protocols in untrained participants (Beasley, Plowman, & Fernhall, 1989; Hermansen & Saltin, 1969). In addition, other com-

4 VO PREDICTION 31 mon field tests, such as the Rockport Fitness Walking Test (Kline et al., 1987) and 1.5-mile run (Cooper, 1968), use imal treadmill VO scores as the criterion or dependent variable. This suggests that cycle ergometer tests would, on average, underpredict VO as compared to other field or laboratory tests designed to estimate treadmill VO scores (Cooper, 1968; Ebbeling et al., 1991; George et al., 1993; Kline et al., 1987; McArdle et al., 197). Moreover, when subimal cycle ergometer protocols are used to estimate aerobic capacity for research, epidemiology, the military, or for classroom and laboratory experiences, the true aerobic capacity ( VO ) and perhaps the fitness category may be underestimated. Thus to promote predictive consistency, it may be best that all common field tests, including subimal cycle ergometer tests, use the same criterion measure. A final concern is that popular subimal cycle protocols (ACSM, 1995; Astrand & Ryhming, 1954; Golding et al., 1989) employ relatively slow pedal rates (e.g., 50 rpm). Several possible explanations are available for choosing relatively slow pedal rates. Slow pedal rates may have ensured that even-numbered power outputs were utilized when using Monarch cycle ergometers (e.g., 1 kp 50 rpm 6 m/rev = 300 kpm min 1 ). Slow pedal rates may also accommodate the limited functional capacity of those who are less fit or diseased. Swain and Wright (1997) indicated that early researchers found the economy of effort was highest at moderate cycling pedal rates (33 60 rpm) and suggest that this may be the reason that the developers of subimal cycle tests chose to use a cadence of 50 rpm. Recently, researchers have suggested that higher pedal rates are actually more economical and preferred among those individuals with cycling experience (Coast & Welch, 1985; Hagberg, Mullin, Giese, & Spitznagel, 1981). Interestingly, Swain and Wright (1997) found no significant difference in VO predictions when participants cycled at 50 or 80 rpm, and therefore proposed that either cadence could be used depending on the background or preference of the client. Because of the current limitations of subimal cycle ergometry, this study was designed to (a) generate a valid VO prediction equation that could be used in place of nomograms or the charting and extrapolation method, (b) develop a VO regression model using standard treadmill VO scores as the criterion measure, and(c) adopt a faster pedal rate that is more appropriate for healthy, young adults. METHODS Participants Healthy volunteers (N = 17), with ages from 18 to 39 years, voluntarily participated in this study. All participants provided written informed consent prior to data collection, as approved by the Institutional Human Subjects Review Committee.

5 3 GEORGE ET AL. To screen for contraindications to exercise testing, all participants completed a brief preexercise questionnaire. Body mass (kg) and height (m) were measured using a standard physician s balance beam scale with participants dressed in lightweight exercise apparel and without shoes. Participants over 30 years of age had resting blood pressure and a resting electrocardiogram recorded prior to the imal graded exercise test (GXT). In addition, participants were advised to abstain from caffeine, tobacco, alcohol, and large meals for at least 3 hr, and exhaustive exercise for at least 48 hr before the subimal or imal exercise tests. All participants completed both tests in a random order, within 14 days of one another. When the imal GXT preceded the subimal cycle test, at least 48 hr of rest was required between tests. During the GXT and the subimal cycle ergometer test, exercise heart rates were assessed using an electronic monitoring system (Polar CIC Inc., Port Washington, NY) and self-reported ratings of perceived exertion (RPE) were based on a 15-point scale (Borg, 198). Maximal Exercise Test Participants performed the imal GXT on a calibrated motor-driven treadmill (Model 65, Quinton Inc., Seattle, WA). Indirect calorimetry, using a mixing chamber configuration, was used to measure oxygen consumption during the GXT. Minute volumes were measured with a Ventilation Measurement Module (Sensor Medics Inc., Yorba Linda, CA) and fractions of O and CO were measured by a mass spectrometer (Marquette Inc., St. Louis, MO). An online computer program (Consentius Inc., Sandy, UT) calculated and printed VO and respiratory exchange ratio (RER) values every four breaths. Prior to exercise testing, the mass spectrometer was calibrated with standard gases of known composition and the ventilation measurement module calibrated with a 3-L Rudolph syringe. The treadmill GXT protocol required participants to walk at a brisk pace at level grade for 3 min, followed by jogging at a self-selected speed at level grade ( mph) for an additional 3 min (George et al., 1993). Participants used hand signals to inform the test administrator when a comfortable jogging pace was achieved. Thereafter, the treadmill grade was increased.5% every min (treadmill speed remaining constant), until participants achieved volitional fatigue and were unable to continue despite verbal encouragement. HR was recorded as the highest observed heart rate during the final stages of the GXT. The highest full-minute oxygen uptake value observed during the final stages of the GXT was recorded as VO. VO values were considered imal when at least two of the following three criteria were satisfied (Kline et al., 1987): (a) RER 1.1, (b) imal heart rate of less than 15 bpm below age-predicted HR (0 age), and (c) leveling off of VO despite an increase in work.

6 VO PREDICTION 33 Subimal Cycle Test The pedal rate, power output, and exercise heart rate guidelines used for the modified subimal cycle ergometer test were based on current subimal cycle protocols (ACSM, 1995; Astrand & Ryhming, 1954; Golding et al., 1989; Nagle, 1973) and pilot work completed prior to data collection. The goal was to ensure that participants achieved a moderate subimal exercise intensity. Figure 1 contains a flowchart of the subimal cycle ergometer protocol. A calibrated Monarch cycle ergometer (Model 818E, Monarch, Varberg, Sweden) was utilized, and before each test the seat height was adjusted so the legs of the participants had about a 5 bend in the knee at imal leg extension. An electronic counter attached to the ergometer quantified total pedal revolutions so that actual pedal rates could be determined. Power output (kpm min 1 ) was computed with the formula kpm min 1 = (pedal rate [rpm]) (ergometer resistance [kp]) (6 m/rev) and then converted to watts (1 W = 6.1 kpm min 1 ). A metronome was used to help participants maintain a constant pedal rate of 70 rpm. An initial -min warm-up (1.0 kp; 68 W) was used to help participants establish a steady pedal rate. Following the warm-up, if exercise heart rate was between 10and175bpm,theworkrateremainedconstantforanadditional3min.Ifexercise heart rate was below 10 bpm after the -min warm-up, workload was increased by 1.0 kpformenwithabodymass 73kg(160lb)andby0.5kpforallwomenandmen withabodymass<73kg.ifsteady-stateheartrateremainedbelow10bpmafterthe first exercise stage, work rate was increased by an additional 0.5 kp for all participants and participants continued to pedal at a frequency of 70 rpm for an additional 3 min. This process continued until a steady-state heart rate was achieved between 10 and 175 bpm. Heart rate was considered steady state when consecutive heart rates between the second and third minute were within 6 bpm of each other (ACSM, 1995). The workload at which a steady-state heart rate between 10 and 175 bpm occurred was recorded, as well as the pedal frequency, steady-state heart rate, and RPE. To assess test retest reliability, a sample of 34 participants (17 women, 17 men) performed the modified cycle protocol on separate days. Both subimal cycle ergometer tests were performed within a 5-day period. Mean test retest differences between predicted VO values were evaluated with the test retest data for each participant. Data Analysis One-way analyses of variance (ANOVAs) were used to determine if significant sex differences existed between each of the demographic and exercise

7 FIGURE 1 Subimal Cycle Ergometer Protocol. 34

8 VO PREDICTION 35 response variables. Subimal cycle ergometer power output (W), steady-state heart rate, sex, age, and body mass (kg) were used in multiple linear regression analyses to generate the best model to estimate treadmill VO. Dummy coding was utilized for the sex variable (0 = women and 1 = men). Interactions between independent variables (sex, age, body mass, power output, and exercise heart rate) were evaluated for significance in reducing the residual sum of squares in the regression model. Pearson product moment correlations (r), standard errors of estimate (SEE), and standardized beta weights were computed to evaluate the strength of the regression models. The predicted residual sum of squares (PRESS) statistics (Holiday, Ballard, & McKeown, 1995) were computed to estimate the degree of shrinkage one could expect when the VO prediction equation is used across similar, but independent samples. A one-way ANOVA model was used to derive intraclass correlation coefficients to evaluate the test retest reliability of estimated VO from the modified cycle ergometer protocol. The level of statistical significance was set at p <.05. RESULTS Of the 17 participants, 16 failed to satisfy the VO criteria and were dropped from the study. Descriptive statistics, along with subimal and imal exercise data, for the total, female, and male samples are presented in Table 1. Each independent variable utilized in the regression analysis was statistically significant in predicting observed VO (Table ). Moreover, there were no statistically significant interactions observed among the independent variables. Multiple linear regression resulted in the following prediction equation (Table ): VO = Sex (0 = women; 1 = men) Age (year) Body Mass (kg) Power Output (W) Heart Rate (bpm), which had acceptable validity (r =.88, SEE = 3.1 ml kg 1 min 1 ). Standardized beta weights for sex, age, body mass, power output, and exercise heart rate equaled 0.70, 0.8, 0.87, 0.63, and 0.3, respectively (Table ). PRESS statistics (r PRESS =.87, SEE PRESS = 3.4 ml kg 1 min 1 )revealed minimal shrinkage (Table ). Plots of predicted versus observed VO values for the female and male samples are presented in Figures and 3, respectively. The reliability study (n = 34, Figure 4) yielded an acceptable test retest intraclass reliability coefficient (r =.95, SEM = 1.47 ml kg 1 min 1 ; Table 3) for VO estimations across days, although the female (r =.93, SEM = 1.1 ml kg 1 min 1 ) results were more reliable than results for the males (r =.74, SEM = 1.88 ml kg 1 min 1 ).

9 TABLE 1 Descriptive and Exercise Data for Total, Female, and Male Samples Variable Total a Females b Males c Age (years) 8.1 ± ± ± 6.3 Height (m) 1.74 ± ± ± 0.06 Body mass (kg) 71.4 ± ± ± 11.1* Subimal cycle test (final stage) Pedal frequency (rpm) 70.3 ± ± ±.3 Force (kp) 1.64 ± ± ± 0.30* Power output (W) ± ± ± 0.8* Heart rate (bpm) 14.7 ± ± ± 11.4* Heart rate (%HR ) 74.6 ± ± ± 5.* RPE (15-point scale) 1. ± ± ± 1.3 Maximal treadmill test VO (ml kg 1 min 1 ) 44.4 ± ± ± 5.6* HR (bpm) ± ± ± 6.9 RPE (15-point scale) 19.1 ± ± ± 3.0 RER (VCO /VO ) 1.18 ± ± ± 0.05 Note. All values are M ± SD. RPE = ratings of perceived exertion. a n = 156. b n = 80. c n = 76. TABLE Validation and Cross-Validation Results of the VO Regression Equation (n = 156) Variable Coefficients β Weight a Multiple regression equation Intercept Sex (0 = women; 1 = men) 9.104* Age (yr) 0.676* 0.75 Body mass (kg) * Power (W) * Exercise heart rate (bpm) * Validation statistics R =.88 SEE = 3.1 ml kg 1 min 1 SEE (% VO ) = 7.1 Cross-validation statistics R p =.87 SEE p = 3.4 ml kg 1 min 1 SEE p (% VO ) = 7. Note. SEE = standard error of estimate; PRESS = predicted residual sum of squares. R = Pearson product moment correlation; SEE = SD(1 r ) ½ ; SEE(% VO )=(SEE/M VO ) 100; R P =(1 [PRESS/SS total ]) ½ ; SEE P = (PRESS/n) -½. SEE p (% VO ) = (SEE p /M VO ) * 100. a Standardized multiple regression coefficients. *p <

10 VO PREDICTION 37 FIGURE Scattergram of observed versus predicted VO (ml kg 1 min 1 ) for the female sample (n = 80). The modified cycle ergometer test appeared to elicit a moderate, subimal level of exertion with (M ± SD) exercise heart rate, percentage of HR, and RPE values equal to , 74.6 ± 6.0, and 1. ± 1.3 bpm, respectively (Table ). Work loads (M ± SD) for men and women equaled 1.9 ± 0.3 kp (or ± 0.8 W) and 1.3 ± 0.3 kp (or 90.8 ± 1.4 W), respectively. DISCUSSION The multiple regression model (r =.88, SEE = 3.1 ml kg 1 min 1, Error% [SEE/M] = 7.1%) generated in this study compares favorably with other subimal VO estimation tests. In general, the Astrand and Ryhming (1954) nomogram and extrapolation method yield correlation coefficients between.70 and.85, SEEs between.5 and 6.0 ml kg 1 min 1, and Error %s between 10 and 15% (Greiwe, Kaminsky, Whaley, & Dwyer, 1995; Lockwood et al., 1997). Other comparable subimal field tests, involving walking, jogging, and running, also

11 38 GEORGE ET AL. FIGURE 3 Scattergram of observed versus predicted VO (ml kgû1 minû1) for the male sample (n = 76). exhibit similar predictive accuracy in estimating VO (Cooper, 1968; Ebbeling et al., 1991; George et al., 1993; Kline et al., 1987). To date, relatively few researchers have evaluated the reliability of subimal cycle ergometer tests. Recently, Lockwood et al. (1997) reported a relatively low mean reliability coefficient (r =.61, n = 100) for the Astrand and Ryhming (1954) test nomogram that was repeated three times on separate occasions. Lockwood et al., however, did not describe the number of men and women in this analysis or provide a sex-specific reliability coefficient. Hartung, Blanco, Lally, and Krock (1995), on the other hand, found the Astrand and Ryhming test nomogram to be very reliable (r =.91) in a sample of 37 healthy women ages 19 to 47 years. Greiwe et al. (1995) evaluated the reliability of the extrapolation method in 15 men and 15 women, ages 1 to 54 years, and reported a relatively high coefficient (r =.86), but noted that certain individuals displayed a large variation between subimal trials. Nevertheless, like the Lockwood et al. study, no sex-specific analysis was provided in the Greiwe et al. study, possibly because of their small sample size. In this study, the women s test retest reliability coefficient (r =.93, Table 3) was similar to the Greiwe et al. study, but the men s value was lower (r =.74, Table 3). Accord-

12 VO PREDICTION 39 FIGURE 4 Scattergram of predicted VO (Trial 1) versus predicted VO (Trial ); n = 34. ingly, it appears that men exhibit lower test retest reliability than women when performing a subimal cycle ergometer test; however, additional investigation is needed to substantiate this finding. Based on the principles of regression, the Astrand and Ryhming (1954) nomogram and the extrapolation method should, on average, accurately estimate observed cycle VO values, but underestimate observed treadmill VO values. The reason for this is because the criterion measure of these two methods is imal cycle data that tend to be 10% to 0% lower than imal treadmill scores. However, not all researchers have found that these two methods accurately estimate imal cycle scores or underestimate imal treadmill VO values. Zwiren et al. (1991), for example, tested 38 women (M ± SD = 33 ± 3 years) and reported that the Astrand and Ryhming nomogram overestimated observed cycle VO scores by 0% and observed treadmill VO scores by 8.5%. Similarly, Siconolfi et al. (198) found comparable overestimations in 63 men and women when using the Astrand and Ryhming nomogram. The extrapolation method tends to overestimate both observed cycle and treadmill VO scores (Greiwe et al., 1995; Lockwood et al., 1997; Swain & Wright, 1997). In contrast, Lockwood et al. found that the Astrand and

13 40 GEORGE ET AL. TABLE 3 Test Retest Means and Intraclass Reliability Coefficients for Estimated VO Sample Trial 1 Trial ICC SEM 95% CI Total (n = 34) 44.8 ± ± to 48 Women (n = 17) 39.7 ± ± to 4 Men (n = 17) 49.8 ± ± to 54 Note. Values are M ± SD; estimated VO (ml kg 1 min 1 ) computed from the regression model (Table ). ICC = intraclass correlation coefficient; SEM = standard error of measurement (ml kg 1 min 1 ); 95% CI = 95% confidence interval (ml kg 1 min 1 ). Ryhming nomogram underestimated observed treadmill VO scores by about 15% to 17%. Others have found similar underestimations using the Astrand and Ryhming nomogram (Davies, 1968; Jessup, Tolson, & Terry, 1974; Rowell, Taylor, & Wang, 1964). Several other factors may influence the accuracy of subimal cycle ergometer tests: (a) validity of the underlying assumptions of linearity of the heart rate and oxygen uptake relation, and (b) constancy of the oxygen cost of external work on a cycle ergometer. Accuracy of the age-predicted HR, and day-to-day variation in heart rate also influence the accuracy of subimal cycle ergometer tests. Several investigators have provided excellent explanations as to why subimal cycle ergometer tests may not accurately estimate VO scores (Davies, 1968; Hartung et al., 1995; Rowell et al., 1964; Swain & Wright, 1997). Another factor that greatly influences the predictive accuracy of a VO regression model is its generalizability or how accurately it predicts observed VO when applied to a new sample. According to Thomas and Nelson (1996), there is normally some shrinkage (a decrease in predictive accuracy) when a regression equation is applied to an independent sample; however, this error can be minimized by ensuring that the cross-validation sample is similar to the target population. Consequently, when cross-validating this regression equation (Table ) participants should be similar to the validation sample (Table 1) with respect to age (18 39 years), body mass ( kg), power output ( W), subimal heart rate values ( bpm), and observed VO values (8 6 ml kg 1 ). In addition, the cross-validation sample should be large enough to adequately represent the target population. When this is achieved, the predictive accuracy of this field test should approximate the PRESS statistics (r PRESS =.87, SEE PRESS = 3.4 ml kg 1 min 1 ) presented in Table (Holiday, Ballard, & McKeown, 1995). A unique feature of this subimal cycle ergometer test is that the pedal cadence is 0 rpm higher than other subimal cycle ergometer protocols (ACSM, 1995; Astrand & Ryhming, 1954; Golding et al., 1989). The rationale was to minimize local muscle fatigue (at a given power output) and provide a comfortable cadence for relatively fit individuals. Nagle (1973), for example, suggested that a

14 VO PREDICTION 41 slow pedaling rate leads to local muscle fatigue because the contraction relaxation phase of the active muscle is prolonged, impairing normal blood flow. In addition, the effects of momentum are reduced at slower pedal rates. Although the pedaling rate preference of the participants (between a 50 vs. 70 rpm) was not evaluated, relatively low RPE scores (1. ± 1.3) were observed for this protocol. One limitation was that selecting a work load below 1.0 kp was not possible since the Monarch cycle ergometer flywheel tended to freewheel without constant resistance at 70 rpm. For this reason, the lowest feasible power output for the current cycle ergometer test is 68 W, which may prove too demanding for individuals with a very low cardiorespiratory fitness ( VO < 8 ml kg 1 min 1 ). According to the ACSM (1995), the five general purposes of physical fitness testing are to (a) provide data that are helpful in developing exercise prescriptions, (b) collect baseline and follow-up data that allow evaluation of progress, (c) motivate participants by establishing reasonable and attainable fitness goals, (d) educate participants about the concepts of physical fitness and individual fitness status, and (e) evaluate the probability of disease via risk stratification. As with any field test, the cycle protocol developed in this study may also be useful to some degree in satisfying each one of these five purposes. In particular, this cycle protocol and accompanying regression equation (Table ) were designed to clarify the interpretation and classification of baseline and follow-up VO predictions by establishing a common criterion measure (e.g., treadmill VO scores) across a number of field tests involving walking, running, stepping, and cycling (Cooper, 1968; Kline et al., 1987; McArdle et al., 197). In terms of developing exercise prescriptions, individuals who wish to cycle for exercise can use data from the subimal cycle protocol (exercise heart rate, work rates, and ratings of perceived exertion) to help fine-tune a proper exercise training intensity. On the other hand, when a more precise exercise training intensity prescription is desired, it may be necessary perform a imal graded exercise test or to perform a test that involves a mode of exercise that corresponds to the type of exercise performed during the exercise program (e.g., perform walking tests when prescribing walking programs or use cycle VO scores when prescribing specific cycling exercise intensities). In conclusion, the subimal cycle ergometer test developed in this study yields relatively accurate estimates of treadmill VO values in young, healthy adults. The proposed cycle protocol requires only a moderate level of exertion, and is a convenient and time-efficient means of estimating cardiorespiratory fitness. Minimal shrinkage should be realized when this regression model (Table ) is used to predict VO on other young, healthy adults who possess a similar age, body mass, and fitness level as this sample. Future research is now warranted to compare the reliability and generalizability of this subimal cycle ergometer test with other common field tests.

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