71A - Fit and Well Column for May 16th, 2004

71A - TITLE: "Intensity versus Duration in Exercise"

Dear David and Trish,

As a result of reading your column, and finally applying at least some of your suggestions, I am seeing major results in my health and fitness. I’ve begun to lose weight (without starving myself) and feel much more energy and vitality. Thank you.

However, I do have one major point of confusion. In past columns, you have mentioned intensity and duration in your programs. How are the two related? And what should I be concentrating on… intensity OR duration of exercise.

Any assistance will be, as always, greatly appreciated.

Sincerely,

Cindy in Davidsonville

Dear Cindy,

Intensity is the amount of effort that you invest in a specific movement and/or exercise. It is subjective, meaning that it can not be quantified easily. For example, a well-trained athlete can run 30 minutes at 3.5 M.P.H. with very little effort, and therefore the amount of INTENSITY is low. Conversely, take someone who has lead a sedentary lifestyle and ask him or her to do a fast walk for 5 minutes at 2.6 M.P.H. OUCH! Takes a lot of effort, and is extremely intense. So, intensity is a function of fitness, and the work output to reach an adequate level of intensity actually increases as one gets more fit! Get better, work harder! Sounds like a bad deal, but it really isn’t.

As you increase work to gain intensity, the functional benefits increase proportionately. So you become a more and more efficient working, and playing, machine! Challenging movements and stress become easier to handle, and, of course, your risk for disease, accidents, and a "beer belly" drop exponentially! Not to mention other areas of gravitational impact!

Duration, on the other hand, is just that… the amount of time that it takes to perform a certain movement, or combination of movements. In aerobic conditioning, if you move for a longer period, you burn more calories. If you do more reps per set in resistance training, you offer more challenge to the muscle groups involved.

So we see that the actual work output, and the subsequent benefit of the work, is dependent on a combination of both intensity AND duration!

The body is programmed primarily for survival. This means that it attempts to perform any movement in a manner that is most energy efficient. It also means that it is continually attempting to store energy to prepare for the long lean winter or the dinosaur chase. Unfortunately, our winters aren’t that long and lean, and dinosaurs only seem to entertain kids and come in very unusual colors!

So when you exercise, you’re asking your body to do something that is contrary to the principle of homeostasis. You’re asking it to work beyond its present capability… either by getting stronger, or going longer. Both DO NOT feel comfortable, but are necessary for progress.

I call this the Survival Assurance Syndrome (SAS), and you really need to be aware of this tendency of the body to protect itself against any overload condition. The bottom line here is that you must have a plan, and a strategy, to combat this natural dynamic.

Well, as if the SAS wasn’t enough, the body has another tool in its repertoire of survival that makes it difficult to continue to make progress both anaerobically and aerobically. We call this Systemic Adaptation. This is the dynamic whereas the body adjusts and adapts to any challenge or stress in a way that maximizes conservation of energy, and promotes continued storage of fuel (fat!). It seems like our wonderful bodies are just making our task harder and harder. In a way, it does. But we must just consider this a challenge!

In order to benefit from any exercise program, you need to reach, and exceed, the System Adaptation Threshold (SAT). This is where the body CANNOT compensate or adapt to the stress by changes in position or execution. In other words, it MUST get stronger, or get fitter. THIS is where we want to go with any exercise program.

While working out in different fitness centers throughout the world, and here at our local Gold’s Gym, Trish and I are amazed at how many people equate simple movement with beneficial exercise. It’s NOT so!

Limb movement IS beneficial in keeping muscles toned, maintaining joint mobility and range of motion, and moderately inducing the heart to work harder. However, just moving is not sufficient to make fitness gains. If you’re reading a magazine or watching CNN or chatting with a enighbor whilst you’re exercising, chances are that your intensity is much too low!

And then some people judge the intensity of their workouts by whether they broke a sweat or not. This is a very inaccurate gauge. I can tell you first-hand that when I weighed 275 pound, I broke a sweat just walking a block. That wasn’t intense exercise, I was just TOTALLY out of shape!

Power and Endurance for Sports and Fitness.

It is important to remember that many individual and team sports (e.g., badminton, tennis, soccer, and basketball) present power requirements that span a wide range. A soccer player must sprint, jog, jump, and sprint again repetitively for 90 minutes. And a busy Mom taking care of a two-year old might be doing both, and more!

The two types of fitness desired by most persons interested in healthy living are aerobic fitness and strength fitness.

When performing aerobic exercises, a common way to normalise exercise intensity is to express it as a percentage of VO2max. This means that the Olympic champion and the Sunday fun-runner can both take some meaning from a session when they are asked to run at 80% of their VO2max. It would obviously be silly to ask them both to run at six-minute miles and expect them both to get the same benefit from the session.

What this means is that rather than expressing an intensity as an absolute value, it is expressed as a relative value. In other words, rather than asking an athlete to run for 30 minutes at six-minute miles, we ask him or her to run at THEIR OWN 10K pace. This is because different people have different abilities.

We have found that the most convenient, and often the most accurate, method of determining intensity in aerobic exercise is by either frequent or constant heart rate monitoring. Many modern machines have these built in. There is a fairly complicated formula for determining the range of heart rate that will be most beneficial to you. This is based primarily on age, level of fitness, and other factors. Ask a trainer or medical professional for some advice in this area.

Measuring the amount of intensity in strength training is fairly easy. Overload in strength training exercise depends primarily on anaerobic glycolysis and, because it causes muscle lactic acid accumulation, it becomes extremely uncomfortable. The muscle literally "stops working". This is called "working to failure". This is a great technique, but must be practiced carefully in order to avoid injury, especially at the point of overload. A hundred pound over your ehad, and YIPES… OVERLOAD. Then OUCH!

There is a system of assessing muscle strength and power based on repetitions of movements performed to exhaustion. Repetition Maximum (RM) is the highest number of times that a particular mass can be lifted. For example, a person is tested doing the bench press with different masses (80 to 150 kg) and is able to lift 150 kg once, and, of course, other weights more often. The weight that the subject can lift only once is the 1 RM; the 150-kg lift is accepted as the measure of this individual's strength for the particular movement. In subsequent tests, the athlete can lift 110 kg 10 times and no more. Therefore, 110 kg is identified as 10 RM. Similarly, a 90-kg weight can be lifted 20 times (20 RM), and 130 kg five times (5 RM).

Knowledge of your RM-to-mass relationship allows you to tailor your exercise program in terms of the masses needed to elicit 12 to 15 RM on "light days," 7 to 10 RM on "medium days," and 3 to 5 RM on "heavy days." Our standard strength workout program usually consists of five or six sets for each muscle group exercised one or two times per week. Varying the workout among light, medium, and heavy days is one aspect of "periodization." R refers simply to a number of repetitions, while RM designates only the number of repetitions to exhaustion.

It is important to note that all of these intensities for strength exercise can be stressful and challenging, even the so-called light days. Reaching exhaustion in only 15 repetitions to build strength in muscles involves a much higher intensity per repetition than an aerobic program for these same muscles which, if it involved 40 minutes of cycle ergometer exercise or running, would entail 2,400 pedal revolutions or 4,000 running steps for each leg.

Remember, strength exercise produces the greatest adaptations in type 2 (fast twitch) muscle fibers. Aerobic exercise produces the greatest adaptations in type 1 (slow twitch) muscle fibers and in the cardiovascular system that delivers the oxygen.

Strength exercise programs are designed to increase the force that one can exert for a particular movement involved in sport, in an activity of daily living, or in rehabilitation following loss of strength through injury or disease. This also plays a role in weight control, by modifying the basal metabolism.

Aerobic exercise programs are designed to enhance cardiovascular health, improve performance for endurance athletes, burn calories, and rehabilitate cardiac muscles following infarct or other cardiac insult.

When you work out, you naturally want to succeed. Many people push the limits of their body to do that. Please be aware that you need to be very careful NOT to do too many high intensity workouts, especially without recovery periods in between. Even doing two or three workouts a week of high aerobic or anaerobic intensity in each discipline puts a tremendous strain on the body.

After your conditioning objectives are identified, you can develop a program that will be effective in achieving desired adaptations in the tissues and organs required for improving performance. You need to balance exercises that are complimentary to your lifestyle (compensates for movements and dynamics that ARE NOT engaged in normal daily routines, and supportive to specific movements that ARE engaged in (sport-specific and functional adjunct).

Be aware that some activities can be identified that either make no contribution to the desired fitness or might actually be counterproductive. For example, distance runners should not engage in rigorous strength-development programs, because such activities enlarge those bulky type 2 muscle fibers and increase the body mass carried during a race, which would slow running speed. Runners must perform endurance training that enhances cardiovascular function and increases aerobic metabolic capability in those serrated type 1 muscle fibers.

Conversely, Olympic power lifters and football players should not engage in rigorous aerobic conditioning, because it enhances the oxidative capacity of skeletal muscle cells at the expense of explosive power. Strength athletes need to enlarge and increase the anaerobic capabilities of type 2 muscle fibers. By the same token, extensive aerobic conditioning would make a high jumper jump lower or slow the charge of a football lineman.

So what should YOU do? This calls for a complete lifestyle assessment, taking into consideration your lifestyle, age, genetic makeup, medical history and condition(s), and, of course, your objectives. Complicated? For sure! But absolutely worthwhile. So don’t just move… work harder, work smarter, and IMPROVE!

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