The debate between high intensity and high volume training has been a perennial topic since the early days of scientifically-grounded training. Interval training was developed in the 1930’s by the German coach and academic, Woldemar Gerschler. He based his recommendations on the theory that the heart muscle would be strengthened by the increase in cardiac stroke volume that occurs as heart rate drops immediately following an intense effort. A decade later, Gerschler’s compatriot, sports physician Ernst van Aaken proposed that the crucial requirement was delivering copious amounts of oxygen to the heart, and this could best be achieved by running long distances at relatively slow paces. It is noteworthy that a large volume of slow running also increases delivery of oxygen to the leg muscles. Van Aaken’s approach was later developed by New Zealander, Arthur Lydiard, based largely on trial-and-error adjustments of his own training. Lydiard’s method led to medals for his athletes, Peter Snell, Murray Halberg and Barry Magee in distances from 800m to the marathon at the Rome Olympics in 1960. While Lydiard promoted a high volume approach to building basic aerobic fitness, his program also included periodization – a progression from base building to a period of race specific training and final sharpening immediately prior to competition.
Meanwhile, interval training retained its devotees and underpinned the golden age of British middle distance running that reached its pinnacle with Seb Coe’s Olympic gold medals in the 1500m in 1980 and 1984. By the end of the century, Japanese academic, Izumi Tabata had demonstrated that repeated very intense brief maximal efforts lasting only 20 seconds separated by even briefer recovery periods, produced impressive increases in aerobic capacity (reflected in increases in VO2max) while also enhancing anaerobic capability.
Meanwhile, devotees of high volume, less intense training, led by charismatic individuals such as John Hadd and Phil Maffetone, emphasized the risk that focussing on high intensity training might undermine sound long term development. So what has the past decade contributed to this long-standing debate?
I think that three main strands of evidence have advanced the debate. These strands are: evidence from physiological investigations; the training of African distance runners; and evidence from a small number of fairly well conducted controlled comparisons of different training protocols
The fundamental principle of training is that training produces stress on the various physiological systems within the body, such as the cardiovascular system, skeletal muscles and the nervous system, and subsequent adaptive change as the body responds to that stress leads to increased fitness. The past decade has seen an explosion of knowledge about the multitude of biochemical signalling processes that trigger these adaptive changes. In addition to the hormones produced by the major endocrine glands, there are a vast number of other relevant signalling molecules, including the numerous cytokines that regulate inflammation (the cardinal process that mobilises repair in tissues throughout the body) and growth factors that promote changes in many tissues. In particular, growth factors and hormones promote the activation of satellite cells in muscle. These satellite cells are a type of stem cell that fuse with muscle cells to repair and strengthen them.
While this explosion of knowledge does provide useful clues regarding the way the body might react to various forms of training, at present the complexity of the information precludes any simple answer to the high volume v high intensity debate. It does however provide support to both sides, indicating that the best answer will prove to be a combination of the two.
In light of concerns that high intensity training might destroy the aerobic enzymes that catalyse the chemical transformations involved in aerobic metabolism in the mitochondria of muscle cells, it is of particular relevant to note that a series of studies, Gibala and colleagues at McMaster University in Canada have demonstrated that high intensity interval training is as effective as high volume training for developing these aerobic enzymes. Furthermore, Bangsbo and colleagues in Copenhagen reported that speed endurance training consisting of six to twelve 30 second sprints 3-4 times/week for 6 – 9 weeks improved ability to pump the potassium ions back into muscle cells. Potassium ions are expelled from muscle during exercise. The depletion of potassium within the muscle probably plays an important role in fatigue. Bangsbo demonstrated that the improved ability to pump potassium back into muscle cells was accompanied by an average improvement of 18 seconds in 3 Km race time, and an average improvement of 60 seconds in 10 Km time, in a group of 17 moderately trained male endurance runners
The most striking feature of elite distance running in the past decade has been the dominance of African runners, mainly from the highlands of Kenya and Ethiopia. There have been many anecdotal accounts that make it clear that high volume training, with several training sessions per day, is an important aspect of the training program of virtually all elite Africans. Usually the day’s program includes one session of quite low intensity running, but many accounts also describe other sessions of quite intense running – especially sustained tempo efforts. I will not attempt to review all this information here, in part because of its diversity but even more importantly, it remains unclear just how much cultural factors (such as running to school in childhood); multiple genetic factors; and up-bringing at high altitude have contributed to the African dominance. It remains to be demonstrated convincingly that the training methods employed in Africa can adapted to produce similarly impressive performances by non-Africans.
I will nonetheless draw attention specifically to the training methods adopted by Renato Canova, coach to many of the leading African half-marathoners and marathoners. I have described Canova’s training previously. In his lectures and writing, Canova places little emphasis on low intensity running, perhaps because the athletes he trains have already achieved extensive development of capillaries and other aspects of type 1 fibre development. Nonetheless, the training dairies of the athletes he coaches reveal that in addition to the relatively intense sessions there is a large amount of low intensity running. For example about 80% of the training of Moses Mosop is at an easy pace, with occasional sessions as slow as 5 min/Km (which should be compared with his marathon pace of around 3 min/Km). Canova advocates a periodized approach. The crucial feature of the race specific phase is long runs at near race pace.
Controlled comparisons of training programs
As mentioned above, some of the studies comparing high intensity interval training with standard endurance training, such as the study by Bangsbo and colleagues, demonstrate greater improvement in performances over distances from 3Km to 10Km with the high intensity training, while others, such as those by Gibala and colleagues report similar gains in performance with high intensity training and conventional endurance training, although the high intensity programs achieved similar benefit from a much smaller volume of training. However, those studies were performed over a time scale of approximately 8 weeks. This is scarcely long enough to exclude the possibility that high intensity training might result in a harmful accumulation of stress.
The question of longer term effects was tested in a study by Esteve-Laneo and colleagues from Spain. They randomly allocated 12 sub-elite distance runners to one of two training programs: a polarised program involving a large amount of low intensity training and small volume of moderate and high intensity training; and a threshold program involving a predominance of training near lactate threshold and a small amount of higher intensity training, for a period of five months. Training was classified in three zones: low intensity below the first ventilatory threshold (VT1) corresponding to the point where lactate rises to around 2 mM/litre; moderate intensity between VT1 and the second ventilatory threshold (VT2) corresponding to the point where lactate exceeds 4 mM/litre; and high intensity, above VT2 during which lactate accumulates rapidly. In the polarised program the proportions of low-, moderate- and high-intensity training were 82%, 10% and 8% while the proportions in the threshold program were 67%, 25% and 8%. At the end of the program, the group allocated to polarised training achieved significantly better performances in a 10.4Km cross country race.
More recently, Stoggl and Sterlich from Austria performed a study comparing a 9 week polarised training program with three other programs: high intensity; high volume (low intensity) and predominantly tempo training, in a sample of national class endurance runners, triathletes, cyclists, and nordic skiiers. The polarized training group exhibited the greatest improvement in VO2 max (+ 11.7%) and time to exhaustion (+17.4%). The high intensity group achieved a 4.8% increase in VO2 max and an 8.8% time to exhaustion 8.8 percent. The high intensity group lost 3.8% of body weight, which Stoggl and Sterlich attributed to a harmful catabolic state. Improvements were small and insignificant for the other two training programs. It should be noted that these athletes were a national standard and had probably achieved the improvement that might be expected from either a high volume of low intensity training or from a predominance of tempo training.
Neal and colleagues used a cross-over study design in which a group of well-trained cyclists underwent polarised training and threshold training, each for 6 weeks in randomised order. Similar baseline fitness was established by a 4 week de-training period before each training period. The proportion of training time in low-, moderate and high intensity zones was 80%, 0%, 20% in the polarised program, and 57%, 43% and 0% in the threshold program.The polarised training produced greater increases in peak power output, lactate threshold and high-intensity exercise capacity (time to exhaustion at 95% maximum work rate).
Summary and Conclusions
Stephen Seiler, a Texan sports scientist based in Norway for the past decade, presented a summary of the evidence from the controlled comparisons of different training programs and also from studies that have examined the proportions of training time that elite athletes spend in different intensity zones, at a lecture delivered in Paris in October 2013. He provided a compelling argument for polarised training. However, despite the evidence that many elites follow a polarised program, the role of key sessions at a pace near to race pace in the training recommended by Renato Canova indicates that at least a modest proportion of threshold training is beneficial for marathoners. Furthermore, Canova recommends a moderate degree of periodization with a clearly defined period of specific preparation for key races.
Overall, it is likely that any sensible training program will produce benefit for an unfit athlete provided it is consistent. However for an athlete who has achieved a plateau of fitness, it is probable that a polarised program with proportions of low-, moderate- and high-intensity of approximately 80%, 10%, 10% is most effective. Nonetheless, during a period of preparation for a specific race the key sessions should incorporate running at a pace near to race pace.