During the early months of the New Year, a trip to your local gym often means long lines at the juice bar, a clamoring for treadmills, and not a free bench in the house. With all the enthusiasm for health, one might expect everyone to meet their goals, but you may be surprised. According to the International Health Racket and Sports Club Association, 68% of all gym memberships are purchased in the month of January, but a mere 20% of those memberships are used regularly after February. Why? Study participants reported that boredom, and frustration were the two primary reasons for non-attendance.

As a personal trainer, I have taken on many clients who have come to me after experiencing a steady drop-off in progress-- despite several hours exercising per dayafter the first month. If this sounds like you, it is important to understand that exercise is not about quantity, but intensity. The human body will naturally adapt to any physical condition, which eventually results in fewer calories burned for the same amount of effort.

To get over this hurdle, it is important to keep the body guessing by frequently changing reps, sets, and exercises, yet always maintaining a high level of intensity. The first thing I do with my clients, many of whom are used to long walks on the treadmill, is to shorten rest periods in between exercises which results in fewer moments wasted and better overall results.

Rather than spending 45 minutes on the treadmill at a steady pace, studies suggest that 20 minutes of interval training-- involving short periods of running at a pace that boosts your heart rate to 80-90% of maximum capacity, followed by a steady pace that allows your heart rate to fall back to normalhelps to more efficiently burn both carbohydrates and fat. Even after you are done, it is not uncommon for your metabolism to remain elevated for several hours-- resulting in sustained fat loss.

For weight training, this same approach can be applied by training multiple muscle groups per workout with high repetitions (12-15) and shorter rest periods (60-120 seconds). Interval training pushes the body to it's limit, so it is important to wait at least 24-48 hours in between each workout.

Interval training has been adopted by numerous athletes to boost muscular endurance, and increase performance by training the aerobic and anaerobic systems. Anaerobic means without oxygen, and during a period of intense exercise, this system uses carbohydrates stored in the muscles (glycogen) for fuel. Once the exercise is complete, the body to goes in to "oxygen debt", making the lungs and heart work harder to recover. This causes the aerobic systemor the system you use when at restto burn more overall calories.

According to the American College of Sports Medicine, short bursts of high intensity exercise are far more efficient in burning fat, and overall calories than longer periods of repetitive exercise. One example of this can by observed by comparing the training of sprinters to marathon runners. While marathon runners undoubtedly run longer distances, their bodies tend to hold more body fat than relatively muscular sprinterswho run shorter distances at higher intensities. This is due to a difference in muscle tissue which burns fat and is created by forcing the body to adapt to different conditions.

But you don't need to be a world-class athlete to take advantage. Intensity can be applied to virtually any goal based on the following guidelines:

Cardio:

1) Warm up with 5-10 minutes of slow, steady walking on a treadmill or elliptical.

2) Cardio intervals should last between 30-120 seconds followed by rest periods of equal length.

3) Bring your heart rate down to around 100-120 beats per minute during the rest interval.

4) To improve, increase intensity or duration of intervals, but not both at the same time

5) Allow between 24-48 hours between each session

Strength Training:

1) Stretch out before your workout.

2) Each workout should include exercises that work the upper and lower body.

3) Pick exercises which work multiple muscle groups (such as squats, bench press, dead lifts, and pushups).

4) Choose a relatively high volume of sets (15-20) of 12-20 repetitions each.

5) Rest periods should last 90-120 seconds.

6) Workouts should last no longer than 45 minutes to an hour, and should only be done 2-3 times per week.