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Cardio Exercise vs. Weight Training
September 24, 2007
Lose weight quickly. Drop inches in days. The top secrets to weight loss.
Slogans like these can be found almost anywhere these days: on billboards, in magazine articles, during news reports, and on infomercials. It’s virtually impossible to miss them. The frequency of these messages reflects the prevalence of weight problems in the United States. According to the 2003-2004 National Health and Nutrition Examination Survey, 66% of U.S. adults are considered overweight or obese (http://www.cdc.gov/nccdphp/dnpa/obesity/faq.htm). Data collected by the Center for Disease Control’s Behavioral Risk Factor Surveillance System (BRFSS) in 2006, shows that only four states have a prevalence of obesity under 20% and two host populations with over 30% obesity (http://www.cdc.gov/nccdphp/dnpa/obesity/trend/maps/index.htm). Such present serious issues as excessive weight is a major risk factor for heart disease, cancer, stroke, diabetes, achy joints, and other serious health problems.
With the trend of obesity on the rise, great amounts of money and attention have been directed toward regimens for losing weight and maintaining healthy lifestyles. One key component of many of these programs is exercise. This, however, raises the question: what is the best way to exercise? Is it more beneficial to perform aerobic (cardiovascular) or resistive (strength) training if weight loss is the main objective?
When addressing this topic, it is first important to understand some basic terms frequently used in weight loss literature:
Aerobic Exercise - physical activity that puts stress on the heart and lungs to increase work output due to a higher demand for oxygen. This includes running, walking, biking, and swimming.[i]
BMI (Body Mass Index) - the method used to compare height to weight as a measurement of body mass.
BMI = weight (kg)/height (m²) [ii]
Calorie - the unit of measurement that describes the amount of heat needed to increase the temperature of one gram of water by one degree Celsius. It is the unit used to quantity the energy in food, although the term “Calories” found on nutritional labels is actually kilocalories (1 kcal = 1000 cal).[iii]
Lean Body Mass (LBM) - the mass of the body excluding that of fat.[iv]
MET - (standard metabolic equivalent) the unit of measurement to describe the amount of oxygen exhausted by the body during physical exercise. One MET is comparable to the quantity of oxygen expended when the body is at rest.[v]
Metabolism - the collection of chemical processes that occur within a living organism. It is often used to refer to the breakdown of food and its conversion into energy.[vi]
Overweight - the condition of having a BMI between 25.0 and 29.9
Obesity - the condition of having a BMI of over 30.0
Resistive Exercise - physical activity involving the repetition of movements to isolate and build specific muscles. Also referred to as resistance training or strength training. This typically involves weightlifting.[vii]
Resting Energy Expenditure (REE) - the amount of calories used by the body during a sedentary 24-hour period.[viii]
How Exercise Works:
Regular exercise usually refers to physical activity five or more days a week and is an essential part of most weight-loss programs. Regardless of the type (aerobic or resistance), exercise has been shown to aid in weight loss as it helps to burn more calories. As explained by the website, http://www.weightlossforall.com, ninety percent of the calories exhausted by the body each day are due to the metabolic processes of the muscle cells. Such is the case as the muscles, which account for the majority of the Lean Body Mass (LBM), are responsible for movement. Therefore, when exercise increases the mobility of the muscles, more calories are used. The greater the speed, effort, and/or regularity of muscle contractions, the greater the increase in calories burned and lean muscle produced. Ultimately, an increase in LBM heightens caloric processing as it is the greatest consumer of calories during periods of rest.
Also, important to realize is the hierarchy of which the body’s resources are exhausted. The initial source of energy, lasting approximately thirty seconds, is ATP, the energy molecule of the body. Carbohydrates, the body’s short-term energy storage units, are utilized next. Then, if the physical activity is performed at a steady pace beyond five minutes, the body will transition to burn fat calories, which is necessary for losing weight. The longer the duration of exercise, the greater number of fat calories used. The standard rule for weight loss is that one pound of weight is lost for every 3500 kilocalories burned. It is recommended that exercise be performed for 20-30 minutes daily.
Cardio or Weight-Lifting- The Public View:
While the necessity for exercise is apparent, the method for accomplishing it is not straightforward. Throughout the media and the exercise and health fields, the message is inconclusive. Depending on the source of information, weight training, aerobic exercise, or a combination of the two is the best type of exercise to produce results.
According to an article published in U.S. News & World Report summarizing the opinion of a personal trainer, strength training via weight lifting is the superior form of physical activity. The trainer, Jim Karas, author of The Cardio-Free Diet, claims that resistance exercise is more efficient at “building muscle, maintaining bone density, and goosing your metabolism” (Hobson***). Everything that can be accomplished in aerobic exercise can be obtained during resistive training in a fraction of the time. He counters criticisms that strength training does not provide cardiovascular conditioning by declaring that the exertion of lifting coupled with quick transitions between exercises provides the needed strain on the heart. Furthermore, Karas believes that the benefits of cardio workouts are over-exaggerated. These exercises are often stressful for the joints and burn fewer calories than is usually assumed which results in many cases of overeating.
Conversely, an article in the Washington Post, “Cardio vs. Weights: The Battle Is Over”, states that both types of exercise are important and should be practiced. However, aerobic exercises more easily produce results and usually conclude in burning more calories. For one, participating in cardio exercise daily is ideal while it is only recommended that weight training be done two or three times a week in order to give the muscles time to recuperate. This limitation in itself prevents greater caloric consumption from resistive training. Further limitations were observed by CDC in their “Compendium of Physical Activities Tracking Guide”. In this material, activities were classified based on MET (standard metabolic equivalent) to determine their respective intensity levels and use of calories. Circuit training (strength training) was considered equivalent to running at five miles per hour as both required eight MET. However, as both types of exercise increased in intensity, the results were imbalanced. Heavy lifting involved 6 MET while running six miles per hour, or a ten minute mile, required 10 MET. As is evident, a weight training workout must be much more rigorous to receive the same results of less intense cardio and only cardio can obtain the highest level of calorie burning. Such suggest that if the need to choose arose, aerobic exercise would provide greater benefits.
Yet the necessity for both aerobic and resistance training is also stressed. As each type provides a different type of workout, there are pros and cons to both. As is pointed out by the National Exercise and Sports Trainers Association (NESTA), cardio workouts provide a prolonged level of activity that challenges the heart and lungs and improves the body’s ability to oxidize and release fats while weight training allows the body to grow stronger and gain bone density. All of the aforementioned benefits are important to overall fitness. Discovery Health expands upon this, adding that aerobic exercise also provides increased endurance, muscle stamina, and weight loss while resistance training improves strength, muscle tone, and lean body mass, which is advantageous for losing weight. Also, important to take into consideration are the risks involved with both. Cardio exercise can lead to stress fractures, dehydration, and shin splints while resistance training may cause a variety of injuries due to improper use of weights and machines.
What the Experts Say:
With all the conflicting views on exercise circulating through health clubs and the media, numerous research projects have been completed to find the true answer to weight loss by exercise. While each project used slightly different criteria to assess the effect of exercise, the benefits of both aerobic and resistive workouts were made evident.
In an experiment involving thirty-nine healthy, overweight or obese older men, the effects of cardio and weight training were measured by level of glucose disposal (Ferrara, et al., 2006). As a carbohydrate, glucose is a source of energy utilized by the body during physical activity. An increase in disposal would suggest an improved metabolic state. To measure this quantity, the subjects, divided in two groups based on exercise regimen, received insulin infusions and were then monitored as their bodies broke down the sugar. The results of this experiment showed that the two types were equally effective in raising the glucose consumption.
Furthermore, this study displayed slight changes in weight, fat mass, and percent body fat. The cardio group showed a slight, but significant drop in all three categories with a mean decrease of 1.8% weight, 6.1% fat mass, and 4.8% body fat (Ferrara, et al., 2006). On the other hand, strength training resulted in an average of a 1.6% increase in weight and no significant change in fat mass or percent body fat. The ability of cardio exercise to decrease weight was further supported by a study performed on twenty dieting subjects that were prescribed to two similar workout programs. In this case, body weight decreased significantly more in the aerobic group than the resistive group (Bryner, et al., 1999). However, this aerobic group also lost a significant percentage of lean body mass, accounting for some decline in weight, while the resistive group retained more LBM, an important factor of long-term weight loss. Differences in decrease of body fat, percent body fat, and BMI remained statistically insignificant, unlike the study of older men.
Interestingly, another study of obese men showed a lack of net weight loss among both groups (Borg, et al., 2002). In this case, the ninety obese middle-aged men were split into three groups: no exercise (control), walking (aerobic), and resistance training. All groups were put on a diet, followed by a weight maintenance program. During these stages, body weight and composition were measured by underwater weighing techniques. Following both of these periods, all groups showed no net change in weight (which researchers deem a result of a lack of discipline). However, it is noted that both the control and aerobic group observed gain in weight and abdominal circumference during the weight management stage, while the resistant training group was able to sustain their weight loss through the regulated periods. Such suggests that the benefits to strength training are more prolonged than that of cardio exercise.
Resting Energy Expenditure, or REE, was also used as an indicator of exercise effectiveness. REE is important as it accounts for the body’s use of calories during periods of non-activity and helps to prevent weight gain (Hunter, et al., 2006). Multiple studies suggest that aerobic training is significantly more successful at improving REE. As sixty minutes of cardio had already been shown to increase REE for up to twenty hours following a workout and LBM, often associated with strength training, was a known contributor to caloric consumption, both aerobic and resistance training were measured to see determine their effect on REE after forty minutes of activity. Forty-five women were randomly divided into a control (non-exercise) group and two exercise groups and put a specific diet for twenty-five weeks while the exercise groups participated in their respective activity. The levels of REE were measured at nineteen, forty-three, and sixty-seven hours post-exercise following a twelve hour fast. The aerobic training group showed a significant increase. A fifty kilocalorie difference was found between nineteen and forty-three hours and a thirty-four kilocalorie difference between forty-three and sixty-seven hours for the aerobic training (Hunter, et al., 2006). Resistance training, on the other hand, showed no significant change in REE. Such has been demonstrated on multiple occasions including another study involving overweight women, in which resistance training actually reduced REE (Wadden, et al., 1997). Yet, it is important to note that researchers suggest that this may have been due to the level of the workout experienced by the resistance group as strenuous strength training has been shown to increase REE more than moderately intense cardio workouts fourteen hours post-activity (Hunter, et al., 2006)
Exercise is a vital ingredient to maintaining a healthy lifestyle, promoting fitness, and losing weight. Especially in an era of rapid increase in the prevalence of weight disorders, it is important to establish a regular workout routine, preferably five or more days per week, and stick with it. As reflected in Borg, et al, 2002, a lack of discipline can often result in a depletion of any success in losing weight.
With regards to whether cardio or weight-lifting is better at shedding the pounds, the answer is both. While various public views and studies pointed to one or the other, the overall consensus highlights the importance of both, as each provides a different aspect of fitness. Aerobic exercise is more likely to cause initial weight loss and increase REE following workouts. Resistance training builds LBM, which is an essential mechanism for burning calories during rest and experiencing long-term weight loss.
For the most successful weight loss experience, integrate cardio and weight-lifting in an intensive workout program. Remember, the effort and time put into exercise directly affects the amount of calories, especially from fat, that can be burned.
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[ii] Consumer FDA (see References above)
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