The Len Kravitz Thread

ForemanRules · 11-05-2006, 11:53 AM

Instead of a billion zillion Len Kravitz threads with his links and articles I thought one is enough. I will add to it from time to time and will give you the link to his site so you can read all the great studies he has done.
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http://www.drlenkravitz.com/

ForemanRules · 11-05-2006, 11:54 AM

The Fitness Professional's Complete Guide to Circuits and Intervals
By Len Kravitz, Ph.D The deluge of various interval and circuit training programs in the health fitness industry has launched exercise classes and training programs to a modernistic level of sophistication. These programs offer new and different ways to improve aerobic and anaerobic conditioning. One of the primary objectives for personal trainers and fitness instructors is to develop the most effective conditioning programs for their clients and students. This article will describe the benefits of these training systems as well as define the fundamentals with which you need to design competent interval and circuit training programs.

Tenants in Designing Training Programs
There are two basic physiological considerations that need to be addressed in designing any conditioning program. First, the major source of energy utilized to perform the given activity must be identified. Table 1 illustrates the relationship of the body's three energy systems in terms of power (calories per minute) and capacity (total amount of calories). The two anaerobic energy systems (ATP- PC and lactic acid) are involved in physical exertion lasting less than two minutes. The power potential for these energy systems is moderate to high while their capacity to sustain the work is moderate to low. Contrariwise, the oxidative energy system has a low power potential with a high capacity to sustain the physical activity. It is important to elucidate that at any moment during training all three energy systems will be involved. However, the training program will indicate which energy system is being stressed.

Table 1. Summary of Energy Systems

Power Capacity Duration
Energy System (Calories/Minute) (Total Calories) of Activity
__________________________________________________ ___________________________
ATP-PC High Low 0-30 seconds
Lactic Acid Moderate Moderate 30-120 seconds
Oxidative Low High Greater than 120 seconds
__________________________________________________ ___________________________
The second consideration involved in program design is developing a progressive overload system that will develop that particular energy source. Closely associated with the development of any exercise plan is the concept of specificity of training. It is helpful to acknowledge that even if the overall program goal is general fitness, as compared to sport-activity training, the specificity of program design is important to address. For instance, in general conditioning programs, perhaps all three energy systems will be involved, with emphasis determined by which system best meets the students' goals.

Elements of Conditioning
Regardless of the mode of training, the essential elements of conditioning that will determine the effectiveness of the program involve the application of intensity, duration and frequency.
Intensity in cardiorespiratory endurance directly affects the body's acute and chronic adaptations by eliciting numerous bodily changes in respiration, resting and submaximal heart rate, oxygen utilization, stroke volume (amount of blood pumped per heart beat), cell substrate utilization of fats and carbohydrates, and blood flow in and out of the muscle. Similarly, in resistance training the body's musculoskeletal system undergoes changes reflective of the loads with which it is challenged.

The duration of the activity will also directly affect the training effect realized from the activity. Anaerobic training incorporates repeated brief periods of high intensity exercise alternated with recovery periods during the training session. Continuous aerobic training encompasses longer, sustained duration of the activity at a lesser intensity.
Conditioning programs vary in the frequency, or days per week, that they are performed. In addition, the level of fitness of the students as well as their stage of training help define the number of days per week to participate in the physical activity. Generally, an exercise program with a frequency of 3 to 5 times per week over a period of six to eight weeks is satisfactory in achieving a meaningful training effect. It should be noted that maintaining a level of fitness does not require the frequency it took to attain the training effect.

The challenge facing the fitness professional is how to best manipulate, progressively overload, and intermix intensity, duration, and frequency with a variety of modes of activity, to help your clients reach their goals. Fortunately a number of different training programs are available to the fitness professional including circuit training, interval training and interval-circuit training.

Circuit Training
Circuit training was developed by R.E. Morgan and G.T. Anderson in 1953 at the University of Leeds in England (Sorani, 1966) . The term circuit refers to a number of carefully selected exercises arranged consecutively. In the original format, 9 to 12 stations comprised the circuit. This number may vary according to the design of the program (See Table 2 for an example circuit format). Each participant moves from one station to the next with little (15 to 30 seconds) or no rest, performing a 15- to 45-second workbout of 8 to 20 repetitions at each station (using a resistance of about 40% to 60% of one-repetition maximum). The program may be performed with exercise machines, hand-held weights, elastic resistance, calisthenics or any combination.

By adding a 30-second to 3-minute (or longer) aerobics station between each station, referred to as aerobic circuit training, the method attempts to improve cardiorespiratory endurance as well (although this has not been conclusively supported in experimental research). Variations of this aerobic circuit training model include performing 2, 3, 4 or more exercise stations in series, and then performing the aerobics station. For example, following Table 2, the participants might perform the following model (2 stations in series alternating with aerobics):
1. Chest press
2. Leg press
3. 3-minute aerobics
4. Row pull
5. Lunge
6. 3-minute aerobics
7. Shoulder press
8. Lat pull
9. 3-minute aerobics
10. Biceps curl
11. Triceps extension
12. 3-minute aerobics
13. Heel raise
14. Seated abdominal machine
15. 3-minute aerobics

ForemanRules · 11-05-2006, 11:56 AM

Table 2. Example of Circuit Training Format
Exercise Muscle Groups
1. Chest press (pectorals, anterior deltoid, triceps, coracobrachialis, subscapularis)
2. Squat or leg press (hamstrings, quadriceps, gluteals)

3. Row pull (latissimus dorsi, middle and posterior deltoid, rhomboids, infraspanatus, teres minor)
4. Lunge (hamstrings, quadriceps, gluteals)
5. Shoulder press (anterior deltoid, upper trapezius, pectorals-clavicular, coracobrachialis)
6. Lat pull (latissimus dorsi, teres major, pectorals-sternal)
7. Biceps curl (biceps brachii, brachialis, brachioradialis)
8. Triceps extension (triceps brachii, anconeus)
9. Heel raise (gastrocnemius, soleus)
10. Seated ab (machine) (rectus abdominals, internal and external obliques)
__________________________________________________ _______________________
Note: The following circuit can be done with resistance equipment, free weights, or elastic resistance. Adding an aerobics station between one or more stations is aerobic circuit training.

Benefits of Circuit Training
Numerous investigations have been completed measuring the physiological benefits of circuit weight training. Circuit weight training has been shown to increase muscular strength from 7% to 32% while decreasing the percent of fat from 0.8% to 2.9% (Gettman & Pollock, 1981) . Gettman and Pollock's review of the literature also showed an increase of fat-free weight (1 to 3.2 kg) with no subsequent change in body weight. Kilocalorie expenditure has been estimated to be approximately 5 - 6 kcal per minute for women and 8 - 9 kcal per minute for men (Hempel & Wells, 1985; Wilmore, Parr, & Ward, 1978) . In terms of cardiovascular function, studies have shown little to mild improvement in aerobic capacity (5% to 9.5%) from participation in circuit weight training as compared to other aerobic modalities (5% to 25%) (Kass & Castriotta, 1994; Peterson, Miller, Quinney, & Wenger, 1988) . Kass and Castriotta support the contention that the mild increases in aerobic capacity are due primarily to increases in fat-free mass from the circuit weight training, and not changes from the main factors affecting aerobic capacity: cardiac output (heart rate x stroke volume) or arterial-venous oxygen difference (exchange of oxygen and carbon dioxide at the cellular level).
Traditionally, individuals with cardiovascular disease and hypertension have been discouraged from performing any type of resistance exercise. However, circuit training performed at a moderate intensity (40% of repetition maximum) in cardiac patients has demonstrated significant increases in strength (13% to 40%), with no cardiac or orthopedic complications (Kelemen et al., 1986; Stewart, Mason, & Kelemen, 1988) . Furthermore, circuit weight training does not appear to elevate resting blood pressure or heart rate, and may beneficially lower resting diastolic blood pressure in borderline hypertensives (Harris & Holly, 1987) .
Very little information is available on the psychological benefits of participation in circuit weight training. However, with law enforcement officers positive changes in mood, anxiety, depression and hostility have been observed (Norvell & Belles, 1993) .

Interval Training
The last few decades has seen the introduction of interval training which has had considerable influence on sports conditioning. Interval training involves alternating periods of work and rest during a training session. It is a program that varies the intensity within the training session by interspersing a work bout of a higher intensity with a rest period of lower intensity; then another work bout is completed, once again followed by a rest period, and so on through the workout. This method of training is credited to Dr. Woldemer Gerschler of Germany who pioneered it around 1930 (Stone & Kroll, 1986) . The premise of interval training is that an individual can produce a greater amount of work in a training session if the work bouts are spaced between periods of rest or relief. For instance, a highly motivated athlete may be able to maintain near maximal intensity exercise for 10 minutes before becoming too exhausted to continue. Yet, if the athlete were to work at near maximal intensity for 3 minutes interspersed with 3 minute recovery periods the pace may be maintained for an hour before experiencing the same degree of fatigue (MacDougall & Sale, 1981). Manipulating the length of the work and rest intervals in interval training will designate which energy systems are being overloaded. Table 3 describes the unique terms used to represent the variables of concern in interval training.
Table 3. Terms Specific to Interval Training

Term Definition
Work Interval Time of the high intensity work effort.

Recovery (Relief) Interval Time between work intervals. The recovery interval may consist of light activity such as sitting or walking (passive recovery), or mild to moderate exercise such as jogging (active recovery).

Work/Recovery Ratio Time ratio of the work and recovery intervals. A work/recovery ratio of 1 to 3 means the recovery interval is three times that of the work interval. For instance, a 1 minute work interval of anaerobic exercise at a high intensity followed by a relief interval of light jogging for 3 minutes has a 1 to 3 work/recovery ratio.

Cycle (or Repetition) A work interval and recovery interval represent one cycle. Since a recovery interval follows a work interval, some resources report the number of work intervals as repetitions.

Set A set is the specific number of cycles. For instance, a series of 4 work/recovery cycles represents one set of 4 cycles (or one set of 4 repetitions).

ForemanRules · 11-05-2006, 11:57 AM

How Interval Training Improves Cardiorespiratory Endurance
In activities exceeding 2 1/2 minutes the main factor limiting performance becomes the muscle's capacity to produce energy from the oxidation of glycogen and fat stores. Thus the rate of oxygen delivery to the powerhouse of the cell (mitochondria) is a determining factor in aerobic activities. The delivery of oxygen to the mitochondria is dependent upon 1) the rate at which oxygen is delivered to the muscle and 2) the rate at which the muscle can take-up (extract) oxygen. Therefore, aerobic endurance requires the ability to pump large quantities of blood to the working muscles (cardiac output) and the exercising muscles ability to extract oxygen from the blood (arterial-venous oxygen difference).

Maximal cardiac output, the maximal amount of blood the heart can pump in one minute is the product of heart rate and stroke volume (blood volume ejected by the heart per beat). Since maximal heart rate does not increase with training, changes in cardiac output are due to changes in stroke volume. It should be noted that maximal stroke volume is reached at approximately 40% to 50% of VO2 max (Fontera & Adams, 1986) . The heart's response to interval training is somewhat analogous to the muscle's response to the overload of resistance training. In resistance training, the muscle responds to the load of the weight and the total number of repetitions performed (repetitions X sets). In interval training, the resistance the heart overcomes is related to greater ventricular filling from enhanced venous return, and greater contractility leading to more complete emptying. Theoretically, an advantage of interval training is its ability to intermittently overload the heart for a brief period of time beyond which could be achieved during a single continuous bout at the same intensity. Similar to total repetitions in resistance training (where rest periods are interspersed between sets), the alternating work and relief intervals in interval training are proposed to allow for more cardiovascular work to be accomplished in the training session.

The high intensity work bouts of interval training may also help train the fast-twitch motor units, as well as the slow-twitch motor units, enhancing the anaerobic and aerobic energy systems. This may lead to more effective utilization of fats and carbohydrates. Another proposed benefit of interval training is that it improves the muscles' buffering capacity (a substance's capability of neutralzing both acids and bases), thus delaying the onset of fatigue due to the accumulation of lactate during anaerobic exercise (Wilmore & Costill, 1988) . Other cardiorespiratory changes realized with interval (and continuous training) include an increase in muscle capillary density, an increase in myoglobin (the oxygen carrying protein in muscle), an increase in mitochondrial enzyme activity, and an increase in mitochondria size and/or number (MacDougall & Sale, 1981) .
Table 4 provides general guidelines for designing interval training programs based on the energy systems involved and the work times of the activity. As in all program designs, the intensity of the work bouts as well as the specificity of the program should be prescribed to best meet the fitness level of the participants.

Table 4. General Guidelines for Designing Interval Training Fitness Programs

Energy System Work
Time Cycles
(# of work intervals) Sets Work/
Recovery Ratio Recovery
Time Type of Recovery
ATP-PC 0-30 sec. 8 to 10 1 to 5 1/3 0-90 sec. Passive

Lactic Acid 30-60 sec.
60-120 sec. 5
5 1 to 5
2 to 3 1/3
1/2 90-180 sec.
120-240 sec. Active or Passive
Oxidative 2-3 min.
3-5 min. 4 to 6
3 to 6 1 to 2
1 1/2
1/1 4 to 6 min.
3 to 5 min Active
Active or Passive
Modified from Mathews & Fox (1976).

Is Interval Training Better Than Continuous Training for Improving VO2 max?
A simple answer to such a long-standing debate is no. Equally strong arguments can be made regarding the physiological benefits of continuous training vs. interval training. In fact, no research data conclusively suggest one form of training to be superior to the other. Therefore, in establishing a year-long exercise program, finding a balance between both methods is encouraged. Some of the benefits to highlight with interval training include:
1) Increased enjoyment from the variety of the interval training format
2) Potential for greater total work in a shorter period of time
3) Enhanced utilization of fats and carbohydrates
4) Efficient stimulation of fast- and slow-twitch muscle fibers
5) Improved anaerobic and aerobic power and capacity
6) Potential reduction in injury due to variation of workout intensity
7) Potential reduction in overtraining by controlling the amount and time of the high intensity work intervals and work relief intervals
8) Increased exercise adherence
9) Enhanced sports performance
10) Effective weight management
The following are some suggested interval training designs that may be easily incorporated in exercise classes and programs.
Interval Aerobic Training: Combination Step and Combo-Impact Aerobics
This program follows the guidelines in Table 4 for increasing the oxidative energy system and has been shown to improve cardiorespiratory endurance, increase fat-free mass, and decrease fat mass (Kravitz, Heyward, MacLean, Ruby, & Leadbetter, 1992) . It involves a 1 to 1 work/recovery ratio combining 4 minutes of step training with 4 minutes of combo-impact aerobics (Table 5). Following an appropriate warm-up the workout begins with a 4 minute interval of step training (120 bpm) at 60% to 75% heart rate intensity (11 to 13 perceived exertion rating). At the completion of the 4 minutes of step training a 4-minute combo-impact aerobic interval (150 bpm) begins, at a heart rate intensity of 75% or higher (14 to 17 perceived exertion rating). Four to 6 cycles of this alternating step and combo-impact aerobic are completed (thus, 1 set of 4 - 6 cycles).

Table 5. Interval Step and Combo-Impact Aerobics Program

Type of Work Length of Time Heart Rate Intensity Music (bpm)
{Borg (1983) scale}
Aerobic - Step 4 minutes 60% to 75%
{11 to 13} 120 bpm
Aerobic - Combo-
impact 4 minutes 75% and above
{14 to 17} 150 bpm

Modifying for special populations (senior, obese, entry level student, etc.) is attainable by simply altering the intensities of the intervals to safely accommodate the fitness level of the special population. Table 5 presents the step training as the moderate intensity with the combo-impact aerobics as the higher intensity (work) interval. For variety, the instructor may change the step training interval into the work interval (by using more power moves throughout) and switch the combo-impact aerobics segment to the moderate intensity interval (using lower intensity low-impact combinations). One point to emphasize is that the participant remains in her/his target zone during the entire workout.

ForemanRules · 11-05-2006, 11:57 AM

Interval-Circuit Training
A very popular training program with many instructors nationwide is a system that combines step training with muscle conditioning. Universal agreement of the name of this program is lacking, although it appears to be a modification of a program coined interval circuit weight training developed by O'Shea (O'Shea, 1987) . As opposed to aerobic circuit training, where the participant rotates to different pieces of equipment, in this interval-circuit program (as it has been labeled) the participants remain at one station (the step), alternating step training with different work bouts of muscle conditioning.
The most popular format of this interval-circuit program appears to be 1 to 1 1/2 minutes of muscle conditioning alternating with 3 minutes of step training (thus a 1 to 3 or 1 to 2 work/recovery ratio), suggesting that it combines anaerobic and aerobic design guidelines. The unanswered question of this specific training format is what are the benefits? To realize more physiological information about this format, this author decided to do a laboratory case experimental study.

The Interval-Circuit Training Case Study
After preliminary pilot testing the 1 1/2 minutes vs. the 1 minute work intervals of muscle conditioning (combined with the 3 minutes of step training) it was decided to do a case study using the 1 1/2 minute work interval. This is because the 1 minute muscle conditioning interval appears to be very rushed (often too short) to complete an adequate muscle conditioning segment. Since the muscle conditioning segment in this format is muscular endurance, we decided to test this program under two conditions: 1) performing the muscle conditioning segments with an upper body exercise only and, 2) performing the muscle conditioning segments with a combined upper body and lower body exercise.
The first step of this case study was to complete an informed consent form and health history questionnaire for the volunteer subject (a 30-year old, 123 lb female fitness instructor). Next, we determined the subject's VO2 max (48.85 ml.kg-1.min-1) and HRmax (180 bpm) using a treadmill test. The following day the instructor came back into the lab to test the two experimental conditions (see photos 1 and 2). The subject was instructed to do the trials between a 13 to 15 on the perceived exertion scale representing an intensity between somewhat hard and hard.
The results of each 18-minute trial are graphed in figure 1 and figure 2. Note the dissimilarities in heart rate and oxygen consumption with these two figures. In the interval-circuit (I-C) upper-lower body trial, the subject's oxygen consumption (VO2) stayed within 50% to 60% of her VO2 max throughout the step and toning segments. Conversely, in the I-C upper body only trial the subject's oxygen consumption ranged from just below 40% VO2 max in the toning segments to 60% VO2 max during the step intervals.
The average heart rate intensity of the I-C upper-lower trial (146 bpm, 81% HRmax) was practically the same to the I-C upper body only (144 bpm, 80% HRmax) trial. However, these results clearly support (examining figures 1 & 2) what has been stated by others (Parker, Hurley, Hannion, & Vacarro, 1989) , that heart rate monitoring is a poor indicator of actual oxygen consumption in aerobic dance (and step) activity.
The caloric expenditure of the I-C upper-lower body trial for the subject was 7.48 kcal/min compared to 6.34 kcal/min for the I-C upper body only trial. This caloric expenditure is moderately better than that summarized above in circuit training (5 - 6 kcal/min women) programs. Table 6 shows how to calculate Kcal expenditure for various body weights.

Table 6. Calculation of Kilocalories from Two Interval-Circuit Formats

I-C Upper-Lower Body Format I-C Upper Body Only Format
Determine weight in kilograms (kg) by dividing weight in pounds by 2.204
Multiply your weight in kg by .13333
Example: 65 kg person
65 x .13333 = 8.66 kcals per minute Multiply your weight in kg by .11301
Example: 65 kg person
65 x .11301 = 7.34565 kcals per minute
All inferences from this single case study must be guarded, and certainly warrant further investigation. However, these early findings do suggest that the I-C upper-lower body training method may possibly maintain or improve aerobic capacity while increasing muscular fitness (see photos of upper-lower body exercises). The caloric expenditure of both interval-circuit programs suggest that each system may be considered worthwhile for exercise and weight-management programs.

Circuit and Interval Training Conclusion
Circuit training and interval training systems are splendid for improving physical fitness and exercise performance. These techniques may also bring variety and enjoyment to the students in your classes. You are encouraged to combine the science presented above with your own unique creativity and design new interval and circuit training programs for your classes. Give IT (interval training) a try.

Exercise Descriptions of the Upper-Lower Body Interval Circuit
NOTE: When alternating these exercises with step training, the student may wrap the elastic resistance around one hand or her waist during the step training interval. In that way the student doesn't have to bend up and down to pick up and put down the elastic resistance.

Squat with triceps extension
With the arms held behind the neck, begin descending into a squat while extending the arms outward. As the legs extend from the squat slowly bring the arms to the beginning position. Alternate doing sets of single- and double-arm triceps extensions.

Biceps with squat
With the legs shoulder width or slightly wider, squat down with the buttocks making sure the knees travel over the toes. Curl the arms at the elbow as you squat down. Return to starting position. Alternate doing sets of single- and double-arm biceps curls.

Row with squat
Stand with legs shoulder width apart and arms extended in front of the torso. Cross the handles of the exertube. While squatting down, pull the wrists towards the chin, lifting the elbows vertically. Lower slowly to the starting position. Alternate doing sets of single- and double-arm rows.

Single-arm cross-over with side lunge
Stand with one foot on step, on top of exertube, holding handle slightly above the knee. Keeping a slight bend at the elbow, bring the arm across the midline of the body. Hand is facing direction of action. As arm begins crossing midline of body, perform a lunge (with leg on step) in same direction of arm. Do 16 repetitions with both arms.

Arm extension with lunge
Stand with tube under foot on step, with rear leg 3 feet back. Concentrate on lowering down to about a 90 degree angle lunge with the front leg as the arms move rearward, past the side of the torso. Keep the palms facing backward during the action. Return to starting position. Do 16 repetitions and then switch to other leg.

Arm flexion with lunge
Stand in a forward lunge with the back leg on the exertube. Arms are extended out to the side of the body with the palms facing forward. Bring the arms forward to just below shoulder height while lowering down in a lunge. Arms return slowly back to the side of torso. Do 16 repetitions and than switch to other leg.

Squat with chest press
Place exertube behind back. With legs slightly wider than shoulder width, squat rearward with buttocks sitting backward as the arms press forward. Return to starting position.

Shoulder press with lunge
Put one foot on the step and the rear foot on the exertube in a lunge position. Hold the exertube next to the shoulders. Extend the arms upward as you lunge downward in the lunge. Return to starting position. Alternate single- and double-arm shoulder presses.