This article on interval training is divided into five parts for easier reading:
- Part One: Background.
- Part Two: Exercise Methodology.
- Part Three: Types and Variations of Interval Training.
- Part Four: Advantages and Disadvantages of Interval Training.
- Part Five: Miscellaneous.
PART THREE: TYPES & VARIATIONS OF INTERVAL TRAINING
As outlined in Part 01 (Section 1.3), there are a variety of terms for interval training, although the basic principle of varying between bouts of faster and slower periods is consistent. Generally, what defines the form of interval training is how the variables (Part 02, Section 2.4) are used by the coach and/or athlete.
In simple terms, academic wisdom suggests there are two different types of interval training (Billat, 2001a):
- Aerobic Interval Training: “Aerobic training is defined as an interval training which elicits aerobic metabolism at a higher ratio than anaerobic metabolism.” (Billat, 2001a, p.21), which can be further divided into:
- Short aerobic interval training (10-30 seconds each exercise interval).
- Long Aerobic Interval Training (30-60 seconds each exercise interval).
Sometimes referred to as “repeated maximal sprints” or “maximal dynamic exercise” (Billat, 2001b, p.77), or even supramaximal sprint training.
- Anaerobic Interval Training (Billat, 2001b): An anaerobic activity is defined as energy expenditure that uses anaerobic metabolism (without the use of oxygen) that lasts less than 90 seconds, utilising an exhaustive effort (Wilmore & Costill, 2004).
This section outlines some of the well-known, amongst many, interval training methods available.
3.1 ‘Old’ Interval Training
“One of the most influential coaches of the inter-war years who adopted a more scientific approach was the German physiologist Woldemar Gerschler. Along with his colleague Herbert Reindell at Freiburg University [Germany], he pioneered scientific interval training.” (Carter, 2011, p.67).
Gerschler used extensive physical and psychological tests to help guide and advise his runners. Gerschler and his colleagues, Hans Reindell (a medical doctor and physiologist) and Helmutt Roskamm authored and published (together and separately) a number of scientific papers, articles and books on interval training.
Gerschler’s method was designed to maximise cardiovascular fitness using a series of short, fast runs that were repeated a number of times. It trained the development of the heart during the recovery intervals. The time of the exercise interval and the recovery interval was crucial and therefore a stopwatch was required – with a common criticism being that this form of training was a slave to the stopwatch.
Gerschler’s method focused on cardiac physiology and the adaptations that can be made in training the heart, and was based on three principles:
- Exercise increases heart rate and rest slows it down;
- Repeated physical exercise will slow heart rate while pumping the same volume of blood; and
- The volume of blood for each individual is constant.
Based on their work, Gerschler and Reindell formulated the Gerschler-Reindell Law. Gerschler and Reindell concluded from their experiments that the heart rate did not surpass 180 bpm – that represented the limit. From this point they allowed 90 seconds to return to 120-125 bpm and then the next interval could commence. If it took longer, it was because the effort was too hard or too long. Gerschler felt it was the recovery that strengthened the heart. He felt that there was a strong stimulus of the stroke volume immediately after the beginning of the recovery phase, so the recovery became a big focus hence the name interval training. The recovery was a walk in the beginning stages and then a jog as the runner gained fitness.
Gerschler’s method gave very rapid improvements in performance and as the heart became fitter and returned to 120 bpm more quickly the recovery intervals became naturally reduced. This natural reduction in the recovery interval due to increased fitness was combined with increasing the total number of repetitions to progress the training, rather than increasing the speed of the repetitions.
Early on, this form of interval training was very rigid and strictly guided by the Gerschler-Reindell Law. However, as it became more accepted and widespread, coaches and athletes began to experiment and move beyond the strict guidelines developed by Gerschler and Reindell.
3.2 ‘New’ Interval Training
“‘New Interval Training’ is simply and very specifically any repetition training where what the athlete does during the ‘recovery intervals’ is crucial and actually has a profound effect on the training of the metabolic energy systems.” (Thompson, 2010).
Although a stopwatch can be used with this form of training, it is meant to be more rhythmic and dictated by the perception of pace (i.e. the athlete judges how fast they are running). New interval training is based on a concept first developed in 1975 and formulised in 1994 by Peter John L. Thompson, a British coach, known as Lactate Dynamics Training (LDT) (Thompson, 2010). Thompson (2010) describes LDT as:
“…any form of training where lactate production is deliberately increased by the intensity of exercise and then alternated with periods of less intense activity. In this way the muscle cells learn how to both use and clear the produced lactate during the less intense recoveries. This alternating of pace produces a massive improvement in running economy, the vVO2max and tlimvVO2max, all of which are very strong predictors of performance.”
Thompson states that LDT is very similar to fartlek training, further commenting that “Properly done, Fartlek training is a classic form of Lactate Dynamics Training and trains the lactate shuttle in an environment away from the track.”
The major difference between the old and new interval training techniques is the transition from the work period to the recovery period, which Thompson (2010) describes as a “Roll-on Recovery”. Unlike Gerschler’s method in which a runner could stop, walk or jog during the recovery period, Thompson’s method entails a continuation of running but at a less intense pace, as he describes:
“What does ‘a very active, roll-on running recovery’ really mean in practice to the athlete? To get an idea of this it can be useful to ask an athlete to imagine that they are riding a bicycle. When you are pedalling along it is like being in the faster repetition distance of the session. When you come to the recovery interval it should feel like you stop pedalling but you do not touch the brakes at all you just roll on, naturally maintaining the active recovery pace.”
3.3 The Fartlek Method
“… this relatively unscientific blending of interval and continuous training introduced to the United States in the early 1940s had particular application to exercise outdoors over natural terrain. The system used alternate running at fast and slow speeds over both level and hilly landscape.” (Katch, McArdle & Katch, 2011, p.436).
Katch, McArdle and Katch (2011, p.436) inform us that “Fartlek training, developed in 1937 by Gösta Holmér (1891–1983), means ‘speed play.’” Fartlek training is also known as alternative pace training, the Swedish natural method or just the Swedish method. Holmér, a Swedish coach and runner, based this new training method after the Finnish runner Paavo Nurmi.
Unlike traditional interval training that involves specific timed or measured segments, fartlek training sessions are less structured and do not require systematic manipulation of work-rest intervals. For example, varying the pace throughout the run by alternating between fast runs and slow jogs. In a manner similar to the rate of perceived exertion (or RPE), when conducting a fartlek session the runner determines their pace based on ‘how it feels’ at the time (Katch, McArdle & Katch, 2011), meaning the runner can experiment with their pace and endurance and is therefore a useful method for beginners. It provides an ideal means of general conditioning and off-season training, but it obviously lacks the systematic quantified approached of interval and continuous training.
However, when applied properly, the fartlek method “will overload one or all of the energy systems.” (Katch, McArdle & Katch, 2011, p.436). Porcari, Bryant & Comana (2015, p.391) state:
“This training format provides a sequence of different intensities that stress both the aerobic and anaerobic systems, something rarely achieved with exclusive steady-state training (aerobic), and different from traditional interval training (anaerobic with specific work-to-rest ratios). Consequently, this training format can be adapted to meet the needs of intermittent-sport athletes by essentially mimicking the changes of pace that occur during these events (e.g., rugby, soccer, football, hockey, and lacrosse).”
Fartlek can be conducted virtually anywhere but is great on a soft surface, ideally the pinewood needle surface of a forest path and on undulating ground so that there is plenty of uphill and downhill running. It can then be a combination of great quantities of easy running, interspersed with sprints and periods of resistance running up hills. The sprints and uphill work will force the body into periods of anaerobic work, resulting in oxygen debt. This debt must be repaid during the lower intensity parts of the run. Consequently, this method educates the body to improve its oxygen uptake and speed of recovery.
Variables in fartlek include (Thompson, 2010):
- Distance: originally 12 km, with up to 5,000 metres at faster than race pace.
- Speed (or pace or intensity): varying from gentle jog to faster than race pace.
- Terrain: flat, soft, undulating and hilly.
- Frequency: three to five times per week.
During the 1950s, Percy Cerutty, an Australian coach, adopted the fartlek method. “He combined beach running in heavy sand, sand dune training on dunes over 25 metres high with speed play over the undulating trails of the cliff tops, as well as on the flat beach and dirt roads.” (Thompson, 2010).
In summary, the fartlek method of training combines aspects of continuous and interval training and stresses both the aerobic and anaerobic energy pathways.
3.4 The Tabata Method
During the 1990s, Izumi Tabata and his colleagues published what is considered a landmark paper (Izumi et al., 1996). In their study using 14 physically fit, young, male subjects, Tabata and colleagues compared two training protocols, examining improvements in both aerobic and anaerobic fitness.
- In experiment one, seven subjects performed steady state exercise (moderate-intensity endurance training) five days per week on mechanically braked cycle ergometers, with each session performed at 70% of VO2max for 60 minutes (total of 300 minutes per week).
- In experiment two, seven subjects performed exhaustive intermittent training (high-intensity interval training) five days per week on mechanically braked cycle ergometers, with four sessions performed at workloads equivalent to 170% of VO2max. The subjects completed seven to eight reps, with the workload progressing by 11 watts on subsequent sessions when more than nine intervals could be completed. Each set involved a 20-second work interval followed by a 10-second recovery interval, totalling approximately 4 minutes of work per session. On the fifth day, the subjects completed a 30-minute interval at 70% of VO2max, followed by only 4 sets at 170% of VO2max.
Both protocols improved aerobic capacity, but only experiment two increased anaerobic capacity.
- Experiment 1:
- Aerobic capacity: increased by 9% (52.9 to 58 mL/kg/min); and
- Anaerobic capacity: no increase.
- Experiment 2:
- Aerobic capacity: increased by 13% (48.2 to 55 mL/kg/min); and
- Anaerobic capacity: increased by 28%.
Tabata and colleagues made reference to Medbø and Burgers 1990 work on the effect of training on anaerobic capacity with regards to intense exercise of short duration, stating that it was heavily dependent on energy from anaerobic sources (Medbø & Burgers, 1990).
An anaerobic activity is defined as energy expenditure that uses anaerobic metabolism (without the use of oxygen) that lasts less than 90 seconds, utilising an exhaustive effort (25)
Unfortunately, the nature and results of this study have largely been misinterpreted by many fitness professionals who market Tabata training (and other permutations) to the general public. Although the study used 14 physically fit, young, male subjects exercising on bicycle ergometers, this form of training has a number of permutations and is now performed with many different population groups (e.g. deconditioned individuals, females and older adults) and includes other forms of cardiorespiratory exercise (e.g. treadmill, elliptical and sprints), and even resistance training (e.g. body weight and externally loaded resistance), were it can be problematic to conduct training at 170% of VO2max. It could be argued that the only commonality between these forms of exercise is the 2:1 WR Ratio. Some have also moved away from the eight interval protocol.
“The training protocol used in experiment 2 was first introduced by Kouichi Irisawa, who was a head coach of the Japanese National Speed Skating Team. The training has been used by the major members of the Japanese Speed Skating Team for several years.” (Tabata e al., 1996).
Although Irisawa developed the training method, it was Tabata’s paper and his name that became inexorably linked with this form of interval training. The Tabata method of interval training is also known as the Tabata Protocol and, occasionally, the Koichi Protocol. Tabata lent his name to a protocol that helped to promote the interval training movement to the general populace. Prior to the 1990s, interval training had generally been the preserve of elite athletes.
Horst (2008, p.94) suggests that the Tabata method differs from traditional interval training in three ways:
- “First, the twenty-second work interval is much shorter than traditional intervals.
- The second difference, then, is that this shorter work interval must be performed with 100 percent exertion; and
- Third, the rest interval is just ten seconds, which is so brief that very little recovery can occur before the next work interval begins.”
Peter Coe, the father and coach of the famous British runner Sebastian Coe, used an early model in the 1970s (Coe, 2013, p.38-39).
In summary, the ‘original’ Tabata method of training is twenty seconds of high-intensity exercise followed by ten seconds of rest (a 2:1 work-to-rest ratio). This interval is repeated eight times to create four minutes of the most gruelling training you can imagine. There are now a number of permutations
3.5 High-Intensity Interval Training
“High intensity interval training (HIIT) involves repeatedly exercising at a high intensity for 30 seconds to several minutes, separated by 1-5 minutes of recovery (either no or low intensity exercise).” (Gibala & McGee, 2008, p.58).
“HIIT generally involves alternating bouts of higher-intensity exercise (20 seconds to 5 minutes) sessions with either true rest or light- to low-intensity recovery workloads throughout an exercise routine and has traditionally been used to train athletes who require high levels of both aerobic and anaerobic fitness (e.g., track, team sport athletes).” (Porcari, Bryant & Comana, 2015, p.92).
Individuals work at 90% or more work rate (high-intensity) for a set time, followed by recovery (low-intensity) for a set time. The WR Ratio is usually unequal, with the work rate lasting seconds or minutes. This is repeated approximately 2-6 times, with sessions lasting between 10 and 30 minutes – although the exact structure is sport- and person-specific.
Rest periods are intended to be too short to provide complete recovery, and completing subsequent intervals in a partially recovered state is a key part of what makes these efforts effective.
HIIT training, also sometimes known as High-intensity Intermittent Exercise (HIIE), attempts to decrease the overall volume of training by increasing the effort expended during the high-intensity intervals – which are brief but challenging.
Alternative names and variations of HIIT include:
- Power Interval Training (PIT; or Power Intervals).
- Sprint Interval Training (SIT; or Short Sprint Interval Training):
- Functional Threshold Power (FTP) Intervals, which explicitly considers lactate threshold (LT), and (All Out) Miracle Intervals. Both are typically used in cycling.
- A commonly studied SIT model is repeated Wingate Tests.
- “Training adaptations are highly specific to the type of activity and to the volume and intensity of the exercise performed. […] Similarly, the marathon runner would not concentrate on sprint-type interval training.” (Kenney, Wilmore & Costill, 2012, p.212-213).
- VO2Max Intervals.
- Steady State Intervals.
- Short Work-to-Rest Ratio Intervals, performed in series.
- HIIT Aqua (also known as Aqua HIIT, HIIT Splash or Water-based HIIT). HIIT training in the water generates cardiovascular and metabolic benefits without high impact, and with additional benefits facilitated by the properties of water:
- The pressure and resistive forces of water (hydrostatic pressure) aids venous return (blood flow back to the heart), which results in an increase in stroke volume.
- This effect decreases heart rate even though the exercise intensity is at a peak level.
- This decrease in heart rate and rapid recovery time makes water-based HIIT suitable for a range of participants.
HIIT, and its variants, is not for new or beginning exercisers; you need to have a basic level of cardiorespiratory fitness first.
The most common HIIT intervention used in studies is the Wingate Anaerobic Test developed in the 1970s (Bar-Or, Dotan & Inbar, 1977).
3.6 The Wingate Anaerobic Test
Developed in the 1970s in Israel (Bar-Or, Dotan & Inbar, 1977), the Wingate Anaerobic Test (WAnT), also known as the Wingate Test and Wingate Protocol, measures (Bar-Or, 1987; Cooper et al., 2004):
- Lower-body peak power;
- Anaerobic capacity; and
- The reduction of power, known as fatigue index (FD.
The WAnT, usually on a cycle ergometer, is conducted as follows:
- It is a 30-second all-out exhaustive (at an intensity of over 90% of maximal oxygen uptake, also known as 90% of VO2 max) ergometry test where the athlete pedals against a resistance that is set at a certain percentage of their body weight.
- The power output is measured throughout the test by the number of revolutions the athlete can achieve on the ergometer during those 30 seconds.
- The peak power recorded is the maximal power output achieved for 5 seconds of the test, usually the first 5 seconds.
- The anaerobic capacity, or average power, is recorded and averaged over the entire 30 seconds of the test.
- The lowest power output is an average of the lowest 5 seconds seen during the test, usually the last 5 seconds.
- Finally, the difference in power output from highest to lowest is recorded as the FI.
Each 30 seconds of cycling at maximum effort is separated by 4 minutes of recovery, repeated 4-6 times per session, with three sessions per week (Bar-Or, Dotan & Inbar, 1977; Boutcher, 2011). This results in only 2-3 minutes of exercise at maximum intensity and 15-25 minutes of low intensity exercise per session, making it a time efficient method of exercise. The ability to evaluate these measurements makes the WAnT a valuable test for coaches, athletes, and research scientists.
Two major energy sources are required during the WAnT (Wilmore & Costil, 2004):
- The first is the adenosine triphosphate-phosphocreatine (ATP-PCr) system, which lasts for 3 to 15 seconds during maximum effort.
- The second system is anaerobic glycolysis, which can be sustained for the remainder of the all-out effort.
Thus, the WAnT measures the muscles’ ability to work using both the ATP-PCr and glycolytic systems. Many sports (including football, sprinting, football, baseball, lacrosse and gymnastics) use anaerobic metabolism extensively during competition.
Less demanding protocols may be utilised for sedentary, overweight populations, which is important to remember when considering exercise as prevention and management of cardiovascular and metabolic disease.
3.7 The Timmons Method
In 2012, Doctor Michael Mosley undertook a form of interval training, that came to be known as the Timmons Regime, as part of a BBC documentary ‘Horizon: The Truth About Exercise’ (Mosley, 2012).
Jamie Timmons, professor of ageing biology at the University of Birmingham, is a proponent of a few short bursts of flat-out intensity. Mosley (2012) describes Timmons method:
“It’s actually very simple. You get on an exercise bike, warm up by doing gentle cycling for a couple of minutes, then go flat out for 20 seconds. A couple of minutes to catch your breath, then another 20 seconds at full throttle. Another couple of minutes gentle cycling, then a final 20 seconds going hell for leather. And that’s it.”
Mosley repeated this routine over four weeks, “making a grand total of 12 minutes of intense exercise and 36 minutes of gentle pedalling.” Mosley also completed pre- and post-regime testing for:
- Insulin sensitivity, which improved by 24%; and
- Aerobic fitness, which did not improve at all – it was revealed that Mosley was a ‘non-responder’.
“There was a possibility that I wouldn’t improve. Not because HIT [high intensity training] doesn’t work but because I’ve inherited the wrong genes.” (Mosley, 2012).
In research conducted as part of the HERITAGE Family Study, results suggest that individuals will respond to exercise in very different ways, with some of this difference due to their genes. In one international study (see link) 1,000 people were asked to exercise four hours a week for 20 weeks. Their aerobic fitness was measured before and after starting this regime and the results were striking. Although 15% of people made huge strides (known as super-responders), 20% showed no real improvement at all (known as non-responders). There is no suggestion that the non-responders were not exercising properly, it was simply that the exercise they were doing was not making them any aerobically fitter.
3.8 The Copenhagen Method
Another more recent interval training method follows the research of Gunnarsson and Bangsbo published in 2012, called the 10-20-30 Training Concept, more commonly known as the Copenhagen method (Gunnarsson & Bangsbo, 2012).
In this study, 18 moderately trained runners (6 females and 12 males) were divided into a high-intensity training (10-20-30) group and a control group to compare the effects of both methods on the health profile, muscular adaptations, VO2max, and running performance of the study participants.
While the control group continued their normal training methods during the seven-week study, the 10-20-30 group implemented a format of 30 seconds of low-intensity running at less than 30% of maximal intensity, 20 seconds of moderate-intensity running at less than 60% of maximal intensity, and 10 seconds of high-intensity running at more than 90% of maximal intensity (i.e., a 60-second exercise interval). This interval was repeated five times (i.e., 5 minutes of continuous exercise) before taking a 2 minute recovery, and the entire circuit was repeated three to four times.
At the conclusion of the study, VO2max in the 10-20-30 group was 4% higher, and performance in a 1,500 metre and a 5 km run improved by 21 and 48 seconds, respectively. Furthermore, in the 10-20-30 group, systolic blood pressure was lower by 5 mm Hg, and total and LDL cholesterol were lower by 0.5 and 0.4 mmol/L, (19.3 and 15.5 mg/dL) respectively, in comparison with the control group.
The results demonstrated that this method of training, with short, near-maximal bouts (e.g., 10 seconds), can improve health, fitness, and performance despite large reductions in training volume. This format of training with slightly longer recovery intervals is generally better suited for most individuals contemplating HIIT.
3.9 The Paarlauf Method
The Paarlauf method, or Paarlauf training, is a competitive form of interval training and is not a very commonly used form of running. Paarluf means ‘pair run’, and it is a competitive relay for two or more people.
The relay comprises at least two teams of two runners, with one team member running whilst the other(s) rests, and can be used as a team version of a fartlek session. Formal areas to run the session include athletics tracks and informal can be areas marked out in outdoors/green spaces (i.e. a parks).
Although the exact structure differs, the distance of the race is (usually) unspecified with only a minimum and maximum time being given (so the runners can determine their pace), thus a race could last from 10 to 45 minutes. Number of laps can be used instead of a time.
After a certain time has elapsed – this time is decided prior to the race but unknown to the runners – the referee blows a whistle and the competitors ‘rest’ for a period of one minute. The winning team is the one who has carried the baton the furthest.
The two runners can decide how they wish to share the running. For example, they can either run interval quarter miles or every other furlong, jogging across the track to regain the baton.
As a training workout, the number of runners can be increased to a team of 4, 6 or 8. With 8 runners, they could spread out over 400 metres and move with the baton from 60-100 metres with about 55 seconds rest before the next effort.
3.10 Interval-Circuit Training
“Introduced in the Scandinavian countries in the 1960s and 1970s, interval-circuit training combines interval training and circuit training into one workout.” (Kenney, Wilmore & Costill, 2012, p.223).
The circuit may be 3,000 to 10,000 metres in length, with stations every 400 to 1,600 metres (437-1,750 yards). The individual jogs, runs, or sprints the distance between stations; stops at each station to perform a strength, flexibility, or muscular endurance exercise in a manner similar to that in actual circuit training; and continues on, jogging, running, or sprinting to the next station. Trim Trails are very similar.
These courses are typically located in parks or in the country where there are many trees and hills. Such a training regimen can benefit almost any type of individual and provide diversity to what might be an otherwise monotonous training regimen.
3.11 Interval Training Variations
Manipulation of the interval training principles (Part 02, Section 2.4) provides the opportunity for a wide variety of interval training sessions. Outlined below are some of the more commonly used variations:
- Individual Interval Training Options:
- Repeats (see Section 3.11.1): The same distance, done a set number of times. Repeats of 400 metres, one lap of the track, are the most common, but distance runners may do repeat 1,000s or miles to improve their stamina. Repeats can also be run at anticipated race speed to develop a sense of pace and avoid going out too hard.
- Ladders (see Section 3.11.2): Progress from shorter to longer repetitions; i.e 200, 400, 600, 800, 1000. Recovery interval can be constant or increase. Ladders can also be run long to short.
- Pyramids (see Section 3.11.3): An up and down ladder together, i.e. 400, 600, 800, 600, 400. Advanced runners may be able to do multiple pyramids.
- Cut-downs (see Section 3.11.4): Designed to improve one’s finishing kick. Several longer repeats are done to create fatigue, then the runner performs shorter, faster reps to develop the ability to run hard when tired.
- ‘Ins-and-Outs’: Usually done over a mile or longer, accelerate the straightaways and jog the turns, or sprint 50 metres, jog 60.
- Group Interval Training Options:
- Indian Runs: As everyone runs in single file, the last person in line sprints to the front. When he gets there, the next person goes, and so on.
- Relay Races: Pick teams, then pick a lane, then pick a workout. Try six times 400 metres with two-person teams, the last place team buys refreshments.
- Handicapping: ‘The last shall be first and the first shall be last.’ Runners stagger their start of each repetition by ability level, from slowest to fastest. The faster runners try to catch the slower ones.
3.12 Who Uses Interval Training?
“While interval training is traditionally associated with track, cross country, and swimming, it is appropriate for all sports and activities.” (Kenney, Wilmore & Costill, 2012, p.220).
Kenney, Wilmore and Costill (2012, p.221) informs us that “One can adapt interval training procedures for each sport or event by first selecting the form or mode of training and then manipulating the following primary variables [Part 02, Section 2.4] to fit the sport and athlete…”
Seiler and Seiler (2008, p.33) state “Interval training is a common practice among sprint runners, basketball players, hockey players and all other athletes that train their bodies to provide short periods of intense power and speed.” They also state that interval training is useful for practitioners of martial arts (Seiler & Seiler, 2008).
Horst (2008, p.94) informs that “The Tabata Protocol is a highly specific method of interval training that is popular among elite speed skaters, cyclists, middle-distance runners, and swimmers; but serious climbers can benefit from this training strategy too.”
In summary, with an understanding of interval training, almost any coach and athlete can utilise interval training within their training programme provided that the training variables fit the sport and athlete.
3.13 Interval Training in the Military
Fitness is paramount to being successful in the military, especially the army. Recruits are expected to be able to excel in all physical tests and meet the physical demands of being a soldier.
The key to this success is a training regimen aimed at (amongst other components of fitness) increasing cardiovascular capacity, both aerobic and anaerobic. As such interval training in the military environment is designed to provide exercise to groups of soldiers at intensities which suit each individual’s fitness level.
Interval training can promote fitness in a broad range of areas, including aerobic capacity, anaerobic capacity and speed. It can also aid in delaying the onset of mental and physical fatigue, an important element on the battlefield.
In addition, interval training can be organised to exercise a number of fitness components in a short period of time. A little imagination can make interval training an excellent addition to a unit’s total physical fitness programme.
The British Army has been using interval training since at least the 1980s. From 1990, as a recruit and then trained soldier, I participated in interval training and, as a military fitness instructor, I designed and delivered interval training.
At the end of the 1960s, an American group of researchers focused on interval training in a military context (Fox et al., 1966; Mathews et al., 1967). The purpose of their study was to determine which of the following three interval training programmes produced the greatest cardiorespiratory fitness:
- A programme consisting entirely of short, repetitive running;
- A programme consisting entirely of long but less repetitive running; and/or
- A programme consisting equally of short- and long-distance running.
In the first of two papers, Fox and colleagues (1966) found that:
- Short repetitive running was necessary for maximum improvement of cardiorespiratory endurance;
- Long less frequently repeated running was less necessary than was short distance running for improvement of cardiorespiratory endurance; and
- Both types of running, however, are probably necessary physiologically and for proper leg conditioning, reduction of leg injuries and for variety and motivational purposes.
In the second of two papers, Mathews and colleagues (1967) found that:
- Cardiorespiratory endurance was increased significantly by a 7 week interval training programme;
- A training frequency of 4 days per week compared with 2 per week produces greater improvement only in submaximal exercise and recovery heart rates; and
- Maximal oxygen consumption is improved by the same magnitude by a 7-week interval training programme with 2 workouts per week as it is with 4 and 5 workouts per week.
Since the 1960s, interval training has evolved as a training methodology within the military, just as other aspects of the military have evolved in recognition of a modern and 360 degree battlespace.
High-intensity functional training (HIFT) programmes, known by some as extreme conditioning programmes (Poston et al., 2016), are designed to address multiple fitness domains and have become very popular, especially in the US. CrossFit, SEALFIT and the US Marine Corps’ High Intensity Tactical Training (HITT) are well-known versions (Haddock et al., 2016). Poston et al. (2016, p.627) describe modern military interval training:
“High-intensity functional training (HIFT) is a promising fitness paradigm that has gained popularity among military populations. HIFT programs emphasize varied functional movements (i.e., movements requiring universal motor-recruitment patterns in multiple movement planes such as lifting, pulling, and throwing) done at relatively high intensity. Rather than biasing workouts toward maximizing a specific fitness domain (e.g., running programs for aerobic endurance), HIFT workouts are designed to promote general physical preparedness. This is particularly important for military populations who need to have superior physical conditioning to respond to occupational and warfare-specific tasks.”
HIFT programmes stress both aerobic and anaerobic energy pathways and are balanced in addressing power, strength, flexibility, speed, endurance, agility, and coordination (USMC, 2006; Roy et al., 2010; Haddock, Poston & Jahnke, 2011).
The USMC HITT programme was first visualised under the ‘Concept for Functional Fitness’ in 2006. It is endorsed by the National Strength and Conditioning Association’s (NSCA) Tactical Strength and Conditioning (TASC) Department, and is available online and via a mobile application (USMC, 2014). Train the Trainer courses are delivered by certified Strength and Conditioning Specialists and Combat Fitness Specialists. Each HIIT session provide an active dynamic warm up; core stability and flexibility; speed, agility and endurance; and strength and power.
The USMC also offers an aquatic version of the HITT programme known as Aquatics Maximum Power Intensity Training (AMP-IT). It is designed as a high intensity fitness class that will increase muscle endurance, improve cardiovascular-respiratory function and aid in injury rehabilitation.
Although Haddock and colleagues (2016) recommend HIFT programmes becoming the standard for military physical training, they observed that no large scale randomised trials comparing traditional military physical training with HIFT programmes on both health and injury outcomes had been conducted. The same researchers had announced earlier in the year they would be undertaking such a study (Poston et al., 2016).
Ultimately, military personnel (especially Infantry) require competence in multiple fitness domains, being able to undertake both aerobic and anaerobic activities over short-, mid- and long-distances often carrying heavy rucksacks (20-100 lbs). Long distances may include patrolling (from 5 to 50 km) carrying equipment and then being involved in a fire-fight moving from cover to cover over short distances (1-400 m), whereas mid-distances (400 to 5000 m) may involve a unit moving across town to reinforce another unit in a fire-fight with superior opponents.