Two popular aerobic cross-training methods are: (a) circuit training, and (b) interval training. They are often used by individuals in the maintenance phase of conditioning who want variety in their workouts in order to prevent boredom and injury due to overuse. However, they both offer other benefits and advantages to athletes and special populations.
An advantage they both share is time-efficiency. The duration of a typical circuit or interval workout is 20-30 minutes, not including warm-up and cool-down. Another similarity is the way they use both aerobic and anaerobic metabolic pathways to provide the energy for muscle work. This article will explore the principles and methods of designing effective group exercise programs using circuit and interval training.
What is Circuit Training?
Circuit training (CT) is considered one of the basic systems of weight training. Typical weight training workouts are conducted in what is called a priority system, which involves working one muscle group or performing one type of exercise to completion and then going on to the next exercise and so on. By contrast, CT involves repeating exercises and muscle group work through a series of stations.
For many years, CT was used in schools and athletic facilities to accommodate large volumes of participants in the shortest amount of time with a limited variety of equipment. In fact, expensive equipment or large, bulky machines are not necessary to perform an effective workout. Body weight exercises, such as push-ups, squats, and lunges, are excellent exercises to include in a circuit. CT provides the flexibility of modifying each station to the needs and limitations of the participant’s fitness level and space available. From beginner to advanced, CT is considered one of the most efficient modes of accomplishing a complete workout in a short period of time.
Numerous studies have been conducted to compare the effects of circuit weight training on cardiovascular fitness and the cardiovascular disease (CVD) risk factors. Studies evaluating circuit weight training show an average improvement in V02max of 6%. This compares to an average improvement in V02max of 18% during typical steady state aerobic activities, such as running, cycling, or jogging. It may be concluded from this information that circuit weight training should not be the only method used when one of your goals is to improve your cardiovascular fitness. Circuit weight training will, however, sufficiently maintain cardiovascular fitness. To better understand the role of CT in your fitness program, it is important to describe the actual format of a typical circuit weight training workout and some of the variations that could be applied.
Goals of CT
1. Improved cardiovascular fitness
2. Improved muscle strength and endurance
3. Reduced body fat levels
4. Increased flexibility and injury prevention
5. Improved glucose tolerance and insulin sensitivity
6. Improved serum lipid levels (e.g., total cholesterol, total cholesterol/HDL, and LDL/HDL ratios)
7 Improved self-esteem and emotional fitness
Circuit Training (CT) for General Fitness
CT can be completed two to four times per week. As with resistance training, there should be 48 hours between sessions that work the same muscle groups. The following 10 exercises: upright row, bench press, leg press, arm curl, lat pull-down, leg curl, leg extension, triceps push-down, seated press, and seated high row, use all the major muscles in the upper and lowerbody and would provide a complete whole-body resistance training workout.
For general fitness, a resistance should be chosen that allows the station to be completed for the prescribed period of time (45-90 seconds). Resistance may also be applied by using body weight exercises, free weights, medicine balls, and elastic tubing. Progression can come through either increasing the station time or decreasing the rest intervals. Implement only one change at a Lime however. A total of one to three circuits is typical with a rest period of 1-3 minutes between each circuit.
This type of circuit can also be used by athletes during dosed or off-season training. Two or three circuit resistance training sessions can be interspersed with two to three cross-training cardiovascular workouts. Routines can be developed purely for strength development, for improving endurance, or some combination of the two.
When designing a circuit, each station should work a different muscle or group of muscles so that the overall energy output can be maintained throughout the session. Since each station is performed with maximal effort in a very short period of time, the major energy system being used for this format is the anaerobic glycolytic pathway, The major energy source being utilized is muscle glycogen or stored carbohydrates. The energy cost for a 20-minute circuit workout has been shown to average approximately 200 kcal (less for women than for men). It is an excellent means of burning calories, but stored fat does not play a significant role. Because many exercisers have a concern for weight control, the circuit may take on a variety of changes that will affect the energy pathways utilized as well as the energy sources.
Super circuit formats include a cardiovascular-type of station incorporated within the circuit of weight training exercises. Equipment, such as a stationary bicycle, stair climber, treadmill, rowing machine, or stepping platform, may be used or the participant may choose to jog in place, jump rope, perform calisthenics (e.g., jumping jacks, high kicks) as the aerobic component. As long as the overall intensity of the workout is maintained, the resulting cardiovascular improvement will be accomplished. By altering the time sequence, the energy pathways utilized will also allow for increased usage of stored fat as an energy source. A common pattern used would be I minute of muscle conditioning activity followed by 2-3 minutes of cardiovascular activity. With careful planning, this format could be adapted to a group exercise class.
Peripheral Heart Action System
Peripheral heart action system is a training session divided into several sequences of exercises. A sequence is a group of exercises, each for a different muscle group. The number of repetitions per set of each exercise may vary, but usually 8 to 12 repetitions is the norm. An exercise may combine several muscles or muscle groups or may isolate only one. All of the exercises in the sequence are repeated three times in a circuit fashion before moving on to the next sequence, which will involve doing different exercises for the same muscles. The number of sequences may vary from four to six per session.
The goal of the peripheral heart action system is to keep blood moving from one body part to the next. It is an extremely fatiguing program if a major goal of your workout is to increase cardiovascular endurance. The short rest periods and maintenance of a relatively high heart rate make this program very similar to normal circuit weight training. A cardiovascular station could also be incorporated between the exercise sequences. There is no specified time interval for the exercise sequence as long as the rest periods between exercises are kept short. The following shows a sample four-sequence peripheral heart action session.
In today’s fast-paced society, time efficiency is an important consideration when choosing a workout. CT has always been considered one of the best ways to see good cardiovascular and muscle strengthening results in a shorter exercise time. More dedicated exercisers also recognize the benefit of variety. Whether in a group exercise classroom or in the weight room, you can design a fun, intense, and motivating circuit workout. Be creative by using hand-held weights, balls, tubing, bands, or partner resistance. You may want to set up stations around the room, or if there is enough equipment for each participant, everyone can work simultaneously doing the same exercise. Decide what muscle groups you wish to work and what exercises will best accomplish the goals. Check form and alignment, and practice the exercises without weights or resistance before starting.
Some instructors who teach CT at clubs have a dedicated room with a variety of equipment permanently installed at strategic stations. However, you can also transform any room into a circuit training class using portable equipment. Instructors can develop a loyal following by providing participants with an extremely time-efficient workout that addresses muscular conditioning along with cardiorespiratory training.
Remember, CT is done quickly. In order to achieve the strength training and cardiovascular benefits, the rest periods are kept brief. Emphasize posture, full range of motion, and control through muscle resistance. CT can be an exciting addition to your present workout schedule, especially if you are interested in the benefits of cross-training.
What is Interval Training?
Interval training (IT) combines high and low-intensity intervals in a single workout. By incorporating IT into their existing exercise programs, group exercise instructors can discover an effective means for training both aerobic and anaerobic systems. Participants can maximize desired fitness results through this unique approach.
Working Aerobic and Anaerobic Systems
The ultimate goal of IT is to push both the aerobic and anaerobic systems to their maximum limits. Alternating brief periods of high-intensity work with low-intensity recovery periods (commonly referred to as the intervals) results in overloading both energy systems. It is important to understand that during steady state exercise, sufficient oxygen is supplied to, and utilized by, the working muscles. Hence, there is a balance between oxygen available for the body’s use and the intensity level of the activity.
However, as the exercise intensity is increased to the point that oxygen demands can no longer be met, anaerobic metabolism contributes to the energy requirements of the activity. An example of this would be a sprinter running a fast 440-yard dash and then “actively” recovering with a slow run. Or, a group exercise participant might perform a series of high-intensity power moves for 3 minutes followed by 1 minute of body conditioning work combined with low-intensity squats. Continually incorporating this type of work/rest program into any existing aerobic (cardio) training program will enable your students to reap the many benefits of IT.
Why IT Works
Unlike a program that strictly trains the aerobic system, IT allows your participants to train both the aerobic and anaerobic systems. The greatest concentration for increased oxygen and carbon dioxide exchange occurs during the high-intensity portions. It is at this level of intensity that the accumulation of lactic acid tends to be the greatest. This continual build-up of lactic acid will eventually hinder muscular contraction and overall physical performance. However, by decreasing the intensity for a brief period of time, active recovery can occur because the body’s ability to utilize oxygen and deliver nutrients to the working muscles is then increased.
During this decreased intensity portion, the incorporation of hand-held weights, elastic bands or tubing, medicine balls, BOSU, or even calisthenics are excellent ways for your participants to increase muscular strength and endurance and to help eliminate toxic by-products, such as lactic acid. Hence, the participant pushes to an anaerobic training state, promotes muscular strength and endurance while actively recovering, and still remains in an aerobic training state. It is crucial to remember this important point: the participant remains in an aerobic training state if-and only if-the heart rate stays above the training threshold. If the heart rate drops below this level during the active recovery period, the aerobic training state is not maintained.
Making IT Work
Research indicates that significant physiological improvements occur if IT is implemented two to three times per week. However, this will vary depending on the present fitness level of your participants and the exercise goals. For example, an individual concerned with improving his/her general fitness level will reap minimal “interval” benefits by participating in IT only one time per week.
A highly trained athlete will gain significant “interval” improvements by participating more times per week. However, as an effective instructor, you must remember that IT can be very stressful at any level of participation. Therefore, be aware of the possibilities of overtraining-related injuries and monitor your programming accordingly. Providing your participants with a safe and effective workout scenario is your number one priority.
Work/Active Recovery Ratio
The work interval is known as the high-intensity portion of the workout. The active recovery interval consists of low-intensity movement. Both combine to make up what is called a cycle. Generally, the number of cycles in a workout is once again dependent on your participants’ current fitness levels and exercise goals.
In attempting to increase the exercise intensity to an anaerobic threshold for a brief period, have your participants select an intensity of 85% age-predicted maximum heart rate (HR max). However, it is important to assess individual fitness levels when determining intensity levels. An extremely fit student might reach an anaerobic training state at 90% HRmax, whereas an individual new to exercise might reach this state at 70% HRmax. Without metabolic testing, it is virtually impossible to determine at exactly what heart rate intensity level an individual will reach the anaerobic training state. Therefore, inform your participants that there are other indicators that the an anaerobic training state is near, such as (a) dramatic increases in heart rate, (b) increases in breathing depth and frequency, (c) possible hyperventilation, and (d) muscle fatigue.
Participants can also monitor their intensity levels using the 10-point Rating of Perceived Exertion (RPE) scale. According to the 2010 ACSM guidelines, moderate intensity represents a RPE of 5-6 with noticeable increases in heart rate and breathing while a RPE of 7-8 with much higher increases in heart rate and breathing represents vigorous intensity. Remember, safety is the first concern, and for many, prolonged exercise at high-intensity levels is very demanding and may be potentially dangerous.
How long your participants exercise with high-intensity movement and recover with low-intensity body conditioning segments is dependent upon their exercise goals, present fitness level, and the primary energy system (aerobic vs. anaerobic) they want to train. Let’s examine two extreme examples of interval work-outs. First, a track athlete is likely to work with intervals of a one-to-one ratio-sprint for 1 minute and actively recover for the next. Or, another athlete might do what’s known as “mile repeaters”-running a “hard” mile, followed by an “easy” mile.
Conversely, a long distance person will work with intervals of a two-to-one ratio-recovering only half the time he/she works. Remember, the long distance runner’s goal is to push hard for longer periods of time than the track athlete (who needs short bursts). That is why it is critical for the effective instructor to tailor the interval workouts to the goal of the participant, if at all possible.
Taking IT to the Class
Begin your class with a 10-minute warm-up that will prep the joints, begin to increase core body temperature, and prepare it for more strenuous exercise. Design the warm-up so that the heart rate begins to reach 50-60% HRmax near the end of the warm-up period.
Once this is accomplished, the interval segment begins. Each interval is 4 minutes in duration and consists of 3 minutes of high-intensity power moves, jumping jacks, knee lifts, and plyornetrics, immediately followed by 1 minute of active recovery body conditioning. During the 3-minute high-intensity period, encourage your participants to work at 80-94% HRmax.
Three minutes is an optimal time because those participants who are extremely fit may challenge themselves for the entire time, or newcomers to this type of training may be encouraged to stay “more aerobic,” working up to 94% HRmax in the latter portion of the cycle. A music fade for 5 seconds is essential between work and recovery periods. It cues your participants that change is about to occur.
Then, the active recovery portion begins incorporating hand-held weights, elastic bands or tubing, BOSU, medicine balls, or even simple calisthenics to promote body conditioning. During this period, your participants’ exercise intensity should be decreased to 55% HRmax. This is the optimal intensity for increasing blood perfusion and removing lactic acid while remaining in an aerobic training state. This 3-minute/1-minute format should be followed for 6 sets, completing the interval period in 24 minutes.
A post-aerobic cool-down, in which the movement lowers the heart rate to below 55% HRmax, should follow the interval segment. A 10-minute abdominal section to isolate eccentric (lengthening) contractions follows the cool-down, and a super stretch completes your participants’ workout.
Now that you have a basic understanding of the physiological responses of IT and a general format of implementation, following several guidelines will allow you to make your participants’ first interval class a success. First, while making your interval music, include a 5-second music fade between each work and recovery period. As mentioned earlier, this cues participants that change is about to occur and is also a great place to begin a heart rate check if needed.
It also serves to educate the participants as to how their bodies are responding to the varying intensities. Most industry music companies have also designed interval music for purchase, should you choose not to develop you own.
Several ideal upper/lower body combo conditioning moves make the interval class format a success during active recovery periods, and promote muscular strength and endurance.
- Shoulder press with hand-held dumbbells/side lunges
- Upright row with elastic tubing/squat
- Lateral twist with medicine ball/front lunges
- Biceps curls with hand-held dumbbells/front lunge to BOSU
- Triceps press with elastic tubing/split lunge squat
These combinations of upper and lower body movements provide total body conditioning while the body actively recovers from each work segment.
Beats per minute (bpm) during the high-intensity portion should be from approximately 150-160 bpm. Music for the active recovery periods shouId be 120 bpm. This allows for muscle isolation.
Remember, IT is peaks and valleys in exercise intensity. IT not only improves all three energy systems, but also helps promote muscular strength and endurance. If you want to maximize student results and literally provide them with the key to achieving success in any personal fitness program-try IT.