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Skinny Without Willpower

Tuesday, March 10, 2009


What’s better for fat loss: Aerobics or Weight Training?

Energy expenditure in the body from any activity follows one of three pathways:

1) Aerobic: Any activity that is performed at a low to moderate intensity for more than 90 seconds, allowing oxygen to release energy through metabolism, is usually called an aerobic activity or more commonly referred to as cardio.

2) Anaerobic (ATP-CP): Any activity that utilizes Adenosine Tri-Phosphate (ATP) stored in the muscle cells. ATP is the immediate source of energy and is exhausted in about 3-5 seconds during a muscle contraction.

3) Anaerobic (Lactate/post ATP): As soon as the ATP in the cells is exhausted the body resorts to the breakdown of glucose for energy. This results in the production of lactate and hydrogen ions, ultimately leading to fatigue.

Cardio or aerobic exercise uses the Aerobic energy pathway while resistance or weight training uses the two anaerobic energy pathways. During exercise cardio burns about 20% more fat compared to weight training. But the flip side to this is that weight training results in increase of muscle mass that continues to burn calories in the rest state, thereby increasing your basal metabolic rate (BMR). Muscle cells are active tissues that require the conversion of blood glucose (from food) to glycogen thereby restricting the conversion of food calories to fat. So considering the long term fat burning capabilities of weight training vs. cardio, the former is the clear winner.

Both types of exercises have some pros and cons. The pros in favor of cardio are:

1) Increased cardiovascular function: the increase in the oxygen requirements when doing cardio increases your heart-rate since there is a higher need for oxygen carrying blood supply to the working muscle tissue.

2) Decrease in body fat: cardio exercises increase the capacity of working cells to absorb oxygen and glucose that are necessary for energy expenditure. This lowers blood glucose thereby reducing the calorie to fat conversion during the activity.

3) Cardio is fun and safe: Swimming, bicycling, jogging, brisk walking can all be fun.

The cons against cardio are:

1) Decreased muscle mass: The human body is an intelligent system and any endurance based exercise will, in order to maximize the efficiency, shed any unnecessary weight be it fat or muscle. So in effect cardio doesn’t discriminate between fat loss and muscle loss and only the muscles involved in the endurance exercise will be partially spared while the other muscles will atrophy. That’s why marathon runners have puny little chests and toothpick arms and not very big legs either.

2) Decreased strength/power/speed: again related to atrophy of all unrelated muscles.

3) Duration of activity: Aerobics has to be of a certain duration to be effective for fat loss. The energy for the first 20 or so minutes comes from either blood glucose (from food) or from muscle glycogen. Body fat is only used up after muscle glycogen stores are depleted. So in order to burn any fat the aerobics activity has to be done longer than 20-30minutes.

Likewise the pros in favor of weight training are:

1) Increased cardiovascular function: Even though anaerobic exercises don’t require the added oxygen to burn calories but nevertheless require the transport of nutrients like protein, amino acids and blood glucose to the working cells, thereby increasing the circulation and heart rate, although not as much as in a cardio workout.

2) Decrease in body fat: weight training increases muscle mass. The muscle cells constantly convert blood glucose to glycogen thereby reducing the calorie to fat conversion. This effect happens long after the activity has ceased. As a reference about 3lbs of muscle burns 120 calories/day even when it’s inactive. So if you gained 10lbs of muscle (which could perhaps take over a year of intense weight training) you would be burning the same amount of calories per day that a 140lb person would do in a jogging session at 5 mph for 45 minutes every day. Considering that you could be sleeping and still burn as many calories as the jogger, I think it’s a bargain worth shooting for.

3) Increased muscle mass: Isn’t that obvious.

4) Increased strength/power/speed: this one is also obvious. Consider the leg muscle, who do you think is stronger and more powerful and moves faster, a sprinter or a marathon runner? The sprinter of course!

5) Body Sculpting: With weight training you have the flexibility to sculpt your body to desired shape. If you want big arms there are exercises for just that. If you want big chest or shoulders, there are exercises for that. If you want a “V” taper to you upper body, there are back exercises for that. And if you want wash-board six-packs there are exercises for that.

6) Age-reversal effect of Weight Traning: Many researchers have shown that moderate amounts of weight training releases human growth hormone and testosterone, the two hormones that have shown age-reversal effect in humans. In several cases people that performed weight training demonstrated muscle mass, cardiovascular fitness, coordination and bone density comparable to those who were 20 years younger than them.

And the cons against weight training are:

1) Weight training can be dangerous: Its best to have a certified trainer teach the basic moves of weight training for safety reasons especially in compound body exercises like the squat, bench press and the dead lift. Don’t do it based on some videos you have watched on youtube.

2) Weight training is not as much fun as cardio: What is fun about repeatedly moving a certain weight from point A to point B set after set?

Physical fitness is a compromise of cardio-respiratory endurance, strength, flexibility, power, speed, coordination, agility, balance, accuracy and toughness. To pursue fitness excellence you must physically train to “optimize” your performance in all of the physical abilities and not “maximize” your performance in any one ability at the expense of all others.

I believe to get the best results one has to use a combination of both types of training methods. I have found that its best to do cardio and weight training on separate days or at least keep the workouts separate, for example do aerobics in the morning and weight training in the evening or vice versa. No matter which method you choose, remember that the best results come from perseverance and don’t happen overnight so stick to it and the results will follow.

Here is some additional reading on this subject:

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