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Journal of Exercise Physiologyonline

April 2014

Volume 17 Number 2

J
Editor-in-Chief
Tommy Boone, PhD, MBA

Review Board
Todd Astorino, PhD

Julien Baker, PhD

Steve Brock, PhD

Lance Dalleck, PhD

Eric Goulet, PhD

Robert Gotshall, PhD

Alexander Hutchison, PhD

M. Knight-Maloney, PhD

Len Kravitz, PhD

James Laskin, PhD

Yit Aun Lim, PhD

Lonnie Lowery, PhD

Derek Marks, PhD

Cristine Mermier, PhD

Robert Robergs, PhD

Chantal Vella, PhD

Dale Wagner, PhD

Frank Wyatt, PhD

Ben Zhou, PhD

Official Research Journal of the American Society of Exercise Physiologists

ISSN 1097-9751

Official Research Journal of the American Society of Exercise Physiologists
ISSN 1097-9751
EPonline

The Impact of a Self-Selected and Imposed Intensity on Cardiorespiratory Fitness and Body Composition in Obese Women
Luís A. G.Freitas¹,Kleverton Krinski²,Hassan M. Elsangedy³,Rosemari Q. Freitas⁴,Julia Z. Durigan¹,Anita A. Feitosa¹,Rafael Pinto¹,Silas S. Dias¹,Giulianna C. Silva¹,Gustavo A. Arruda¹,Sandro S. Ferreira⁵,Antônio C. Dourado¹,Sergio G. DaSilva⁵
¹Department of Physical Education, State University of Londrina, Brazil; Federal University of São Francisco Valley, Brazil; ³, Federal University of Rio Grande do Norte, Brazil; ⁴University of North Parana, Brazil; ⁵, Federal University of Parana, Brazil

ABSTRACT

Freitas LAG,Krinski K,Elsangedy HM,Freitas RQ, DuriganJZ, FeitosaAA,Pinto R,Dias SS,Silva GC,Arruda GA,Ferreira SS,Dourado AC,DaSilva SG. The Impact of a Self-Selected and Imposed Exercise Intensity on Cardiorespiratory Fitness and Body Composition in Obese Women. JEPonline 2014;17(2):44-52. The purpose of this study was to investigate the impact of self-selected and imposed exercise intensity on cardiorespiratory fitness and body composition in 75 obese women. The subjects were divided into: G1 (self-selected intensity); G2 (intensity 10% above ventilatory threshold); and G3 (control group, no exercise). The exercise program consisted of 12 wks. The findings demonstrated a significant improvement in cardiorespiratory fitness (VO₂max and HR_VT) in G1 (3.55 mL·kg^-1·min^-1) and in G2 (9.69 mL·kg^-1·min^-1). There were no significant changes in body composition. In conclusion, the 12-wk program of self-selected and imposed exercises resulted in an improvement in cardiorespiratory fitness with no significant changes in body composition. The self-selected intensity demonstrated to be an important strategy in order to promote engagement of obese subjects in an exercise program.
Key Words: Aging, Obesity, Aerobic Exercise, Physical Fitness

INTRODUCTION
Obesity has achieved epidemic levels over the last few decades, reaching underdeveloped and developed countries . According to the World Health Organization (WHO), there are regions in which 73% of the population is overweight and/or obesity . The accumulation of excess body fat is associated with the onset of diabetes, cancer, heart disease, hypertension, and other diseases that decrease health and well-being . The management of obesity rate in countries at risk plays an important role in public health, since the decrease of Body Mass Index (BMI) influences the control and reduction of numerous diseases. It also contributes to the economy in reducing the financial cost of annual treatments by governments .
Regular exercise, with or without dieting, is an important strategy in the control and management of obesity related diseases and disabilities . In fact, the results of previous studies (16,21) show that regular exercise provides important health benefits. But, in order to maximize the effects of exercise on body fat, the relationship between intensity and duration of exercise had to be clarified. Several studies indicate that the relationship between the two results significant effects as long as the exercises are moderate to vigorous intensity or of the intermittent type exercises . Interestingly, there are only a few studies that have observed this effect in obese subjects following a few months of intervention without dieting.
An important factor that must be taken into account when prescribing an exercise program to obese individuals is that they present with sedentary habits and, as a result, a low fitness level . Thus, the prescription of a high intensity exercise program can result in unpleasant sensations and a low involvement in the exercise program. On the other hand, the self-selected exercise intensity approach seems intuitively better in the promotion of an exercise intensity that is sufficient to result in positive physiological benefits to the subjects’ health. Also, it is reasonable to expect that the exercisers are more likely to stay with the self-selected exercise intensity program than an intensity set by someone else. However, scientific inquiries that have observed the effect of an exercise program on self-selected intensity in obese population are scarce. Thus, the purpose of this study was to investigate the impact of self-selected and imposed exercise intensity on cardiorespiratory fitness and body composition

METHODS

Subjects and Experimental Design

This study included 75 obese volunteer women who were randomly divided into 3 groups: G1 (self-selected intensity); G2 (intensity imposed 10% above ventilatory threshold); and G3 (control group, no exercise). Each group was assisted individually for both information and the experimental procedures of the study. Each subject performed pre- and post-intervention. After recruitment, selection, and separation of the groups, the subjects underwent an assessment of anthropometric parameters that included body weight, height, body fat percentage, and waist circumference. Then, the subjects were submitted to the evaluation of cardiorespiratory fitness in order to start the process of intervention. The intervention program lasted 12 wks with the exercise sessions divided into 3 times·wk^-1 for a total of 36 sessions. The same schedule of exercises was kept throughout the program. The subjects were instructed to maintain their daily activities, which included no change in their eating habits during the duration of the program. For control purposes, food and daily activities evaluation was carried out through recall of the last 7 days. Physical activities not supervised were monitored throughout the study with a Digi-Walker Pedometer (model DW-200, Yamax, Tokyo, Japan). After 12 wks, the subjects repeated the anthropometric and physical fitness evaluations. All subjects were instructed not to consume products containing alcohol and caffeine. They were also asked not to eat before the tests.

Intervention Program

The walking sessions for groups 1 and 2 were performed on a 400 m official tartan track (lane 1) that was demarcated meter by meter, supervised by an experienced fitness trainer. The exercise dose was closely monitored in each session. To monitor each bout of exercise, the distance traveled was recorded and heart rate (HR) was observed during the walk. The Borg scale (6-20) was also used as was the Feeling Scale (FS) in accordance with the procedures of DaSilva et al. to assess the subjects’ level of fatigue and feeling (pleasure/displeasure) during and at the end of each session. All exercise sessions were conducted individually to avoid any possible effect on the responses to the exercise. Each session began with a 5-min warm up and ended with a 5-min cooling followed by a 5- min stretching period.

During the self-selected intensity training, the subjects (G1) completed 12 wks of self-selected walking supervised exercise. The duration of each exercise session was 30 min on 3 non-consecutive d·wk^-1. All subjects were given the instructions: “You are supposed to choose a walking intensity of your preference. The session is supposed to last 30 min. Intensity must be as high as enough so that you have a good workout, but not so high that when exercising every day or on every other day it stop you from continuing to exercise. The intensity must be appropriate for you” . During the imposed intensity training, the subjects (G2) underwent 12 wks of imposed walking speed, intensity 10% above the ventilatory threshold (determined in the incremental test to exhaustion) controlled by the HR. Each exercise session lasted 20 min, with 3 non-consecutive d·wk^-1. Throughout the session, all subjects were verbally encouraged and given feedback to continue their efforts in maintaining the submaximal prescribed zone (~110% of VT). Although the subjects in the control group did not participant in physical exercise, they were instructed to maintain their current level of physical activity throughout the study.
Incremental Test to Exhaustion

The incremental exercise treadmill test to exhaustion (model Super ATL, Inbramed™, Porto Alegre, Brazil) was performed using the standard protocol proposed by Bruce , which consisted of 3-min stages of 3 min for the evaluation of the VO₂max. All subjects were verbally encouraged to continue the exercise to the point of exhaustion. Among the criteria used to achieve VO₂max, the subjects had to meet at least two of the following three criteria: (a) a plateau of O₂ (changes <150 mL·min^-1); (b) respiratory exchange ratio (RER) ≥1.10; and (c) heart rate (HR) of 10 beats·min^-1 within the maximum level expected for age . Heart rate (HR) (beats·min^-1) was measured continuously using a Polar monitoring system (Polar Electro ™, Oy, Finland). A portable analyzer K4 (Cosmed, Rome, Italy) was used to measure O₂, carbon dioxide production (CO₂), and pulmonary ventilation (V_E, STPD). The expired gases were collected and analyzed breath-by-breath. Before each test, the analyzer was calibrated. To determine VO₂ at ventilatory threshold (VO_2VT), the standard procedure of visually identifying the point at which the ventilation plot ratio of oxygen consumption per minute (V_E/VO₂) versus the ventilation ratio of CO₂ production per minute (V_E/VCO₂) deviates from normalcy was used.

Anthropometric Measurements

Body mass was measured with an electronic scale (Toledo scale, São Paulo, Brazil) with a precision of 0.1 kg. Height was measured with a stadiometer (Sanny stadiometer, São Paulo, Brazil) with an accuracy of 0.1 cm. The Body Mass Index (BMI) was calculated by dividing weight by height squared (kg·m^-2). To evaluate the abdominal circumference, the abdominal region of interest was defined manually adjusting the lines between L1 (top) and L4 (bottom) and the inner edge of the costal for the whole body scan. The waist circumference (WC) was measured in duplicate horizontally at a point immediately above the iliac crest on the midaxillary line in minimal breathing with an accuracy of 0.1 cm. Abdominal obesity was defined when the waist circumference was greater than >88 cm for women. To evaluate body composition, the subjects were instructed to wear light clothing while measurements were taken without their shoes and jewelry. Body composition was measured by a densitometer (DPX-IQ, Lunar Corporation, Madison, Wisconsin, USA). Each subject was placed on the table in supine position with arms sufficiently separated from the trunk. The results were analyzed using the software GE Medical System under the supervision of an endocrinologist. The fat percentage, total body fat mass and trunk were obtained. Abdominal fat was determined by DXA .

Statistical Analysis

For a description of the data a descriptive analysis with average ± standard deviation was used. The Student’s t test was used to compare the pre- and post-exercise program in each group. The 3 x Control 2 factorial ANOVA (imposed intensity x self-selected intensity x Control) x (pre x post) with repeated measures was used, which was followed by the post hoc Tukey HSD test for "n" unequal. The dependent variables were the aspects related to body composition and physiological indicators. Normality was verified by the Shapiro-Wilk test and the homoscedasticity by Levene's test. The level of significance was set at P≤0.05. All data were analyzed using SPSS for Windows version 17.0 software.

RESULTS

Table 1 shows significant cardiorespiratory differences after 12 wks of intervention (compared to baseline) in both G1 and G2 groups. Table 2 indicates that no significant differences in body composition were found after the 12-wk intervention.

Table 1. Cardiorespiratory Responses Before and After 12 wks of Intervention (Mean ± SD).

	Baseline	12 wks	Δ%	t
G1 (n = 22) VO₂max(mL·kg^-1·min^-1) *	19.56 ± 3.9	23.08 ± 5.03	18.00	0.004
VO_2VT(mL·kg^-1·min^-1)	14.92 ± 3.9	17.85 ± 3.86	19.64	0.009
VO_2VT (%)	76.56 ± 10.85	78.92 ± 12.69	3.08	0.650
HR_max (beats·min^-1)	173.8 ± 6.5	172.81 ± 6.85	-0.21	0.162
HR_VT(beats·min^-1)*	143.50 ± 15.7	161.67 ± 12.71	12.66	0.000
HR_VT(%) *	82.99 ± 9.0	93.55 ± 6.26	12.71	0.000
G2 (n = 12)
VO₂max(mL·kg^-1·min^-1) ¶	15.88 ± 2.9	24.50 ± 2,62	54.28	0.000
VO_2VT(mL·kg^-1·min^-1) ¶	11.57 ± 3.1	24.48 ± 3.23	111.58	0.000
VO_2VT (%) ¶	64.87 ± 18.8	87.54 ± 8.24	34.95	0.003
HR max (beats·min^-1)	177.18 ± 8.0	177.00 ± 8.87	-0.10	0.166
HR_VT(beats·min^-1) ¶	145.73 ± 17.3	159.09 ± 12.26	9.17	0.004
HR_VT(%)	82.14 ± 7.5	89.85 ± 4.53	9.39	0.004
G3 (n = 19)
VO₂max(mL·kg^-1·min^-1)	20.38 ± 5.91	20.23 ± 6.67	-0.74	0.548
VO_2VT(mL·kg^-1·min^-1)	17.23 ± 5.0	17.75 ± 6.49	3.02	0.919
VO_2VT (%)	84.89 ± 9.20	86.92 ± 11.86	2.39	0.718
HR max (beats·min^-1)	176.53 ± 10.05	176.41 ± 9.90	-0.07	0.164
HR_VT(beats·min^-1)	149.59 ± 13.52	154.06 ± 9.66	2.99	0.222
HR_VT(%)	84.84 ± 7.31	87.37 ± 3.73	2.98	0.220

*baseline G1 different 12 wks G1 (P≤0.01); ¶baseline G2 different do 12 wks G2 (P≤0.01)

Table 1. Body Composition Before and After 12 wks of Intervention (Mean ± SD).

	Baseline	12 wks	Δ%	t
G1 (n = 22) Body fat (%)	47.24 ± 3.743	46.34 ± 3.65	-1.905	0.084
Body fat (kg)	39.78 ± 6.29	39.07 ± 6.92	-1.845	0.171
Lean mass (kg)	42.39 ± 5.48	42.94 ± 5.80	1.423	0.189
BMC (kg)	2.51 ± 0.41	2.52 ± 0.38	0.256	0.749
Weight (kg)	82.17 ± 10.28	82.00 ± 11.08	-0.20	0.526
G2 (n = 12)
Body fat (%)	49.25 ± 2.97	47.94 ± 2.58	-2.659	0.078
Body fat (kg)	42.22 ± 10.42	42.90 ± 5.79	2.153	0.607
Lean mass (kg)	41.73 ± 3.92	43.35 ± 5.52	3.838	0.105
BMC (kg)	2.41 ± 0.34	2.37 ± 0.34	-1.543	0.698
Weight (kg)	85.61 ± 8.78	86.24 ± 10.04	0.73	0.717
G3 (n = 19)
Body fat (%)	47.53 ± 4.36	48.76 ± 3.74	2.587	0.006
Body fat (kg)	41.89 ± 8.74	42.09 ± 8.68	0.461	0.775
Lean mass (kg)	42.41 ± 5.53	42.41 ± 4.89	-0.040	0.926
BMC (kg)	2.35 ± 0.26	2.41 ± 0.28	2.377	0.056
Weight (Kg)	84.45 ± 12.83	84.15 ± 12.85	-0.35	0.004

Table 3 shows the distribution of body fat before and after the 12-wk intervention period. The results indicate that no significant differences between pre- and post-exercise intervention variables except for G2 in waist circumference. All other mean differences between the groups were not significant.

Table 2. Body Fat Distribution Before and After 12 Wks of Intervention (Mean ± SD).

	Baseline	12 wks	Δ%	t
G1 (n = 22) BMI (kg·cm^-2)	34.29 ± 2.75	34.62 ± 3.47	0.962	0.343
WC (cm)	108.45 ± 7.86	107.56 ± 8.03	-0.820	0.067
Android fat (%)	55.30 ± 4.55	54.00 ± 5.44	2.350	0.102
Gynoid fat (%)	53.12 ± 4.72	52.42 ± 4.52	-1.317	0.208
Ratio A/G	1.04 ± 0.08	1.03 ± 0.09	-0.961	0.321
G2 (n = 12)
BMI (kg·cm^-2)	35.95 ± 4.52	35.86 ± 4.52	-0.250	0.883
WC (cm) **	109.89 ± 7.72	107.77 ± 9.45	-1.929	0.031
Android fat (%)	56.85 ± 3.12	55.00 ± 2.73	-3.254	0.174
Ginoide (%)	54.76 ± 4.73	54.00 ± 4.36	-1.387	0.247
Ratio A/G	1.04 ± 0.10	1.02 ± 0.08	-1.923	0.073
G3 (n = 19)
BMI (kg·cm^-2)	35.05 ± 3.07	35.73 ± 2.96	1.940	0.002
WC (cm)	105.42 ± 10.39	108.14 ± 9.93	2.580	0.115
Android fat (%)	54.77 ± 6.75	55.41 ± 6.47	1.168	0.607
Gynoid fat (%)	54.76 ± 5.04	54.82 ± 5.22	0.109	0.942
Ratio A/G	1.00 ± 0.08	1.01 ± 0.10	1	0.673

*Significant difference of P≤0.01; **Significant difference of P≤0.05

DISCUSSION

Physical exercise has been reported by health professionals as an important tool to fight obesity . The regular practice of physical exercise, besides assisting in reducing body fat and preventing disease, promotes improved physical fitness and self-esteem . Different forms of exercise can promote health benefits for obese subjects. The purpose of this study was to investigate the impact of self-selected and imposed exercise intensity on cardiorespiratory fitness and body composition in obese women.
The results related to cardiorespiratory fitness showed significant differences in the intervention groups G1 and G2. The imposed intensity provided better results in VO₂max, %VO_2VT and VO_2VT with less time in each exercise session (G2). The exercise in self-selected speed, despite having been performed with lower intensity and longer duration, also showed a significant increase in VO₂max and VO_2VT after 12 wks of intervention.
The results of this study concur with previous investigations that claim exercise programs of moderate and/or vigorous intensity provide improved fitness for sedentary, overweight, and obese subjects . Furthermore, it was observed that a self-selected intensity exercise program at 30-min can improve the physical fitness of obese subjects.
Despite demonstrating marked improvement in cardiorespiratory fitness, G2 showed high dropout rates, starting with 25 and finishing with 12 subjects. G1, with minor changes in cardiorespiratory fitness index showed a low dropout rate of 3 subjects, thus ending with 22 subjects. These findings are in agreement with earlier research that exercise intensity is negatively related to pleasure and adherence. The greater the intensity of the effort lowers the affective sensations of pleasure and, therefore, lowers the adherence to exercise . In fact, according to Lind et al. , the high intensity and the loss of autonomy from imposed activity results in an affective decline that can influence the permanence of the subject in the exercise activity.
Although ACSM (11) states that weight loss is related to the amount of exercise per week and its dose-response relationship [i.e., an exercise program with moderate intensity of: (a) ˂150 min·wk^-1 of exercise should promote a minimum weight loss; (b) ˃150 min·km^-1 a modest loss between 2 to 3 kg; and (c) 225 to 420 min·wk^-1 a high weight loss 5 to 7.5 kg], no significant changes were observed in any of the components related to body composition. Thus, the present study did not show any significant results for weight loss and body fat due to the weekly schedule destinated to the exercise (˂150 min·wk^-1).
Foster-Schubert et al. demonstrated in their study how the calorie-restricted diet, exercise, and the combination (diet and exercise) during 12 months resulted in a loss of body weight in overweight and obese women. However, while the results were significant for all of the interventions, exercise performed alone contributed the least to weight loss. The combination of diet and exercise is the key to producing a significant effect on body weight.
Other investigations also state the effectiveness of diet and exercise in combating excess fat . Thus, the non-controlling caloric intake in this study, the volume of exercises (i.e., the number of days per week), and the total exercise time may have been the primary factors that failed to produce a change in weight and body fat. However, Boutcher et al. points out that gender, energy balance, behavioral, and physiological factors may also be involved in preventing weight loss.
The distribution of body fat associated with obesity and central adipose tissue identified by intra-abdominal or visceral (android and gynoid fat) showed no significant results after 12 wks. This finding disagrees with previous studies that showed a period shorter than 16 wks may provide reduction in visceral fat . Brill et al. found that 12 wks of exercise with a duration of 30 or 60 min provided similar visceral fat loss. However, the subjects performed exercise 5 d·wk^-1 with accompanying diet. Vissers et al. published in their meta-analysis that, after 12 wks of exercise without caloric restriction, there were changes in visceral adiposity in overweight and obese subjects. Thus, it appears that the consistency of fat loss is related to the volume of exercise performed during the period.
CONCLUSION
The present study demonstrated that self-selected exercise and prescribed activity above the ventilatory threshold can provide benefits in cardiorespiratory fitness and prevent the increase of weight in obese subjects during 12 wks of exercise. For significant changes in body fat, a diet must accompany the exercise program. Although the imposed exercise provided major changes in cardiorespiratory fitness, the self-selected intensity promoted greater adherence of the subjects. The latter can be used as a strategy when starting a physical exercise program for obese subjects.

Address for correspondence: Luís Alberto Garcia Freitas, Departamento de Ciências do Esporte, Universidade Estadual de Londrina, Rodovia Celso Garcia Cid, 445, CEP: 86.057-970- Londrina, PR, Brasil, Telefone, +55 43 3714000, Email: lfreitas@uel.br

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