Calorie Burning: It's time to think "Outside the Box"
7 Programs that Burn a lot of Calories
Len Kravitz, Ph.D.
One of the main goals of an exercise program is the development and maintenance of cardiorespiratory fitness. In addition, many people engage in aerobic activities to advance their health status, lessen disease risk, modify body composition, reduce stress and improve cardiovascular fitness. There are numerous exercise devices and modes to choose from for developing aerobic fitness. It is important to select a device/mode of exercise that uses the large muscles of the body in a continuous, rhythmical fashion, and that is reasonably uncomplicated to maintain at a desired intensity. Fitness professionals and personal trainers are continually seeking new and better programs to help clients attain their aerobic activity goals, as well as maximizing the caloric expenditure in their endurance workouts. The debate among fitness professionals for that ONE 'optimal' calorie burning exercise program design is ongoing, with limitless possibilities. The focus of this article is not to try to answer this singular question, but to provide exercise specialists with multiple calorie burning program options for their students.
Classification of Aerobic Exercise Modalities
The American College of Sports Medicine (ACSM, 2006) classifies aerobic exercise modes by the varying skill demands of the activity. Group I activities provide a consistent intensity and energy expenditure that are not dependent on the participant's skill level. These would include activities such as walking, stationary cycling, running, machine-based stair climbing and elliptical training. With Group II activities, the rate of energy expenditure will vary, depending on the person's performance ability. With higher skill levels, a person can work harder and longer, and consequently burn more calories. Activities in the Group II category would include group-led aerobics, outdoor cycling, step aerobics, hiking, swimming, water aerobics and inline skating. The Group III activities, such as basketball, racquet sports, and volleyball are highly variable in terms of energy expenditure due to the performance demands of the activity. Some other factors to consider when selecting a mode of exercise for a client include personal interest, equipment availability, physical needs and injury risk. For long-term cardiovascular health and caloric expenditure, it is practical to select a variety of physical activities and exercise modes that sufficiently stimulate the heart, lungs, and muscles.
Intensity of Exercise: Optimizing Energy Expenditure
A major way to maximize energy expenditure is to vary and progressively increase the intensity of the exercise. (See Side Bar 1. for a detailed explanation of what determines caloric expenditure during exercise and Side Bar 2. for an explanation how energy expenditure is measured.) It is important to choose a mode of exercise that can be adjusted or graded to overload the cardiorespiratory system. For instance, treadmill walking can be made much more challenging by increasing the treadmill grade or speed. Cycling intensity can be made more demanding by increasing the pedaling resistance. In addition, choosing a mode that allows for high intensity intervals to be rapidly interspersed with low-to-moderate intensity intervals is beneficial for an effective workout.
It may be helpful to educate clients and students that additional health and fitness benefits will be attained as the intensity of exercise increases (Swain and Franklin, 2006). In their excellent review of literature, Swain and Franklin conclude that there are greater 'cardioprotective' benefits (lowered risk to coronary heart disease, hypertension, stroke, diabetes and other diseases associated with cardiovascular disease) from higher aerobic exercise intensities as compared to moderate aerobic exercise intensities. Practically speaking, when working with students of all fitness levels, Swain and Franklin's review indicates that a progressive increase in exercise intensity, as a client improves her/his fitness level, is a relevant health promoting program design initiative to always keep in mind.
Upper and Lower Body Mode Considerations
Some exercise modes involve both the 'upper and lower body' muscles, such as swimming, rowing, simulated skiing, and some elliptical cross-training products. Although these types of exercise engage more muscles, they do not necessary engage as much muscle mass as running, a 'lower body only' exercise mode, and so will expend fewer calories at a similar level of intensity (Kravitz, Robergs and Heyward, 1996). Some persons also choose to carry hand-held weights in hope of enhancing energy expenditure when walking or running. Although the use of hand-held weights slightly increases the intensity of the exercise, research reveals that this additional equipment does not elicit greater improvement in overall aerobic capacity (Kravitz, Heyward, Stolarczyk and Wilmerding, 1997). However swimming involves much less pressure on the bones and joints, which allows swimmers to exercise for a longer period of time, thus possibly expending as much or more energy as some higher intensity workouts. Also, some 'upper and lower body' exercise modes, such as simulated skiing, require a fairly proficient skill development phase before fully realizing the energy expenditure benefits.
Cycling and recumbent cycling are two very popular non-weight-bearing exercise modes, whereas walking and jogging are popular exercises in the weight-bearing category. At the same level of intensity, most persons will expend modestly more calories performing a weight-bearing activity (Kravitz et al., 1997). An additional benefit of weight-bearing exercise is maintaining bone mass and preventing osteoporosis. However, with cycling and recumbent cycling there is much less trauma to the muscles and joints, heart rate is generally lower, and thus longer exercise bouts are possible. In summary, alternating weight bearing and non-weight bearing as well as 'upper and lower body' and 'lower body only' modes may be the most beneficial strategy for preventing overuse problems, promoting positive health outcomes and motivating clients to adhere to their exercise programs.
Seven Exercise Programs that Burn A Lot of Calories
As highlighted in the introduction, there are countless ways to create, modify and combine exercise programs to burn an ample amount of calories. To bring together the 7 different program ideas in this article, widespread internet searching in empirical and scientific databases was initially completed using several key words and praises such as interval training, high intensity interval training, supramaximal interval training, best calorie burning workouts, endurance training, optimal cardiovascular exercise workouts, excess post-exercise oxygen consumpion (E.P.O.C), maximizing oxygen consumption and more. In most scientific studies, researchers have the subjects train at a certain level of their maximal aerobic capacity (VO2max). Most recreational exercisers do not have that physiological data to simulate comparable workout intensities. Alas, since the rating of perceived exertion (RPE) is very associated with percent maximal oxygen consumption values, an effort has been made to provide RPE units as a guide for the exercise intensity. RPE is frequently used to establish an exercise intensity using the exerciser's overall feelings of exertion. An 'adapted' 6 to 20 RPE scale rating is shown in Figure 1 which has additional subjective markers (as this is often confusing to some people) to help clients understand how to use this rating more effectively. Importantly, for each calorie burning program presented, fitness professionals and personal trainers are encourage to MODIFY appropriately for the fitness level and specific needs of clients. A frequency of workouts is not reported so as each exercise professional and personal trainer can determine what is suitable for her/his clients. To avoid overtraining and overuse injuries, it is not recommended to do back-to-back high intensity workouts during a week of training.
6 No exertion at all: This would be analogous to sitting and relaxing
7 Extremely light: This is very easy standing movement.
8
9 Very light: This is similar to casual walking.
10
11 Light: This is comparable to the intensity of a light warm-up.
12
13 Somewhat hard: This is a workout intensity that feels mildly challenging.
14
15 Hard: This is a workout intensity that feels difficult.
16
17 Very hard: This is a very demanding workout intensity.
18
19 Extremely hard: This is a rigorous intensity that cannot be maintained.
20 Maximal exertion: This is an all-out exercise exertion.
Figure 1. Rating of Perceived Exertion Scale
Adapted from: Borg, G.A. (1982). Psychophysical bases of perceived exertion. Medicine & Science in Sports & Exercise, 14(5), 377-381.
Program One: High Intensity Aerobic Interval Training (Perry et al., 2008)
High intensity aerobic interval training is popularly referred to as a HIT or HIIT program by many exercise enthusiasts and scientists. These workouts are described as a compromise between sustained moderate-intensity training (MIT) and sprint-interval training (SIT).
Mode: This workout can be completed on most modes of exercise.
Protocol: Subjects completed 10 exercise intervals lasting 4 minutes interspersed with 2-minute rest intervals where the subjects did not exercise.
Intensity: The subjects in this study were at 95% of their actual heart rate max during the 4-minute intervals, which would be analogous to a 17-18 on the RPE scale. (Reminder, modify intensity appropriately for clients.)
Duration: This total workout takes close to one hour to complete.
Comments: This research study demonstrated that this HIIT program resulted in significant whole-body and skeletal muscle capacities to oxidize (burn) fat and carbohydrate in previously trained individuals. Other recent research with a similar protocol shows very similar results (Talanian et al., 2007). During the 2-minute rest period, light exercise may be a preferred option to consider (as opposed to just passive rest).
Program Two: High-Volume Continuous Circuit Resistance Training (Gotchalk et al., 2004).
Traditional circuit training programs incorporate 9 to 12 exercise stations in the circuit. Each participant moves from one station to the next with little (15 to 30 seconds) or no rest, performing a 15- to 45-second workbout of 8 to 20 repetitions at each station. Resistances range between 40% to 60% of one-repetition maximum (1RM).
Mode: This program can be preformed on most exercise equipment available in a weight training facility.
Protocol: The circuit consists of performing 10 repetitions of the following exercises: leg press, bench press, leg curl, latissimus pull-down, arm curl, seated shoulder press, triceps push-down, upright row, leg extension, and seated row. The subjects completed 5 circuits in this study. All repetitions were performed at a 40 repetitions/min cadence with 2-5 second rests between exercises (the time needed to quickly change to the next exercise station).
Intensity: The subjects trained at 40% of their 1RM. This would be analogous to training at a light-to-moderate perceived intensity level for each exercise. Note that the RPE scale is not defined for resistance training exercises, so guide each client to ascertain her/his light-to-moderate level for each exercise.
Duration: This total workout takes approximately 17 to 20 minutes to complete.
Comments: In designing high-volume continuous circuit resistance training programs, alternate upper and lower-body joint actions to provide an optimal muscle recovery in this swiftly moving program. Also, for muscular balance about a joint, try to incorporate opposite action exercises (i.e., flexion and extension at the elbow). As well, by substituting some multi-joint exercises (for some of the single joint exercises), which involve more muscle mass, a higher caloric yield should result. This investigation showed that performance of this circuit of exercises, at the specific level of intensity, elicited oxygen consumption values (39% to 51.5% of VO2max) that met established guidelines of the American College of Sports Medicine (ACSM, 2006) for the recommended intensity (40% to 85% of VO2maxR) of exercise for developing and maintaining cardiorespiratory fitness.
Program Three: Sprint Interval Training (SIT) (Burgomaster et al., 2008).
Paton and Hopkins (2004) classify intensity bouts based on intensity with specific durations as follows: supramaximal training (also referred to sprint interval training or SIT) is all-out cardiovascular effort lasting less than 2 minutes. Maximal training is a maximal effort of aerobic exercise lasting from 2 to 10 minutes. Submaximal exercise is an exertion lasting greater than 10 minutes at a pace close to the anaerobic threshold. The authors further describe the anaerobic threshold as an intensity that can be sustained for approximately 45 minutes.
Mode: This workout can be completed on most modes of exercise.
Protocol: Subjects completed 4-6 sprint (or supramaximal) intervals lasting 30 seconds interspersed with 4.5 minutes of light exercise at a self-selected pace.
Intensity: The subjects in this study performed at an all-out effort which would suggest about a 18-20 RPE rating. Reminder, this workout involves a very forceful effort bout which can easily be modified to a much less vigorous exertion for clients not prepared for that rigorous of a stimulus. During the self-selected 4.5 minute recovery exercise period a RPE of 8-9 units is appropriate.
Duration: This total workout takes 20 to 30 minutes for the 4-6 sprint intervals, respectively.
Comments: The research (Burgomaster et al., 2008) with this program demonstrates that short duration SIT training produces similar cellular fat metabolism adaptations comparable to traditional endurance programs. A secondary benefit of this supramaximal training is that it has been show to elicit E.P.O.C. (exercise after-burn of calories) values that are twice as great as comparable submaximal training bouts (Laforgia et al, 1997).
Program 4. Indoor Fartlek Play Training (no study citation).
Fartlek training was developed in the 1930's in Sweden. Farlek means 'Speed Play', and this training strategy combines various length and intensity bouts of continuous and interval training. This type of training stresses both the aerobic and anaerobic energy pathways and there are many variations of this training, but little data-based research.
Mode: The use of multiple modes depending primarily on availability.
Protocol: Randomize 2-min, 4-minute or 6-minute bouts of exercise on the different modes while changing modes, intensities and duration in an unstructured or random order. Below is an example with a treadmill, elliptical trainer and cycle ergometer.
Rotation 1: treadmill (2 min), elliptical trainer (4 min), cycle ergometer (6 min);
Rotation 2: elliptical trainer (6 min), cycle ergometer (4 min), treadmill (2 min);
Rotation 3: cycle ergometner (4 min), treadmill (4 min), cycle ergometer (4 min)
Intensity: During the 2-min duration have the client train at a RPE of 15 (Hard). With the 4-min duration have the student train at a RPE of 13 (Somewhat hard). For the 6-min duration have the client train at a RPE of 12 (between Light and Somewhat hard).
Duration: Duration should follow ACSM (2006) guidelines, which recommend 20-60 minutes of continuous cardiorespiratory exercise.
Comments: Indoor Fartlek play training adds a lot of variety and 'fun' to a workout because it can be constantly changing. Fitness professionals are empowered to take this randomized and unstructured training concept and develop other variations.
Program 5. Metabolic High Volume Conditioning (Burgomaster et al., 2008).
Metabolic conditioning is a sports training approach to conditioning that specifically addresses the intensity, duration and anaerobic and aerobic characteristics of the specific sport (Gamble, 2007). Prolonged sessions of moderate-intensity exercise &Mac179; 60 minutes at 65% of peak oxygen uptake have been shown to significantly improve endurance capacity and whole body carbohydrate and fat oxidation significantly (Burgomaster et al., 2008).
Mode: This workout can be completed on most modes of exercise.
Protocol: Perform continuous submaximal aerobic exercise on the selected mode.
Intensity: Intensity is 65% of VO2peak which would be about a 14 RPE (Somewhat hard).
Duration: Duration is 40-60 minutes of sustained cardiorespiratory exercise.
Comments: Long slow distance training protocols are a foundation in training strategies that elicit shifts towards improved fat and carbohydrate metabolism. In addition, Quinn, Vroman and Kertzer (1994) showed that 60 minutes of sustained aerobic exercise (at 70% VO2max) resulted in a significantly higher E.P.O.C. as compared to 20-min and 40-min protocols at the same intensity.
Program 6. Step-Wise Interval Training (Jacobs and Sjodin, 1985).
There are many new different types of interval training programs and this step-wise program proves to be an interesting variation of endurance training.
Mode: This workout can be completed on most modes of exercise.
Protocol: Start at a relatively easy workload (cardiovascular warm-up) for 5 minutes of exercise and then increase intensity about 10-15 percent. At the end of each subsequent 4-minute exercise stage increase the work load about 10-15 percent for the first 4-minute training period. This program can be halted when a particular intensity level is reached or a specific duration is attained.
Intensity: The initial work intensity should be about an RPE of 11. Then, depending on the means of increasing the intensity on the mode (i.e., speed, grade, stride, etc) increase the intensity roughly 1 RPE with each subsequent 4-minute stage (i.e., program starts at an RPE of 11; after 4 minutes the intensity becomes a 12; after 4 minutes the intensity becomes a 13; after 4 minutes and intensity becomes a 14. This continues until a specific time or intensity level is attained.
Duration: Duration should follow ACSM (2006) guidelines, which recommend 20-60 minutes of continuous cardiorespiratory exercise.
Comments: The idea of employing a step-wise interval training program was of great interest to the researchers in studying muscle enzyme and blood lactate responses to progressively increasing exercise intensities. As a training program this concept provides a unique interval program that adds variety and challenge to a cardiorespiratory workout.
Program 7. Near-Maximal Interval Training (Gormley et al., 2008).
The researchers in this investigation showed that vigorous-intensity exercise is more effective for improving maximal aerobic capacity than moderate intensity exercise in a healthy adult population at low risk for cardiovascular disease. This study also adds to the mounting body of data that higher intensity exercise leads to potentially improved benefits in cardiovascular health (Swain and Franklin, 2006).
Mode: This workout can be completed on most modes of exercise.
Protocol: The subjects did a 5-minute cardiovascular warm-up which transitioned into interval training consisting of 5-minute work intervals at a near maximal intensity followed by 5-minute recovery intervals at a low level of work. In this study the subjects repeated the near maximal and recovery interval sequence 5 times (totally 55 minutes including the 5-minute cardiovascular warm-up).
Intensity: The 5-minute cardiovascular warm-up was completed at 75% of the subjects heart rate reserve (HRR), which would be about almost 15 on the RPE scale. The near-maximal interval was at about 95% of the subjects HRR, or around 17-18 on the RPE scale. The recovery interval was at 50% HRR, in the region of a 12-13 RPE.
Duration: This total workout takes 55 minutes.
Comments: The researchers did 2 weeks of progressively increasing cardiovascular training before the subjects (ages 18-44 yr), who had no more than one risk factor for coronary heart disease, completed this study. As has been stated a few times in this article, personal trainers and fitness professionals should modify appropriately for the fitness level of needs of students and clients.
Side Bar 1. What determines caloric expenditure during exercise?
At rest, the body expends energy to maintain the functions of cells that are essential for life. The continual pumping of blood by the heart demands energy, as does the continual ventilation (movement of air into and out) of the lungs. In addition, maintaining a life supporting environment within and around cells requires a constant breakdown of certain energy releasing molecules. This energy is also used to form the molecules necessary for repairing cells, storing energy (glycogen and triglycerides), fighting infection and processing nutrients obtained from digestion. These energy demanding functions combine to form the body's resting metabolic rate (RMR), which can vary from approximately 800 to 1500 Kcals depending upon body size, body fat percentage, muscle mass, diet (strict calorie restriction can noticeably reduce RMR), body temperature, health status, and glandular function.
Adenosine triphosphate (ATP) is the main molecule the body uses as a means to use chemical energy to perform cellular work. Exercise adds to the caloric expenditure of the body, as muscle contraction involves the need to repeatedly form and breakdown ATP. The energy released from the breakdown of ATP fuels the contraction of skeletal muscle, thereby adding to the energy demands of the body and raising caloric expenditure. During exercise the increase in caloric expenditure is predominantly due to the contraction of skeletal muscle. A moderate energy increase is also due to an increase in the energy demands of the heart and the ventilatory muscles in the lungs.
Side Bar 2. Understanding Caloric Expenditure Measurement?
Caloric expenditure can be measured directly, which requires the measurement of the heat released by the body, or indirectly by measuring ventilation and the exchange of oxygen and carbon dioxide by the body. These methods are termed direct calorimetry and indirect calorimetry, respectively. For numerous methodological reasons, the method of indirect calorimetry is the most suitable and accurate to evaluate caloric expenditure during exercise.
When a person exercises and expends calories, the muscles use oxygen and produce carbon dioxide as they liberate energy from carbohydrates and fat. Therefore, quantifying the consumption of oxygen and production of carbon dioxide is an indirect means to measure the calories that are expended and used by the reactions of the exercising muscles. The relationship between oxygen consumption and caloric expenditure is an area of exercise physiology research referred to as calorimetry.
The contribution of carbohydrate and fat to energy metabolism (the process of chemical changes to provide energy) can be determined from the ratio between carbon dioxide production and oxygen consumption. This is referred to as the RER, or respiratory exchange ratio of carbon dioxide to oxygen consumption. There is greater carbon dioxide production from carbohydrate catabolism as compared to fat catabolism. Thus, the lower the carbon dioxide production relative to oxygen consumption, the greater the contribution of fat catabolism to caloric expenditure. Lastly, oxygen and carbon dioxide analyzers are utilized in indirect calorimetry to determine the exercise energy expenditure as well as the relative contributions of carbohydrate and fat.
Side Bar 3. Four Controversial Calorie Burning Questions
1. How does hign intensity interval (HIIT) training help in burning more fat?
As the intensity of exercise increases the body is definitely using more carbohydrate as fuel for that specific workout. However, at the cellular level scientists feel this overloading stimulus also involves some of the same molecular signaling messages that induce increases in muscle capillary density, mitochondria proteins (energy factory of cells), fatty acid-oxidation (burning) enzymes and other regulatory proteins (Burgomaster et al., 2008; Barr, 2006). So, the connection with HIIT and improved fat metabolism appears to be associated with ADAPTATION changes that occur at the molecular level of muscle.
2. How many more calories do you burn with the addition of each pound of muscle?
The scientific estimation is approximately 7.0 kcal/lb per day (Elia, 1992). However, the important 'unsung' central message is not about the additional caloric yield from this additional muscle, but how much more capable the person will be able to workout longer and harder (due to the exercise training). It is this training effect that will add consistently and considerably to the caloric deficit from exercise.
3. Will you burn more calories from fat if you exercise first thing in the morning on an empty stomach.
The substrate that most effectively powers your workout is carbohydrate. Fat definitely contributes, but carbohydrates in the form of glucose are the body's favorite exercise fuel. After a night's sleep, the muscles are very depleted of glycogen, the stored form of glucose. Therefore, the muscles will be lacking in the energy substrate they needs to work hard and long. In addition, the brain utilizes glucose for all of its fuel needs. Therefore, the muscles of the body and some brain functions may be impaired due to exercising in this fasted situation. Encourage your clients to have a light carbohydrate snack (such as some fresh fruit, yogurt and trail mix) before the morning workout to properly fuel the workout and safeguard themselves from bodily harm.
4. Why is caloric expenditure lower during exercise involving the upper body?
Exercise involving the upper body musculature is generally complicated by the relatively small muscle mass. The smaller muscle mass is less effective than a large muscle mass in inducing the return of blood flow to the heart, thus reducing the volume of blood pumped by the heart each beat. In addition, for a given intensity, contraction of the upper body musculature provides greater resistance to blood flow than for lower body exercise, resulting in a greater increase in blood pressure. These factors result in a lower energy (caloric) expenditure with the upper body muscles as compared to the lower body musculature.
Final Message
As researchers and practitioners continue to discover new ways to challenge the human body, novel and unique training programs will emerge. Go ahead, give these ideas a chance and 'think outside the box.'
References:
American College of Sports Medicine. (2006) ACSM's Guidelines for Exercise Testing and Prescription 7th Edition. Philadelphia, PA: Lippincott Williams & Wilkins.
Barr, K. (2006). Training for endurance and strength: lessons from cell signaling. Medicine & Science in Sports & Exercise, 38(11), 1939-1944.
Burgomaster, K., Howarth, K.R., Phillips, S.M., Rakobowchuk, M., MacDonald, M.J., McGee, S.L., and Gibala, M.J. (2008). Similar metabolic adaptations during exercise after low volume sprint interval and traditional endurance training in humans. Journal of Applied Physiology, 1, 151-160.
Elia, M. “Organ and Tissue Contribution to Metabolic Weight.” Energy Metabolism: Tissue Determinants and Cellular Corollaries. Kinney, J.M., Tucker, H.N., eds. Raven Press, Ltd. 1999. New York: 61-79.
Gormley, S.E., Swain, D.P., Renee, H., Spina, R.J., Dowling, E.A., Kotipalli, U.S., Gandrakota, R. (2008). Effect of intensity of aerobic training on VO2max. Medicine & Science in Sports & Exercise, 40(7), 1336-1343.
Gotshalk, L.A., Berger, R.A., and Kraemer, W.J. (2004). Cardiovascular responses to a high-volume continuous circuit resistance training protocol. Journal of Strength and Conditioning Research, 18(4), 760-764.
Jacobs, I. and Sjodin, B. (1985). Relationship of ergometer-specific VO2 max and muscle enzymes to blood lactate during submaximal exercise. British Journal of Sports Medicine, 19, 77-80.
Kravitz, L., Robergs, R.A., Heyward, V.H., Wagner, D.R. and Powers, K. (1997). Exercise mode and gender comparisons of energy expenditure at self-selected intensities. Medicine & Science in Sports & Exercise, 29(8), 1028-1035.
Kravitz, L, Heyward, V.H., Stolarczyk, L.M. and Wilmerding, V. (1997). Does step exerise with handweights enhance training effects? Journal of Strength and Conditioning Research, 11(3), 194-199.
Laforgia, J., Withers, R.T., Shipp, N.J., and Gore, C.J. (1997). Comparison of energy elevations after submaximal and supramaximal running. Journal of Applied Physiology, 82(2), 661-666.
Paton, C.D. and Hopkins, W.G. (2004). Effects of high-intensity training on performance and physiology of endurance athletes. Sportscience, 8, 25-40
Retrieved 1/7/09: sportsci.org/jour/04/cdp.htm
Perry, C.G.R., Heigenhauser, G.J.F., Bonen, A. and Spriet, L.L. (2008). High-intensity aerobic interval training increases fat and carbohydrate metabolic capacities in human skeletal muscle. Applied Physiology, Nutrition and Metabolism, 33: 1112-1123.
Quin, T.J., Vroman, N.B., and Kertzer, R. (1994). Postexercise oxygen consumption in trained females: effect of exercise duration. Medicine and Science in Sports and Exercise, 26(7), 908-913
Swain, D.P. and Franklin, B.A. (2006). Comparison of cardioprotective benefits of vigorous versus moderate intensity aerobic exercise. American Journal of Cardiology, 97: 141-147.
Talanian, J.L., Galloway, S.D.R., Heigenhauser, G.J.F., Bonen, A., and Spriet, L.L. (2007). Two weeks of high-intensity aerobic interval training increased the capacity for fat oxidation during exercise in women. Journal of Applied Physiology, 102, 1439-1447.
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