There is little doubt that ability to minimise acid accumulation in muscle and blood while running at race pace is a major determinant of performance at distances from 5K to marathon. However the question of how best to train to achieve this ability is less clear.
This ability depends on several different physiological capacities. On the one hand, there are capacities such as cardiac stroke volume, capillary supply to muscles, and aerobic enzymes in the mitochondria that contribute to the overall capacity to generate energy aerobically, and thereby minimise production of lactic acid. On the other hand are the physiological capacities that determine the ability to transport and utilise lactic acid. These include the transport molecules located in cellular membranes that transport lactic acid out of the fibres, especially type 2 fibres, where it is generated. After transport out of type 2 fibres it can be taken up into type 1 fibres with the same muscle where it can be used as fuel, or carried via the blood to other organs such as the heart where it can be also used as fuel, or to the liver, where it can be converted by the process of gluconeogenesis into glucose and thence stored as glycogen. All of these physiological capacities contribute to the ability to minimise lactic acid accumulation at race pace and all can be trained, to at least some extent, by sustained running at threshold pace.
Specificity v Variety
Many coaches and athletes, including renowned coach Jack Daniels, have argued that the optimum form of training to minimise lactic acid accumulation at race pace is threshold training (i.e. sustained running at a pace in the vicinity of the threshold at which lactic acid begins to accumulate rapidly) or cruise interval sessions, in which epochs of moderate duration at a pace a little above lactate threshold alternate with recovery epochs at a lower pace to allow some dissipation of the acidity. Threshold training is consistent with the principle of specificity: namely that the most efficient way to enhance the ability to sustain race pace is to train at a pace near to race pace.
However, there are several reasons to question the principle of specificity Perhaps most important is the likelihood that if you rely on running near threshold pace as the main way to enhance this ability, your body will make use the physiological capacities that are already well developed to achieve the target pace during training sessions. If some of the required physiological capacities are less well developed, it might be more efficient to spend time training is a manner that challenges those less developed physiological capacities. For example, if ability to transport and utilize lactic acid is relatively weak, high intensity intervals will generate large surges of lactic acid and will challenge the mechanism for transporting and utilizing lactic acid.
As discussed in a recent post, many different types of training session, ranging from long runs at a moderate aerobic pace; threshold runs; to high intensity intervals can help develop the various physiological capacities required to minimise acid accumulation while running at race pace. In general, it is likely to be best to employ a varied training program that utilises all of these types of training to promote that all of the required physiological capacities. The proportion of the different types of training should be adjusted according to the athlete’s specific needs and also to the goals of the phase of training. During base building, when a substantial volume of training is required to build overall resilience while also building a large aerobic capacity, it is best to place the focus on lower intensity running to avoid accumulation of excessive stress. Nonetheless, some more intense training should be included in the phase, in part because it is an efficient way to develop aerobic capacity (as demonstrated by the many studies of high intensity interval training) and also because a judicious build-up of intensity develops the resilience of tissues to cope with high intensity in the pre-competition and competitive seasons.
To minimise risk of injury, there should be a gradual build of the intensity of the sessions training during base-building; intense training should generally be avoided when tired; and within any intense session, thorough warm up is crucial. As discussed in my recent blog post, there are some grounds for proposing that risk of injury might actually be higher during sustained running at threshold pace than during more intense interval sessions provided you take adequate precautions to minimise risk of injury. Nonetheless, there is little doubt that threshold sessions have an important part to play in the training of a distance runner. But rather than regarding such sessions as the universal answer to the question of what session to do to enhance the ability to sustain race pace, it is more sensible to utilise these sessions to achieve more specific goals.
One of the truly specific roles of the threshold session is training the body to integrate all of the physiological capacities required for distance racing. The human body is a multi-organ system in which each individual organ, especially heart, lungs, muscles and brain, but also other organs such as liver and adrenal glands, plays a specific role in distance running performance. Threshold training promotes the required integration of this diverse orchestra of organs. For the most part, this integration occurs unconsciously. We do not need to think about it. This truly amazing integration of different physiological processes occurring in different organs is achieved by an intricate network of nerves, hormones and other signalling molecules, without the need for conscious intervention. Indeed attempts to intervene consciously often led to less efficient integration, as is indicated by the finding that in some instances, runner who focus on internal processes such as breathing run less efficiently than runners who focus on things in the external world.
Brain and mind
The brain via its role as the central processing unit of the nervous system and also as a high level regulator of the endocrine system, plays a cardinal role in this integration. For the most part, the brain carries out its integrating role non-consciously, but we would be missing out on two of the very valuable features of threshold training if we ignored its value in training conscious brain processes.
The first of these is the development of the confidence that butresses the self-talk that is sometimes necessary to overcome a self–defeating internal dialogue during a hard race. In general I try to avoid doing demanding threshold sessions when I am tired or stressed because of the risk of injury at such times, but sometimes a scheduled hard session cannot reasonably be deferred. This is the time to make a virtue of necessity and use the session as an opportunity to prove to your doubting mind that you really are capable of pushing through pain. In fact quite often it is helpful to reframe the word ‘pain’ in such circumstance, because what our mind might tend to interpret as pain during a threshold session on a stressful day should more accurately be described as a level of effort that we are not confident that we can sustain for more than another few minutes. Almost invariably we can sustain this level of effort for longer. Demonstrating this provides evidence to buttress the self-talk we might require in a subsequent occasion in a hard race.
In my view, even more important than the development of mental strength to deal with hard races is the opportunity that threshold training offers to facilitate the ability to get into that almost magical state known as the zone. When we are in the zone running seems almost effortless. We feel exhilarated, in control, and above all, confident. The zone is a state of consciousness, but it is not a state that we can easily adopt consciously. When it occurs it can feel like a state of grace endowed upon us by something outside of ourselves. Nonetheless we can facilitate it. Threshold running can provide great opportunities for developing the ability to facilitate it.
In my younger days, for several years I lived in a house facing the beach in Brighton, a sea-side suburb of my home town, Adelaide. My favourite Sunday morning run took me from sea level to the summit of Mount Lofty, the highest point in the Adelaide Hills. I ran up the gorge of Sturt Creek and through Belair National Part to the summit. My return journey started with a steep descent of Waterfall Gully, followed by an almost level run on pavement via the eastern and southern suburbs of the city, back to my sea-side home. The total journey was around 25 miles. It was my version of the run that Lydiard’s athletes did regularly on Sunday morning in the Waitakere Hills above Auckland, though perhaps a little more demanding in both terrain and distance. My ascent of more than 2000 feet was often quite a slog, but the descent though Waterfall Gully was exciting.
Nowadays there is a well-made walking path from the lowest waterfall to the summit, but in those days, almost fifty years ago, the gully was wild. In many places the most feasible route involved hopping from rock to rock in the bed of the stream itself. On a good day, when my legs felt strong and sure as I leapt nimbly from rock to rock, I emerged onto the road below the lowest waterfall thoroughly exhilarated. On such days, I ran a large portion of the remaining distance at a fast tempo, around 10K race pace, aided by the slight descent with average slope of about 1% to sea level. Even now, decades later, I have a clear memory of the sense of power and confidence as I ran. Around that time I was able to recreate the same sensation of power and confidence during several races. Those races are among the most cherished memories of my running career.
Even in a polarised training program that places the main emphasis on a high volume of relatively low intensity training with a small amount of high intensity training, there is a place for threshold training, perhaps around 10% of total training. Those sessions have a crucial role to play in training the body to integrate the diverse physiological capacities required for distance running, and in particular, provide a valuable opportunity for training the brain to achieve integration of mind and body.