Running Basics

Publication date

7 Mar 2024

Estimated reading time

17 min read

Metab­o­lism

What is run­ning? It’s the trans­for­ma­tion of poten­tial chem­i­cal energy from food into kinetic energy of move­ment (and heat).

For our mus­cles to con­tract, we need adeno­sine triphos­phate (ATP) — our energy cur­rency.

From this adeno­sine triphos­phate, we break off one phos­phate group, releas­ing energy for con­trac­tion, and get adeno­sine diphos­phate (ADP) and free phos­phate. From adeno­sine diphos­phate, we can also break off another phos­phate and get more energy, phos­phate, and adeno­sine monophos­phate, but this is a rarer process. If our cell doesn’t have ATP, it can no longer do work. There­fore, when we break down ATP, we need to quickly restore it — reat­tach the phos­phate back.

Right now, we already have some amount of ATP in our cells, so when we start moving, we’ll first break down these ready-made ATPs. This will last us a couple of sec­onds.

All our energy sys­tems that we’ll exam­ine fur­ther are busy reat­tach­ing phos­phates back to ADP.

Creatine Phosphate

First, cre­a­tine kinase or phos­pho­cre­a­tine kinase kicks in — an enzyme thanks to which we can get ATP from cre­a­tine phos­phate.

We take cre­a­tine phos­phate (CrP), break off the phos­phate from it, attach it to ADP, and get cre­a­tine and adeno­sine triphos­phate. This process is bidi­rec­tional, mean­ing it can go in reverse (to restore CrP con­tent in the cell).

Actu­ally, all our sys­tems turn on simul­ta­ne­ously: both the cre­a­tine phos­phate system, and gly­col­y­sis, and lipol­y­sis, and aer­o­bic processes in the mito­chon­dria. But they all finish their work at dif­fer­ent times. So, cre­a­tine kinase is one chem­i­cal reac­tion pro­duc­ing 1 ATP, while fast gly­col­y­sis is about 10 reac­tions pro­duc­ing 2 ATP. There­fore, while we’re wait­ing for gly­col­y­sis to bring us its ATPs, we use cre­a­tine phos­phate as a buffer energy source. We also use it, for exam­ple, if we need to sud­denly speed up during our marathon to over­take some­one. Cre­a­tine phos­phate will last for 8–10 sec­onds. Then we’ll need to restore it again.

Glycolysis

The next ATPs will come from the first part of gly­col­y­sis, the so-called anaer­o­bic gly­col­y­sis, or gly­colytic, or „fast” gly­col­y­sis.

The essence of glu­cose metab­o­lism is this: We take a carbon chain, break it into pieces, get­ting a little bit of ATP, send the pieces to the mito­chon­dria, add oxygen there, and get a whole bunch more ATP.

Here’s the first part of the process — anaer­o­bic gly­col­y­sis. We run on this from a few sec­onds to a minute. While wait­ing for ATPs from the next, aer­o­bic part.

Here, for exam­ple, we take one such beau­ti­ful glu­cose mol­e­cule.

Glu­cose is a chain of six car­bons, we break it in half and get two pyru­vates (pyru­vic acid), each with three car­bons plus two ATPs as a bonus (net yield):

Or pyru­vate and lac­tate. In the pic­ture where glu­cose was turn­ing into pyru­vate, you can notice if you count all the let­ters that sev­eral hydro­gens (H) dis­ap­peared some­where. Lac­tate is the same pyru­vate, but plus two more hydro­gens:

Pyru­vate can pro­ceed right into the mito­chon­dria to pro­duce a bunch more ATP (about 15 from one pyru­vate), and lac­tate can exit the cell and go either into a neigh­bor­ing cell, into a cell of a neigh­bor­ing muscle, and also go into the mito­chon­dria to follow the same path as pyru­vate, or into the blood, to the brain, to the heart (the brain and heart feed well on lac­tate), or to the liver, the liver will col­lect sev­eral lac­tates and con­vert them back into glu­cose, then send the glu­cose back into the blood and to the mus­cles.

Let’s sum up: we broke glu­cose in half, get­ting a little bit of energy, added oxygen to the halves, sent them to the mito­chon­dria, broke them down fur­ther there and got a bunch more energy. Actu­ally — this is all one process, but ancient phys­i­ol­ogy researchers decided to call the first stage an anaer­o­bic process (because oxygen isn’t required to break down glu­cose into pyru­vate, although it’s present in the cell and used in sub­se­quent stages), and the second stage — aer­o­bic (because oxygen is nec­es­sary for it).

The process of ATP for­ma­tion in mito­chon­dria is also called cel­lu­lar res­pi­ra­tion. And the mito­chon­dria itself is called the „pow­er­house of the cell,” as it’s the main source of energy for the cell.

The main source, but a very slow one. „A hun­dred thou­sand mil­lion” reac­tions have to happen there. But the essence of these reac­tions is this: took food scraps (pyru­vate from glu­cose or fatty acids from triglyc­erides), added oxygen, got carbon diox­ide and water as output, resyn­the­siz­ing a bunch of ATP in the process.

Lipolysis

Lipol­y­sis is sim­i­lar to gly­col­y­sis. We take a triglyc­eride (fat), which con­sists of glyc­erol and three fatty acids attached to it.

We break off the fatty acids from glyc­erol. Look how many carbon chains there are :) Here are 16 carbon bonds drawn for each fatty acid. From one such fatty acid (palmitic acid, C16), we’ll get a whop­ping 106 ATP mol­e­cules in the mito­chon­dria.

There are two prob­lems — first, this is no longer „a hun­dred thou­sand mil­lion” reac­tions, but „five hun­dred thou­sand mil­lion” reac­tions, and second, these triglyc­erides still need to be deliv­ered to the cell from the places where we store fat (far away).

Here’s what the expen­di­ture of fats and car­bo­hy­drates looks like for some person. I drew the thresh­olds and zones myself roughly based on my under­stand­ing.

But the fat metab­o­lism curve looks dif­fer­ent for dif­fer­ent people. Depend­ing on their fit­ness level and other fac­tors.

Stores and Speed

Glu­cose is stored in the form of glyco­gen. About 300–500 grams in mus­cles and 80–100 in the liver. Total about 400–600 grams, which gives approx­i­mately 1600–2400 kcal. This will last us for a com­pe­ti­tion last­ing approx­i­mately one and a half to two hours of intense run­ning.

80% of all energy in the human body is stored in the form of fat, in the form of these triglyc­erides. Approx­i­mately 70,000–75,000 kcal. You can con­sider this reserve inex­haustible.

Let’s sum­ma­rize:

• We get energy fastest from creatine phosphate, but there’s very little of it — 8-10 seconds and it’s gone.
• Slightly slower, but we get more energy from fast glycolysis — 30 seconds to 2 minutes and it’s gone.
• Even slower, but even more from aerobic glycolysis — until glycogen stores are depleted (90-120 minutes at marathon pace).
• And very slowly, but a lot from fat oxidation.

I imag­ine it like this: we’re sit­ting in front of the TV and must con­stantly eat some­thing. We simul­ta­ne­ously:

• pull out our food stash from our pocket (creatine phosphate) and start eating,
• send the wife to the kitchen for food,
• send grandpa to the garage for lard and pickles.

The wife pulls out a bag of chips from the cup­board and throws them to us, while she starts cook­ing some proper meal (aer­o­bic gly­col­y­sis). We’re eating the thrown chips in the mean­time (anaer­o­bic gly­col­y­sis). When the wife brings the proper meal, we’ll make a stash in our pocket again. And send her to make the next meal (and chips). In an hour, grandpa will return, we’ll get lard (fat metab­o­lism), and send grandpa to the garage again. If we’re facing a TV marathon and can eat slowly, we can start send­ing the wife less often, grandpa’s lard will be enough. But if we need to eat very quickly. Then we’ll stop send­ing grandpa alto­gether (too much hassle), but we’ll send the wife back and forth very often. (#sorry :)

Inten­sity Zones. Lac­tate

In this whole process, we want to mea­sure some­thing to under­stand the inten­sity at which we’re trans­form­ing energy. One para­me­ter we can mea­sure is the amount of lac­tate in the blood.

Blood lac­tate con­cen­tra­tion depends on its pro­duc­tion and con­sump­tion. Lac­tate is pro­duced not only in fast muscle cells, but also in red blood cells, in the brain, in the gas­troin­testi­nal tract. Lac­tate is con­sumed in slow muscle cells, fast muscle cells (they both pro­duce and con­sume it simul­ta­ne­ously, just in dif­fer­ent pro­por­tions), the liver (when needed), the heart (it espe­cially loves lac­tate and feeds on it at every oppor­tu­nity), as well as in the brain and adi­pose tissue.

When we start moving, the amount of lac­tate in the blood even decreases at first, since lac­tate is fuel.

When we add inten­sity, the lac­tate level in the blood starts to increase grad­u­ally, but not much. We’re break­ing down glu­cose, lac­tate exits into the blood but quickly goes back in for ATP pro­duc­tion. Then, as the load increases, the lac­tate level starts to increase notice­ably. This is the point of begin­ning blood lac­tate con­cen­tra­tion growth. This point on the „lac­tate level/inten­sity” graph is called LT1 — first lac­tate thresh­old. The approx­i­mate lac­tate con­tent here is 1.5–2 mmol/L. Since the uti­liza­tion of pyru­vate and lac­tate is tied to oxygen con­sump­tion, this point can also be noticed nearby on another graph, the oxygen con­sump­tion graph. And it’s called the first ven­ti­la­tory thresh­old, VT1. In Russ­ian, this is called the aer­o­bic thresh­old.

In the three-zone model, this point is the bound­ary between the first and second train­ing inten­sity zones.

Fur­ther, we con­tinue to increase inten­sity, lac­tate con­tin­ues to grow. But the trick is that if we stop increas­ing inten­sity, then the growth of lac­tate level also stops. That is, at each pace here we can stay for some rea­son­able extended amount of time with­out drown­ing in lac­tate. This is called Lac­tate Steady State. Actu­ally quasi steady, since noth­ing is con­stant and after some time drift will begin anyway. This is the zone that cyclists love for train­ing, here’s their „sweet spot,” some­where around here we run a marathon.

But then, at some point, if we con­tinue to increase inten­sity, lac­tate will start to grow expo­nen­tially. And despite the fact that the pace will be con­stant, lac­tate will still grow, because we’ve already started to exceed our abil­ity to uti­lize it (con­di­tion­ally — there are almost no free mito­chon­dria left). This tran­si­tion point is called LT2 — second lac­tate thresh­old, MLSS — max­i­mal lac­tate steady state. The approx­i­mate lac­tate con­tent here is 4 mmol/L. Here will also be the second ven­ti­la­tory thresh­old. And in Russ­ian this is called LTHR — lac­tate thresh­old heart rate — a bas­tardized name, since there’s no tran­si­tion to anaer­o­bic metab­o­lism here. We just need more energy, we just con­tinue to break down even more glu­cose, get­ting crumbs of ATP from it, but can’t keep up with the fur­ther process — break­ing down pyru­vate/lac­tate.

Here is also where FTP — func­tional thresh­old power — is located, the inten­sity at which you can last for about an hour. Jack Daniels also calls this inten­sity the com­pe­ti­tion pace for 1 hour. What’s inter­est­ing is that actu­ally, not many can sit here for an hour, and you could call this the pace of com­pe­ti­tions last­ing from 20 min­utes to an hour. For us, this is prob­a­bly the com­pe­ti­tion pace for 10–15 km.

If we take these two thresh­olds, we get Dr. Stephen Seiler’s zone system. He was the first to intro­duce the term polar­ized train­ing, 80/20.

People inter­preted his theory as mean­ing that 80% of train­ing should occur below LT1 and 20% — above LT2. But he now claims that actu­ally he means „inten­sity,” which always goes together with time at that inten­sity. There­fore, train­ing between LT1 and LT2 he also counts in these 20%. Just these should be longer dura­tion work­outs. He also claims that after train­ing below LT1 the body recov­ers quickly (they mea­sured HRV), lit­er­ally in an hour, and above — slowly, a day.

Having these two thresh­olds, you can get not only a three-part zone system, but also a five-part one. Then the second zone will be around LT1, and the fourth — around LT2.

In Garmin, for exam­ple, you can choose to have the watch cal­cu­late heart rate zones based on the second lac­tate thresh­old heart rate, then we get exactly these five zones in mean­ing:

Oxygen. VO2max

After we’ve stepped over our LT2 or LTHR, we still have one more point ahead that we can mea­sure — VO2 max, max­i­mum oxygen con­sump­tion. This means, as is clear from the name, that after cross­ing the LT2 we’re still increas­ing the use of our aer­o­bic system, since oxygen con­sump­tion is grow­ing, and we need oxygen pre­cisely for the aer­o­bic system. Which is our main system.

Thus, the VO2max indi­ca­tor is the max­i­mum indi­ca­tor of our main energy system’s capac­ity. High VO2max reflects our high abil­ity to pro­duce energy.

What limits VO2max? Let’s recall our process: we need to drag food to the cell, break it down, drag the scraps to the mito­chon­dria, drag oxygen to the mito­chon­dria, drag this oxygen to the cell with blood through cap­il­lar­ies, for this fill the blood with oxygen and push it to the muscle. Each point of this process is a lim­iter. At each point adap­ta­tions occur.

Fuel

If we have little fat and car­bo­hy­drates, we have noth­ing to break down, noth­ing to oxi­dize. We’ve hit the ceil­ing already here.

Train­ing increases our glyco­gen depot, improves the work of hor­mones, enzymes reg­u­lat­ing the amount and deliv­ery of glyco­gen. Top ath­letes train and look for other clever ways to deliver as much glu­cose as pos­si­ble to cells during train­ing.

Spe­cial train­ing improves our abil­ity to deliver and break down fats. For exam­ple, research shows that in top ath­letes there’s always a „droplet” of fat in the cell right next to the mito­chon­dria, ready for use. We usu­ally don’t have that.

It’s claimed that train­ing in the FatMax zone (usu­ally 50–70% of VO2max, approx­i­mately zone 2) strongly pro­motes the devel­op­ment of fat metab­o­lism.

Mitochondria

Thanks to train­ing, the quan­tity of our mito­chon­dria and their qual­ity increases. If we have few of them, we have nowhere to actu­ally bring this food and oxygen.

Slow train­ing in zone 2 par­tic­u­larly pro­motes increas­ing the quan­tity of mito­chon­dria.

And fast train­ing in zone 5 par­tic­u­larly pro­motes improv­ing their qual­ity, size.

It’s claimed that train­ing in the FatMax zone (zone 2) is the most opti­mal way to develop our mito­chon­dr­ial net­work.

Oxygen Delivery

Inside the cell, oxygen moves to the mito­chon­dria with the help of myo­glo­bin. Its quan­tity is also a lim­it­ing factor and devel­ops with train­ing.

Oxygen must reach the cell through a net­work of cap­il­lar­ies. The cap­il­lary net­work is a lim­it­ing factor and devel­ops with train­ing.

In blood, oxygen trav­els by attach­ing to hemo­glo­bin in red blood cells. The greater the blood volume, the more hemo­glo­bin in this blood, the more oxygen we can deliver. Top ath­letes have higher blood volume. Just by trans­fus­ing some addi­tional blood, one can increase VO2max. And you can also inject ery­thro­poi­etin, a hor­mone that increases the number of red blood cells → which means the abil­ity to deliver oxygen to mito­chon­dria will increase → which means, with other sys­tems trained, VO2max will rise.

Blood Oxygenation

Blood oxy­gena­tion occurs in the lungs. A system that for most people is not a lim­it­ing factor. This is evi­denced by such facts that a person can live and even run marathons with one lung. Also, the oxygen sat­u­ra­tion of cap­il­lary blood, which we all mea­sured with a pulse oxime­ter during COVID, is a more or less con­stant value, even during heavy inter­val work.

Note: in elite ath­letes at peak load, exer­cise-induced arte­r­ial hypox­emia (decreased blood oxygen sat­u­ra­tion) can occur.

Heart

The volume of blood ejected by the heart is usu­ally called „Car­diac Output” or (in Wikipedia) „minute volume of blood cir­cu­la­tion”. It’s cal­cu­lated as the prod­uct of Heart Rate (per minute) and Stroke Volume (amount of blood ejected per beat). In this for­mula, we train stroke volume. We train it by increas­ing heart size and by strength­en­ing its walls.

Slow train­ing in zone 2 par­tic­u­larly pro­motes increas­ing heart size.

And fast train­ing in zone 5 par­tic­u­larly pro­motes strength­en­ing, thick­en­ing of the heart walls.

Here’s how the process works: we have sys­tole — the phase when the heart con­tracts and ejects blood, and dias­tole — the phase when the heart relaxes, fills with blood and feeds itself. When our HR increases, accord­ingly, the time for sys­tole+dias­tole decreases. It decreases due to the reduc­tion of dias­tole time. And this means that we col­lect less blood with each beat, and also that we feed the heart itself worse and worse.

When we just start run­ning, this causes an increase in HR, it also pro­vokes an increase in Stroke Volume. Car­diac Output and the rate of blood return to the heart increase. How­ever, as HR increases, dias­tole time short­ens and, con­se­quently, we have less time to fill the heart with blood. Despite the fact that fill­ing time is less, Stroke Volume still remains high. HR con­tin­ues to increase fur­ther, Stroke Volume grad­u­ally decreases due to reduced fill­ing time. Car­diac Output sta­bi­lizes, as the increase in HR com­pen­sates for the decrease in Stroke Volume, but at very high HR values, Car­diac Output will even­tu­ally even decrease, since fur­ther increase in HR can no longer com­pen­sate for the decrease in Stroke Volume.

Let’s add num­bers for clar­ity.

1. Here we start running, initially, when HR increases from resting state to about 120 beats per minute, Cardiac Output level will grow.
2. When HR increases from 120 to 160 bpm, Cardiac Output remains stable, as the increase in frequency is compensated by the decrease in heart filling time and, consequently, Stroke Volume.
3. HR continues to rise above 160 beats per minute, Cardiac Output decreases, as Stroke Volume decreases faster than HR increases.

These approx­i­mate num­bers and the fact that coro­nary cir­cu­la­tion feeds the heart during dias­tole (which means this abil­ity decreases as HR increases), show that from the point of view of opti­mal heart train­ing specif­i­cally, it’s most ben­e­fi­cial to train with­out climb­ing high in heart rate (for the guy in the exam­ple — this is the zone of 120–160 beats per minute).

Also, excess train­ing at high heart rate and defi­ciency at low leads to a small heart with thick walls. And this is con­cen­tric car­diac remod­el­ing (patho­log­i­cal if extreme).

Inten­sity Zones. Sum­mary

If we take our pre­vi­ous pic­ture with five zones and add VO2max to it, and count it as a sep­a­rate zone, after which there’s still life, we’ll get a more stan­dard and applic­a­ble train­ing model:

Zone 1 — Active Recovery

RPE (Rate of Per­ceived Exer­tion) < 2. For some it’s walk­ing, for some it’s jog­ging, for some even faster. You can chat so that your inter­locu­tor won’t even notice you’re exer­cis­ing.

Zone 2 — Base Endurance Training

RPE — 2–3. Around the first lac­tate thresh­old. Imag­ine you could run like this all day if needed. But you already need to con­cen­trate a bit. You can still chat, but your inter­locu­tor will notice you’re train­ing now, but it won’t inter­fere yet. What Jack Daniels calls Easy pace. For me, this is a heart rate of 130–150.

Zone 3 — Tempo

RPE — 4–5. Some fartlek. Or you can run a long one with friends (but alone you don’t want to run this fast any­more). You’re already breath­ing rhyth­mi­cally, work­ing. What Jack Daniels calls Marathon pace.

Zone 4 — Threshold

RPE — 5–6. Around the second lac­tate thresh­old. Hard to talk. Men­tally tough. What Jack Daniels calls Thresh­old pace. Long inter­vals with short active rest. For me, this is a heart rate of 160–167.

Zone 5 — VO2max

RPE — 7–8. Very hard to talk and think. What Jack Daniels calls Inter­val pace. Inter­vals of three to five min­utes (800m — 1500m). And the same amount of rest. Main devel­oper of max­i­mum aer­o­bic power.

Zone 6 — Anaerobic

RPE > 8. What Jack Daniels calls Repeats pace. Inter­vals of 30 sec­onds to 1.5 min­utes (200m — 600m). Rest a lot between repeats. Develop speed, form, run­ning econ­omy.

Or like this:

Inten­sity Zones. Mea­sure­ment

Inten­sity zones can be mea­sured in lab­o­ra­to­ries. This is cool, but needs to be done peri­od­i­cally because they’re con­stantly moving. You also need to prop­erly choose a spe­cial­ist and mea­sure­ment pro­to­col.

You can deter­mine VO2max in the lab­o­ra­tory and cal­cu­late zones as per­cent­ages of it. You can deter­mine LTHR in the lab­o­ra­tory and cal­cu­late zones as per­cent­ages of it. You can deter­mine max­i­mum heart rate and rest­ing heart rate and cal­cu­late zones as per­cent­ages of them. But all this will be writ­ten with a pitch­fork on water. Con­stantly moving. And the per­cent­ages them­selves are dif­fer­ent depend­ing on the ath­lete’s char­ac­ter­is­tics and fit­ness.

You can cal­cu­late zones based on com­pe­ti­tion results. Com­pe­ti­tions deter­mine our max­i­mum capa­bil­i­ties most accu­rately and ade­quately, if, of course, we approached them com­pe­tently :) For this, we use Daniels’ (VDOT) or McMil­lan’s cal­cu­la­tors.

Or you can use RPE.

Prac­tice

Man­ag­ing stress, signal, pace.