Endurance Training– Anaerobic Threshold, HIIT / Strength or Maffetone?

For the previous two months I interrupted my normal program of physical training and racing to put into practice the Maffetone training principles – where both “slower and less are better” – supposedly! There were several reasons for making this choice:

The thought of another season with similar improvement limits as all the previous ones was frustrating – so it was important to risk experimentation.
The ketogenic diet I’m using is very successful – but so far training had not been altered in any way to align with this.
The combination of appropriate nutrition and exercise is fundamental to health – particularly concerning “inflammation”.
There was potentially much more to gain than to lose.
The first week – as a trial – revealed a remarkable readjustment of my resting heart rate from around 36 bpm to 56 bpm.
Despite several weaknesses and errors in Maffetone’s science it still sounds very convincing. (But so do opposing theories!)
It is highly counter-intuitive and that’s always a very good sign.
There is a seriously impressive list of elite athletes who swear by this method.
Being fed up with confusion and unstructured or vague ideas of training – and constantly dealing with the unpredictable consequences.
Curiosity.

The program was followed carefully for almost two months. Quite frankly it is extremely frustrating! Running and cycling over the same courses – never above the aerobic threshold – showed no improvement whatsoever and if anything the times became slower at the same heart rate. Eventually I decided to throw in the towel and stop. Setting out on my usual 40km bike circuit with about 1200m vertical – not having done any anaerobic activity whatsoever for two months and having witnessed an apparent deterioration of performance across the board – all expectations were rock bottom. Making up for two months of self-imposed imprisonment I just went flat out from the start, without a warm up – and really enjoyed it. It was literally letting the heart free! To my complete amazement by the end of the workout I was 3’10” ahead of my previous fastest time of the year at 1hr 37min 15 secs and wasn’t even tired. Weird, weird, weird! Perhaps Dr Maffetone is right after all. The workout starts with a big climb of 8km and there was no gain there over previous efforts – but it was over the long distance that endurance held out better and high output could still be maintained. “Surprised” – is an understatement!

Maffetone Principle

The Maffetone Formula for aerobic heart rate was ignored because it is dependent on age adjustments – and that principle is known to be incorrect. Age only affects the heart rate for sedentary people – otherwise it is fixed for adults. Instead I used a figure quite close to the (180 – Age +5) formula and derived it from observations related to nasal breathing. Basically if you are aerobic you do not breathe heavily. It might seem like a contradiction as when aerobic you use the most oxygen – but heavy breathing is really to expel CO2 which has to be eliminated during anaerobic activity to balance the lactic acid entering the bloodstream – maintaining a strict blood PH level. When nasal breathing any increased effort to breathe is very noticeable and so the feedback is clear. The pulse rate corresponding to this threshold for me is 136 bpm. Maffetone training therefore had to be from 126 to 136 – with 136 being the “aerobic maximum”. It’s important to have breathing feedback because the heart rate monitor can show anomalies or simply run out of power on occasion (laser HRMs) and the breathing might be your only clear reference. When forced to choose between a strange heart reading and breath I default to breathing feedback.

During the two months when out training everybody and their dog overtook me at one point or another. Sometimes on climbs I’d be in bottom gear and have to slow the pedalling right down to keep the heart rate low. People overtaking would have no idea what was really taking place so it became one gigantic exercise in battling against the ego. Internal dialogue would swing between embarrassment, panic and pure frustration. Even worse was when running and being overtaken by groups of girls often with big bottoms. The only thing stopping me from pulling my hair out is that I don’t really have enough now.

On the positive side, it’s quite relaxing training slowly and knowing that you will get to the end feeling un-stressed. The entire goal here is to avoid all stress – because the body can’t distinguish between emotional or physical stress and so releases hormones such as cortisol regardless. Too much of those hormones means too much inflammation and then failure to recover properly or build performance. Slow training therefore means it’s time to get through some tedious books by using either “text to speech” or audio books. This way you kill two birds with one stone. Distance shouldn’t be enough to cause tiredness either. It’s also a great time to work on form and technique, self-correcting and drilling good mechanics into the body.

All the above is fine – but when you believe that zero progress taking place – having sacrificed most of the summer and foregone the racing season – then it becomes a problem. The really hard part of Maffetone’s program is the psychology and self-restraint, while all the time feeling an undercurrent of disbelief. The program is for everyone who wants to build endurance or avoid over-training at any level of sport from beginner to elite.

Resting Heart Rate

Perhaps I wouldn’t have gone very far with all of this if it wasn’t for an astonishingly rapid readjustment of my resting heart rate when starting this program. Early in the summer my resting heart rate had dropped down to only 36 bpm but I had no idea that this could be an early sign of overtraining. Within days of switching to the Maffetone program this minimum heart rate had climbed to 56 bpm – and more or less remained there from then on. The unusually low heart rate is apparently due to the parasympathetic autonomous nervous system suppressing the adrenal hormone production and is a precursor to adrenal fatigue. This probably more than anything else convinced me to stay on track. Also, when eliminating all overtly anaerobic work it immediately eliminated issues with recurrent diarrhoea. Maffetone is also the only sports oriented doctor I’ve seen who advocates a ketogenic diet and barefoot running technique – having done so since the 1970s! Basically, his logic across the board is remarkably coherent, even though he makes clear mistakes with scientific detail.

Maffetone and HIIT contradictions

From the beginning it was obvious to me that there are many error’s with Dr Phil Maffetone’s theory. Using an age based formula for any aspect of heart rate limit determination is not much better than guesswork. His claims that the goal is “pure aerobic” activity is clearly nonsense – especially when he claims that 97% of energy can be derived from pyruvate because the pyruvate is a by-product from anaerobic muscle activity in the first place. The current HIIT (High Intensity Interval Training) craze makes exactly the opposite mistake. Dr Doug McGuff claims for example that there is no such thing as “cardio” training. He asserts that either strength or HIIT will produce tons of pyruvate (both burned aerobically immediately and converted to lactic acid for storage, transportation and later aerobic use) and that simply the process of clearing the lactic acid will give all the aerobic development required. He even states that without pyruvate from the anaerobic system that there is no aerobic activity. This is clearly incorrect because it makes the false assumption that everything follows a chain of events based on glucose metabolism and that nothing else exists. We burn fat too Dr McGuff. What’s shocking is that those two top academics in this field make such ludicrous statements – which then leave everyone utterly confused.

Basic Metabolism

The only essential macronutrients for a human being are fat and protein. We can generate all of our own glucose and that comes from aerobic metabolism of fat and protein. When exercising – even from a fasting or ketogenic state (not consuming carbohydrates and allowing a period of weeks for the body to adapt correctly) – our blood sugar levels go up, not down. While the body burns fat it produces glucose and ketones (similar molecules). The glucose then feeds the anaerobic system which then produces pyruvate which then becomes the only carbohydrate to be fed into the aerobic system. In fact the aerobic system is providing the bulk of energy as it burns fat, ketones and pyruvate – and also provides the glucose. If however glucose is eaten then it will go directly into the anaerobic system. Note: During exercise glucose is used anaerobically without an increase in insulin so it does not interfere with fat metabolism – which is why even ketogenic athletes can take glucose supplements during effort without coming out of ketosis (ketone production and burning). Extremely intense sprint energy is supplied by a separate anaerobic system using Creatine Phosphate (CP) and just below that the anaerobic system burns glucose to give out energy directly – again only for relatively brief high intensity work. Sustained work – both fast and slow requires aerobic energy. For fast aerobic work we need the pyruvate by-product from the anaerobic system not the actual energy produced from glucose. For slow aerobic work we can rely mainly on fat metabolism alone. Energy itself however comes from only one molecule – ATP – adenosine triphosphate. Those different metabolic processes are all about the rapidity and quantity of ATP being created. Different tasks require the muscles to exploit different mechanisms and so the muscles have a wide range of different types of fibres (at least seven types). It’s no accident that when going too fast we tend to produce pyruvate far faster than we can burn it. Pyruvate when not used immediately by the aerobic system is converted into lactic acid. Lactic acid can cross the blood/brain barrier and can provide fuel for the brain and it is the preferred fuel for the heart – though ketones are also preferred (28% improved heart function). Pyruvate is simply packaged up as lactic acid to allow it to be transported around the body – to the brain, heart, organs and other muscles – as aerobic fuel. Some is reconverted back into glucose. When being burned it first converts into lactate plus H+ ions, which is why the terms lactic acid and lactate are often used interchangeably. The release of H+ ions is considered by some scientists to be the reason for lactic acid tolerance having an upper limit – but even that isn’t completely certain. What is certain is that we only have about a spoonful of sugar in our entire bloodstream and it is a big mistake to rely on carbohydrates or carbohydrate loading as an endurance athlete – because feeding on those shuts down fat metabolism (and glucose production) on a long term basis.

Four paths

Anaerobic Threshold: It’s generally claimed that anaerobic threshold (AT) training gives the best results in endurance training. This is a fairly high but steady state level of 4 mmol/l lactic acid measured in the blood. The modern name is “Ventilatory Threshold” – which I think means that it’s just below the point were you begin gasping for air. It’s pretty certain that frequent sustained training at this level is not optimum and will lead to overtraining issues. However it’s also how most people train.
HIIT/Strength: The HIIT advocates claim that repeated excess production of pyruvate (lactic acid) will by default provide all the aerobic endurance development necessary automatically – and that the aerobic system is actually autonomous. Well if this was really so simple then Usain Bolt would be a fantastic marathon runner as well as the top sprinter in the world – but he probably couldn’t even finish a marathon. He may even have the same VO2 max parameters (aerobic capacity) as a great Marathonian but it won’t help him – so something else is going on!
Maffetone: Maffetone councils strongly against strength training as part of a development program – only recognising its optional use at a later stage if at all.
Mark Allen: Mark Allen, six time Hawaii Ironman champion and World Champion triathlete, prodigy of Maffetone, states that when the Maffetone program doesn’t work for somebody then it’s usually because they are not including strength training!

So which path is the right one – considering they are all contradictory?

Biomarkers

While Maffetone views things from a perspective of health and takes a conservative approach based upon an intelligent ketogenic diet – the HIIT advocates are really covertly promoting bodybuilding and tend towards “Paleo” nutritional beliefs. For example “High Intensity Interval Training Explained” by James Driver states early on that CT (Continuous Training) is inferior to interval training in every way …. Quote: “I’m sure you can relate to the fact that developing the ability to run long distances at a steady pace would not have enabled our ancestors to catch prey or escape predators.” Well he couldn’t be more wrong if he tried to be. The fact is that humans can out-run over distance almost every species of animal on the planet, which is a major factor in how we caught them but we can’t run fast enough to escape any predator! Justification for the bodybuilders hinges also largely upon a contrived system of “biomarkers” which are used to determine the effective age and vitality of a body. At the very top of this list is “Muscle Mass” and second comes “Strength”. Somebody better have a word then with Chris Froome and Nairo Quintana because they obviously don’t rate very highly there. The following is from Clarence Bass’s web article comparing Maffetone with McGuff (Strength training): (I modified some items on the list as they are different from Bass’s account when seen on Amazon.com! In “Biomarkers” (Simon & Schuster, 1991), Evans and Rosenberg isolated the following signposts of vitality that can be altered for the better by changes in lifestyle:

Muscle Mass
Strength
Basal Metabolic Rate
Body Fat Percentage
Aerobic Capacity
Blood Pressure
Insulin Sensitivity
Cholesterol/HDL Ratio
Bone density
Ability to regulate Internal Temperature

Significantly, all 10 biomarkers can be revived or improved through strength training.

People like to lock onto information like this and almost make a religion out of it to justify their viewpoints and products. However there is no reason why this model should be the only one. The fact is that muscle mass and strength can also inhibit aerobic capacity and in turn training for aerobic capacity would improve everything except muscle mass and strength – so what? Ask Chris Froome perhaps. Bass unjustifiably uses this biomarker theory to criticise Maffetone. Experiments cited where people improve endurance far more effectively with strength training or HIIT compared to actual aerobic training do not appear to consider the specifics of endurance (the level, event or performance of the athlete) or even mention how this “endurance/aerobic” capacity is measured. Two major “biomarkers” are missing here. One is “Telomeres” and another is “Inflammation” . From “Runner’s World” article august 5, 2013 : Telomeres are DNA strands at the end of chromosomes that, current thinking goes, work like the plastic tips of shoelaces to prevent fraying (in this case, the fraying of genes). As telomeres shrink with age, cellular susceptibility to disease increases. Therefore, having longer telomeres, the theory goes, should provide protection against disease, and result in a lower biological age (compared to chronological age) than someone with shorter telomeres. Australian researchers report that ultrarunners have telomeres that are 11% longer than those of age-matched sedentary people. As a result, the researchers write, the ultrarunners have a biological age 16 years less than their chronological age (which was an average of 43). “The ultramarathon runners from our study performed an average 40 to 100 kilometres [25 to 62 miles] of running each week,” Charchar said. “A large percentage of recreational runners would accrue a similar volume of training each week.” Interestingly, searching around the web I’ve not been able to find any comparative telomere studies for HIIT or strength training. The other major missing biomarker type here is “inflammation”. Even cholesterol quantities, lipoprotein types and ratios are not such a big deal compared to inflammation. In fact statistics show that longevity is increased with higher cholesterol levels. By the way, in his book “Big Book of Endurance Training and Racing”, Maffetone describes cholesterol as a fat. Cholesterol is not a fat it is an alcohol and there is only one single type! One thing for sure is that HIIT and any strongly anaerobic activity will increase inflammation. A small amount of inflammation is adaptive and constructive – but chronic levels are destructive. HIIT handles this by keeping sessions brief and allowing lots of time for recovery. Maffetone however claims that literally any degree of anaerobic activity will cause enough inflammation to prevent the aerobic system from properly developing and can lead to injuries in general. He is also quite specific here about aerobic development in that he is referring especially to a type of aerobic muscle he terms “fast aerobic”. Maffetone asserts that there are seven known types of muscle fibre but that in reality there are probably many more making a full spectrum. We also know that high anaerobic capacity does suppress the aerobic function – both in terms of development and in terms of accessing existing aerobic capacity (VO2 max). For example to get Usain Bolt to run a marathon he most likely wouldn’t have to strengthen his aerobic system – he would have to weaken his anaerobic system. Whether he would be good at a marathon or not I haven’t a clue.

What’s interesting here is that the HIIT doctrine makes sweeping statements that it produces the most effective aerobic/endurance benefits – but without being in any measure specific about the claims. If they are measuring VO2 max then sure the aerobic capacity has gone up – but as a sprinter and marathon runner can both have the same VO2 max then this tells us nothing about performance – and in effect aerobic endurance will be expected to suffer at some point. Does the HIIT improve endurance for highly trained athletes or just for sedentary people? With Maffetone being convinced that even short doses of anaerobic activity puts an end to aerobic development.there there is a clear contradiction between the two approaches. Maffetone measures the aerobic performance of people directly (elite to beginner) and the HIIT people do not do this – so their claims appear to be too vague. Maffetone does everything to avoid inflammation and yet appears to still generate aerobic development – thus supporting key biomarker health issues without adding risk. Muscle mass and Strength do not even come into the picture. However if you were a bodybuilder then like the Paleo and HIIT advocates (who all seem to be bodybuilders) you would of course want to insist that this contrived biomarker system is the ideal reference. There is one other “biomarker” I’d like to define myself – and that’s “Chronic Injuries”! It’s not normally seen as a biomarker but the reality is that most people get derailed from exercise programs and activity due to injury. Something like 40% of all runners are injured at any given moment. HIIT and sustained anaerobic running are certainly going to raise the risk of mechanical injury. This is also one of the key motivations behind the Maffetone approach. In the HIIT book I mentioned earlier the author claims that most people give up CT (continuous training) – like long distance running – due to boredom. This is not true – they give up due to injury or just general lack of commitment. Running – even slowly – is not boring – it is extremely meditative and mentally engaging – plus enormously stress relieving. Sure, doing this indoors changes that a lot – but those activities are essentially outdoors oriented and that’s where they belong – not in a gym.

So where are we with all of this?

The goal we have to keep in mind is to improve fast endurance. It’s clear that the descriptions of aerobic and anaerobic from both Maffetone and McGuff are incorrect or misleading. (Despite Maffetone being more coherent in general). You cannot have Maffetone’s “pure” aerobic activity and you cannot have McGuff’s total dependence on anaerobic function. Mark Allen then interjects that those not succeeding with Maffetone need to include strength training. We already know that AT training is not optimal. To recap….

Anaerobic Threshold (AT) : Only train at the 4 mmol/l lactic acid level
HIIT/Strength: Only train anaerobically
Maffetone: Only train up to aerobic max (within a heartrate zone of 10 bpm below up to aerobic max)
Mark Allen: Train only Maffetone or add strength training depending on results

If anything jumps out here it’s that the terminology – aerobic/anaerobic – just doesn’t appear to be explained correctly in accepted conventional terms. Here’s a definition of aerobic respiration from Wikipedia. Not only is this completely unhelpful regarding insight into training or diet, it’s also highly misleading as it gives the false impression that glucose is the primary element in the whole metabolic process. This appears to be where all the confusion sets in with the basic terminology being extremely weak and misleading. The standard model of aerobic respiration gives the impression that it is a subset of anaerobic metabolism. In consequence, what McGuff (Strength/HIIT) is saying – that the entire aerobic function is dependent on anaerobic glucose metabolism (glycolysis) – is simply wrong. When Ranulf Fiennes and Dr Mike Stroud (nutritionist) walked across the South Pole they used radio isotope tagged water to be able to accurately measure blood parameters from daily samples. Normally blood sugar levels start to be a problem for people when they drop below 4 mmol/l but with their ketogenic diet both of them measured 0.2 to 0.3 mmol/l later on during the trek – and they were expending enormous amounts of physical energy pulling sleds unassisted. According to medicine their blood sugar levels were so low should have been dead. They were clearly functioning mainly on fat and ketones – aerobically – producing and eating just enough carbohydrates for essential bodily functions and some energy. In contrast Maffetone’s “pure aerobic” claim is actually referring to when all the pyruvate produced by glycolysis – anaerobic metabolism of glucose – is directly consumed by the aerobic system and not converted into lactic acid. Elite marathon runners tend to run in competition with a steady state of only 1 mmol/l of lactic acid – so they have a large aerobic system gobbling up all the pyruvate very efficiently – up to 97% of it according to Maffetone. However that is not the definition of “aerobic” – but is another common misinterpretation. The runner still needs to produce this big quantity of pyruvate and that’s a completely anaerobic process. Here Maffetone is describing aerobic/anerobic in terms of what happens after the pyruvate is produced – and that’s wrong! It seems that each expert makes errors slanted completely towards justifying their own theories. So far there is nothing actually against Maffetone in practical terms. Exclusive HIIT/Strength training however definitely does not make sense and and neither does AT training. With them eliminated that leaves Maffetone and Mark Allen.

Moving On…

The best correct source of information regarding the aerobic and anaerobic systems that I have found is at Lactate.com. They provide incredibly good explanations about the systems but unfortunately not a lot of detail regarding training. Also unfortunately they do not seem to have discovered Maffetone.They recommend a few books – two of which happened to be already in my library. One book is “Swimming Fastest” by Maglischo. Maglischo bases all of his endurance training around Anaerobic Threshold training – below AT, at AT and above AT. With Lactate.com selling lactate blood testing devices I can see why that makes sense – but it is not coherent with their explanations of how the metabolic systems work.

Aerobic/Anaerobic Riddle Resolved

Increasing aerobic capacity is always a beneficial.
The anaerobic system acts as a gatekeeper or control valve for the aerobic system.

A trained endurance athlete will easily be outsprinted by an average couch potato – because the couch potato will have a higher Anaerobic Capacity. What this means is that the “rate of production of lactic acid” will be higher for the couch potato and all factors considered the couch potato wins.

If the endurance athlete focuses on sprint intervals then Anaerobic Capacity will increase – but this will reduce access to the athlete’s current Aerobic Capacity (due to accumulation of lactic acid and H+ ions) and so accessing the full VO2 max becomes impossible.

An elite sprinter will have an extremely high Anaerobic Capacity and although might possess an equally well developed Aerobic Capacity (High VO2 max) it will be impossible to use much of it. Because the bulk of energy overall comes from the aerobic system the anaerobic system ends up acting as a gatekeeper over the aerobic system. It can take years to build a strong aerobic system but only a small amount of anaerobic training is required modify the combination of the two systems for specific performance goals. The anaerobic system is rapidly trained – but improving the aerobic system requires new capillaries, increased mitochondria, enzymes – an entire infrastructure. Increasing the anaerobic capacity at any point literally blocks access to existing aerobic capacity. This is why the HIIT doctrine is not correct. Even if it did build aerobic capacity (VO2 max) you would not be able to use it. In addition it is also clear that anaerobic work actually inhibits the effective development of an aerobic system (which for high performance you want to be with “fast aerobic” muscle fibre). We want our speed from gobbling up pyruvate rapidly (aerobic) not directly from burning glucose (anaerobic) and tolerating high lactic acid. Where Mark Allen steps in is when an individual has a naturally low Anaerobic Capacity and cannot even produce enough pyruvate to feed the aerobic system. This individual would have to do some work to strengthen the anaerobic system. Strength training would suffice. Maffetone has found with experience that the “fast aerobic” function is developed to top elite competitive level often without any strength training. This certainly corresponds to the above model of the aerobic/anaerobic systems with the anaerobic system acting as a gatekeeper. Provided there is a normal anaerobic capacity it can provide all the pyruvate required for a big aerobic system – instead of piling it up as lactic acid and bogging the whole system. Some ATP/energy will come from the glycolysis but most will come from direct and efficient aerobic pyruvate consumption – up to 97% as Maffetone claims – and this is what feeds the “fast aerobic” muscle fibres – which are specifically trained in the heart rate zone advised by Maffetone (without interference from inflammation – or suppression of VO2 max expression). To achieve a high performance some argue (Maglischo) that both aerobic and anaerobic systems may need to develop and that this requires a stepping-stone form of approach by using different training techniques – but this brings us back to a layered AT approach – all the training being above the aerobic threshold. This is what even the Lactate.com website is alluding towards. However Mark Allen is not advising this and is not contradicting Maffetone’s more holistic approach which clearly respects nutritional and health issues. For Maffetone the only anaerobic work necessary for most people is competition itself – during which all aerobic development will come to a halt.

N=1 Experiment

Why did I feel that after two months Maffetone wasn’t working for me? First of all it’s easy to doubt the Maffetone system due to it being so counter-intuitive. Recordings of daily workouts were not showing any sign of progress but in reality there was too much noise in the data to see any. The difference between an off day or a good day would swamp any other variables. There are weird things that you spot too when limiting your effort to a set heart rate and using it as biofeedback (instead of just observing and recording it for post analysis). For example I found out that if my body was very tired from a six hour bike ride the previous day – then I could actually run faster at the same fixed aerobic max heart rate (136 bpm). When fresh the heart rate would rise far more easily and so I’d end up running more slowly. Some days – usually a few days into recovery from something demanding – the heart would shoot up seemingly out of control and it was impossible to say if it was some sort of anomaly or the equipment. When that would happen I’d slow down or just switch to using nasal breathing as a reference – because the breathing wasn’t misbehaving. There is a MAF test (Maximum Aerobic Function) which should be carried out over 5 km every week – running specifically at the aerobic threshold (136 bpm) but I couldn’t see the point because I was doing that anyway over 11.2 km – however I was neglecting to warm up etc. so no doubt this added to inaccuracies. Only going full bore around the usual 40 km training route made it apparent that something interesting was developing with the Maffetone training. Being significantly faster than with any comparative effort this year – plus dealing with a strong headwind – was a remarkable and unexpected outcome which proves that endurance has altered. What’s interesting here is that an all out effort seems to narrow the data noise and is a clearer indicator of whether there is development or not – at least in my case. In the light of all the above information it’s of interest to look at the results of a laboratory sports running test I had done in 2006 when I was overweight (currently today around 67 kg) and not doing any endurance activity over 10 km in running or any road racing on a bicycle (only short hard mountain bike rides). HR(bpm) Speed (km/hr) Lactate (mmol/l)

116 10 2.3
146 12 3.1
161 14 4.0
170 16 6.2
174 17 10.1

VO2 max49 (ml/mn/kg) Weight 72.61 kg The conclusions were :

Very good aerobic capacity development
Rated “medium good athlete” overall – excellent for age – (Schvartz-Reibold scale)
Good lactic acid tolerance at 10 mmol/l

At the time of that test I bought the Polar book “Training, Lactate, Heart Rate” and tried to make use of this. It was all about training at Anaerobic Threshold – the 4.0 mmol/l lactic acid level – which was also the advice given to me from the doctor who carried out this test. I was to aim to train at around 14 km/hr in running. Needless to say this didn’t work out very well and I just let it go after a while. Placing all of this now in the context of the aerobic/anaerobic systems it’s obvious that all my speed came from anaerobic energy and there was a lot of lactic acid floating around. This is hardly surprising considering all winter would be spent downhill skiing (anaerobic) and I never did any specific endurance training or engaged in long events of any kind. The surprise is that there is a good aerobic development which indicates that rather than focus on building an aerobic system I should focus on reducing anaerobic capacity instead. The Maffetone training approach does both.