Generally runners accepts that in order to build sustainable fitness a prolonged period of very low intensity running must be completed first so we build large reserves of low-stress endurance and prepare the body for the rigours involved in faster running.

This approach likely began with Arthur Newton from the 1920ies onwards epitomised in his ‘Newtonian Law’ to ‘start gently and progress gradually’. Scientific rationales for the approach folllowed in the 194oies when German physician Ernst Van Aaken created a system now largely forgotten in the English speaking world. Van Aaken trained Harold Norpoth – the 5000m silver medallist at the 1964 Tokyo Olympics and three time medal winner in the European Championship. He eventually set a 2000m world record of 4:57 in 1966. Van Aaken’s approach consisted of very low intensity build-ups for the vast majority of training including a trademark session of 400 m running and 100 m walking for distances up to 10 miles and more. Van Aaken was ahead of his time in his understanding of how lower intensity exercise nourished every cell in the body creating a healthy environment whereas higher intensity created a toxic environment which – if overdone – lead to long-term health damage.

At the same time Arthur Lydiard and Percy Cerutty through the enormous success of their prodigies made endurance-based training methods the foundation for most athletics training schedules although both were exponents of slightly higher level stamina efforts once an athlete had gotten past the initial phase of ‘simply learning how to run’.

In recent times the Maffetone Method has soared back to popularity. Dr Phil Maffetone – who coached Ironman legend Mark Allen among many others – had worked out a heart rate formula expressed as the point where the long-term ‘clean’ aerobic energy system provides almost all of the energy for the activity. In this state the ‘rest and digest’ parasympathetic nervous system is more dominant than at higher intensities and the stress load on the body lower – reducing the risk of over-training. The Maffetone method uses heart rate – which is a symptom of the amount of stress the body is experiencing – in terms of energy demands and otherwise to ensure athlete’s did not push themselves too far because they had lost touch with the true sensation of ‘easy’. It is common for athletes to feel more comfortable at ‘steady’ once this has become the default while actually loading more stress on the body than they can potentially handle day after day.

Many modern brands such as Mark Sisson’s Primal Fitness and Lee Saxby’s ‘Born to Run’ and others have developed similar recommendations but this tradition runs back to the very roots of athletics history and has never been forgotten by running or athletics coaches – but was replaced by sexier ‘HIT training’ by fitness trainers and personal coaches who did not grow up steeped in athletics and running lore and who had not heard of Lydiard’s ‘tireless state’ when you can just ‘run and run and never get tired’.

In 2012, I saw the power of this system myself as my ‘MAF pace’ (my pace at a heart rate of 143 as it was then) was 4:40 and the vast majority of my build-up to a series of 8 personal bests from 5000m to the marathon was run at 4:40 to 4:50 min/km pace (at MAF or below). Yet there are times when this low intensity approach does not work. MAF coaches will teach you to first try to reduce the heart rate further as the non-improvement may be a sign you have an underlying condition or are hyper-stressed and need to further lower you training load to receive adaptations. But I have seen exceptions to this rule too where despite continuous super-low running there is no improvement and instead the runner get’s indefinitely stuck in ‘the plodding state’.

Sometimes this is because of a chronic injury – in such cases the brain shuts off our potential to run at full speeds to avoid you damaging the body irreversibly. Stubborn runners will sometimes fail to notice this as the true root cause of their inability to run at any heart rate at the paces they used to. Their conscious minds are happy to push through the pain while their subconscious puts on the brakes. But there is another scenario: we make a common mistake today in the athletics and running coaching community too focus too much on energy system development. We see a necessity to persist with low intensity running in order to continue to stimulate the aerobic systems adaptations. Yet this system – while highly scaleable – has limits and cannot be viewed in isolation. The aerobic energy system dominates when the demand on the body is relatively low so it is more of an effect of the demand than an outcome goal in itself. Moreover, training ‘energy systems’ is reductionist and the science on what adaptations are triggered by what training is still incomplete and evolving.

When I have seen athlete’s incapable of improving their pace at lower intensities I therefore do not always conclude an underlying condition or injury – sometimes they are ‘stuck’ in the ‘plodding state’. There is a constraint somewhere which results in the pace of runs not going up even when the aerobic system is probably healthy and responding. I prefer to simply experiment in these cases: using higher pace runs, using fast strides or using explosive work with a known transfer to running, in order to ‘blow through the plateau’. The barriers could also very well be simply mental – a brain with no real experience in faster running and thus it never elects the possibility until it is pushed to do so.

In Arthur Lydiard and Percy Cerutty’s day this issue did not generally arise for two reasons:

• Runners generally began the long endurance build-ups AFTER a season of learning to race or simply racing in cross-country and roads. This ‘jolted’ the body’s out of what Lydiard termed ‘the plodding state’ meaning runners ‘had a bit of pace in the legs’ by the time they began to do the ‘slower miles’
• Runners in those  times had greater muscular strength on average and thus were less likely to have a constraint in that area to limit pace

Modern runners who could have come from an entirely sedentary background could face the problem that their physical strength is so low that the body is unable to tolerate faster running even after prolonged period of slow running. In such a case the bottle-neck shifts from the expected place – the aerobic energy supply – to another place – the ability of the body to cope with the forces involved in faster running. Unable to safely cope with greater forces, the brain will not allow it. In this case the trick is to find out the best way to increase the athletes tolerance which generally is a combination of strength and coordination work.

As a final note – some runners become psychologically stuck in the ‘plodding state’ – unable to shake themselves into a zone of slightly less comfort and in such cases you need to look at workouts that challenge that comfort zone. Running at 10 minute/mile and 6 min/mile is not the same even if you could learn to do it at the same energy demand – there are other differences between running at the two speeds both in terms of how the movement manifest and the level of forces to be absorbed – and this is where an approach that solely practices low speed ‘mono-pace’ runs into limitations. We may not get the adaptations we need to move on in all of the areas within our body that need them.