Science of Speed
For Fat Loss & Building Strength - Sprint Don't Walk!
#1: Burn More Belly Fat with Sprint Intervals
A large number of convincing studies show that high-intensity interval training is the best conditioning strategy for losing belly fat. In contrast, one research group that has conducted a number of experiments comparing aerobic and anaerobic training for belly fat loss write, “Disappointingly, aerobic exercise protocols have led to negligible fat loss.”
The reason anaerobic interval training works so much better is that it requires the body to adapt metabolically—your body is forced to burn fat to sustain the level of intensity being asked of it. It also elevates energy use for more than 24 hours post-workout, which has a dramatic effect on belly fat loss.
For example, a 2008 showed that a 6-week program increased the amount of fat burned during exercise by 12 percent and decreased the oxidation of carbohydrates—obviously, a favorable result for losing fat. More impressive, a 2007 study showed that in as little as 2 weeks, active women who performed interval training experienced a 36 percent increase in the use of fat for fuel during exercise.
Interval training is so effective for fat loss because it taps into different energy pathways than aerobic exercise. Simply, aerobic exercise tends to burn carbohydrates first and activate pathways that are degrading to muscle, whereas high-intensity exercise such as weight lifting and sprinting will burn a greater percentage of fat, enhance the body’s production of enzymes involved in fat breakdown, and activate pathways that lead to muscle development.
The other reason anaerobic intervals are superior for belly fat loss is that they increase excess post-exercise oxygen consumption (EPOC) a huge amount. A 2006 review showed that protocols that are more anaerobic in nature produce higher EPOC values than steady-state aerobic training because the trained muscle cells must rest restore physiological factors in the cells, which translates to a lot of energy expenditure.
Additional research on high-intensity training (HIT) programs noted that “the effect of regular aerobic exercise on body fat is negligible” whereas research into high-intensity exercise “indicates that it may be more effective at reducing subcutaneous and abdominal (visceral) body fat than other types of exercise.”
One study that compared the effect of high-intensity exercise (60 sprints of 8 seconds each, 12 seconds rest) with aerobic exercise (60 percent of maximal oxygen uptake for 40 minutes) found thatHIT resulted in significant decreases in overall fat mass, while the aerobic exercise group had a fat gain of 0.44 kg on average. The HIT group also had a significant 9.5 percent decrease in visceral fat, whereas the aerobic group had a non-significant increase of 0.2 kg or 10.5 percent. Of related interest is that the HIT group decreased fasting insulin significantly more than the aerobic group (31 versus 9 percent).
A second study found that in men with type 2 diabetes, an eight-week program that mixed aerobic and anaerobic exercise (twice a week of 45 minutes of aerobic exercise at 75 percent of max, and once a week of 5 sprints for 2 minutes at 85 percent) had a significant 44 percent decrease in visceral fat, with a 58 percent improvement in insulin sensitivity. They had no change in bodyweight but did have a 24 percent increase in thigh muscle cross sectional area, indicating muscle development, which accounted for the fact that they didn’t decrease bodyweight.
A third study performed on obese women compared a 16-week low-intensity protocol with a high-intensity protocol, based on rating of perceived exertion—not a very scientific indicator, but I’ll mention it anyway. The protocols produced comparable volumes of work as well as almost equal calories burned and miles completed. Despite this, only the HIT protocol yielded significant changes in metabolic markers or visceral fat loss. They lost significantly more total and visceral fat than the low-intensity group. Interestingly, both groups had similar exercise adherence to the program with 80 percent of each group completing the study, indicating that the high-intensity protocol was not too demanding for an obese, previously untrained population.
High-intensity exercise is effective because it increases exercise and post-exercise fat burning and may yield decreased post-exercise appetite. During exercise and after HIT, fat burning increases to remove built up lactate and hydrogen ions. Elevated growth hormone also supports fat burning and is a result of HIT programs.
#2: Lose Belly Fat With Sprint Intervals: The Proof
The following are examples of the superiority of anaerobic interval training for belly fat loss from the research:
- A 12-week high-intensity interval training program produced a 17 percent decrease in belly fat in overweight young men. Subjects lost 1.5 kg of belly fat and 2 kg of total fat, while building 1 kg of muscle. Fat burning was increased by 13 percent due to the 3-day a week program of 20-minutes of cycling in which the subjects sprinted for 8 seconds and then did 12 seconds of recovery, repeating these intervals for a total of 60 sprints.
- The same 20-minute cycling interval program produced 2.5 kg of fat loss in young women in 15 weeks, and the majority of the fat loss come from the legs and abdominal area. The sprint intervals were compared to a steady-state aerobic program that produced no fat loss.
- A 16-week study had trained athletes perform either a sprint interval protocol or steady-state running four days a week. The sprint interval protocol varied each day, but an example of one of the workouts used was 10 intervals of 30-sec sprints with 90 seconds rest. The sprint interval group lost 16 percent or 1 kg of visceral fat as well as 2 kg of total fat, compared to the endurance group that lost no belly fat, but did lose 1.4 kg of lean mass. The belly fat loss appears to be small, but be aware that subjects were lean, trained athletes to begin with and had less belly fat to lose than overweight subjects.
- An 8-week interval program using both high- and moderate-intensity intervals decreased belly fat by 44 percent in middle-aged men with type 2 diabetes. Subjects increased quad muscle size by 24 percent and improved insulin sensitivity by 58 percent—a dramatic improvement that highlights the other mechanisms involved in belly fat loss (muscle building, insulin health & blood sugar management).
#3: Sprints Take Less Time than Aerobic Exercise
Not only do sprints help you lose MORE belly fat, they help you lose it FASTER and with LESS training time. Repeatedly, studies show that more fat loss is achieved in high-intensity programs that use 20 to 25 minutes of training time than those that use 45 or 50 minutes of aerobic training time.
Scientists write that anaerobic intervals are overwhelmingly preferable to aerobics for producing belly fat loss, and that the estimated optimal dose of aerobic exercise necessary to lose belly fat appears to be 3,780 calories expended per week. This is an enormous volume of exercise that would require 1 hour of moderate intensity aerobic cycling 7 days a week to burn 550 calories a day so that you could lose even a pound a week!
In less than half the time you can get better results with anaerobic training. A 1994 study is indicative of this: Participants did either 20 weeks of aerobic training or 15 weeks of intervals (15 sprints for 30 seconds each) and lost nine times more body fat and 12 percent more visceral belly fat than the aerobic group.
What is so interesting about this study is that the energy cost of the aerobic program over the whole study period was 28,661 calories, whereas for intervals it was less than half, at 13,614 calories. In less time, the interval group lost much more weight—nine times more weight. How do researchers explain it?
Aside from greater fat oxidation and higher EPOC, hormone response plays a major role…
#4: Sprints Improve Hormone Response for More Belly Fat Loss
Sprint intervals and anaerobic exercise in general improve your entire endocrine system. Both training modes enhance the cells’ sensitivity to insulin, making anaerobic training a successful treatment for diabetes.
Perhaps most important, anaerobic exercise also elevates growth hormone (GH) —a powerful fat burning hormone that helps restore tissue and build muscle—much more than aerobic training. GH is released by the body in greater quantities in response to physical stress above the lactate threshold, which is the reason heavy, sprints are so effective.
Another hormone called adiponectin that is released from fat tissue during exercise also helps burn fat. Emerging scientific evidence shows that any time you perform forceful muscle contractions, adiponectin is released, and then your body produces a substance called PGC1 that is like a “master switch” that enhances muscle and metabolic functions, thereby burning belly fat. Naturally, anaerobic training is most effective for increasing adiponectin and PGC1 to burn fat since sprints and especially weight lifting require extremely forceful muscle contractions.
#5: Anaerobic Training Produces Less Cortisol For More Belly Fat Loss
Cortisol is the stress hormone that is elevated when you are under both physical and psychological stress. Research shows cortisol is chronically higher in endurance athletes—one study found that aerobic athletes had significantly higher evidence of cumulative cortisol secretion in their hair than controls.
In addition, cortisol is generally elevated more following aerobic training than anaerobic training. Part of this has to do with the fact that strength training and intervals do elevate cortisol, but they also elevate anabolic hormones such as GH and testosterone that counter the negative effects of cortisol.
If GH and testosterone are not elevated, cortisol overwhelms tissue, having a catabolic effect that leads to gradual muscle loss and fat gain. By doing aerobic training without strength training, you will lose muscle, lower your metabolic, rate, and gain fat. Worst of all, high cortisol causes chronic inflammation, which lead to belly fat gain over time—all-around bad news!
#6. The more aerobic volume, the more your brain ages. Therefore, senile dementia in Olympic athletes is proportionate to the annual volume of aerobic works.
#7. Slow long distance aerobic work is not a guarantee of cardiac health. Actually top cardiologist Dr. Bijan Pourat considers it “junk exercise”. He espouses resistance training for cardiac patient.
#8. Aerobic training can help you lose fat if you are just starting to exercise. Although it is not the most effective type of exercise for fat loss, aerobic-style cardio can work if you are new to exercise.
The Duke study used sedentary, out of shape, overweight people. The aerobic training they did was fairly intense (80 percent of max heart rate), so it's no surprise that they lost body fat. Being overweight and out of shape, and then exercising at that intensity for 40 minutes 3 times a week for 8 months can clearly lead to fat loss.
#9: In the long run, aerobic training is useless for fat loss. In a Duke study the aerobic group only lost an average of 1.6 kg of fat (not much!) and they didn't build any muscle, which is where we see the fault in the plan. By decreasing body weight, the aerobic group lowered metabolism, while improving aerobic conditioning.
They were “in shape” and thinner, but no stronger, and they had decreased their resting energy expenditure. In order to maintain that fat loss, they would need to eat less, change their macronutrient proportions, or exercise longer and more intensely.
For example, in the 2006 study of runners, only the runners who tripled their weekly mileage from 16 km/week to 64 km/week did not gain fat over the 9-year study. That's a huge increase that would naturally triple the amount of training time required to prevent fat gain.
#10: Doing smart anaerobic training, you can lose more fat quicker, while building muscle so that you raise your metabolism. For example, in a study of women that compared an anaerobic resistance training program with an aerobic protocol, the heavy load training group lost nearly 5 kg of body fat, gained about 3 kg of muscle, and had dramatic increases in strength. The women who did the high rep, aerobic-style lifting program had no change in body composition.
The benefit of building muscle is that your hard work lasts longer if you quit exercising: A study that tested what happens when subjects stopped exercising for 3 months after doing aerobic or resistance exercise found that a resistance training group maintained improvements in strength, muscle, and cardiovascular fitness longer than an endurance group.
The benefit of resistance training is even more pronounced for people who are in shape. In trained male athletes, a 6-week heavy load strength training program with multi-joint lifts (deadlift, squat, military press, chin-up, and bench press) allowed them to lose 1 percent body fat , while gaining 1.3 percent muscle mass for a dramatic improvement in body composition.
Compare that to the Duke study: The aerobic group also lost 1 percent body fat but gained no muscle, resulting in a less valuable body composition; the resistance group lost 0.65 percent body fat percent and gained 2 percent muscle; the concurrent group lost 2 percent body fat and gained 1.4 percent muscle mass.
The most favorable body composition was seen with the concurrent group, but it took double the time. When you consider the long-term effect of such a time-consuming, stressful program, it certainly is suboptimal.