Personal trainers are continually faced with the challenge of creating fun, diverse, and multi-dimensional training programs. Training programs that are challenging and rewarding ensure motivated and satisfied individuals which can lead to a higher clientele adherence rate.
Personal trainers are responsible for providing programs that incorporate resistance training, cardiovascular training, and flexibility training. Depending on the individual’s fitness level and goals, these training variables can be modified over time for variety, increased intensity, and can help when they hit a plateau in the training program. Interval training can be incorporated into a cardiovascular training program to help individuals reach and set new goals (1,3).
Interval Training Defined
Interval training is a type of cardiovascular training that incorporates high-intensity bouts of work followed by lower intensity bouts of work, or rest, that is repeated for a specific number of repetitions depending on the fitness level of the individual (2). The rest periods allow for a buffering of lactic acid from the blood ensuring recovery for the next high-intensity interval (4). There are four variables to consider when designing a program (2):
- Intensity or speed of each interval
- Distance or time of each interval
- Active rest or rest of each interval
- The total number or intervals or repetitions to be completed during the workout
These variables will be determined by the goals the individual wants to achieve in the training program. The three energy systems that can be challenged during interval training are ATP-PC (sprints or shorter intervals), anaerobic (moderate distance or time), and aerobic (longer distance or time). All three energy systems will have different workloads and recovery times due to the intensity, and the time allowed for the buffering of lactic acid and replenishment of ATP so that the following interval may be completed at a high rate of work (Tables 1 and 2).
For individuals who are less fit, repetitions and work-to-rest ratios may be modified to meet their needs. Instead of using a 1:1 ratio, a 1:3 or 1:4 may be used until they have achieved a higher level of fitness (4).
Table 1: Energy Systems
|Energy System||Workload||Recovery (work:rest ratio)||Repetitions|
|ATP-PC||10 sec||30-60 sec (1:3- 1:6)||6-10|
|Anaerobic||1 min||2 min (1:2)||4-8|
|Aerobic||3 min||3 min (1:1)||6-12|
Note: Repetitions should be based on current fitness level of individual
Table 2: Age and Intensity
|Age Range||Heart Rate Goal|
Benefits of Interval Training
As mentioned before, adding interval training to a current fitness program can help an individual overcome a plateau in their current training program and add variety by changing up the program design. These two things alone can help with adherence and keep clients motivated so that they may reach their fitness goals.
Research has also shown positive physiological changes when incorporating interval training into a program. An increased VO2 max, decreased resting blood pressure, and an increased insulin response are just a few physiological changes that can be experienced when comparing interval training to slow, steady-state exercise (4).
In a study by Tremblay et al. a group of endurance trained individuals were compared to a group of high-intensity interval trained individuals and even though there was a significant difference in the energy expenditure with the endurance group expending more calories, the interval group had a much greater reduction in skinfold measurements at the end of the study (1,4,5).
In another study, untrained adults performed six weeks of interval training, each session (three per week) included 10 4-min bouts at 90% of peak oxygen consumption, and each interval was followed by 2 min of rest. At the conclusion of the study, researchers found an increase in peak oxygen consumption and power output, 9% and 21 % respectively (3). The study also concluded there was a decrease in lactate accumulation and an increase in fat oxidation, which suggests that interval training is an effective training method for increasing fat oxidation and the ability for muscle to oxidize fat (3).
Although, there are many benefits with interval training, caution should be used before incorporating it into a training program. Due to high intensity, near maximal training loads, individuals should have a solid foundation of cardiovascular fitness. Recovery times and maximal heart rate percentages can be adjusted depending on their current fitness level.
Once an individual can complete 20-30 min of continuous exercise, bouts of 1-2 min of more intense exercise may be incorporated followed by 1-4 min of recovery time. Interval training can be performed on multiple pieces of cardiovascular equipment or outside on the track; the possibilities are endless. Table 3 includes examples of interval training on a treadmill, stationary cycle, and sprint work on a track. The treadmill example will display a 1:1 work-to-rest ratio (1:2 ratio for the stationary bike) and the sprint intervals will give an example of how to perform intervals using distance. Examples and max heart rates (estimated) are based on a health 30-year-old adult male.
Table 3: Treadmill, Stationary Bike, and Sprint Intervals Examples
|Mode of Exercise||Warm-Up (WU)/ Cool-Down (CD)||Intervals||Max Heart Rate|
|Treadmill||5 min walking (WU) 5 min walking (CD)||5 x 3 min (jog/run) 5 x 3 min (walk/active rest)||170|
|Stationary Bike||5 min cycling (WU) 5 min cycling (CD)||8 x 1 min (intense) 8 x 1 min (active rest)||170|
|Sprints||Dynamic warm-up (WU) 5 min walking (CD)||10 x 50 yards (sprint) 10 x 50 yards (walk)||170|
- Fox, EL. Interval training. Bulletin of the Hospital Joint Diseases 40: 64-71, 1979.
- Karp, J. Interval training for the fitness professional. Strength and Conditioning Journal 22: 64-69, 2000.
- Perry, CG, Heigenhauser, GL, Bonen, A, and Spriet, LL. High-intensity aerobic interval training increases fat and carbohydrate metabolic capacities in human skeletal muscle. Applied Physiology Nutrition Metabolism 33: 1112-1123, 2008.
- Schoenfeld, B, and Dawes, J. High-intensity interval training: Applications for general fitness training. Strength and Conditioning Journal 31(6): 44-46, 2009.
- Tremblay, A, Simoneau, JA, and Bouchard, O. Impact of exercise intensity on body fatness and skeletal muscle metabolism. Metabolism 43: 814-818, 1994.