Szrmmay.-The object of this investigation was to establish a group-normahzed perceptual response, using the Borg 15-category rating of perceived exertion (WE).
Perceptual and Motor Skills, 2003,96, 739-747. O Perceptual and Motor Skills 2003
RATINGS O F PERCEIVED EXERTION AND ENERGY EXPENDITUKE DURING LIGHT T O MODERATE ACTIVITY ' FREDRIC GOSS, ROBERT ROBERTSON, SERGIO DASILVA, RICHARD SUMINSKI, JIE KANG, AND KENNETH METZ
Center for Exercise and Health-Fitness Research University of Pittsburgh. Szrmmay.-The object of this investigation was to establish a group-normahzed perceptual response, using the Borg 15-category rating of perceived exertion ( W E ) scale, that is consistent with the Surgeon General's recommendations for physical activity intensity. This normaLzed response is defined as a range of W E s corresponding to a target physiological outcome during exercise common to a speczied group of individuals. 24 college-age students (12 men; 12 women) underwent a progressive exercise test administered on a semi-recumbent leg cycle machine to estimate V 0 2 peak and 12 6-min. exercise trials on a combined arm and leg exercise machine. Three trials were conducted per day, and at least 24 hr. separated testing sessions. RPEs beween 7 and 10 were consistently estimated during trials categorized as light to moderately intense (35 to 53% V 0 2 peak). These exercise intensities resulted in an energy expenditure of between 5.38 (SD= 1.37) to 7.56 (SD=0.60) and 3.58 (SD=0.58) to 5.30 (SD=0.97) kcal. min.-' for these men and women, respectively. RPEs corresponding to 7: extremely light to 10: very light or light are sufficient in healthy young college students to achieve the target activity with respect to exercise intensity. Therefore, this group-normalized perceptual response, i.e., W E = 7 to 10, may be expressed as a prescriptive reference enabling college-age individuals to produce an exercise intensity designed to promote health and studied longitudinally to assess the effects long term.
Regular participation in aerobic exercise has been shown to enhance car&ovascular fitness and reduce the risk of premature death and chronic diseases, such as coronary artery disease, hypertension, Type I1 diabetes mellitus, and colon cancer (Blair, Kohl, Paffenbarger, Clark, Cooper, and Gibbons, 1987; Powell, Thompson, Casperson, & Kendrick, 1987). Despite the growing body of scientific evidence h l u n g a physically active lifestyle to both the length and quality of life, it has been estimated that only 22% of adult Americans regularly engage in activities designed to promote health and fitness (Department of Health and Human Sciences, 1996; U.S. Department of Health and Human Services, 1996). Part of this reluctance to become physically active may be h k e d to the public's perception that relatively intense, protracted exercise is necessary to reahze health and fitness benefits. Therefore, the United States Centers for Disease Control and Prevention (CDC) 'Please address correspondence to Fredric Goss, Ph.D., Center for Exercise and Health-Fitness Research, School of Education, University of Pittsburgh, 113 Trees Hall, Pittsburgh, PA 15261.
740
F. GOSS, ET AL.
and the American College of Sports Medicine (ACSM) in conjunction with the President's Council on Physical Fitness and Sport and the Surgeon General have released statements promoting the value of daily physical activity (American College of Sports Medicine, 1993; Department of Health and Human Sciences, 1996). These "Exercise Lite" recommendations stress that daily physical activities do not need to be intense and of prolonged duration. Rather, light to moderately intense, i.e., brisk walking, discontinuous activities totaling 30 min. d produce important health benefits. Information concerning the group-normalized perceptual response to this magnitude of exertion may be valuable in promoting physical activity. Such response is defined as a range of ratings of perceived exertion (WE) that corresponds to a target physiological outcome during activity common to a group of indviduals. Ratings of perceived exertion are widely used to prescribe and regulate exercise intensity in various athletic, clinical, and pedagogical settings. In addition, the intensity of household and occupational activities is often influenced either consciously or unconsciously by individual perceptions of exertion. Ratings of perceived exertion may be defined as "The subjective intensity of effort, strain, dscomfort, and/or fatigue that is experienced during exercise and physical activity" (Noble & Robertson, 1996). The Borg 15-category scale is perhaps the most widely used W E measurement to assess ratings of perceived exertion (Borg, 1971). This scale is simple to use, does not require sophisticated instrumentation and has been shown to be vahd and reliable (Noble & Robertson, 1996). Therefore, the objective of this investigation was to established a group-normalized perceptual response in college-age students, using the Borg 15-category scale, consistent with the Surgeon General's recommendations for physical activity intensity.
Subjects Twenty-four college-age students (12 men and 12 women) participated. Important subject characteristics are presented in Table 1. Subjects were physically active and free of cardiovascular, metabolic, and orthopedic limitations. Procedure Prior to the experimental trials V 0 2 peak tests were administered on a semirecumbent leg cycle machine (Nordic Track; Total-Body Fitness System). The seat of the exercise machine was positioned so the knees were slightly flexed as the legs extended and the foot pedals were in the farthest position from the body during pedahg. The seat position for each subject was recorded and replicated during all subsequent tests. The initial workload con-
PERCEIVED EXERTION: PUBLIC HEALTH LMPLICATIONS
74 1
TABLE 1
SUBJECTS' CHARACTERISTICS Characteristic
Sex Women
Age, yr.
M
SD Height, cm
M
SD Weight, kg
M
SD % Fat
M
VOz peak, 1 . min.-'
M
V 0 2 peak, ml . kg-' . min.-'
M
HRpeak,beats . m i . - '
M
RE%eak
M
SD SD SD SD SD
Men
22.9 5.1 163.9 5.9 59.0 7.6 23.6 3.5 2.045 ,286 34.8 3.7 187.8 12.9
22.4 1.6 177.9 7.2 82.6 11.5 16.0 5.9 2.938 .3 13 36.1 5.7 182.0 11.7
1.15 0.07
1.19 0.07
sisted of unloaded p e d a h g , i.e., zero resistance, at a cadence of 60 rev. min.-'. After 3 min. the resistance was increased one unit. Subsequent increases in exercise intensity were achieved by increasing the resistance setting two units every 3 min. until Stage 6, i.e., 60 rev. mh.-', resistance=9 units. This represented the maximum resistance setting for the exercise machine. At this point, the pedaling frequency was increased by 10 rev . min.-' for each additional 3-min. workload, i.e., Stages 7 , 8, and 9. Tests were terminated when subjects could no longer maintain the appropriate pedaling rate. Oxygen consumption (V02), ventilation (VE, STPD), and the respiratory exchange (RER) ratio were obtained every 30 sec. using open circuit spirometry. The aerobic metabolic system, which was controlled by an Apple IIe computer, consisted of an Applied Electrochemistry S-SA 0 2 analyzer, a Beckman LB-2 C 0 2 analyzer, and a Parkinson-Cowan flow meter. The electronic gas analyzers were cahbrated immediately prior to each exercise test using standard reference gases. Heart rate (HR) was measured during the last 30 sec. of each workload using an Eaton Care Telemetry system. Criteria for V 0 2 peak was the attainment of at least two of the following: (1) a plateau in oxygen consumption with an increase in exercise intensity, (2) a respiratory exchange ratio greater than 1.1, and (3) heart rate within 10 beats. min.-' of each subject's age predicted maximal heart rate. Ratings of perceived exertion (Borg 15-category scale) for the overall body ( W E ) were obtained during the final 30 sec. of each workload. A standard definition of perceived exertion and instructional set for use of the Borg scale was read to
742
F. GOSS, ET AL.
the subject prior to each exercise testing session (Noble & Robertson, 1996). Low and high perceptual anchors were established during these tests using standard anchoring procedures (Noble & Robertson, 1996). Each subject completed 12 exercise trials on the Nordic Track Total Body Fitness System (Table 2). Trials were 6 min. in duration. Subjects were randomly assigned to a counterbalanced sequence. Subjects completed three exercise trials during each testing session. At the completion of each 6-min. exercise trial, subjects remained seated on the exercise machine. Subsequent exercise trials were not initiated until heart rate returned to within 10 beats . min.-' of the pretest resting value. At least 24 hr. separated testing sessions. Oxygen consumption, VC02, RER, VE STpD, and WE were obtained during the final minute of each trial. Caloric expenditure for each trial was calculated using the RER and absolute steady state V 0 2 (McArdle, Katch, & Katch, 1996). During the leg trials that included arm activity, the hands were placed shoulder width apart on a lightweight metal bar. Subjects then performed arm-extension movements similar to a standard bench press at a rate equal to one-half the leg pedahng frequency. As such, subjects completed either 20 or 30 complete arm repetitions each minute. TABLE 2 EXPERIMENTAL TRIALS
Note.-N
Leg Pedaling Frequency ( r e v . min.-')
Leg Resistance Units
Arm Activity
40 40 40 40 40 40 60 60 60 60 60 60
0 0 2 2 4 4 0 0 2 2
N Y
N Y N
Y
N Y N Y
4
N
4
Y
= n o arm activity, Y = arm activity.
Statistical Analysis Separate two-way repeated-measures analysis of variance (sex x trial) was used to examine the aerobic metabolic and perceived exertion responses to semirecumbent leg-only cychg and combined arm and leg exercise. Significant main and interactive effects were probed with Scheffi post hoc analysis. Significance was established a priori at .05 for all analyses. Pearson product-moment correlations were calculated to estimate the relation benveen the
743
PERCEIVED EXERTION: PUBLIC HEALTH IMPLICATIONS
perceptual and physiological responses. These correlations were conducted for the male and female cohorts separately and on the combined subject pool h e . , N = 24).
Perceptual Responses A main effect for sex ( p < .05) was noted for WE. Women reported significantly greater exertional perceptions. A significant interaction for sex x trial ( p < .05) was also observed for WE (Table 3 ) .
RATINGS OF
TABLE 3 PERCEIVED EXERTION DURING SEMIRECUMBENT LEGCYCLING AND COMBINED ARM EXERCISE AND LEGCYCLING
RPM = 40 Lee Resistance/Arm ActivitP O/N k'Y 2/N 2 N 4/N - 4 N
WM = 60 Lee Resistance/Arm ActivitP O/N 0 j b 2/N 2 N 4/N ' 4 N
6.4 0.5
6.8 KgLM 7.1LM 7.gLM7.qnLM 9.qLM 0.9 1.6 1.5 0.7 1.0 1.6
Men
M SD
8.2 1.9
6.5 0.5
7.5 0.9
6.8 7.gLM 0.6 0.8
Women
M
6.6 7.5 6.5 7.8 7.3 8.3LM SD 0.9 1.2 0.7 1.2 1.0 1.3 Resistance,=O, 2, o r 4; Arm Activicy=Y, Yes; mo erate Intensity acuvlues, I.e., 35.53% V 0 2 peak.
Ty
6.6 8.9LM 7.6LM 9.qLM 9.gLM 10.2 1.7 1.6 1.8 2.3 0.7 1.4 N , No. LM RPEs correspond to light to *p
