Sports Conditioning: Understanding the Basic Science


  This article is meant to provide general overview of the basic principles underlying the “conditioning” part of the “Strength & Conditioning” equation. Sports conditioning is about achieving and sustaining the maximum amount of power output inside the requirements of a sport or physical activity. In a more general sense, one could define conditioning as “not getting tired easily while practicing your sport”. If that’s what you’re looking for, make yourself comfortable and keep on reading.

Make yourself comfortable and get ready for science!

Energy Systems

  “Energy systems” are the different mechanisms via which the body can use energy substrates to provide energy to the muscle fibers for muscle contraction and force production. Understanding how the different energy systems work and interact with each other in order to satisfy the different energy demands of the body is fundamental to understanding how to work on your conditioning.

But first, a few words about the energy substrates:

All energy comes from the main substrates: ATP (adenosine triphosphate), PCr (phosphocreatine), glycogen/glucose (glycogen is essentially glucose in packaged form) and fatty acids (often simply referred to as “fat”). ATP is the only chemical compound that can be used by the muscle fibers as energy to produce force, so PCr, glycogen and fat are used by the energy systems to create ATP, which then is used by the muscle finders to produce power.

Basic facts about the energy substrates:
  • a very small amount of ATP is stored in the muscle cells and is ready to be used immediately
  • a very small amount of PCr is stored in the muscle cells
  • substantial (but not unlimited) amounts of glycogen are stored in the body (in the muscles and the liver)
  • the body has virtually unlimited amounts of fat (some in the muscles and most in the adipose tissue)

And now the energy systems:

The ATP/PCr System - very high power/very short duration

The ATP/PCr system is anaerobic (“aero” means “air”, and “anaero” means “no air”, i.e. it doesn’t use oxygen) and provides energy FAST but can only provide energy for a very short time. Power being the rate of work production, “fast energy” translates to high power production. It uses what little ATP is ready and waiting inside the muscle cell, and it also uses what little PCr is there to create new ATP. When going all out, both those substrates will start getting depleted within 8-10 seconds. It will generally take around 3-5 minutes for phosphocreatine stores to be nearly fully restored, a process which takes place in the mitochondria and utilizes the aerobic energy system (kind of like recharging your cellphone).

The Glycolytic System - high power/limited duration

The glycolytic system is also anaerobic, it provides energy fast and can provide energy for a fairly long but still limited amount of time. It uses glycogen to create new ATP, which is a pretty fast procedure but not quite as fast as PCr to ATP, and it also creates some “byproducts”. Those byproducts are metabolized by the aerobic system, but if the exercise intensity is high the aerobic metabolism can’t keep up with glycolysis and accumulation of byproducts occurs.

The main problem with the glycolytic system duration in high-intensity attempts is not the depletion of substrates, but the accumulation of byproducts (once thought to be lactic acid) that lower the pH of the muscle cells and render them useless (that’s why in the last few meters of a 400m sprint you “stiffen up” and can barely will your legs to move). Some of those byproducts are gradually metabolized in the mitochondria of the muscle cell and the rest enter the blood and are metabolized in other cells, thus the pH of the blood also drops (this process is sometimes referred to as “buffering”). A fair indicator of this procedure is the blood lactate level (Lactate accumulation, proton buffering, and pH change in ischemically exercising muscle) and the process of the blood (and the muscle cells) returning to normal levels can take north of 10 or even 20 minutes if the original lactate accumulation was really high.

The famous “anaerobic threshold” (AT), which you’ve probably heard of before, sometimes interchangeably referred to as “lactate threshold” (LT) or “onset of blood lactate accumulation” (OBLA), is basically roughly the level of continuous effort above which glycolytic byproducts accumulate. Anywhere bellow that threshold you can sustain your activity for a very long time, anywhere above that threshold fatigue will eventually occur (the further above the threshold, the faster the byproducts will accumulate, and thus the faster you will get fatigued). The terms AT, LT and OBLA are not exactly identical, for further information you can start here: Anaerobic Threshold: The Concept and Methods of Measurement

The Aerobic System - low power/unlimited duration

The aerobic system provides energy slowly but can last for a fucking long time! The aerobic system is all about the mitochondria, which use oxygen to burn fat and glycolytic byproducts, and through many many slow chemical reactions they produce ATP and CO2. No byproducts are produced and the aerobic system can go on and on for hours as the substrates are virtually unlimited. Another thing the mitochondria do is use oxygen to restore the PCr stores and to help avoid/delay the accumulation of glycolytic byproducts that lower the muscle pH (sort of like “aerobic recycling”). This little detail can have significant implications in maintaining a higher energy output, as well as in recovering faster between bouts of higher energy production. It takes a couple of minutes for the aerobic system to “wake up”, that’s why sometimes when you start running the first couple of minutes may feel more tiring until you “find your pace”.

Unlike the anaerobic systems, the aerobic system relies not only on energy substrates but also on oxygen supply. The oxygen pathway is simple: you breathe, oxygen goes into your lungs, it diffuses into your blood, the heart pumps the oxygen-rich blood through the vessels to your limbs and the oxygen is diffused from the local capillaries into your muscle cells and eventually into the mitochondria. The aerobic system can be divided in two components: the central or “oxygen transport system”, comprising of the lungs and the cardiovascular system (the heart, the blood and the blood vessels), and the peripheral or “oxygen uptake/consumption system”, comprising of the muscle capillaries and the aerobic system-related parts of the muscle cells (the number and size of the mitochondria, the myoglobin content and the various aerobic enzymes concentrations). Those two components together determine the VO2max and both components can be limiting factors to maximum aerobic power production.

Barring health-related issues (like chronic lung issues, iron deficiencies, or different forms of anemia), the main limiting factor in the oxygen transport system is the cardiac stroke volume (SV, i.e. the amount of blood your heart pumps with each beat). The most effective type of training to improve your stroke volume seems to be lower-intensity/longer-duration work, because at high intensities, as the heart rate increases, there isn’t enough time between heart beats for the ventricles to full up. Your resting heart rate (RHR) is a rough indication of your SV (generally speaking, the lower your RHR the higher your SV).

The oxygen uptake system can be significantly influenced by both lower-intensity and higher-intensity training (start here for more info). An important difference here is that, while the adaptations of the oxygen transport system can be equally applied to all types of exercise (running, swimming, MMA, etc.), the adaptations of the oxygen uptake system are muscle-specific.

Energy System Interaction

This graph shows the theoretical ATP production over time when exercising at 100% effort:

But what happens when you are not doing a continuous all-out effort?

Here is the simplified description: At low intensities, the aerobic system burns fat and provides clean but slow energy. As the energy demands rise and the aerobic system alone is too slow to satisfy them, there is an increasing glycolytic system contribution and the aerobic metabolism gradually shifts from burning fat to burning glycolytic byproducts. As the intensity increases, the aerobic system reaches a point (when it crosses the AT) where it can no longer keep up with the glycolytic byproduct accumulation and the pH starts dropping. While the aerobic and glycolytic systems function in a continuum, the ATP/PCr system can be seen as a separate mechanism that provides brief bursts of energy, sort of like pushing the “nitro” button, but then needs some time to recharge.

For more details on energy system interaction, this article is a good place to start: Interaction among Skeletal Muscle Metabolic Energy Systems during Intense Exercise

And now, lets move on to the good stuff:

Building your Conditioning

The goal of conditioning training is simple: build up your energy systems so they can supply adequate energy for the type/rate/frequency of power production necessary for optimal performance in your sport. How you are going to reach that goal can be a bit more tricky, with countless training modalities thrown around (LSD, HIIT, threshold training, alactic training, lactacid training, whatever-the-fuck-training, and so on), but there can be some sense to all the madness:

Improving your Aerobic Power Capacity

A strong aerobic system allows for higher power production for a longer time (this obviously holds true for all but the very short-duration activities) as it results in a higher power output before reaching the AT and a higher power output and longer time to fatigue after surpassing it. For this reason, a good “aerobic base” is considered necessary for athletic conditioning development, as it offers the foundation to more effectively train and improve the anaerobic energy systems.

The initial stage of aerobic system development commonly includes large amounts of lower-intensity/longer-duration training, which results in central (increased SV) as well as peripheral (increased capillarity and increased mitochondrial quantity/size/enzymes - mainly in the slow-twitch muscle fibers, as these are the only fibers recruited) adaptations, while the second stage uses increasingly greater amounts of higher-intensity training to cause predominately peripheral adaptations (in both the slow-twitch and the fast-twitch fibers). The initial stage provides the grounds for the second stage to be more effective, because it develops the cardio capacity to provide adequate blood to the harder working muscles and develops the ability of the slow-twitch fibers to better deal with the greater glycolytic byproducts of the second stage.

Swimming is a great choice for general aerobic work due to its incorporating a great amount of muscle mass.

Improving your Glycolytic Power Capacity

  Glycolytic power production is dependent on three main factors: the “buffering capacity” (mainly dependent on the aerobic system adaptations, resulting in a higher AT), the capacity of the glycolytic energy system for max energy production (mainly dependent on the quantity and activity of local anaerobic enzymes), and the tolerance of a lowered pH (aka “acidosis tolerance”).

  As was already mentioned, the glycolytic system functions in a continuum with the aerobic system. The aerobic adaptations will improve the buffering capacity, the glycolytic power will be improved by training at or above the AT, and the acidosis tolerance will be improved by training above the AT with intensities/durations that will result in high lactate levels. On top of that, targeting maximal glycolytic power involves bouts of short duration and long breaks (wait a few more minutes for more on this).

It is generally believed that, while functioning in the same continuum, there is some degree of an antagonistic relationship between aerobic and glycolytic adaptations. That is to say, high volumes of aerobic training are generally believed to suppress the anaerobic enzymes, while frequent glycolytic training resulting in high lactate levels is generally thought to have the potential to harm overall endurance (maybe via damage on local aerobic adaptations on the slow-twitch fibers and/or via muscle damage and/or via hormone suppression). That is not to say higher-intensity work isn’t effective, as there is a good amount of evidence for its effectiveness. A good rule of thumb is to increase the workload and intensity gradually and to allow for adequate recovery (for muscle repair, glycogen replenishment and hormonal replenishment) between high-intensity sessions stressing the glycolytic system (HISS and HIIT), which is not that much different than what you’re doing with resistance training.

Rowing can be an option for non-specific upper-body conditioning.

Improving the ATP/PCr Power Capacity

  The ATP/PCr system duration can improve via a small increase in the substrates (stored ATP and PCr) and it’s power production may be also able to improve ever-so-slightly via a small increase in enzymes. The general potential for improvement in ATP/PCr energy production seems to be fairly limited and the main factors for improving explosive power production is not the energy system itself but rather the architectural adaptations in the working muscles (increased max strength, increased RFD, improved neuromuscular coordination for each particular motor pattern, etc.).

  All this doesn’t matter that much, as the type of training you would do to improve the ATP/PCr capacity is the same as the type of training you’re doing to increase the architectural properties: very short bouts of maximal effort with very long rest in-between bouts (to allow for the PCr to be fully “recharged”).

Building your Conditioning from the Ground Up

  A very general blueprint for conditioning training progression of an average beginner athlete starting from point zero could look like the following:
  1. a lot of lower-intensity work (ideally, this phase is carried out in developmental stages of young athletes): long-lasting structural adaptations towards a greater SV, local adaptations in the slow-twitch fibers (greater capillarity, more powerful mitochondria)
  2. some lower-intensity + some higher-intensity work (threshold training, or intermittent training slightly above AT): possible adaptations towards maintaining max SV at higher heart rates, local adaptations in the slow-twitch fibers, local adaptations in some faster-twitch fibers
  3. some lower-intensity + some very-high-intensity work: maintaining the previous long-lasting adaptations, building up the ability of the entire local aerobic system component to support all-out anaerobic efforts (both slow and fast-twitch fibers), building up anaerobic power
  • ATP/PCr power production is not directly dependent on the aerobic-glycolytic continuum, other than the fact that a higher aerobic capacity will translate to a faster PCr recharge (which can be rather important for a sport like MMA). ATP/PCr work is more related to the S&P part of the training equation, rather than the conditioning part and it is integrated in the general S&P progression which goes sort of like this: first improve strength, then improve power/speed, repeat.

  Keep in mind that, in a tactical sport like MMA, some smaller or greater amount of stimuli for adaptations/maintenance is going to come from actual sport training. You must also keep in mind that, while adaptations in the transport system are general and will fully transfer from one type of activity to another, the adaptations in the local components are generally muscle specific. So while super-intense cycling training that totally kicks your ass might make you a beast of a cycler, it won’t fully translate to MMA. That is why non-sport-specific conditioning is there to supplement the main sport work, rather than replace it.

Tennis is another example of a tactical sport where non-sport-specific conditioning is only there to supplement main sport work.

Ok, you sort of understood all that. But what exactly are you going to do in training? 

Training Modalities

Here is a brief description of the different ways you can work on your energy systems and how you should take your particular sport into consideration in order to program your training:

Low-Intensity Steady State (LISS)

  Also referred to as “long slow distance” (LSD), the name is pretty self-descriptive: intensity is bellow the AT and duration is very long (generally 40+ minutes). For any sort of meaningful adaptations you need to be working above ~120 bpm.

Threshold Training

  This is a steady state effort at the AT, with a general duration of roughly 20-40 minutes. It can be carried out as a single continuous effort, or it can be split up to several parts with small breaks (breaks lasting between 10-30 seconds).

High-Intensity Steady State (HISS)

  This is a steady sate effort above the AT, with a general duration of roughly 10-20 minutes. It can be carried out as a single continuous effort, or it can be split up to several parts with small breaks (breaks lasting between 10-30 seconds). Either way, it will result in significant levels of acidosis.

High-Intensity Intermittent Training (HIIT)

  Maximal or near-maximal bouts of effort, with a general duration of roughly 20 seconds to 2 minutes (endurance athletes may opt for up to ~5 minutes per bout). The break times can vary from 5-10 seconds for the 20-second intervals to ~3 minutes for the 2-minute intervals. This is sometimes referred to as “lactic tolerance training”.

Anaerobic Power Training

  Short bouts with very long breaks. When targeting the glycolytic system power production, the bouts typically last 15-30 seconds, and when targeting the ATP/PCr system the bouts typically last 5-6 seconds. Breaks generally last between 1-5 minutes.

The prowler can be used to add external resistance to HIIT and anaerobic power work.

Analyzing your Sport’s Energy Demands

  In order to come up with an effective conditioning program you need to analyze the energy demands of your sport to come up with specific conditioning goals. If you’ve read all of the above, it should be obvious that a sport like soccer (where the players can cover as much as 10 km per game or more) can have significantly different energy demands than a sport like volley (with short fast movements and explosive jumps). The main factors that determine the energy demands of your sport are the different types of activity involved and their duration, as well as the specific muscles/motor-patterns that are used (MMA examples in parentheses):
  • very-short/very-explosive spurts of activity (e.g. jumps, single power shots, takedown shoots, explosive sweeps) are mainly powered by the ATP/PCr system
  • high-intensity/medium-duration spurts of activity and static holds (repetitive jabs and combos, clinch grappling, a long takedown attempt, ground grappling) are mainly powered by the glycolytic system
  • lower-intensity/longer-duration activity (movement around the ring, recovery between rounds) is mainly powered by the aerobic system

  One last thing to take into consideration is that it’s not only about your sport, but it’s also about your position (in team sports) or even your personal style (in sports like MMA). In a sport like soccer, if you are the goalkeeper you will have significantly different energy demands compared to the field players, and in a sport like MMA, if your style is based on wrestling and grappling you will have significantly different energy demands compared to a style based on staying outside, stuffing takedowns and throwing power shots.

That's it, now make a plan and go to work!

Frequently Asked Questions

Q: I weigh 500 lbs. and I'm 5 feet tall, how do I lose weight?

A: Eat properly (adequate protein/EFA/micro intakes), create a caloric deficit (via eating less and/or burning more through any activity you can safely engage in), do some sort of strength training to retain muscle during weight-loss. For more info, have a look at this article.

Q: I've been training and/or doing various sports on and off for years. How do I know if I have a good aerobic base?

A: The aerobic capacity is usually estimated via measuring your VO2max through direct (graded tests with inhaled/exhaled gasses measurements) or indirect (field tests, like the Beep Test or the Cooper Test) ergometric tests, and comparing that with normative data for your age/gender and sport.

An easier way to get a rough idea of your aerobic capacity is through practical means. For instance, if you can spar/do bag work for multiple rounds at a 50-60% intensity without getting too winded, or if you can run 8km at/under 40 mins without coming to the verge of death, then your aerobic base is decent.

You can get a very rough indication of your aerobic capacity through your resting heart rate (generally the lower your RHR, the higher your stroke volume); athletes with good aerobic capacity tend to have a RHR under 60 bmp (athletes in endurance sports can get lower than 40 bmp). RHR is in no way a precise indication, but if your RHR is 80 then you'd probably benefit from steady-state work.

Q: Does it matter what types of exercises I use for interval training? I've heard some people say that running up hills is the best kind of interval training. Others swear by the prowler and yet others say conditioning ropes are the absolute best.

A: It matters. When it comes to localized adaptations (especially those from higher-intensity work), which muscles are incorporated (and even under which specific motor patterns) is important to get a better carryover to your actual sport.

Keep in mind that exercises can have different effects depending on how you use them (e.g. hill sprints can be used as ATP/PCr work to get stronger/more explosive, but can also be used as HIIT to work on lower-body endurance), and that they can have different effects depending on your deficits (e.g. if your aerobic system is lagging it may become the limiting factor to something like burpees).

Q: How about 'circuit training'? Is it effective to pick a bunch of exercises like lifting light weights, doing kinds of jumps, doing pullups and stuff like that, and just cycle through them continually, as quickly as possible?

A: Circuits can be useful for saving time when training for strength/hypertrophy/local muscular endurance, easing into training after a lay-off, and can even have cardiovascular benefits (look up PHA circuits for more on this). But when it comes to picking a random bunch of exercises and bundling them together into a circuit that feels hard and makes your muscles burn, you need to take a step back and ask yourself: "what are my goals and how is this going to help me achieve them?"

Q: How can I taper to reach optimal condition for my particular event?

A: The specifics of tapering can vary depending on the exact energy demands of your upcoming event. In general, the preparation plan for conditioning goes from high-volume/lower-intensity to lower-volume/higher-intensity while increasing the sport-specificity of your training, just like you would with S&P. The last 1-2 weeks need to have a particularly low volume of work, most of it having to do with your exact event, to allow for a full architectural/neural/metabolic recovery before the event. In a sport like MMA, making weight for a fight can be another thing to take into account.

Q: I've heard conditioning inhibits strength gains. Can I do both conditioning and strength training?

A: Short answer: Doing moderate amounts of LISS on your off days should be fine. When it comes to more intense endurance work, you might want to program it within a larger periodization plan.

Long answer: There is a significant number of studies on concurrent strength/endurance training, but the findings are contradictory: many studies find no inhibition, others do (for more, you can start by reading this). It seems that moderate LISS will not significantly harm any strength gains if done separately from strength training (as in 8 hours separately or more). It also seems ATP/PCr power work can be merged with your S&P programming (as was already explained). Other than that, the safest route might be to periodize your training, doing strength maintenance work when engaging in big amounts of endurance training, and visa versa (when your main goal is max squat gains, including 3 sessions of HIIT per week stressing the lower body might not be the best choice). In other words, use your brain: HIIT is typically like multiple high-rep sets to failure for the muscles involved; you wouldn't incorporate multiple workouts of multiple high-rep sets to failure during your max strength phase, would you?

Q: Athlete X has great conditioning and I've heard he never does any LISS. That means I shouldn't do any either, right?

A: Athlete X might have done long hours of LISS training in his younger formative years (which you might or might not have done), might have a genetic predisposition towards a high aerobic capacity (which you might or might not share), and might be getting an adequate training stimuli through his skills training to maintain his aerobic adaptations (a full-time professional athlete usually has the work capacity, as well as time availability, to train long hours on a daily basis). The training that works for him might not be optimal for you.

Q: Athlete X has great conditioning and I've heard he never does any HIIT. That means I shouldn't do any either, right?

A: Lets drive this point home: what works for a high-level athlete with different overall training, a different multi-year training history and possibly different genetic predispositions won't necessarily work for you. Conditioning training needs to be tailored to your individual needs.

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