Only 50.6% of the people in the United States are physically active at a level of 30 plus minutes of moderate physical activity 5 or more days per week or vigorous physical activity for 20 plus minutes 3 or more days per week according to the Centers for Disease Control (CDC) Behavioral Risk Factor Surveillance Systems (BRFSS) report for 2009 (3). Based on this data, the goal of fitness professionals should be to increase the level of physical activity of people.
According to the Centers for Disease Control and Prevention publication on Physical Activity and Health, regular physical activity can help the following: control your weight, reduce your risk of developing cardiovascular disease, type 2 diabetes and metabolic syndrome, some cancers, and strengthen your bones and muscles, improve your mental health and mood, improve your ability to do daily activities and prevent falls, and increase your chances of living longer. Based on the ability to improve your risk profile through physical activity, it has become apparent that it is more important to increase the level of physical activity of people.
Low levels of physical activity may potentially lead to obesity, which continues to be a major health concern worldwide. Obesity is associated with an increased risk for many chronic illnesses such as diabetes mellitus, hypertension, cardiovascular disease, and certain cancers. According to Flegal et al (6), in a National Health and Nutrition Examination Survey regarding the population of the United States, “in 2007–2008, the age-adjusted prevalence of obesity was 33.8%”. This brief continued to point out that obesity rates have increased dramatically over the last 25 years. However, no significant change in prevalence has occurred between 2003–2004, 2005–2006, and 2007–2008. Also, according to the Office of the Surgeon General (13), the economic cost of obesity in the year 2000 was $117 billion. Due to the high prevalence and the economic impact of obesity, it is important for individuals to increase physical activity to expend more energy and to avoid a sedentary lifestyle.
As a result of the high incidence and the economic impact of a lack of physical activity that may lead to obesity, it is important to understand the energy expenditure (EE) of common activities such as walking and running that people are able to perform without the expense of a health club or gym membership. Establishing levels of EE for walking and running in people of an average fitness level would assist fitness professionals in the design of physical activity programs based on walking and running. Using these activities may help people become physically active at a level high enough to avoid obesity.
The findings of most studies examining EE of walking versus running suggest that running 1600 meters expends a greater number of kilojoules than walking the same distance (4,5,9,10). These studies have primarily used athletes with above average fitness levels as their participants. In addition, none of these studies reported the postexercise EE after the 2 activities. The investigation of oxygen consumption after a 1600 meter walk and a 1600 meter run with people of average fitness levels is needed to determine the total EE including the exercise and postexercise time frame, in both activities.
Excess postexercise oxygen consumption (EPOC) is defined as elevated oxygen consumption after an acute bout of exercise. According to a review by LaForgia et al (11) on the effects of exercise intensity and duration on postexercise oxygen consumption, there is evidence that suggest an exponential relationship between exercise intensity and the magnitude of EPOC.
The purpose of this study was to investigate EE during a 1600 meter walk at 86 m·min−1 and 1600 meter run at 160 m·min−1 using individuals of an average fitness level to assist fitness professionals in the development of programs based on walking and running and to assess excess postexercise EE averaging 5 minute increments up to 30 minutes after the walk and the run.
Experimental Approach to the Problem
This study was a quasi-experimental design to measure the EE of individuals who were of an average fitness level during a 1600 m walk at 86 m·min−1 and a 1600 m run at 160 m·min−1 measuring oxygen consumption. The speeds of 86 m·min−1 for the walk and 160 m·min−1 for the run were chosen as those speeds are achievable for most young average fitness adults. For the purposes of this study, the independent variable is the 1600 m distance, and the dependent variable is EE. Pre-exercise EE was measured for 10 minutes before the walk and run, EE was measured during the walk and run, and postexercise EE was measured for 30 minutes. Based on previous work examining EE postexercise at similar durations and intensities, it was determined that 30 minutes was sufficient to observe a return to a pre-exercise level of EE (7,8,11,12).
This study was approved by the University Institutional Review Board, and all subjects signed an informed consent before testing. Young adults between the ages of 18–30 years were recruited from a variety of university classes. All participants had an average fitness level based on American College of Sports Medicine (ACSM's Guidelines for Exercise Testing and Prescription, 2010) (1) percentile values for maximal aerobic power. The participants of this study represent the general nonobese population. In addition, all participants had to demonstrate the ability to run 1600 meters at the speed of 160 m·min−1 on the treadmill. A total of 30 young adults including 15 females and 15 males volunteered and qualified to participate in the study. Descriptive data are presented in Table 1.
After signing the informed consent, participants reported to the laboratory for 5 different appointments. Participants abstained from vigorous exercise 24 hours before V[Combining Dot Above]o2max testing and refrained from food consumption four hours before coming for each appointment. Liberal consumption of water was allowed.
The first 2 appointments were V[Combining Dot Above]o2max testing with the first of the 2 being a familiarization test. The same test technician performed all testing under the supervision of the principle investigator. All environmental conditions including room temperature and humidity were within the guidelines established by ACSM (2). The criteria utilized to determine attainment of true maximal oxygen consumption were as follows: failure of heart rate to increase with increases in exercise intensity, venous lactate concentration exceeding 8 mmol·L−1, respiratory exchange ratio greater than 1.15, and rating of perceive exertion greater than 17 using the original Borg scale (6-20). During these 2 sessions, participants were asked to perform a maximal graded exercise test using the Bruce Treadmill Protocol, whereas their expired gases were captured utilizing a MedGraphics Ultima Series (St Paul, MN) metabolic cart with BreezeSuite 6.3 software. The metabolic cart was calibrated at the beginning of each testing day and after every third test according to the manufacturer's guidelines. The treadmill was calibrated at the beginning of the study. The purpose of the first V[Combining Dot Above]o2max test was to familiarize the participants with the increasing intensity of the test and wearing the mask and having electrodes attached to them while walking or running. Data from this maximal oxygen consumption familiarization test were not recorded. Following the same procedures as the familiarization test, V[Combining Dot Above]o2max was recorded during the second appointment.
During all subsequent appointments, except the run familiarization, EE was measured pre-exercise during 10 minutes of sitting quietly (last 5 minutes of data used for analyses), during exercise (either walk or run), and after reaching steady state walking on the treadmill at 53.6 m·min−1, participants sat quietly postexercise for 30 minutes of data collection. The third appointment was a run familiarization for 1600 m on the treadmill at 160 m·min−1 to assure that each participant was able to sustain the pace. On the fourth appointment, a coin toss was utilized for random assignment of walk versus run for that day and the opposite was performed on the fifth appointment. The walk test was 1600 m at 86 m·min−1 although the run test was the same as the run familiarization.
Data were examined through the use of the Statistical Package for the Social Sciences Version 16.0 (SPSS Inc., Chicago, IL). Descriptive statistics including the mean (±SD) of the variables were calculated. Paired sample t tests were used to determine if there were differences between the walk and run conditions. Independent t tests were used to determine the differences between females and males. Net EE was calculated by subtracting pre-exercise EE from total EE. Postexercise EE was averaged every 5 minutes, and comparisons were made with pre-exercise EE to determine a return to pre-exercise EE values. Postexercise EE used to determine total EE was calculated by taking the amount of time to return to pre-exercise EE and multiplying that number by the average postexercise EE. An alpha level of 0.05 was set to determine statistical significance.
There was no difference in age between the females and the males. However, the males were taller, heavier, and had higher V[Combining Dot Above]o2max and BMI values (Table 1). EE, total EE, and net EE during the run were all significantly greater than EE, total EE, and net EE during the walk. When adding postexercise EE to the EE during the walk and the run, the run total EE remained significantly greater than the walk total EE (Table 2). In addition, when examining net EE (total EE − pre-exercise EE), the run net EE was greater than the walk net EE (Table 2). When comparing the EE of females versus males, the males consistently expended more kilojoules than the females (Table 3).
Postwalk EE and postrun EE both were not different from resting values by the end of 15 minutes (Figures 1 and 2). For the walk, at 5 minutes postexercise, the mean EE was 60% above rest. By minute 10, the postexercise EE was 10% above rest. For the run, at 5 minutes postexercise, the mean EE was 79% above rest. By minute 10, the postexercise mean EE was 36% above rest; and by minute 15, the mean EE was 11% above rest.
When controlling for body mass, the difference between the walk and the run when all participants were included remained significant (p ≤ 0.01). When examining the differences in EE for the walk compared with the run for the females alone and the males alone, the kilojoules per kilogram remained significantly different (p ≤ 0.02) for both. The difference in EE in kilojoules per kilogram when comparing the females with the males was significant for the walk. However, the differences in EE when comparing the females with the males for the run did not reach statistical significance with a p value of 0.07.
Although the main finding of this study was that walking 1600 m at 86 m·min−1 expends fewer kilojoules than running 1600 m at 160 m·min−1 for both females and males, walking is still a viable option for burning additional calories above baseline values. Although there is a statistical difference between walking and running, it is questionable if the difference is clinically or recreationally significant as the difference is 98.49 kilojoules per exercise bout. However, it could be clinically and recreationally significant when considering exercise sessions of 3 miles per session on 5 days of the week. However, everyone does not like to run and everyone is not in a physical condition that would allow them to run. The findings of this study suggest that walking is a viable alternative to running for caloric expenditure above baseline. The level of physical activity that has been suggested over the years from the 1996 Surgeon General's Report through the latest guidelines from the United State Department of Health and Human Services 2008 Physical Activity Guidelines have consistently stated that for the health benefits realized from physical activity everyone should accumulate 150 minutes of moderate intensity physical activity.
During the 86 m·min−1 1600-m walk in the Hall et al (8) study, the females expended 308.36 kilojoules and the males expended 369.03 kilojoules. In addition, Howley and Glover (9) found that the females expended 251.46 kilojoules and the males expended 357.73 kilojoules for the 86 m·min−1 1600-m walk. Also, King et al (10) found that females expended 279.49 kilojoules and males expended 344.76 kilojoules during the 86 m·min−1 1600-m walk. All 3 studies compare closely with 323.00 kilojoules for the females and 421.75 kilojoules for the males in this study for the 86 m·min−1 1600-m walk. Any differences are likely explained by the mass and age of the participants for the 1600-m walk in the 3 studies.
The same study conducted by Hall et al (8) found that females expended an average of 439.32 kilojoules during the 168.84 m·min−1 1600-m run, whereas males expended an average of 518.40 kilojoules. In addition, Howley and Glover (9) found that females expended an average of 378.65 kilojoules for the 160 m·min−1 1600-m run and the males expended 520.07 kilojoules. Also, King et al (10) reported at the 160 m·min−1 1600-m run, females expended 375.30 kilojoules and males expended 472.79 kilojoules. All 3 studies compare closely with 404.17 kilojoules for the females and 538.06 kilojoules for the males in this study during the 160 m·min−1 1600-m run. Any differences are likely explained by mass, age, and pace of the participants for the 1600-m run in the 3 studies.
In a review by LaForgia et al (11) examining the impact of exercise intensity and duration on EPOC during various exercise modalities including treadmill, cycle ergometer, arm cranking, swimming, and weight training, they concluded that there is evidence to suggest an exponential relationship between exercise intensity and the magnitude of EPOC. In addition, LaForgia et al(11) concluded that larger EPOC values were attained during levels of intensity that would not be well tolerated by sedentary individuals.
During postexercise, EE remained elevated above pre-exercise values for 10 minutes after the walk and 15 minutes after the run. When postexercise EE was added to exercise EE, there was an additional 90.80 kilojoules expended above pre-exercise values for the walk and an additional 192.97 kilojoules expended above pre-exercise values for the run.
Even though more kilojoules are expended after the run, walking still expends a reasonable number of kilojoules based on the ACSM recommendation of at least 4184 kilojoules per week to help someone maintain a healthy body mass when running is not feasible (1). In addition, the ACSM guidelines suggest 30 minutes on 5 days of the week of moderate intensity exercise for 150 minutes total or 20–25 minutes 3 or more days of the week of vigorous intensity exercise for a total of 75 minutes. Based on the findings of this study, walking would expend 3475 kilojoules for 150 minutes a week and running would expend 4980 kilojoules for 75 minutes in a week. Walking at the pace examined in this study falls slightly short of the recommended value. However, adding a few more minutes walking each week would easily meet the recommendations.
When examining the data controlling for body mass, the difference in EE between the walk and the run remained significant. This is in agreement with Howley et al who reported data controlling for mass (9).
In conclusion, the findings of this study suggest that walking and running 1600 meters both expend a significant amount of energy above rest and EE remained elevated for approximately 10–15 minutes after exercise. It may be suggested that due to a significantly greater amount of energy expended during and after a 1600-m run, this activity may be preferable for people who want to expend more calories in half the time it takes to walk 1600 meters at the speeds assessed in this study. However, regardless of which activity is preferred, both walking and running are common physical activities that are effective in expending adequate calories based on the ACSM recommendation of 4184 kilojoules per week (1) in average fitness individuals and may be practiced to help avoid obesity and a sedentary lifestyle. In the absence of a costly gym membership, anyone can increase their energy expenditure by walking or running.
This study suggests that people of average fitness level are able to burn additional kilojoules through walking or running. These are common activities in which most people are able to participate without expensive equipment. It seems that both individuals and fitness professionals believe that you must run to have an adequate EE to maintain a healthy body mass. The findings of this study demonstrate that it is possible to burn sufficient kilojoules to meet the physical activity guidelines through walking. Both fitness professionals and individuals should be confident in prescribing walking and/or running to assist people with weight management.
Additional research in this area should include an assessment of body composition and examine the differences in EE by kilogram of fat-free mass. This would provide additional information to further improve the ability to prescribe the appropriate intensity and time to maintain a healthy body mass.
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2. ACSM's. Health-Related Physical Fitness Assessment Manual (3rd ed). Baltimore, MD: LWW, 2010. pp. 9.
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Keywords:Copyright © 2012 by the National Strength & Conditioning Association.
kilojoule expenditure; oxygen consumption; physical activity