Putting the C in S&C: An Energy Systems-based Approach

Putting the C in S&C

By Marc Lewis and Travis Pollen

Pavlov ConditioningDon’t get us wrong: when it comes to building durable athletes, strength is the foundation. However, oftentimes coaches become so single-minded that they practically forget about conditioning. Or at the very least they misapply it.

Consider the following scenario:

It’s day one of pre-season for [insert intermittent high-intensity sport], and your athletes show up in a sorry state of conditioning.

As an experienced coach, you know that specificity is of the utmost importance. That is, you want to improve your athletes’ efficiency and proficiency in qualities based on the unique demands of their sport. In this case, short-duration, long rest sprints most closely mimic game-like conditions.

After the skill-based work is done for the day, you have a couple of options:

(a) You can run through a few short sprints with plenty of rest, or

(b) You can hold off on the sprints for a few weeks until the players have developed their aerobic base.

Team Running

Plenty of coaches will choose option (a). They’re not wrong, per se, but given their players’ current level of fitness, they’re likely not training the specific qualities they think they are.

Sure, sprints on day one would be subjectively difficult for the athletes (think Pukie the Clown). But without a baseline level of aerobic fitness, the athletes wouldn’t be capable of approaching game speeds, and the objective intensity would therefore be lacking. Not only that, fatigue would likely lead to suboptimal mechanics – especially in inexperienced or younger athletes – and the ingraining of undesirable motor patterns for future practice and competition.

Performance Enhancement or Impairment?

This conundrum begs the following all-important question: is your conditioning program really improving your athletes’ performance, or are you simply driving them into the ground?

Hockey Team Exhausted

To answer this query in the former, a systematic “energy systems-based” approach must be taken. While many volumes have been written on the subject, we’re going to boil down the design of a purposeful and scientifically-based conditioning program to just four steps:

  1. Understanding the energy systems of the human body
  2. Identifying the specific demands of the sport through the needs analysis
  3. Selecting optimal training protocols, parameters, implements, and modalities to elicit the desired adaptations
  4. Specifying a periodization scheme to progress athletes through the season

Step 1. An Energy Systems-based Approach

In order to maximize specificity (Step 2), our approach relies first and foremost on a keen understanding of the energy systems of the human body and the interactions thereof.

Over a decade ago in his book Core Performance, EXOS founder and president Mark Verstegen used the expression “energy systems development” to refer to conditioning. This designation could not be more apropos.

The three energy systems – adenosine triphosphate-phosphocreatine (ATP-PCr), anaerobic glycolysis, and oxidative phosphorylation (aerobic) – work in parallel to power activity, thereby dictating all aspects of conditioning (1). They differ by the intensity and duration of the activity they power as well as the amount of energy they provide per reaction.


Energy Systems Chart

It’s important to note that although one energy system will predominate at any given time depending on the activity, the systems do not work independently. Rather, they’re very much intertwined – each one active, to a degree, at all times in order to power activity.

The precise extent to which each system provides energy at any given moment depends, of course, on an individual athlete’s conditioning (and the resulting anaerobic and aerobic adaptations from that conditioning).

The musculoskeletal adaptations and implications for performance for both aerobic and anaerobic metabolism are summarized in the table (1):

Anerobic Aerobic Adaptations Chart

It All Starts With the Aerobic Base

As we alluded to earlier, intensity of objective load, not subjective effort, determines the energy pathway utilized. In order to access anaerobic pathways at high objective intensities, we must build the proper aerobic base. Without it, deconditioned athletes who are asked to immediately train at high intensities will be training effortfully, but not objectively intensely.

So how exactly does the aerobic base lay the foundation for the anaerobic energy pathways to thrive?

The most fundamental aerobic adaptation involves fuel utilization and efficiency. Developing an aerobic base allows athletes to become glycogen-sparing, through having the ability to produce more energy oxidatively via both fats and carbohydrates. Aerobically trained athletes are thereby able to utilize fat for energy at higher relative intensities, while also producing more energy from carbohydrates oxidatively. This allows the glycogen in the muscles and liver to be used to fuel even higher intensity activity (2, 3, 4).

In addition, aerobic training increases capillary density, which allows for heat, carbon dioxide, and other metabolic byproducts to leave the muscles more quickly. This adaptation equates to faster metabolic recovery times, both between high intensity bouts as well as between games. In a similar vein, aerobic training improves heart rate recovery through improved cardiac function, which also impacts autonomic balance, circulation, and immune function.

Lastly, aerobic training also improves work efficiency, which is the ratio of work output to oxygen cost. In plain terms, aerobically trained athletes conserve energy better when they move, especially when the modality or movement is specific to their competition tasks (2, 3, 4).

These adaptations overlap to improve performance in other ways, as well. For example, aerobically trained athletes are better able to train at higher objective intensities while perceiving those intensities to be lower (i.e. a lower intensity of effort for a given objective intensity). Moreover, these athletes have greater work capacity and ability to recover adequately from those higher volume loads.

Step 2. Specificity and the Needs Analysis

We define specificity, once again, as the targeted improvement of athletes’ efficiency and proficiency for the unique demands of their sport. These unique demands are determined by Step 2 of the conditioning planning process: the needs analysis (5).

When conducting a need analysis, not only do we evaluate the specific athletic qualities required by the sport (and positions within the sport), but we also assess athletes’ standing relative to these demands.

The analysis of the sport begins with the following identifications (5):

  • Level of play: youth, high school, collegiate, professional, or recreational
  • Predominant energy systems: dictated by intensity and duration of work and rest
  • Physiological attributes: muscular strength, endurance, power, etc. that are vital to the sport and skill/task of the athlete
  • Movement patterns and skills: principle and “contrasting” (i.e. those that are absent or less common in the sport)
  • Injuries: common sites and mechanisms
  • Season layout and external factors: phase of season (i.e. pre-season, in-season, post-season), practice and competition schedule, outside stressors (i.e. academics, travel); implications for periodization (see Step 4)

Next, we evaluate the training backgrounds and statuses of the athletes in relation to the above findings, including the following pieces of information (5):

  • Competitive and training background: type, years, frequency, intensity
  • Level of aerobic fitness: physiological (laboratory) and/or performance (field) measures in a modality as closely related to the target activity as feasible
  • Movement screening and technical proficiency: mastery of sports-specific positions and skills
  • Physical exam: injury history, anatomical or physiological risk factors and/or abnormalities

Step 3. Training Protocols and Parameters

Now that energy systems principles and athletes’ needs have been established as per Steps 1 and 2, we must determine the best way to elicit the desired training responses.

Hopefully we’ve hammered home the importance of the aerobic base. But does that mean that we should have every athlete, regardless of sport and position, go out and jog a few miles on the first day of preseason? Of course not! We must now apply the principle of specificity in order to develop the energy systems in the proper context.

Football Team Conditioning

For example, let’s say we have professional football linemen who need to develop an aerobic base. At upwards of 300 pounds, running for hours on end would be ill-advised for several reasons. First, it’s nonspecific; rarely will the players be required to run long distances in competition. It’s also high-risk from an injury perspective. Finally, such training could interfere with important performance parameters like strength and power.

Thus, in order to develop the linemen’s oxidative energy pathway safely, effectively, and in parallel with their sport’s movements, we must employ more “creative” modalities and implements. A few such examples include prowler pushes, tire flips, sandbag carries, and kettlebells swings – all worked within the target heart rate (THR) range of aerobic development (60-80% of heart rate reserve) and not beyond.

For more ideas on conditioning implements, consult the Selected Conditioning Implements table, where we’ve broken down the perks of some of the more popular conditioning implements into two categories, traditional and contemporary.

Conditioning Implements

Specific versus Non-specific

The football lineman example illustrates an important and often overlooked concept. When developing energy pathways that are less specific to a particular sport (i.e. the aerobic system for linemen), specificity of modality and implement is of the utmost importance. That is, in this scenario we want the conditioning work to mimic the game.

Conversely, when developing energy systems that are highly specific to the sport, specificity of modality is slightly less important due to the high training volume using that pathway already accomplished through practice of the sport itself. For example, since a lineman will spend the majority of his practice time developing the anaerobic energy pathways, the modality used in conditioning maybe of a more general nature (i.e. can freely engage in high-intensity sprinting, cycling, or strongman-type training).

See table for an in-depth comparison of specific and non-specific implementation.


Energy Systems Development Pyramid

Our Energy Systems Development Pyramid further illustrates the specific versus non-specific concepts. On the left, we have the aerobic/endurance athlete and on the right the strength/power athlete. Although both types of athletes must build the aerobic base of the pyramid first, the specificity of such training is obviously high for the endurance athlete and low (“general”) for the strength/power athlete. Moving up the pyramid, the degree of specificity/generality for each type of athlete flip-flop.

Energy Systems Pyramid

Manipulation of Training Parameters

In order to target specific energy systems, we tweak the following variables to the desired levels:

  • Volume/duration: During aerobic development, the duration is generally at least 20 minutes, while the volume is low (i.e. one session consisting of 30 minutes of activity between 60-80% of heart rate reserve). During anaerobic development the duration is generally less than 90 seconds while the volume is much higher (i.e. glycolytic development may consist of 6 x 20 second max effort sprints with 3 minute rest intervals).
  • Work-to-rest ratios: Work-to-rest ratios must be determined based on the target energy system. They must enable athletes to recover enough to work the same energy system again upon returning to work. Recovery consists not only of breathing rate, but also replenishment of metabolic stores and clearance of accumulated lactate and other metabolic byproducts. In the glycolytic development example above, 20 seconds of work and 3 minutes of rest equates to a 1:9 work-to-rest ratio. For the ATP-PCr system, up to a 1:20 ratio is not out of the question.
  • Training density: Training density (volume per unit time) can be used to manipulate loading schemes in order to train in a fatigued state (an advanced method), which can replicate “game-like” situations. In addition, training density can be manipulated to progressively overload an energy system (i.e. shortening work-to-rest ratios or increasing volume within a specific time frame).
  • Intensity of load: The objective load can be determined by the percentage of max heart rate, heart rate reserve, VO2max, or VO2reserve. Other objective measures include the heart rate or VO2 at the onset of blood lactate, the lactate threshold, as and metabolic equivalents for physical activities (METs). Most recently, heart rate variability (HRV) has been used as an objective monitoring tool to determine the training agenda for the day and monitor the recovery of their athletes. In most cases, HRV is used in conjunction with a “session rating of perceived exertion” (sRPE) scale, which is a subjective determination of the intensity of a training session.

For more on the above measures and other physiological concepts discussed in this article, check out the Sport and Exercise Physiology Testing Guidelines developed by the British Association of Sport and Exercise Science.

  • Intensity of effort: The subjective load can be determined using a variety of rating of perceived exertion scales (i.e. 10-point scale), as well as the aforementioned sRPE scale. Additionally, coaches can obtain subjective feedback in the form of a formal questionnaire or simple conversation (“How do you feel?”) in order to determine both the quality of training and recovery.

The table illustrates some of the most common techniques for manipulating the above variables in order to elicit specific outcomes:


Step 4. Periodization for Each Unique Situation

Just as we wouldn’t bring our athletes into the weight room on day one and have them squat 400 pounds without developing a baseline of movement efficiency, we also know not to program high-intensity sprint work without first building a solid aerobic base.

Such a foundation — progressed in a periodized manner — enables our athletes not only to reach the desired intensities in practice, but also to recover from such bouts. Furthermore, periodization of aerobic and anaerobic training gives athletes time to adapt, recover, and respond to new and greater training stimuli (8).

Determining the appropriate periodization scheme for conditioning depends on a multitude of factors, as dictated by the needs analysis (Step 3). Above all, time of season and timing are crucial. If the sport has an off-season training component, it provides enough time to develop an aerobic base and periodize subsequent adaptations in a linear manner (i.e. one at a time, “stacked” on top of one another).

In contrast, let’s say our sport has a very short preseason before competition starts. The athletes are deconditioned (i.e. lack the proper aerobic base), but we have limited time to develop all the necessary adaptations. In this case, we must adopt an undulating periodization scheme that allows for the development of multiple energy pathways in a short period of time. We might choose to alternate between days of lower intensity aerobic and higher intensity anaerobic conditioning.

Using undulating periodization, we won’t maximize the adaptations of any of the energy pathways; however, we will be able to simultaneously build the aerobic base and improve the anaerobic system. No matter the periodization scheme, gradual increases in volume, intensity, and recovery techniques are the key to keeping athletes healthy.

Fitting It All In

There you have it: our four-step guide to energy systems-based conditioning.

But you may still be wondering, how the heck does all this conditioning fit in with what you’re already doing from a practice and strength training standpoint?

Here are a few quick tips for maximizing your efforts and time:

  • Strategically organize conditioning and resistance training bouts. When possible, separate sessions by at least three hours.
  • To promote recovery, intersperse higher intensity training with other types of lower intensity training.
  • Refuel properly in between conditioning bouts and strength training (mixed meals with a high-quality protein source of 20-25 grams).
  • Ensure all conditioning has a purpose. Always ask the question, what adaptation are we chasing, and how does what we’re doing improve performance?
  • Use the most effective and efficient modalities and technique available.

For even more ideas on optimizing multiple aspects of training, check out Marc’s write-up, “How To Maximize Concurrent Training.

About the Authors


Marc Lewis, CSCS, TSAC-F, ACSM-EP-C, ACSM-CPT is a graduate teaching/research assistant in the Department of Kinesiology at the University of North Carolina at Greensboro, as well as the co-owner of Winston Salem Personal Training, INC in Winston-Salem, North Carolina.

Twitter: @mtlewis14

Facebook: http://www.facebook.com/marc.lewis.CSCS

Personal Training: www.winstonsalempersonaltraining.com



Travis Polen

Travis Pollen is an NPTI certified personal trainer and American record-holding Paralympic swimmer. He is currently pursuing his Master’s degree in Biomechanics and Movement Science at the University of Delaware.

Facebook: www.facebook.com/fitnesspollenator

Blog: www.FitnessPollenator.com





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  1. Very interesting read; thanks a lot !
    Just to be sure; is there a contradiction between the text (specific vs non specific) and the “energy systems development pyramid” in terms of specificity level / type of athlete ?

      • In the text it says the movement modality needs to be MORE specific when training for the less-dominant energy system as it applies to sport. Then it says the movement modality can be LESS specific when training the more dominant energy system as it pertains to sport. The pyramid would appear to show otherwise.
        So for a distance runner, I would take this to mean that oxidative training could include a broader movement modality, while training the ATP/Phosphagen pathway would require movements most closely similar to running (e.g. sprints). That would not align with the pyramind

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