Introduction
Based on the 2007 recommendations for physical activity by the American College of Sports Medicine (ACSM) and the American Heart Association, individuals should perform either 30 minutes of moderate-intensity physical activity 5 d·wk−1 , 20 minutes of vigorous intensity physical activity 3 d·wk−1 , or a combination of both moderate and vigorous physical activities (7 7 14
The ACSM has established objective guidelines for moderate to vigorous intensity exercise corresponding to 40–85% of oxygen consumption reserve (V[Combining Dot Above]O2 R) or heart rate reserve (HRR) (2
There are several methods currently available for individuals to self-monitor their exercise intensity. The more quantitative of these methods is to have individuals monitor their HR during exercise because the HR has a linear relationship to V[Combining Dot Above]O2 . However, this can be difficult for some people to execute because it likely requires stopping exercise to calculate the HR. Additionally, some individuals may not have the technical skills to accurately palpate their pulse. An alternative is to use an HR monitor, but cost may be a barrier. Another way to self-monitor exercise intensity is with the Borg rating of perceived exertion (RPE) scale. The Borg scale is based on the relationship of an individual's RPE to HR. The drawback of this technique is that the individual must visually see the Borg scale in order for the rating to be accurate; therefore, it is not necessarily applicable to a large percentage of exercisers, particularly under field conditions, because exercisers tend to underestimate their RPE without a visual reference scale (1 rest ), the individual would be given a target number range to count to during exercise, based on a percentage of the CTTrest (%CTT), which would correspond with moderate to vigorous intensity exercise. Thus, individuals can easily assess their exercise intensity anytime during exercise without stopping by simply seeing how high they can count with one breath. The CTT method was developed as a means to semiquantify exercise intensity for individuals to obtain an estimate of their exercise intensity at any time during an exercise bout (9 8 8
The purpose of this study was to further assess the utility of the CTT by evaluating its reliability as a means of estimating cardiorespiratory exercise training intensity in healthy young adults across various modes of exercise. The study's hypothesis was that the CTT method would consistently correlate with moderate to vigorous exercise intensity levels across various modes of aerobic exercise. If found to be so, the CTT could serve as an easy and practical tool to use to direct exercise participants in estimating and monitoring their desired exercise intensity to reach optimal health benefits.
Methods
Experimental Approach to the Problem
The %HRR is one of the criterion measures recommended by the ACSM as a measure of exercise intensity. To evaluate the consistency of the CTT at various exercise intensities, across exercise modes, we used the %HRR as the independent variable. The study required the subjects to participate in 3 separate sessions, scheduled for the same time of the day (±1 hour), within a 2-week time period. During session 1, the HRR was determined from a maximal effort treadmill test using the peak HR achieved during the test and the resting HR of the individual (HRRpeak ). Additionally, the age-predicted maximum HR was determined and used to calculate the HRR as well (HRRAPMHR ). These 2 ways of determining the HRR were then compared.
The %CTT ([count achieved while exercising/CTTrest ] × 100) was the dependent variable in this study. The %CTT corresponding to exercise intensities of 40%HRR, 50%HRR, 60%HRR, 75%HRR, and 85%HRR were obtained on individuals while performing 4 different modes of exercise. The reliability of the CTTrest measure, the key component in the %CTT equation, was assessed by comparing the CTTrest obtained at each of the 3 sessions. Then, the relationship of the %CTT to the range of exercise intensities (%HRR) for each of the exercise modes was compared. These correlations were used to evaluate how well the CTT method corresponded with the HRR method for estimating exercise intensity and the consistency of the CTT method across various modes of aerobic exercise. All testing for this project was conducted in the same year during the months of August, September, and October at the University of Nebraska Medical Center.
Subjects
The subjects were recruited from the University population and local community and had various training backgrounds ranging from 0 to 6 d·wk−1 of exercise participation. Thirty-six of the 37 subjects initially recruited completed the study. One subject developed a lower extremity muscle cramp in the early stages of the treadmill test protocol for which the investigators stopped the test before maximal effort was achieved. None of the subjects completing the study protocol experienced any exercise-related problems. Subject demographics are presented in Table 1 .
Table 1: Subject demographics.*
This study was approved by the University of Nebraska Medical Center's Institutional Review Board, and all the subjects gave their written informed consent before enrollment. The subjects were then screened with a health history questionnaire and the Physical Activity Readiness Questionnaire (PAR-Q) before testing (2
Procedures
The study required the subjects to participate in 3 separate sessions, scheduled for the same time of day (±1 hour), within a 2-week time period. The subjects maintained their usual sleep, diet, and hydration routine during the time of the study but were told not to eat 2 hours before their testing times. During the first session, the subjects underwent a maximal effort treadmill test to determine each subject's peak HR. Using their peak HR and resting HR, the HRR was calculated for each individual (HRRpeak ). In addition, an estimated HRR was calculated (HRRAPMHR ) for each individual using the formula 208 − 0.7age = HRmax to estimate the age-predicted maximum HR (13 rest ] × 100) to %HRRpeak , % HRRAPMHR , and RPE.
Session One
The first session, conducted in the department's research laboratory, consisted of each subject undergoing a maximal effort treadmill test using the Bruce Protocol. Testing was performed using a Quinton Q5000 Stress Test System with a Q55 Treadmill (Quinton Instrument Company, Seattle, WA, USA). The HR and rhythm were monitored continuously throughout the session with a 12-lead electrocardiograph (EKG). Immediately before the test, each subject sat quietly in a chair for 7–10 minutes to allow collection of baseline HR, blood pressure (BP), and EKG measures. The BP was measured by the standard auscultatory technique using a sphygmomanometer (Tycos Tr-1, Welch Allyn, Inc., Skaneateles Falls, NY, USA) and stethoscope (Littmann Classic II S.E., 3M Corp., St. Paul, MN, USA). During this rest period, the test protocol was verbally reviewed, and the subject was reminded that the goal would be to give his or her maximal effort. In addition, standardized instructions for the CTT method and RPE scale were given with the subject confirming understanding.
Perceived Exertion Scale (Borg 6–20 Rating of Perceived Exertion Scale)
At each session, before performing the exercise trial, each subject was shown the Borg RPE category scale (6–20 RPE scale) and instructed on its usage by having the following standardized statement read to him or her (3
“You are now going to take part in a work test. You will be walking on the treadmill (or insert appropriate exercise mode ) at different workloads. We will be measuring your heart rate and blood pressure while you are exercising and when you are at rest. We want you to try to estimate how hard you feel the work is; that is, we want you to rate the degree of perceived exertion you feel. By perceived exertion we mean the total amount of exertion and physical fatigue, combining all sensations and feelings of physical stress, effort, and fatigue. Don't concern yourself with any one factor such as leg discomfort, shortness of breath or work intensity, but try to concentrate on your total, inner feeling of exertion. Try to estimate as honestly and objectively as possible. Don't underestimate the degree of exertion you feel, but don't overestimate it either. Just try to estimate as accurately as possible.”
Counting Talk Test
All the subjects were instructed in the CTT before each session and practiced performing the CTT verbally to 1 of the investigators to ensure that they could perform the CTT appropriately before the exercise trial. The standardized instructions provided to the subjects were as follows:
“Take a maximal breath in and count out loud, at your usual talking pace, using the following sequence; One-one thousand, Two-one thousand, Three-one thousand, Four-one thousand, and so on. Try to count as high as you can before having to take another breath. At no time should you hold your breath when performing this test.”
At rest, an investigator recorded how high the subject was able to count before having to take a second breath. The highest completed CTT number was recorded as the CTTrest .
The CTT, RPE, and BP were obtained during the last minute of each stage of the treadmill protocol. The subjects were provided verbal encouragement throughout the test. A maximal effort on the treadmill test was considered achieved when the subject indicated that they could no longer keep up with the treadmill. Maximal effort by the subjects was also supported by all the subjects having had an RPE ≥ 18 or achieving a HR ≥ 90% age-predicted maximal HR. After the completion of the first session, the resting HR and peak HR achieved were used to determine the HRR. The HRs corresponding to 40% HRR, 50% HRR, 60% HRR, 75% HRR, and 85% HRR were calculated for each individual (%HRR = [(HRpeak − HRrest ) × %] + HRrest ). These HRs were used to direct the exercise intensities in sessions 2 and 3. In addition, the % CTT was calculated (% CTT = [(count achieved while exercising/CTTrest ) × 100]) and recorded along with the RPE at each stage of the test.
Sessions Two and Three
Sessions 2 and 3 were conducted in the University's fitness center and indoor track under field conditions. During each of these sessions, the subjects participated in 2 different modes of exercise. The 4 modes of exercise were as follows: (a) walking/jogging on a flat track, (b) upright stationary cycling (Tectrix BikeMax, Cybex International, Inc., Medway, MA, USA), (c) an elliptical trainer (EFX576i, Precor, Inc., Woodinville, WA, USA), and (d) stair stepper (4400PT, StairMaster® Corporation, Vancouver, WA, USA). The subjects performed the 4 exercises in the order assigned at the time of enrollment. At the beginning of these sessions, each subject was fitted with a Polar HR monitor (Model FS1, Polar Electro Oy, Kempele, Finland) for the continuous monitoring of HR. Additionally, an investigator reviewed the CTT and RPE methods with the subject and provided standardized instructions for these methods as was done in session 1. Under the guidance of an investigator, each subject exercised for five 3-minute bouts at his or her individually calculated HRs corresponding to 40% HRR, 50% HRR, 60% HRR, 75% HRR, and 85% HRR. During the last minute of each exercise stage, the subjects were asked to perform the CTT and give their RPE from an easily visible chart. The HR, CTT, and RPE were recorded at each workload. The % CTT for each exercise stage was then calculated. The subjects were given time to rest between modes to allow their HR to return to within 5–10% of their resting HR.
Statistical Analyses
Data analysis consisted of descriptive statistics for subject demographics. A comparison of peak HRs achieved on the graded exercise test during session 1 and the estimated age-predicted maximum HRs was performed. Because the HR data did not pass the normality test, the nonparametric Mann-Whitney rank sum test was used to perform this comparison. A one-way repeated measures analysis of variance (ANOVA) was performed for the comparison of the subjects' CTTrest across the 3 sessions. Pearson correlation analyses were conducted to determine the relationships of %CTT to %HRpeak , %CTT to %HRRAPMHR , and %CTT to RPE. Statistical significance was set at p ≤ 0.05. All statistical analyses were performed using the SigmaStat software package (Version 3.0; SPSS Inc., San Rafael, CA, USA).
Results
Subjects' HRpeak achieved on the baseline graded exercise test was compared with the age-predicted maximum HR (HRAPMHR ) using the formula 208 − 0.7age = HRmax (13 p = 0.06) was noted between the comparison HRpeak and HRAPMHR . The HRpeak and HRAPMHR were 188 ± 6 and 191 ± 1 b·min−1 , respectively. This allowed for the comparison of the % CTT at various intensities of exercise to % HRR based on HRpeak or the HRAPMHR in the % HRR calculation for the various modes of exercise. Thus, the comparison of the % CTT and % HRR is not dependent upon a maximum effort exercise test being performed as the age-predicted maximum HR can be used to calculate the HRR in healthy young adults.
The resting CTT performed by the subjects at the beginning of each of the 3 sessions was compared for consistency of this measure over time. A one-way repeated measures ANOVA demonstrated no significant difference in the resting CTT counts among the sessions (p = 0.58). The resting CTT mean ± SD for sessions 1–3 were 22 ± 5, 23 ± 6, and 23 ± 6, respectively, demonstrating the reliability of the CTTrest for calculating the intensity based on the %CTT.
Pearson correlations evaluated the relationship of the % CTT to (a) % HRR based on the HRpeak achieved during baseline graded exercise testing, (b) % HRR based on HRAPMHR , and (c) RPE. Table 2 summarizes the correlation findings among these measures of exercise intensity for the study population. The CTT method demonstrated moderate to good correlations with each of the comparison methods for estimating the exercise intensity across the various modes of exercise (12 p < 0.001) across exercise modes and intensity.
Table 2: Correlations of %CTT to %HRR based on peak HR, %HRR based on age-predicted maximum HR, and RPE for each mode of exercise.*
The CTTrest performed by the individuals varied, ranging from 11 to 38. The Subjects with the higher resting CTT demonstrated a larger decrease overall in their % CTT value once exercise was initiated than those with lower CTTrest . To further evaluate the most appropriate exercise intensity recommendations by the CTT method, we compared those individuals with a CTTrest <25 (n = 20) across exercise modes separately from those subjects with a CTTrest ≥ 25 (n = 16). Figure 1 illustrates the relationship between % CTT and % HRR for those individuals with a CTTrest <25 and those ≥25, exercising on the track. Similar findings were noted for the other modes of exercise tested. The Pearson correlation coefficients (Table 3 ) for each group and each mode of exercise were similar between groups and consistent with what was found for the whole study population (Table 2 ). Thus, the % CTT was consistently lower (p < 0.001) in the group with a CTTrest ≥25 for each exercise mode compared with the group with a CTTrest <25.
Table 3: Correlation of % CTT by group (CTTrest < 25 and CTTrest ≥ 25) and by exercise mode to %HRRpeak and %HRRAPMHR .*
Figure 1: Relationship between percent counting talk test and percent heart rate reserve for the exercise mode of track ambulation. The figure demonstrates the relationship for those subjects with a resting counting talk test of <25 (solid line) and those subjects with a resting counting talk test ≥25 (dashed line). %CTT = percent of counting talk test; %HRR = percent of heart rate reserve.
The ACSM guidelines for describing moderate to vigorous exercise intensity based on the HRR method is 40–85% HRR (2 rest <25, exercising at a level of 40–50% CTTrest would place them in the moderate to vigorous exercise intensity range. Those individuals with a CTTrest ≥25, exercising at a level of 30–40% CTTrest would place them in the moderate to vigorous exercise intensity range. Consistency was demonstrated using the CTT method across the various modes of aerobic exercise. As such, the above recommendations for % CTT equating to moderate to vigorous exercise intensity were independent of exercise mode.
Discussion
This study found the CTT method to be consistent across exercise modes for estimating moderate to vigorous exercise intensity in young healthy adults. For individuals with a CTTrest count <25, exercising at 40–50% of the CTTrest count corresponded to moderate to vigorous exercise intensity, whereas the individuals with a CTTrest count ≥25 exercising at 30–40% of the CTTrest count corresponded to moderate to vigorous exercise intensity. These guidelines based on the CTT method are consistent with the current public health recommendations for physical activity intensity by the ACSM (7
Other variations of the Talk Test method have been reported in the literature. One variation is to have subjects respond aloud to scripted questions played to them on a cassette player while exercising and rate their ability to speak comfortably. Using this strategy, Brawner et al. (4 5 2 measures, when exercising up to a level at which they could still comfortably speak. Another talk test variation requires individuals to recite a standardized paragraph and rate their ability to speak comfortably. Using this recitation strategy, Dehart-Beverley et al. (6 10 11 9
In addition, the CTT method demonstrated moderate to good correlations across exercise modes with RPE, another non-HR–dependent method for guiding exercise intensity. However, the RPE scale needs to be easily visible to the individual during exercise for accurate use. Abadie found that when individuals exercising at moderate to vigorous intensity exercise levels did not have the RPE scale visible, perceived exertion was underestimated, resulting in individuals attaining higher HR responses than when the scale was visible (1
Practical Applications
The CTT provides a simple method for recommending appropriate aerobic exercise intensities that are adequate to achieve the current ACSM recommendations regarding moderate to vigorous physical activity intensity. The relationship of the CTT method to the HRR method, using either HRpeak or HRAPMHR in the HRR calculation, allows practitioners to easily check the intensity of the recommended % CTT range to the % HRR whether or not a graded exercise test was conducted before initiating an aerobic exercise training program. For example, an individual with a CTTrest of 24, recommending he or she exercise at a level where he or she can only count to 10–12 (40–50% CTTrest ) while exercising would correspond to a moderate to vigorous exercise intensity level. For an individual with a resting CTT count of 30, recommending he or she exercise at a level where they can only count to 9–12 (30–40% CTTrest ) while exercising would allow them to achieve a moderate to vigorous exercise intensity level. The CTT can be performed by an individual at any time during exercise to assess their intensity without having to stop to take a pulse rate, carry a script or cassette player, or limit exercise only to areas where an RPE scale is readily visible. The CTT provides a semiquantitative method for coaches or practitioners to use to develop a multimodal aerobic exercise prescription for individuals consistent with the ACSM recommendations (2
Acknowledgments
The authors wish to thank Ms. Anne Skinner for her assistance with the data management.
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