I know there are a number of fitness/exercise diaries that are regularly published. I have always wanted to do a series of diaries that go into some aspects of exercise physiology to help people make better choices. I hesitated starting in the past, because I wasn't sure I would have the time to keep up with it. However, now that I have become recently unemployed, I have all the time in the world ;-(
For me, it also represents a type of therapy as I work through this challenging period.
I am going to keep this fairly simple, and to give practical suggestions on how these scientific principles can be applied to your fitness program. My backgroud: Masters in Exercise Physiology; Certified Exercise Specialist by the American College of Sports Medicine; worked as clinical exercise physiologist, cardiac rehabilitation manager, fitness manager for large, hospital-based wellness center; have written a number of articles on fitness and health-related topics and participated in an "Ask the Trainer" website for a large healthcare corporation.
Volume 1 starts with the basic principle that underlies all exercise training: The Stress-Response-Adaptation Principle, sometimes known at General Adaptation Syndrome (GAS). Quite simply, this means that physiological systems respond to appropriate stimuli. Repeated stimuli, or stresses, frequently lead to adaptations.
Not all stimuli have the desired response. Too little stress, and no adaptation occurs. Too much stress, and negative adaptation occurs, i.e. overtraining or injury. So the purpose of any exercise training is to apply the appropriate amount of stress to force the body to adapt in ways that are positive and increase one's functional capacity (or fitness). In other words, your body will do what you ask it to do.
The effectiveness of a stressor, or training stimulus, in creating a postive adaptive response is specific to the individual and is relative to any given point in time or level of conditioning. Obviously, a workout that might result in improvement for a sedentary 60-year old adult would be useless for an Olympic marathon runner. But it also means that the workout that was effective for that 60-year old in week 2 may no longer be as effective in week 4 or 5 and certainly will not be effective in week 11 or 12.
A workout plan--or training stimulus, or exercise precription--is usually described according to the following: Type, Intensity, Frequency, and Duration.
Type refers to the type of activity chosen: running, walking, cyling, lifting.
Intensity refers to the effort level required to mobilize the systems and processes within the organism and move it from the current "status quo" or homeostasis.
Frequency and Duration are the degree and frequency that the simulus is applied, enough to result in the adaptations necessary so that the body can perform at a higher level.
Since this diary is about stress-response, I will focus on intensity. As I mentioned earlier, the training stimulus must be sufficient to initiate adaptaton, but not so intense that it leads to breakdown. I often use a scene from the old I Love Lucy show as an example. Lucy and Ethel take jobs at a candy manufacturer. They are responsible for taking the individual candies that are coming down a conveyor belt and packing them into candy boxes. At first the belt is moving slowly and there are few candies, so they are able to easily keep up. The belt then starts to move more quickly and more candies appear. Lucy and Ethel become increasingly frantic and disorganized, and finally the entire operation falls apart.
The opening scene on the belt is your body at rest in its current state of fitness. It can easily handle what you ask it to do. The first modest increase represents a training stimulus. The women had to work harder and move faster to keep up, but they were able to do so, even though they weren't as coordinated or efficient as they could have been. As the belt speed and candy volume increased even more, they could keep up for short stretches, but grew increasingly frantic in their movements and fell further and further behind. At max speed and volume, everything fell apart.
This is what happens to your body during exercise. The first modest increase in intensity causes you to work harder and be more focused. Repeating that stimulus will result in the body adapting to that workload and becoming more coordinated and more efficient. Going to the second higher level, the body can keep up for short periods, but not for very long. To perform at this intensity, the time interval needs to be short, followed by recovery. This is what is known as interval training, and can be a useful strategy. At the highest, all-out level, a beginner will not be able to keep up--internal systems will go haywire. This is when injuries and other adverse medical events can occur.
How do you measure intensity? Two common methods are heart rate and perceived exertion.
Many exercisers are familiar with the concept of heart rate monitoring. In short, while performing cardiovascular exercise, heart rate is a good gauge of intensity--i.e., the harder you work, the higher the heart rate. There are a variety of formulae for determining ideal heart rate training ranges. The most common is to subtract your age from 220 (220-age) and use that number for your Maximum Heart Rate (HRmax). Exercise heart rate is then calculated as a percentage of HRmax.
A more accurate method is the Heart Rate Reserve (HRR). You still estimate HRmax the same as before, but now you also include Resting Heart Rate (HRrest). HRrest is best measured first thing in the morning while at "rest". To determine your HRR training rate, do the following:
- Calculate estimated HRmax (220-age)
- Measure HRrest.
- Calculate HRreserve: (HRmax-HRrest)=HRreserve
- Calculate desired intensity percentage of HRreserve: For 60% effort: (HRreserve x .60)
- Add that result back to HRrest to determine 60% training heart rate.
Example: 50 year old with a resting heart rate of 60 who wants to work out at a 60% intensity. HRmax=160 (220-60). HRreserve=100 (160-resting HR of 60). 60% of HRreserve=60. Add that back to HRrest and you get a 60% training heart rate of 120 beats per minute.
I like to do heart rate monitoring, and I monitor mine during my workouts, but it takes some experience and insight to really make it effective. I will go into more detail in the next diary, but suffice to say, there are many variables involved with heart rate and you really need to learn about YOUR specific response to exercise before you can use it most effectively.
Rate of Perceived Exertion (RPE) is an effective tool. As the name implies, you pay attention to your general sense of exertion and use an RPE scale to assess your effort level. The most common RPE scale is the Borg Perceived Exertion scale. It looks like this:
6 No exertion at all
7 Extremely light
9 Very light - (easy walking slowly at a comfortable pace)
13 Somewhat hard (It is quite an effort; you feel tired but can continue)
15 Hard (heavy)
17 Very hard (very strenuous, and you are very fatigued)
19 Extremely hard (You can not continue for long at this pace)
20 Maximal exertion
Sometimes you will see a modified version of the Borg scale, listed as a 1 to 10 scale, but I prefer the original.
The scale also corresponds to what is often called the "talk test". The idea is that you should exercise at a level where you can comfortably carry on a conversation (although the listener should be able to tell you are exerting yourself) but not sing a song. If you can only talk with extra effort, that might be an intensity level too high--or certainly higher than you need to be for general health and fitness.
The "conversational level" of exertion corresponds to 12-14 on the Borg scale, the "extra effort level" with 15-17. A beginner can see results at 9-11.
For strength training, the most common measure of intensity is a percentage of the maximum weight you can lift one time--referred to as a 1 Repetition Maximum or 1RM. Since it is not advisable for beginners to perform a 1RM lift, we estimate it by saying your lifting weight should be the amount of weight you can lift 12-15 times while maintaining good form. The 15th rep should be the last one you could do. This is for beginners. More experienced recreational lifters should work at a higher intensity--i.e. at weight that you can lift at least 8 times, but no more than 12. (Again, there are a lot of variations to this that will be addressed in the next volume).
So what does this mean in practical terms?
First of all, if you are beginning an exercise program--or returning from a layoff due to injury, illness, or sloth--you don't have to work that hard to see improvement. A 40% intensity level for 15-20 minutes is enough. At this level, you can work out every day or even twice a day. If 15-20 of sustained activity is too much, then break it into several intervals with 1-2 minutes of recovery. For a beginner, working harder does not get you into shape any faster--it just hurts more.
After about 12 weeks, if not sooner, you should increase the minimum intensity to 55%-65%.
A regular exerciser must be aware that, as the body adapts to a certain level of effort, the intensity, frequency, or duration must be changed/increased in order to see continued improvement (if that is your goal). Exercisers should include variety in their workout routines--do some mild interval training, some harder, shorter workouts, some cross training--to vary the training stimulus so that the body can continue to adapt. A common mistake for experienced exercisers is to get stuck in the same routine. For those who are exercise-averse, these variations do not have to be severe or uncomfortable--interval training doesn't mean running wind sprints--just different enough to provide an alternate stimulus.
The biggest mistake that beginning strength trainers make is to stay at the same weight level and just do more reps. I have seen this with many people, especially adults over 40. They start a routine, and then after 3-4 months they are still lifing the exact same weight--just lifting it 20 times instead of 8-12 or 12-15. Whatever your intensity level, once you can comfortably lift the weight the max number of times with good form, you must increase the weight to continue to progress.
It is also helpful to vary your strength training routine on a regular basis, to go through "cycles" of intensity or modality. Example: rotate through cycles of selectorized machines, free weights, or cable machines. You'll get better overall results and be less prone to boredom or injuries.
- The body repsponds to external stimuli--it will do what you ask it to do.
- "Fitness" is a dynamic condition, so you want to have the right routine for your goals, medical history, and level of conditioning.
- You don't have to kill yourself to see results, but you must maintain a focus and purpose to your workouts.
Here is a list of upcoming topics:
Vol 2: Cardiovascular and Muscular Adaptations to Exercise
Vol 3: Specificity of Training
Vol 4: "Fitness" vs Health--what do those studies mean?
Vol 5: Exercise Myths
Based on poll results, I will go into either more or less detail on each item.