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 ONE: BACKGROUND
“Interval training – Repeated, brief, fast-paced exercise bouts with short rest intervals between bouts.” (Kenney, Wilmore & Costill, 2012, p.581).
This article provides an overview of interval training from the perspective of exercise and fitness. Interval training, a derivative of intermittent training, is a ‘fitness craze’ that has been ongoing for a number of decades, although intermittent training (in some form) can be traced back to at least the 1500s (Mendez, 1960).
Although many may recognise the term high-intensity interval training (aka HIIT), which was popularised in the 1990s, professional athletes have been using some form of interval training since the 1950s. Some sports personalities were utilising a rudimentary form of interval training, from the 1920s, before the term was coined.
Regardless of its origins, interval training has subsequently grown into a huge business and, according to IT Brief, Linkedin (a business networking site) had 450 million members worldwide in 2016 (Barker, 2016), of which 37,185 of these members stated they had interval training as a skill (Linkedin, 2017).
Defining interval training precisely can be somewhat problematic as it means slightly different things to different people. However, most commentators agree that it is higher-intensity bouts of exercise followed by lower-intensity bouts of passive or active recovery which is repeated a number of times.
Interval training can be applied to a variety of sports and exercises, for example running, swimming and press-ups – limitations are generally the imagination of the individual/coach.
As the reader will (hopefully) come to realise from reading this article, the underlying purpose of interval training, and its permutations, is sound. However, for many, the meaning of interval training has been distorted/confused through the plethora of definitions, hybridisation and accretion of its original purpose.
This article will provide the reader with an outline of interval training within the context of the exercise and fitness industry. Section One provides a background to the topic which looks to define some of the terms used, highlight the myriad of definitions in use and offer a brief history. Section Two explains what interval training is, outlines the plethora of substitute terms and the purpose of it. Section Two continues with the training variables to consider and the role of the recovery period, an important variable in interval training. It will discuss some rules for effective training, as well as the ventilator threshold and frequency of training. Section Three outlines some of the types and variations of interval training. Section Four highlights outlines some of the advantages and disadvantages of interval training, as well as points to consider before, during and after a training session. Finally, Section Five provides a summary of the article before providing the reader with some useful publications, links and references.
The aim of this article is to provide a broad overview of interval training, and its permutations. It is not intended to be a comprehensive, all-encompassing article, but will provide the reader with a fundamental understanding of what interval training is about.
1.2 History of Interval Training
This section of the article provides a select, but broad outline of the, history of interval training. For a fuller historical outline on the subject of exercise physiology read the excellent book ‘History of Exercise Physiology’ edited by Charles Tipton, and published in 2014, and for an excellent outline of training theory read Bourne’s 2008 doctoral dissertation (see Part Five).
One of the earliest references to intermittent training is by a Spanish physician, Cristobal Mendez (1500-1561), who published in 1553, in Latin, the ‘Book of Bodily Exercise’ (Mendez, 1960). View Section 1.3 for an outline of alternative names for interval training.
Tipton (2014, p.11) tells us that Mendez suggested that:
“To be beneficial, exercise must be moderate, performed frequently, enjoyable, and continuous (intermittent exercise failed to consume and dissipate humors, causing them to leave by pores opened by the heat of movement), and be associated with a shortness of breath (caused by the increased heat in the heart and the need for more air via increased ventilation).”
During the 1600s, “few physicians advocated strenuous or violent exercise [aka maximal intensity] because they felt, as did Hippocrates and Galen, that it was unhealthy.” (Tipton, 2014, p.11).
From the earliest advocates of exercise, such as Hippocrates and Galen, to the 1600s there was a school of thought that strenuous or violent exercise was unhealthy due in part to the heat produced.
Santorio Santorio (1561-1636), a student of Galileo Galilei, stated that to maintain a ‘youthful face’ individuals should avoid excessive sweating in the heat. He also believed that violent exercise would reduce body weight, advance the aging process, and promote an early death (Santorio, 1676, aphorism 19).
From an anatomy and physiology perspective, the 1600s and 1700s were a major period of scientific discovery and advancement of exercise and fitness knowledge.
In his book, published in 1707, John Foyer (1649-1734, a physician) considered a normal pulse rate to be between 70 and 75 beats per minute (bpm) with, interestingly, a pulse of 140 bpm the highest recorded value. Foyer suggested that if bpm became higher, then death could occur (Foyer, 1707). In 1734, Bryan Robinson (1680-1746), an Irish Physician, noted a bpm of 140 and 150 when individuals ran as hard as possible (Robinson, 1734).
In 1894, the maximum heart rate (MHR) during exercise was identified as being between 160 and 170 bpm (Christ, 1894); in 1913, it was 180 bpm (Cook & Pembrey, 1913); and another decade before 200 bpm was recorded (Tipton, 2014) – Although George Kolb noted heart rates in excess of 230 bpm in rowers in his 1893 book ‘Physiology of Sport’ (Kolb, 1893).
In 1835, Robley Dunglison (1798-1869) was opposed to violent exercise because it caused less oxygen to be inspired and more carbon dioxide to be produced, resulting in suffocation, because it caused aneurysms, haemorrhaging, hernias, and dislocations and sprains. Consequently he favoured moderate-intensity exercise because it promoted blood flow, enhanced the actions of the heart, increased muscle firmness and bulk, and reduced fat around the muscles (Tipton, 2014).
In 1871, Austin Flint Jr. (1836-1915) concluded that violent exercise caused muscle breakdown and resulted in an increased loss of proteins (Flint, 1871).
R. Tait KcKinzie suggested that (McKinzie, 1909):
- Active exercise (aka high-intensity) was an effort that could be violent in nature, involved extensive muscle groups, associated with hypertrophy and muscle damage, and would lead to fatigue (the inability to sustain a given power output).
- Endurance exercise was associated with less effort (reduced intensity), longer durations (>1 hour), and elimination of poisonous waste matter before fatigue occurred. Endurance exercises were advocated because they powerfully affected the heart, lungs, and muscular and nervous systems.
- Passive exercise, which essentially was massage and manipulation, was advocated for conditions of fatigue because it had a beneficial effect on muscles, ligaments, and the circulatory, respiratory, and nervous systems.
In 1910, the association between muscular performance and lactic acid concentration begins when Ryffel mentions that running 12 laps in 2 minutes 45 seconds causes blood lactic acid levels to increase from 12.5 mg/100 ml of blood to 71 mg/100 ml of blood, and that urine values are elevated from 4 mg/h to 362 mg/h after 17 minutes of recovery (Ryffel, 1910a; 1910b).
Billat (2001a, p.14) informs us that “in 1912, the 10,000m Olympic championship runner, Hannes Kolehmainen (Finland), had already used interval training at the specific 10km pace. He had trained using 5 to 10 repetitions of 3 minutes 5 seconds every 1000m (19 km/h). 80 years later the 10km specific interval training is run at 22.7 km/h.”
“LSD training became extremely popular in the 1960s. [and was] introduced in the 1920s by Dr. Ernst Van Auken, a German physician and coach…” (Kenney, Wilmore & Costill, 2012, p.222).
Bourne, writing a doctoral dissertation on the history of training theory, suggests training loads can be divided into one of three periods (Bourne, 2008, p.viii):
- Light Training Load: Leading up to World War I, “where athletes stayed competitive with very little training”;
- Moderate Training Load: Between World War I and II, with “the introduction of innovative training methods – fartlek and interval training.”; and
- Heavy Training Loads: “that occurred between 1945 and 1975”.
Although the 1800s witnessed huge advances in the knowledge and understanding of exercise physiology, Carter (2011, p.67) suggests there was a time lag in regards to training paradigms:
“Beamish and Ritchie have argued that during the inter-war years a ‘paradigm shift’ took place in the understanding of the training of athletes, when a scientific body of knowledge was built concerning human physiology through recorded observations related to exercise, human anatomy and physiology.”
In the 1920 Olympics, Paavo Nurmi (1897-1973), a well-respected Finnish runner and known as the ‘Flying Finn’ or ‘The King of Runners’, won his first Olympic medals: gold in the 10,000, cross-country and team competition events; and a silver in the 5,000 metre event. In the 1924 Olympics Nurmi won the 1,500 metre, 5,000 metre and cross-country events using a rudimentary concept that came to be known as interval training (Racing Past, 2016). He is the only person to complete this treble, and he also set a number of world records during 1924 (1,500, mile, 2,000, 3,000, 5,000 and 10,000 metres). Walking, running and calisthenics were the main elements of Nurmi’s harsh training regimen, as well as interval training (Billat, 2001a). He learned to measure his pace and its effects with a stop watch, and generally never raced without one in his hand. Finnish runners, using Nurmi’s training techniques, went on to dominate distance running until World War II (Racing Past, 2016).
“Analysis of Nurmi’s training program reveals the structured manipulation of running different distances (or intervals) including repeated sprints. The pioneer in this area of training was the Finnish coach, Lauri Pikhala, who in 1920 stressed the balance between work and rest in a method he called “Terrace Training,” with each layer built on the previous [Smit, 1959]. The basic principle of alternating work with recovery periods was further developed (as we shall see later in this chapter) in the late 1930s in the form of interval training.” (Bourne, 2008, p.158).
Mihaly Igloi, a Hungarian coach, was a pole-vaulter prior to becoming a 1,500 metre sprinter (Racing Past, 2015a). Igloi’s motivation for becoming a sprinter was “from watching Polish 10,000 OG [Olympic Gold] champion [Janusz] Kusociński, who according to Frank Litsky would run 200 repetitions in training.” (Racing Past, 2015a). Janusz Tadeusz Kusociński, a Polish athlete, won Gold at the 1932 Olympics, setting a new world record. Athletes coached and trained by Igloi achieved 49 world records and 35 European records. Igloi also broke down runs into sets (e.g. 3x20x200) and utilised pace variety (using the terms easy, fresh, good and hard) (Racing Past, 2015a). Like Woldemar Gerschler, Igloi concluded that interval training was better than LSD training – preferring intense work periods with short rests, in part due to the build-up of lactate (Racing Past, 2015a). Although, unlike Gerschler, Igloi was very secretive about his training methods. However, we know he “had his runners do intervals not once, but twice a day.” (Moore, 2006, p.89-90).
Gerschler develops his interval training method in 1932 (Colwin, 2002) using trial and error (Gerschler, Roskamm & Reindell, 1964). “Between 1935 and 1940 Gerschler and Dr. Herbert Reindell, a celebrated German cardiologist, worked in tandem to provide scientific validation to this method of training.” (Bourne, 2008, p.175). Gerschler and Reindell studied the cardiovascular (CV) effects of interval training, proving that the stimulus for CV improvement occurs during the recovery intervals between runs, when the heart rate decreases from an elevated value. Thus, the emphasis of the workout was placed on the recovery interval, prompting Gerschler and Reindell to call it an ‘interval workout’ or ‘interval training’.
In 1935-36, Rudolf Harbig (1913-1944), a German middle distance runner, started training under Gerschler (Thompson, 2010; Racing Past 2015b), essentially serving as his “guinea pig” (Bourne, 2008, p.176). Under Gerschler’s coaching, Harbig went on to set a number of world records at the 400, 800 and 1,000 metre events (Racing Past, 2015b).
“Fartlek training, developed in 1937 by Gösta Holmér (1891–1983), means ‘speed play.’” (Katch, McArdle & Katch, 2011, p.436). Holmér was a Swedish coach who developed this method of training to counteract the dominance of the Finnish athletes. Thompson (2010) informs us that Holmér developed the fartlek method of training “about the same time that Gerschler and Reindell were experimenting with the original Interval Training.” (Thompson, 2010). Fartlek did not require a track like other forms of training.
Edgar Atzler (1887-1937) and Otto Graf (1894-1965) coined the phrase lohnende Pausen (or worthwhile breaks) to describe the recovery phrases during work intervals (Atzler, 1938; Graf, 1943).
“After the second world war, interval training became a widespread training method used by European runners.” (Billat, 2001a, p.14).
In 1947, Ernst van Aaken (1910-1984), a general practitioner in the small town of Waldneil, formally published his Speed through Endurance Method in Sport und Gymnastik (reprinted in English in van Aaken and Berben in 1971). His method was also known as the van Aaken Method and the Waldneil Endurance Run (in German Waldnieler Dauerlauf). Van Aaken’s method relied on long, ‘slow’ runs with a heart rate of 120-130 bpm, initially with short breaks, after the principle of interval training (Colwin, 2002; The Science of Running, 2016). Van Aaken is reported to have first developed his method after watching Paavo Nurmi break the world record in 1928 for the one hour run (Colwin, 2002). A number of successful athletes used van Aaken’s method of training, including Harold Norpoth (a German runner). The interval principle in endurance training is used only to enable the athlete to cover more distance without fatigue (Colwin, 2002).
Emil Zátopek (1922-2000), a Czechoslovakian long-distance runner and nicknamed the ‘Czech Locomotive’ “adopted the interval training system pioneered by Nurmi” (Racing Past, 2014). Zátopek is best known for winning three gold medals (5,000, 10,000 and marathon events) at the 1952 Summer Olympics in Helsinki (the only person to complete this treble, and it was his first marathon!). In 1951, he broke the hour for running 20 km and, in 1954, broke the 29 minute barrier for the 10,000 metres. He also had considerable success in the late 1940s, breaking a number of records in the 1940s and 1950s. Runner’s World tells us that “Emil Zátopek was inventing interval training, a methodology that would become standard for athletes across almost all disciplines.” (Collins, 2012).
“He [Zátopek] ran in his army boots to save money, claiming they also protected his ankles and developed leg strength. One legend has it that to maximize his training load, he would run on the spot in his boots while on guard duty.” (Racing Past, 2014).
In the 1950s, Woldemar Gerschler (1904-1982) established himself as one of the world’s leading running coaches, developing “…a very specific training regime that became known as interval training.” (Racing Past, 2015b). Gerschler worked at the Institute of Physical Education at the University of Freiburg from 1950 to 1971. As a coach, Gerschler trained a number of successful athletes including Rudolf Harbig, Joseph Barthel, Gordon Pirie and Tomás Barris. Gerschler claimed that his version of interval training produced greater endurance than running long unbroken distances, and in a shorter time period.
Working with Reindell, Gerschler’s training regime emphasised “that it is not necessarily the speed of running repetitions that can provide the primary training effect. In ‘Interval Training’ this primary training effect clearly takes place during the ‘recovery’ intervals between the faster repetition runs or efforts.” (Thompson, 2010). Gerschler and Reindell “claimed that the maximal expansion stimulus on the left ventricle occurred during the immediate postexercise recovery phase. Stroke volume of the heart is larger in the best-trained subjects (17 [Bevegard, Holmgren & Jonsson, 1963], 190 [Wang et al., 1961]).” (Tipton, 2014, p.256).
Gordon Pirie (1931-1991, a British runner) was inspired by Emil Zátopek after witnessing his performances in the 1948 Olympics. As a 21 year old, Pirie raced against Zátopek in the 1952 Olympics, finishing fourth in the 10,000 metre event. “Immediately after the Games Pirie met the German coach Woldemar Gerschler.” (Racing Past, 2011). In 1953, Pirie, under Gerschler’s coaching, achieved two world records and ten British records (Racing Past, 2011). From 1953 to 1961, Pirie had a range of successes mixed with a number of injuries. Pirie also won national titles in orienteering in 1967 and 1968 (Racing Past, 2011).
In 1953, Roger Bannister, a British runner, under the guidance of Franz Stampfl, an Austrian coach, commenced an intensive training programme in which he ran a series of 10 consecutive quarter miles, each in 66 seconds, with two minute rest intervals between them. Gradually, through January and February 1954, he stepped up the pace until by April he could manage the series in an average time of 60 seconds while keeping to the two minute rest intervals. Consequently, Roger Bannister ran the first sub four minute mile. Stampfl advocated a combination of fartlek, interval and repetition training. Bannister’s feat captured the imagination of followers of many sports, consequently creating interest in Stampfl’s training methods. Further, Stampfl’s book Franz Stampfl on Running and Bannister’s First Four Minutes, both published in 1955, were instant bestsellers.
In 1955, three athletes trained by Mihaly Igloi (Sandor Iharos, Laszlo Tabori and Istvan Rozsavolgyi) achieved nine world records (Racing Past, 2016). Unfortunately, due to the Soviet invasion of Hungary in October 1956, the Hungarians were unable to fully demonstrate their prowess at the 1956 Olympics in December.
“Interval training was first described, in [Schweiz und Sportmed] a scientific journal” (Billat, 2001a, p.13), by Reindell and Roskamm (1959) and then a book by Reindell, Roskamm and Gerschler in 1962.
Gerschler’s method of interval training evolved and was most clearly described in a 1963 Track Technique article in which Gerschler (1963) justifies interval training against LSD training, “which through Arthur Lydiard was gaining popularity through runners.” (Racing Past, 2015b). In the article, Gerschler states three reasons why he preferred interval training:
- It takes less time;
- It imposes a more powerful stimulus;
- It permits a more exact control on the intensity of the stimulus and on the duration of the effort.
In swimming in the 1960s, James Counsilman, a US swimming coach, developed a “hurt-pain-agony: scale to assist sensory perception of fatigue at different levels of work intensity, further developing a “hurt-pain-agony” chart (Counsilman, 1968, p.338). “…Counsilman was responsible for the introduction of interval training to swimming…” (Bourne, 2008, p.272).
It was not until the 1960s that famous Swedish physiologist Per-Olaf Ǻstrand (1922-2016) discovered, using a stationary bicycle in a laboratory, what many coaches and runners already knew – that by breaking up a set amount of work into smaller segments, a person can perform a greater amount of work at higher intensity (Ǻstrand et al., 1960).
Ǻstrand and colleagues concluded that heavy work (aka high-intensity) when split into short periods of work and rest (of 0.5 or 1 minute duration) was transformed to a submaximal load on circulation and respiration and was well tolerated during one hour. With longer periods (of 2 or 3 minutes duration) the work output got close to the upper limit of performance and could be fulfilled only with the utmost strain (Ǻstrand et al., 1960).
The 1920s to 1990s is generally considered the era of the ‘old’ interval methods, and from the 1990s as the era of the ‘new’ interval training methods, of which a number are outlined in Part Three.
1.3 Other Names for Interval Training
There are a variety of alternative terms for interval training, including:
- ‘Old’ Interval Training (1920s to 1990s):
- Repetition Training or Traditional Repetition Training;
- Original, Classic or Traditional Interval Training;
- The Gerschler-Reindell law;
- Freiburg Interval or Freiburg Method;
- Intermittent Training or Intermittent Method;
- Non-Exhaustive or Exhaustive Intermittent Training;
- Non-steady State Work or Workout; and
- Interval Workout.
- ‘New’ Interval Training (NIT) (1990s to Present):
- High-intensity Interval Training (HIIT), sometimes abbreviated as HIT;
- High-intensity Aerobic Interval Exercise (HIIE) or Training;
- High-intensity Interval Exercise;
- Power Interval Training (PIT) or Power Intervals (PIs);
- Sprint Interval Training (SIT) or Short Sprint Interval Training (SSIT);
- Short-term Sprint Interval;
- Short-term Intensity Training;
- High-intensity Intermittent Exercise (HIIE);
- Functional Threshold Power (FTP) Intervals;
- Lactate Dynamics Training;
- VO2max Intervals;
- Tabata Method, Tabata Protocol or Koichi Protocol;
- Steady State Intervals;
- Short Work-to-Rest Ratio Intervals; and
- HIIT Aqua, Aqua HIIT, HIIT Splash or Water-based HIIT.
For some commentators, terms such as intermittent, repetition and interval can be used interchangeably. The term interval training will be used throughout this article to avoid confusion.