Exercise physiologists have long recommended that to lose bodyfat, it best to train at a lower intensity level. The higher the level of training intensity, as determined by maximum heart rate, the more the body relies on carbohydrate reserves, such as glycogen and blood glucose.
This appears to be true because carbohydrate is more readily available for quick energy purposes and doesn't require oxygen for metabolism. Fat, on the other hand, does require oxygen for proper combustion, or burning.
Hence, the oft repeated advice that to burn fat, you must exercise at a lower level of intensity that permits maximum oxygen uptake. Canadian researchers from Laval University in Quebec recently challenged this long-held dogma about exercise and fat-burning, however, they put two
groups of men and women on two different workout regimes. One group, which consisted of eight men and nine women, engaged in a 20-week endurance-exercise program that involved cycling four to five times a week for 30 to 45 minutes per session. They used a level of intensity
corresponding to 65 to 85 percent of maximum heart rate, which is typical for an aerobic workout.
The second group consisted of five men and five women who used a higher-intensity program for 15 weeks that featured endurance training combined with high intensity intervals. The results showed that while the high- intensity group burned fewer calories overall, those subjects
showed a fat loss that was nine times greater than the endurance groups. Analysis revealed that the high-intensity group also showed greater activity of muscle enzymes involved in both sugar and fat burning.
The researchers believe that the higher-intensity group lost more fat for several reasons. To begin with, the subjects continued to burn fat after the exercise ended, an indication of higher metabolic rates. In addition, higher-intensity exercise exerts a post exercise loss of
appetite that favors a lower calorie intake. The mechanism at work appears to be increased release of a stress hormone from the hypothalamus called corticotropin-releasing Factor. While it seems that higher-intensity exercise causes greater fat loss compared to the usual
lower-intensity mode, its best not to jump into such exercise until you've developed a sufficient aerobic base, and lower-intensity work is the way to accomplish that.
As you develop more endurance, you can spike your aerobics with high-intensity intervals, where you increase the speed for short periods of two to three minutes. This will produce the effects on fat loss noted in the study described above.
Whole-Body Workouts or Split Routines?
According to many experts, it's best to work the entire body in a single session. Training on the more common split system-exercising different muscle groups on different days-is counterproductive, they say because it exceeds the body's recovery ability. Other authorities believe
it's particularly important for beginners to train the whole body in single sessions, no more than three times a week. To determine the advantages, if any, of either mode of training, researcher-s from McMaster University near Toronto examined their effects on 30 young women.
They reported their results in a recent edition of the Canadian Journal of Applied Physiology. The subjects were divided into three groups: a whole-body group that performed four upper-body exercises for five sets of six to 10 reps and three lower-body exercises for five sets of
10 to 12 reps, twice a week for 20 weeks: a split-routine group that trained upper body twice a week and lower body twice a week: and a control group. The women, who were novice trainees, all got stronger. This is a common occurrence in beginners due to nervous system adaptations.
Even so, the researchers found that half of the muscle gains occurred during the first 10 weeks of training, which indicated a combination of muscle and nerve factors. While both groups produced a similar training response, there were a few minor differences. For example, the
whole-body group showed an increase of leg muscle mass and strength greater than the split group, while the split group showed greeter arm strength. The researchers conducting this study noted several limitations. For one, the greater volume of exercise typical in a more advanced
bodybuilding program makes whole- body training difficult because of time and fatigue. Another problem involved comparing two sessions to four sessions, and the researchers suggest that comparing three weekly whole-body workouts to a six- day-split system may produce different
While some studies show that training three times a week produces greater strength gains than a twice-weekly regimen, the authors note that a twice-a-week program produces 75 to 80 percent of the training effect derived from three weekly workouts.
The popular periodization system was not tested in this study. While periodization makes sense theoretically, the authors say, there is not much scientific research to confirm its effectiveness. The primary advantage of periodization is preventing muscle staleness, and none of the
subjects in this study experienced any degree of staleness-even after 20 weeks of consistent training. The researchers concluded that periodization may be more suitable for intermediate and advanced trainees than it is for beginners.