Somewhere I said that if an idea wasn’t simple enough to be written down on a matchbox, then it was probably too complicated to get across. So, on that premise, my ‘matchbox’ contribution is that the total volume of low-intensity aerobic base training completed before a peak racing season dictates high-intensity anaerobic outcomes as we get towards peak racing. Or, even simpler: Aerobic training defines anaerobic training potential. Or: Steady Quantity defines eventual Intense Quality.

But hold on! Isn’t there constant discussion everywhere about how there’s never really such a thing as totally aerobic or totally anaerobic? Yep- that’s quite correct. However, we as humans need to label everything and put them into their boxes before we can understand what we’re dealing with- so in this case, we have to talk in very black and white terms to ‘frame our conceptual tapestry’ (nice phrase, eh?).

Why Endurance Training?

The whole human body runs on energy derived from food, water, and the air we breathe: the combustion of glucose, derived in one form or another from long chains of glucose molecules stored as starch (glycogen), or glucose already in the bloodstream from the digestion of foods, or glucose from the reassembly and breakdown of fats and proteins. Glucose can be derived from essential fats (triglycerides) by a breakdown process that cleaves the longer-chain fatty acid molecules into several smaller (glucose) units that can be easily transported across the cell membrane (cell wall) into the internal structures of the cell.The end of the process will always result in a release of energy through the extremely rapid breakdown of high-energy phosphate bonds.

There is ample evidence around to demonstrate that a concerted period of low-intensity training volume results in significant increase in CAPILLARISATION within the trained muscle. There is also ample evidence showing that the body thrives best in a slightly alkali environment, as opposed to slightly acidic. (Think milk versus vinegar). Prolonged high intensity training without due low intensity recovery has been known to elevate ACIDOSIS in the body, which in turn mucks up cell membrane walls, lowers immune response, and mucks up normal fatty acid and carbohydrate metabolism, as well as the highest-energy alactic energy system. So everything will be stuffed, and will need days to recover.(See all the references in the book!)

‘Synaptogenesis’(the formation of new synaptic connections within the neuromuscular system) and ‘Angiogenesis’ (the budding of tiny new blood vessels which eventually become capillaries or even larger venules and arterioles) are far more likely in an alkali environment. Intense training can promote a powerful stimulus for angiogenesis, however this will only really occur if the whole system is allowed to recover adequately. The same for synaptogenesis. With intense training, and the necessary very easy days to recover, you’ll lose a lot of steady aerobic work time, and all the benefits that come with that background.

There is absolutely no point in doing faster, more intense work until a modicum of essential, basic fitness has been acquired. This basic fitness would include good tendon strength and elasticity, and a highly developed capillary system that literally “irrigates” the muscles with fresh oxygen, glucose, and fatty acids, and transports the byproducts away quickly.

Once this basic fitness has been acquired, it can be increased methodically over a number of weeks by deliberately running strongly for up to an hour once or twice a week at a level that can be described as “strong”. Build up to the hour steadily in increments of a few minutes each time from a starting level of around 20 minutes within a 1 hour run. The body seems to like variety in its aerobic training, so we include longer slower runs and shorter steady runs on varying courses each week as well.

After a substantial block of consistent training at mainly aerobic levels, but with regular attention to the ’strong’ runs, by the end of 8-12 weeks the body will be substantially faster at all aerobic speeds, due to the proven increase in capillary density. Not only has the physical “plumbing supply and waste removal” capacity been increased, right into the very depth of the muscles, but the oxidative enzymes and energy production pathways within the muscle cells will have gone up significantly. Enzymes are substances that can increase the speed of chemical pathways in the body exponentially in some cases. There are enzymes capable of breaking high-energy bonds between molecules and releasing energy as a by-product, and also enzymes that do the reverse, in order to store energy.

There will be proliferation of ‘mitochondria’ in any muscle cells that can utilize oxygen. Mitochondria are the ‘furnaces’ in muscle cells and other organs that are responsible for mixing these enzymes and fuels in the presence of oxygen to deliver rapid energy by breaking phosphate bonds in the ATP molecule (adenosine tri-phosphate).

At this stage, we have only discussed the muscle fibres being exercised in a general sense.They’re not all in the runner’s legs. The great secret that seems to be ignored by most writers is that muscles are really organs with a nerve supply and a blood supply, like any other. All organs have a sensory feedback to the central nervous system that monitors blood chemistry constantly. Levels of oxygen, carbon dioxide, mineral balance, alkalinity and acidity are relentlessly examined, and subtle changes made to accommodate imbalances or signs of overload. The organ that also benefits greatly is the heart. Steadily, over a number of weeks, it gets a beautiful network of capillaries all through it, so that the general blood supply to the cardiac muscle is very low-pressure even with very high demands. Think of a high-pressure large diameter pipe that feeds off into hundreds of small pipes: No matter what the pressure is in the main pipe (major artery), the pressure in the small pipes (arterioles) is way less, and if they again join up throughout deep muscle beds of smaller pipes again (’anastamosis of capillaries’) the ability of the blood to deliver fuel and oxygen deep into the muscle on an almost individual cellular basis is greatly increased. Likewise the ability of muscle cells to hand back carbon dioxide in exchange for the oxygen, and also for breakdown products of metabolism (metabolites) to be released back into the bloodstream.

With sufficient endurance training, the cardiac mitochondria proliferate too. They’re big and have multi-tasking capabilities in terms of being able to rapidly break down either long fatty acids or glucose so that this particular muscle never runs out of fuels to burn with oxygen.  With many weeks of subtle high-aerobic pressure on the heart, it will develop a thicker left ventricular muscle wall to go with all the dense capillarisation, however later on in the season with near-maximal interval work, this will bring along stroke volume and power even more.

We haven’t even discussed yet that there are broadly speaking three types of muscle fibre in the human; slow twitch and two distinct subtypes of fast twitch. Each one has its own very strong association with a particular energy system and metabolic profile. Slow twitch fibres are thin endurance fibres with low power, vast volumes of mitochondria, and dense capillary supply to the fibres. They are a deep red colour due to to the presence of oxygen-bearing iron complexes (globins) that are the equivalent of the haemoglobin in the red blood cells. Same molecule: only it’s ‘afixed’ within the muscle cell near the periphery, as close as possible to incoming capillaries. The molecule is therefore now named myo-globin due to its presence within the ‘myo’ (or muscle) cell.

Skeletal slow-twitch muscles can bang away constantly for up to 90 minutes, rapidly stripping down fats or glycogen (stored glucose chains) into glucose for delivery into the mitochondria. Slow twitch fibres have enough force to support constant speeds of up to 8.5 miles per hour (13.7 km/hr: nearly 44min 10k pace) for an athlete with normal limb lengths. Thereafter, force comes more and more from fast twitch muscles, while the slow twitch seem to switch to providing metabolic activity to supply the substrates for the fast twitch fibres, rather than force per se. It’s a fascinating division of labour overseen by the central nervous system.

Fast twitch fibres are large powerful fibres with far lower endurance characteristics, and little or no mitochondrial volume. There are various subtypes now being recognized and discussed. One subtype that becomes far more metabolically active with endurance training is the IIA; this is a big strong muscle fibre that has a good capacity to develop oxidative pathways if subjected to endurance training. The other sub-type, the IIB, is extremely powerful and innervated by huge, highly myelinated neurons. Myelin is a derivative of the much-maligned substrate cholesterol, and is laid down more and more along frequently recruited neuronal pathways by Schwann cells, much as one would tape a bike handlebars or a tennis racket. The purpose of myelin seems to be very similar to the purpose of insulation on high-voltage cables- it helps nerve conduction speed up considerably from source to destination. Fascinating recent research indicates that myelination of major pathways could be the holy grail of neuro-motor training.

The IIB fibre is all power and strength, with no mitochondria and no need for oxygen-based fuel combustion. It’s just a very long cellular bag loaded with high-density muscle fibres and very few organelles. Its dominant energy system is the ‘oxygen-independent anaerobic system’. This is also called the ‘alactic anaerobic’ system because it’s activity is all “done and dusted” before the lactic anaerobic system starts to really kick in.

It’s also known as the creatine-phosphate system, because energy is derived extremely rapidly from the very rapid stripping down of the three-phosphate molecule ATP (adenosine triphosphate) to ADP (adenosine diphosphate), then AMP (adenosine monophosphate). Each time a phosphate is booted off in this sytem, energy is released into muscle contraction. The system has up to 15 seconds of rapid activity before it needs to recover, and the now-depleted adenosine molecule picks up new phosphate attachments from intramuscular creatine phosphate stores.

So, in effect, we have two anaerobic systems and two fast twitch fibres subtypes analogous with them. We have one aerobic system and one fibre type analogous with it.

More next post.