Speed of Walking on Aerobic Capacity and Coronary Heart Disease (CHD) Risk Profiles In

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JEPonline

Speed of Walking on Aerobic Capacity and Coronary Heart Disease (CHD) Risk Profiles in Obese Females

Sitha Phongphibool1, Thanomwong Kritpet1, Ornchuma Hutagovit2

1Faculty of Sports Science, Chulalongkorn University, Bangkok, Thailand, 2Department of Physical Therapy and Rehabilitation, Chaleonkrungprachaluk Hospital, Bangkok, Thailand

ABSTRACT

Phongphibool, S, Kritpet, T, Hutagovit, O. Speed of Walking on Aerobic Capacity and Coronary Heart Disease (CHD) Risk Factors in Obese Females.JEPonline 2017;20(1):164-176. The purpose of this study was to determine the effects of speed of walking on aerobic capacity (VO2peak) and coronaryheart disease (CHD) risk profiles in 30 sedentary obese femalesaged 50.2 ± 4.6 yrs old with at least 2 CHD risk factors. The subjects were randomly divided into two groups: (a) speed walking group; and (b) self-paced walking group. Measurements of aerobic capacity and CHD risk profiles were performed at baseline and post-training. Incremental Treadmill Walk Test (ITWT) was only performed in the speed walking group to assess maximal walking speed. All subjects underwent a 10-wk walking intervention. After 10 wks of walking, the results showed that the speed walking group improved in VO2peak (P<0.01), resting heart rate (P<0.01), total cholesterol (P<0.05), and triglycerides (P<0.05) at post-training.The self-paced walking group exhibited significant improvements in resting heart rate (P<0.05), resting systolic blood pressure (P<0.01), and resting diastolic blood pressure (P<0.05) at post-training. Furthermore, the speed walking group exhibited significant absolute improvements in VO2peak (P<0.01), total cholesterol (P<0.05), and triglycerides (P<0.05) when compared to the self-paced walking group. Speed of walking significantly improves aerobic capacity and certain CHD risk profiles in sedentary obese females.

Key Words: Aerobic Capacity, CHD Risks, Obesity, Walking Speed

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INTRODUCTION

Coronary heart disease (CHD) is the most common cause of death globally. The number of individuals affected by CHD is increasing in both industrialized and developing countries. The condition is caused by the buildup of plaque in the coronary arteries, and is believed to be linked to the inflammation process called atherosclerosis. The cause of CHD is multifactorial and many believe that risk factors such as physical inactivity, high blood pressure, cholesterol, triglycerides, LDL-cholesterol, HDL-cholesterol, and CRP (inflammatory marker) contribute to the occurrence of this condition (1,2,6,9). Targeting the risk factors that contribute to the development of CAD can alter the clinical course of the disease (3,14).

Regular participation in physical activity is associated with reduced risk of many non-communicable diseases including CHD and can also modify the risk factors that contribute to the onset of CHD. Walking is a form of physical activity, when perform routinely, can result in physiological benefits such as improve cardiorespiratory fitness, improve physical endurance, and reduce abdominal fat (4,6,12,21). In particular, Tully et al. (27) reported favorable effects of brisk walking on cardiovascular risks.

Brisk walking is a relative term, and it can be slow for some and hard for others (4,5,20,21). Thus, to prescribe brisk may not be a sufficient stimulus for some individuals and might be over exerted for others (15). Consequently, walking at a fixed relative speed to an individual’s maximal walking speed might be a preferred choice in order to elicit changes in aerobic capacity and the CHD risk profile. Therefore, the purpose of this study was to assess the impact of walking speed on aerobic capacity (VO2peak) and CHD risk factors in middle-aged obese women.

METHODS

Subjects

Thirty sedentary obese female hospital employees with the mean age of 50.2 ± 4.6 yrs old (range, 41 to 58 yrs old) with at least 2 risk factors for CHD (i.e., elevated blood pressure, fasting blood glucose, dyslipidemia, high waist circumference, and overweight or obese) were recruited to participate in this study. The obesity classification was in accordance with WHO Asian guidelines: ≥23 kg·m-2 isoverweight; >25 kg·m-2 isobese (31). The subjects were contacted by the primary investigator by telephone to provide the details of the study and the time involvement. The subjects were invited to the orientation session where they filled out a health questionnaire, underwent a physical examination, and blood chemistry phlebotomy.

To be included in the study, the subjects had to be free of hypertension, diabetes mellitus (DM), orthopedic, and neuromuscular problems. Prior to signing the inform consent, all subjects were informed verbally and in writing as to the length of the study, experimental protocol, and the risk of involvement. Then,the subjects were scheduled to return to the laboratory within 48 to 72 hrs to undergo the aerobic capacity assessment and the Incremental Treadmill Walk Test (ITWT).The study protocols and procedures were approved by the Research Ethics Review Committee for Research Involving Research Participants, Health Science Group, Chulalongkorn University, Thailand.

Procedures

All subjects were assessed for anthropometric measurements that included height, weight, and body composition. Blood chemical profile of fasting blood glucose, total cholesterol, triglycerides, LDL-cholesterol, HDL-cholesterol, and hs-CRP were measured via laboratory analysis. The subjects were randomly assigned to two walking groups for the duration of the 10-wk study: (a) the speed walking groupthat required the subjects to walk on a treadmill at the hospital fitness center 7 d·wk-1 for 30 min·session-1at 80% of the speed achieved during the ITWT; and (b) the self-paced walking group that walked on level ground 7 d·wk-1 for 30 min·session-1 at home or their place of choice at their convenience. Both groups were instructed to walk at the same frequency and duration per week, and they were advised to maintain a normal dietary pattern during the study. All subjects performed aerobic capacity assessment at baseline and post-training, but only the speed walking group underwent the Incremental Treadmill Walking Test (ITWT) to assess maximal walking speed at baseline.

Anthropometric Measurements

Waist and hip circumference was measured in centimeters with an anthropometric tape. Waist circumference was assessed at the horizontal plane of the iliac crest. The hip circumference was taken at the largest posterior extension of the buttocks. The waist to hip ratio was calculated from these measurements.

Body Composition

Body composition was assessed by instructing the subjects to empty their pockets and to take off their shoes and socks. They were then instructed to step on the scale and remain on a digital body composition analyzer (Tanita BC-533, Japan) that measured and analyzed body weight (kg), fat-free mass (kg), fat mass (kg), and body fat (percentage).Body Mass Index (BMI) was calculated by dividing body weight in kilogram (kg) by height in meter square (m2).

Resting Heart Rate and Resting Blood Pressure

To assessing resting heart rate, the subjects’ chests were fitted with a wireless heart rate monitor (Polar H7, Finland). The subjects were asked to sit down quietly and undisturbed for 5 min. Heart rate was taken after it was stabilized at a lowest rate. For resting blood pressure measurement, the subjects were instructed to sit in a chair with the left arm resting on the table with the elbow slightly flexed. The blood pressure cuff was placed the left biceps and the resting blood pressure was taken with an automatic blood pressure monitor (Omron SEM-1, Japan).

Aerobic Capacity

The subjects were asked to report to the Sports Science and Health laboratory at the Faculty of Sports Science, Chulalongkorn University for testing.Upon arrival, the subjects were instructed to sit quietly and physiological baseline was measured. The subjects’ chests were fitted with a wireless heart rate monitor (Polar H7, Finland) to assess the resting heart rate. Blood pressure was taken with an automatic blood pressure monitor (Omron SEM-1, Japan). The subjects were informed of the exercising testing procedures and the test precautions.All questions that the subjects had pertaining to the exercise test were answered and clarified. Prior to the testing, the open circuit spirometry metabolic system (Cortex Metamax 3BR2, Germany) was calibrated according to the manufacture specifications and recommendations.

Each subject was attached with a facemask, hooked up to the metabolic system, and was instructed to stand still for baseline physiological measurements on a motorized treadmill (hp-cosmo 4.0, Germany). Using the ramped Bruce protocol (29) and gas analysis system, each subject’s maximal aerobic capacity was determined. The treadmill speed and incline were changed every 15 sec until the subject’s maximal capacity was reached. During the test,blood pressure was assessed every 2 min with the palm aneroid sphygmomanometer (MDF Bravata, USA). Exercise heart rate was recorded every minute (Polar H7, Finland). The subject’s oxygen consumption (VO2), carbon dioxide production (VCO2), ventilation (VE), respiratory exchange ratio (RER), and oxygen pulse (VO2/HR) were continually monitored. Verbal encouragement was provided throughout the test and maximal aerobic capacity was determined by averaging the highest 30 sec of VO2 that was obtained during the test. Testing was terminated in accordance with standard guidelines (1).

Incremental Treadmill Walk Test (ITWT)

After a 20 min rest from the aerobic capacity assessment, each subject in the intervention group underwent the ITWT to determine the maximal walking speed (26).Maximal walking speed was defined as a condition in which a subject was unable to maintain an appropriate walking pace. Thus, the subject resorted to running to keep up with the treadmill’s speed (26). Prior to initiating the test, each subject was fitted with a wireless heart rate monitor (Polar H7, Finland) and a facemask. Then, the subject was hooked up to the open circuit spirometry metabolic system (Cortex Metamax 3BR2, Germany). After standing still for the determination of resting physiological data, the subject wasinstructed to walk on the treadmill starting at 2.5 mi·hr-1with no incline. The speed was increased 0.4 mi·hr-1 every3 min until the subject was unable to maintain the appropriate walking technique (i.e., no race walking, jogging, or running). Gas analysis was used to determine the subject’s VO2 and other physiological responses at maximal walking velocity.

After completion of the ITWT, each subject rested for at least 15 min until the physiological responses (i.e., HR and BP) returned to baseline. Then, the subject underwent an additional walk test to determine the speed at 80% of maximal walking velocity that was obtained from the ITWT for 15 min each to determine oxygen cost and other physiological responses of walking at that intensity.

Walking Program

The subjects were randomly divided into two groups for the 10 wks walking study: the speed walking group and the self-paced walking group. To standardize the walking program, each group was given the same protocol of frequency and duration of walking per week for the duration of the study. The subjects in the speed walking were given a specific walking speed that was obtained previously during the ITWT. They were instructed to engage in treadmill walking at a specified speed at the hospital fitness center. Likewise, the subjects in the self-paced walking were advised to engage in level ground walking on a daily basis. Both groups were instructed to walk continuously for 30 min·session-1 7 d·wk-1. All subjects were advised to maintain their normal dietary pattern. Each subject was contacted periodically by the primary investigator to discuss any difficulties during the 10-wk study.

Blood Chemistry

After the 10-hr fast, the subjects’ blood samples were collected from the antecubital vein while in the sitting position to obtain plasma glucose, total cholesterol (TC), triglycerides (TG), LDL-Cholesterol (LDL-C), HDL-Cholesterol (HDL-C), and high sensitivity C-Reactive Protein (hs-CRP). The plasma glucose, total cholesterol, triglycerides, LDL-Cholesterol, and HDL-Cholesterol were analyzed using the enzymatic color test (Beckman Coulter UA 480, USA). The high sensitivity C-Reactive Proteinvariable was analyzed using the particle enhanced immunoturbidimetric assay (Roche Cobas C501, USA).All blood draws and analyses were performed at the Faculty of Allied Health Sciences Laboratory atChulalongkorn University.

Statistical Analyses

Descriptive statistics were used to analyze the subjects’ baseline characteristics. The variables arepresented as the mean ± SD. Differences within a group (intra-group) were assessed by comparing variables at baseline with the 10-wk data of walking. The extent of the change in variables was calculated by subtracting the baseline results from the 10-wk results. The differences in variables between the two groups were compared using the independent t-test. Statistical significance was set at P<0.05. All statistical analyses were performed using SPSS statistical software version 23 (IBM SPSS Inc., Chicago, USA).

RESULTS

Descriptive characteristics of the subjects in the speed walking and self-paced groups are presented Table 1. The subjects in the two groups were similar in most variables at baseline. However, the speed walking group exhibited significantly higher BMI at baseline than the self-paced group (P<0.05).

Table 1.Baseline Characteristics of Study Groups.

Variable / Total
(N = 30) / Speed Walking
(n = 15) / Self-Paced
(n = 15)
VO2peak (mL·kg-1·min-1) / 22.4 ± 2.9 / 21.8 ± 2.9 / 22.9 ± 2.9
Age (yr) / 50.1 ± 4.7 / 50.0 ± 5.6 / 50.2 ± 3.9
Height (cm) / 155.7 ± 4.6 / 155.7 ± 5.5 / 155.6 ± 3.7
Weight (kg) / 65.1 ± 8.7 / 68.1 ± 10.9 / 62.1 ± 4.3
BMI (kg·m-2) / 26.8 ± 2.9 / 28.0 ± 3.6* / 25.6 ± 1.1
Waist (cm) / 88.3 ± 6.4 / 89.4 ± 8.4 / 87.1 ± 3.5
Hip (cm) / 104.9 ± 7.2 / 104.4 ± 9.5 / 105.3 ± 4.1
WHR / .84 ± .05 / .86 ± .06 / .83 ± .04
%Body Fat / 35.3 ± 3.6 / 35.9 ± 4.3 / 34.7 ± 2.8
Resting HR (beats·min-1) / 85.2 ± 7.9 / 87.5 ± 8.7 / 82.8 ± 6.5
Max HR (beats·min-1) / 163.8 ± 10.3 / 161.6 ± 12.9 / 166.1 ± 6.5
Resting SBP (mmHg) / 131.2 ± 12.3 / 128.7 ± 14.1 / 133.6 ± 10.8
Resting DBP (mmHg) / 76.3 ± 8.0 / 76.8 ± 6.9 / 76.7 ± 9.2
FBG (mg·dL-1) / 101.2 ± 14.3 / 99.8 ± 9.2 / 102.6 ± 18.4
TC (mg·dL-1) / 231.1 ± 53.2 / 237.1 ± 49.2 / 225.1 ± 58.0
TG (mg·dL-1) / 128.9 ± 47.6 / 141.7 ± 52.9 / 116.1 ± 39.2
LDL-C (mg·dL-1) / 145.7 ± 40.6 / 147.5 ± 36.1 / 143.8 ± 45.8
HDL-C (mg·dL-1) / 59.9 ± 10.9 / 58.8 ± 13.5 / 61.1 ± 8.0
TC/HDL-C / 4.0 ± 1.2 / 4.2 ± 1.2 / 3.8 ± 1.3
hs-CRP (mg·dL-1) / 2.2 ± 2.4 / 2.8 ± 3.0 / 1.7 ± 1.4

Values are mean ± SD; BMI = Body Mass Index; WHR = Waist to Hip Ratio; Resting HR = Resting Heart Rate; Max HR = Maximal Heart Rate; Resting SBP= Resting Systolic Blood Pressure; Resting DBP = Resting Diastolic Blood Pressure; VO2peak = Peak Oxygen Consumption; FBG = Fasting Blood Glucose; TC = Total Cholesterol; TG = Triglycerides; LDL-C = Low Density Lipoprotein Cholesterol; HDL-C = High Density Lipoprotein Cholesterol; TC/HDL = Total Cholesterol to High Density Lipoprotein Cholesterol Ratio; hs-CRP = High Sensitivity C-Reactive Protein; *P<0.05

After 10 wks of the walking intervention, the speed walking group showed significant improvements in VO2peak (P<0.01), resting heart rate (P<0.01), total cholesterol (P<0.05), and triglycerides (P<0.05) at post-training. Conversely, the self-paced walking group exhibited significant improvements in resting heart rate (P<0.05), resting systolic blood pressure (P<0.01), and resting diastolic blood pressure (P<0.05) at post-training as presented in Table 2.

Table 2. Change in Fitness, Body Weight, Body Composition, and Blood Chemistry between Baseline and Post-Training in Speed Walking and Self-Paced Groups.

Variables / Pre-training / Post-Training / t / P-Value
VO2peak (mL·kg-1·min-1)
Speed walking / 21.8 ± 2.9 / 25.2 ± 3.4** / -6.730 / .000
Self-Paced / 22.9 ± 2.9 / 23.7 ± 3.2 / -1.922 / .075
Weight (kg)
Speed walking / 68.1 ± 10.9 / 67.9 ± 11.2 / .703 / .494
Self-Paced / 62.1 ± 4.3 / 61.4 ± 4.1 / 1.543 / .145
BMI (kg·m-2)
Speed walking / 28.0 ± 3.6 / 27.9 ± 3.9 / .940 / .363
Self-Paced / 25.6 ± 1.1 / 25.3 ± 1.3 / 1.546 / .144
Waist (cm)
Speed walking / 89.4 ± 8.4 / 87.1 ± 6.2 / 2.088 / .056
Self-Paced / 87.1 ± 3.5 / 86.4 ± 4.3 / 1.022 / .324
Hip (cm)
Speed walking / 104.4 ± 9.5 / 102.9 ± 8.2 / 2.238 / .052
Self-Paced / 105.3 ± 4.0 / 104.5 ± 4.2 / 1.309 / .212
WHR
Speed walking / .86 ± .06 / .85 ± .05 / 1.182 / .257
Self-Paced / .83 ± .04 / .83 ± .04 / .186 / .855
%Body Fat
Speed walking / 35.9 ± 4.3 / 35.4 ± 3.5 / .897 / .385
Self-Paced / 34.7 ± 2.8 / 34.0 ± 4.1 / 1.138 / .274
Resting HR (beats·min-1)
Speed walking / 87.5 ± 8.7 / 80.8 ± 8.7** / 3.790 / .002
Self-Paced / 82.8 ± 6.5 / 76.4 ± 5.7** / 4.326 / .001
Resting SBP (mmHg)
Speed walking / 128.7 ± 14.1 / 121.5 ± 13.7 / 1.935 / .073
Self-Paced / 133.6 ± 10.8 / 127.3 ± 8.3** / 3.201 / .006
Resting DBP (mmHg)
Speed walking / 76.8 ± 6.9 / 77.0 ± 6.8 / -.097 / .924
Self-Paced / 76.7 ± 9.2 / 73.5 ± 7.5* / 2.567 / .022
FBG (mg·dL-1)
Speed walking / 99.8 ± 9.2 / 96.7 ± 14.7 / 1.225 / .241
Self-Paced / 102.6 ± 18.4 / 102.5 ± 18.3 / .127 / .900
TC (mg·dL-1)
Speed walking / 237.1 ± 49.2 / 211.4 ± 33.7* / 2.143 / .050
Self-Paced / 225.1 ± 58.0 / 224.6 ± 62.4 / .161 / .874
TG (mg·dL-1)
Speed walking / 141.7 ± 52.9 / 115.1 ± 33.3* / 2.474 / .027
Self-Paced / 116.1 ± 39.2 / 121.6 ± 36.2 / -1.742 / .103
LDL-C (mg·dL-1)
Speed walking / 147.5 ± 36.1 / 128.5 ± 30.4 / 1.592 / .134
Self-Paced / 143.8 ± 45.8 / 144.1 ± 47.3 / -.098 / .923
HDL-C (mg·dL-1)
Speed walking / 58.8 ± 13.5 / 58.5 ± 13.9 / .142 / .889
Self-Paced / 61.1 ± 8.0 / 60.9 ± 8.1 / .356 / .727
TC/HDL-C
Speed walking / 4.2 ± 1.2 / 3.8 ± 1.1 / 1.487 / .159
Self-Paced / 3.8 ± 1.3 / 3.8 ± 1.5 / -.225 / .825
hs-CRP (mg·dL-1)
Speed walking / 2.8 ± 3.0 / 2.4 ± 1.9 / .984 / .342
Self-Paced / 1.71 ± 1.4 / 1.5 ± 1.1 / 1.196 / .252

Values are mean ± SD; BMI = Body Mass Index; WHR = Waist to Hip Ratio; Resting HR = Resting Heart Rate; Resting SBP= Resting Systolic blood pressure; Resting DBP = Resting Diastolic Blood Pressure; VO2peak = Peak Oxygen Consumption; FBG = Fasting Blood Glucose; TC = Total Cholesterol; TG = Triglycerides; LDL-C = Low Density Lipoprotein Cholesterol; HDL-C = High Density Lipoprotein Cholesterol; TC/HDL = Total Cholesterol to High Density Lipoprotein Cholesterol Ratio; hs-CRP = High Sensitivity C-Reactive Protein; *P<0.05; **P<0.01

The absolute change in fitness, body composition, and blood chemistry are presented in Table 3.After 10 wks of walking intervention, the speed walking group exhibited significant improvements in absolute change inVO2peak (P<0.01), total cholesterol (P<0.05), and triglycerides (P<0.05) when compared to the self-paced walking group.

Table 3. Absolute Change in Fitness, Body Weight, Body Composition, and Blood Chemistry between Baseline and Post-Training in Speed Walking and Self-Paced Groups.

Variables / Speed Walking / Self-Paced / t / P-Value
VO2peak (mL·kg-1·min-1) / 3.4 ± 1.9** / .80 ± 1.6 / 3.972 / .000
Weight (kg) / -.15 ± .85 / -.68 ± 1.7 / 1.071 / .297
BMI (kg·m-2) / -.12 ± .49 / -.28 ± .70 / .733 / .470
Waist (cm) / -2.4 ± 4.4 / -.67 ± 2.5 / -1.300 / .204
Hip (cm) / -1.6 ± 2.7 / -.80 ± 2.3 / -.825 / .416
WHR / -.01 ± .03 / .00 ± .01 / -1.101 / .285
%Body Fat / -.53 ± 2.3 / -.71 ± 2.4 / .208 / .836
Resting HR (beats·min-1) / -6.7 ± 6.8 / -6.4 ± 5.7 / -.144 / .886
Resting SBP (mmHg) / -7.2 ± 14.4 / -6.3 ± 7.6 / -.222 / .826
Resting DBP (mmHg) / .20 ± 7.9 / -3.2 ± 4.8 / 1.416 / .168
FBG (mg·dL-1) / -3.1 ± 9.9 / -.13 ± 4.1 / -1.086 / .287
TC (mg·dL-1) / -25.7 ± 46.5* / -.47 ± 11.2 / -2.045 / .050
TG (mg·dL-1) / -26.6 ± 41.6** / 5.5 ± 12.1 / -2.863 / .011
LDL-C (mg·dL-1) / -19.0 ± 46.2 / .33 ± 13.2 / -1.558 / .138
HDL-C (mg·dL-1) / - .27 ± 7.3 / -.20 ± 2.2 / -.034 / .973
TC/HDL-C / -.41 ± 1.1 / .01 ± .34 / -1.426 / .165
hs-CRP (mg·dL-1) / -.41 ± 1.6 / -.25 ± .82 / -.343 / .734

Values are mean ± SD; BMI = Body Mass Index; WHR = Waist to Hip Ratio; Resting HR = Resting Heart Rate; Resting SBP= Resting Systolic Blood Pressure; Resting DBP = Resting Diastolic Blood Pressure; VO2peak = Peak Oxygen Consumption; FBG = Fasting Blood Glucose; TC = Total Cholesterol; TG = Triglycerides; LDL-C = Low Density Lipoprotein Cholesterol; HDL-C = High Density Lipoprotein Cholesterol; TC/HDL = Total Cholesterol to High Density Lipoprotein Cholesterol Ratio; hs-CRP = High Sensitivity C-Reactive Protein; *P<0.05; **P<0.01

DISCUSSION

Walking on Aerobic Capacity

Cardiorespiratory fitness (CRF), quantified by VO2peak, is associated with a reduced mortality risk (2,3,9,10,11,18,23). Meta-analysis shows that for each MET increase in CRF is associated with a 15% reduction in risk of all-cause mortality and 13% reduction in risk of CVD and CHD events (3,10). Fit individuals have lower all-cause and CVD mortality risk than unfit counterparts, regardless of adiposity classification (2,9,10). Furthermore, improvement in cardiorespiratory fitness translates to a better survival and better prognosis in those with medical conditions (18,23,30). According to Myers (22), VO2peak is a superior predictor of mortality compared with tobacco use, hypertension, dyslipidemia, and diabetes in subjects with or without a confirmed diagnosis of cardiovascular disease (22). Exercise training at sufficient intensity, frequency, and duration is a cornerstone for improving CRF and health, and it has been shown to provide cardio-protective effects against CHD (9,10).