You know strength: time to put the system back in energy system development

A Systematic Approach to Energy System Development for Field Sport Athletes

Introduction

The strength and conditioning field has evolved dramatically over the past decades. We've developed sophisticated periodization models, mastered load management principles, and created individualized programming based on comprehensive testing protocols. Yet despite this progress, one critical component remains dramatically underdeveloped: Energy System Development.

Walk into any coaching clinic and observe the disparity. Coaches take detailed notes on force-velocity curves, conjugate methods, and autoregulation strategies. Don't get me wrong, I love this stuff also! But shift the conversation to energy system development, and the sophistication disappears. Coaches revert back to generic protocols, replacing individualized programming and forgetting the importance of an evidence-based approach. "Mental toughness" becomes a substitute for physiological understanding. Arbitrary work-to-rest ratios replace evidence-based prescription. Athletes deserve better.

This educational gap represents a fundamental failure in our field. We've achieved remarkable precision in strength, power, and speed development while remaining primitive in conditioning methodology. The result is athletes who are incredibly strong but lack the energy system capacity to express that strength under the repeated, high-intensity demands of field sports.

It's time to apply the same systematic, evidence-based approach to conditioning that we've mastered in strength training. This means understanding energy system physiology, implementing individual assessment protocols, and programming with the precision we demand in all other areas.

The Problem: Educational Sophistication Gap

The field of strength and conditioning demonstrates a clear educational hierarchy. Strength training methodology has reached remarkable sophistication, supported by decades of research and practical application. Coaches understand periodization, autoregulation, and individualization principles. They can calculate training loads, manipulate volume and intensity, and adjust programming based on comprehensive assessment data.

The educational system provides excellent knowledge regarding aerobic system development for traditional endurance sports, running, cycling, and swimming, where single-modality training and clear performance metrics dominate. However, the application of conditioning principles to field sports, combined with our own strength-oriented bias in education and practice, has left us breathless when it comes to concrete conditioning systems.

Conditioning methodology for field sports, by contrast, remains largely generic and outdated. This disparity isn't accidental; it reflects fundamental differences in educational emphasis through individual biases and practical application.

This gap has serious consequences. Athletes develop incredible strength but lack the energy system capacity to express it repeatedly throughout competition. Field sport athletes who can squat enormous loads struggle to maintain movement quality during the fourth quarter, leaving them to reduced performance at best, and exposing them to injury at worst. The missing link isn't mental toughness, it's systematic energy system development.

Energy System Physiology: The Foundation

Effective conditioning requires understanding energy system physiology and its interactions during field sport activities. The traditional model of teaching energy systems as distinct entities operating in isolation fundamentally misrepresents metabolic reality. This is not the case; each of our primary energy systems works in conjunction towards the body's master goal: homeostasis. We need to maintain a constant level of ATP to support activity. Fatigue is not just a mental component. Fatigue is the inability to repeatedly express the required force to match the needs of the situation due to a lack of function somewhere along the physiological chain.

The Car Engine Analogy

Think of energy systems like a high-performance car with multiple power sources:

Phosphocreatine (PCr) System = Nitrous Oxide (NOS):

• Immediate, explosive power boost

• Only lasts 7-10 seconds before depletion

• Incredible acceleration and top-end speed

• Needs significant time to "recharge" between uses (50% restoration in ~30 seconds, 95% in ~3 minutes)

• Perfect for drag racing (short sprints, explosive movements)

Glycolytic System = Turbocharger:

• High-performance power for sustained speed

• Works optimally from 15-30 seconds to 1:30-2:00 minutes or so

• Generates a byproduct that eventually limits performance (no, it's not lactic acid)

• Generates lactate, which is used as an intra- or intermuscular fuel source

• Like driving hard up a mountain pass, powerful, but creates exhaust buildup

• Central to sustained high-intensity efforts

Oxidative System = Regular Engine with Cruise Control:

• Steady, reliable, efficient power for the long haul

• Can run indefinitely with proper fuel (oxygen)

• Doesn't overheat or create problematic byproducts

• Also serves as the "cooling system" that clears out metabolic byproducts

• Determines the ability to restore PCr stores and clear lactate

Just like you need all three systems in a high-performance car (NOS for launches, turbo for sustained power, regular engine for cruising), athletes need all three energy systems working together seamlessly for field sport success.

The Energy System Continuum

Energy systems don't function as switches that turn on and off based on exercise duration. Instead, they operate as a continuum, with all three systems contributing simultaneously but in varying proportions based on intensity and duration demands¹.

Side Note: The Lactate Misconception

A critical misconception persists regarding lactate's role in fatigue. Lactate itself is not the villain causing muscle fatigue—in fact, lactate serves as an important fuel source and can be utilized by both skeletal muscle and cardiac muscle during exercise.

The real culprits behind "lactate-associated" fatigue are:

• Hydrogen Ion Accumulation (H+): High-intensity glycolytic metabolism produces hydrogen ions, which lower intracellular pH and create an acidic environment that impairs muscle contraction.

• Metabolic Acidosis: The increasingly acidic environment interferes with calcium release from the sarcoplasmic reticulum and reduces the sensitivity of contractile proteins to calcium.

• Concurrent Metabolic Factors: Accumulation of inorganic phosphate, potassium efflux from muscle cells, and depletion of energy substrates all contribute to the fatigue process.

• Neural Factors: Central nervous system fatigue and altered motor unit recruitment patterns compound the peripheral metabolic limitations.

Understanding this distinction is crucial for conditioning prescription. Training the glycolytic system isn't about "teaching athletes to tolerate lactic acid," it's about improving the body's ability to buffer hydrogen ions, maintain cellular pH, and continue functioning in challenging metabolic environments.

Field Sport Energy System Interactions

Field sports demand sophisticated energy system interactions. A football play requires explosive speed (PCr system), sustained effort during the play (glycolytic system), and rapid recovery between plays (oxidative system). Soccer players need explosive acceleration (PCr), the ability to sustain high-intensity running (glycolytic), and the aerobic capacity to repeat these efforts throughout a 90-minute match (oxidative).

Understanding these interactions is crucial because training one system in isolation fails to prepare athletes for sport demands. Effective conditioning develops the capacity of these individual systems while training their integration during the actual sport-specific activities.

Assessment Foundations: MAS Testing and the Speed Reserve Concept

Just as strength training requires individual assessment through 1RM testing or other means, conditioning demands systematic evaluation of energy system capacity. The most practical and scientifically valid approach I've used centers on Maximal Aerobic Speed (MAS) determination, the conditioning equivalent of a training max that provides an individual reference point for training intensity prescription.

MAS represents the minimal speed that elicits maximal oxygen consumption during progressive exercise testing². Research consistently demonstrates that training at or near MAS intensity maximizes aerobic adaptations³. When athletes spend time above 90% maximum heart rate, significant improvements occur in VO₂max, lactate threshold, and running economy, making MAS the most effective intensity for aerobic system development.

While laboratory-based VO₂max testing provides the gold standard for MAS determination, field-based alternatives offer valid and reliable assessment for practical coaching environments. The Yo-Yo Intermittent Recovery Test Level 1 uses progressive shuttle running with increasing intensity, creating an intermittent protocol that mimics field sport demands while maintaining a strong correlation with laboratory-determined MAS (r = 0.71-0.87)⁴. (Send me a DM and I'll provide a calculator for you!) Similarly, the traditional beep test and Nike Spark Test provide accessible alternatives with established normative data and immediate calculation capabilities.

Beyond MAS determination lies an important theoretical concept that reinforces why speed development should remain a priority alongside conditioning: the Anaerobic Speed Reserve (ASR). This represents the difference between an athlete's maximum sprint speed and their MAS (ASR = Maximum Sprint Speed - MAS), providing crucial insight into exercise economy at submaximal intensities⁵.

The Speed Reserve concept demonstrates why we should always push the needle on speed development. An athlete with a maximum speed of 20 mph and MAS of 10 mph (ASR = 10 mph) will find running at 12.5 mph much less demanding than an athlete with a maximum speed of 16 mph and the same MAS (ASR = 6 mph). The higher speed reserve creates greater physiological headroom, making submaximal efforts more economical and sustainable. This theoretical framework reinforces the importance of concurrent speed and conditioning development rather than viewing them as competing qualities—higher maximum speeds enhance conditioning performance, while improved conditioning capacity supports speed development through enhanced recovery between efforts. Think in systems rather than silos!

The Big Three: Evidence-Based Conditioning Methods

With individual profiling established, in my eyes, three primary conditioning methods provide the foundation for field sport energy system development: Tempo Training, High-Intensity Interval Training (HIIT), and Repeat Sprint Training.

1. Tempo Training: Controlled Speed Development

Tempo training gained prominence through Charlie Francis's work with sprint athletes but has broader applications for field sport conditioning⁷. Francis used tempo runs to develop aerobic capacity while maintaining neuromuscular coordination at controlled speeds.

Extensive Tempo (70ish% Maximum Speed):

• Primary aerobic system development

• Active recovery between high-intensity sessions

• Movement pattern reinforcement at controlled intensities

Intensive Tempo (80-85ish% Maximum Speed):

• Lactate buffering capacity development

• Speed endurance training

• Transition between aerobic and anaerobic systems

Nathan Heaney's article on Sportsmith provides important context for tempo training application, however⁸. While tempo running effectively develops controlled high-speed running and movement quality, it may provide suboptimal aerobic stimulus for sports with high running demands. The typical tempo work-to-rest ratios (1:3 to 1:4) invert optimal aerobic training ratios (1:1 to 3:1), potentially limiting aerobic adaptations. I have found these ratios of (1:3 to 1:4) to be great for my athletes when it comes to improving their aerobic power and capacity; however this is a strong point to argue and might require individual investigation.

Practical Tempo Applications:

• Extensive Tempo: 8 × 100m at 70% max speed, 45-second active recovery

• Intensive Tempo: 6 × 150m at 85% max speed, 2-minute recovery

• Vector-Integrated Tempo: My favorite implementation strategy—combine linear running with lateral and diagonal movements. Get creative.

2. High-Intensity Interval Training (HIIT): MAS-Based Prescription

HIIT represents the most versatile conditioning method when properly prescribed using MAS-based intensities. Research consistently demonstrates that different HIIT protocols target specific energy system adaptations based on work duration, intensity, and recovery periods⁹.

Long HIIT (Mixed System Development):

• Work Duration: 2-4 minutes at 90-105% MAS

• Work-to-Rest Ratio: 2:1 to 1:1

• Physiological Target: Aerobic and anaerobic system integration

• Adaptations: Enhanced lactate buffering and oxygen kinetics

• Example: 4 × 3:00 minutes at 95% MAS, 1:1 W:R

Short HIIT (Aerobic System Development):

• Work Duration: 10-30 seconds at 110-130% MAS

• Work-to-Rest Ratio: 1:2, 1:1, or 2:1

• Physiological Target: Maximize time at VO₂max

• Adaptations: Improved oxygen delivery and utilization

• Example: 3 × 4:00 minutes, 15s:15s W:R at 110% MAS

Supramaximal HIIT (Anaerobic Development):

• Work Duration: 10-20 seconds at 110-130% MAS

• Work-to-Rest Ratio: 1:3 to 1:5

• Physiological Target: Anaerobic power and capacity

• Adaptations: Increased glycolytic enzyme activity and buffering capacity

Individual HIIT Prescription Based on MAS: The beauty of MAS-based prescription lies in its ability to provide an appropriate stimulus regardless of individual fitness level. All athletes work at percentages of their capacity, ensuring optimal adaptation stimulus.

3. Repeat Sprint Training: Field Sport Specificity

Repeat Sprint Ability (RSA), the capacity to perform multiple sprints with minimal speed decrement, represents perhaps the most important physical quality for field sport success¹⁰. Traditional endurance training fails to develop RSA because it doesn't replicate the neuromuscular and metabolic demands of repeated high-intensity efforts.

Complete Recovery Repeat Sprint Training:

• Work: 5-10 seconds maximal sprinting

• Recovery: <20-25s

• Purpose: Develop maximum speed and anaerobic power

• Adaptations: Enhanced PCr system capacity and neuromuscular coordination

• Example: 2 × 5:00 minutes, 30s rolling clock, 5:25s W:R (Done linear or multi-directional)

Incomplete Recovery Repeat Sprint Training (For specific groups):

• Work: 5-15 seconds high-intensity sprinting

• Recovery: 1:2 to 1:4 work-to-rest ratio

• Purpose: Develop repeat sprint ability under fatigue

• Adaptations: Improved lactate tolerance and aerobic contribution to recovery

RSA Training Prescription: The key distinction lies in training purpose. Complete recovery protocols develop speed and power qualities. Incomplete recovery protocols specifically train the ability to repeat efforts under progressive fatigue, the hallmark of field sport demands.

Advanced Integration: 8 Vector Movement System

The 8-vector system from Jordan Nieuwsma and Nick DiMarco has had a huge influence on my training and conditioning methodology. In my opinion, solely relying on traditional linear conditioning fails to prepare athletes for the multi-directional demands of field sports. My primary philosophy around this concept is to work at reducing the change of direction deficit many athletes experience when transitioning from pure training to heavy on-field practice and competition.

The 8 Vector ESD Framework: In the interest of this newsletter, this doesn't need to be a super-structured component. Rather, I want to challenge you to get out and watch the sports you work with. Figure out a few key movement qualities and patterns the athletes are tasked with and develop your training to expose them to these in a controlled and progressive manner.

1. Linear Forward: Traditional sprinting patterns

2. Linear Backward: Backpedaling and deceleration

3. Lateral Left/Right: Side shuffling and cutting

4. Diagonal Forward Left/Right: 45-degree movements

5. Diagonal Backward Left/Right: Retreat angles

Vector-Integrated Conditioning Benefits:

• Movement Competency: Develops coordination and efficiency across all movement planes required in field sports.

• Tissue Robustness: Exposes tissues to varied loading patterns, potentially reducing injury risk through adaptive tissue responses.

• Sport Specificity: Better replicates the unpredictable movement demands of competition.

• Change of Direction Deficit Reduction: Systematic exposure to direction changes during conditioning improves movement efficiency and reduces speed loss during cutting maneuvers.

Practical Vector Integration:

Multi-Directional Tempo:

• Course Design: 40m forward → 20m lateral → 20m diagonal → 40m backward

• Intensity: 75% effort throughout

• Recovery: 60-90 seconds between repetitions

• Purpose: Aerobic development with movement integration

Vector-Based HIIT:

• Work: 45 seconds moving through 6 different vectors

• Intensity: 90% MAS equivalent effort

• Recovery: 45 seconds passive rest

• Purpose: Energy system development with sport-specific movement patterns

Systematic Programming: Periodization Principles

Effective conditioning requires systematic progression following established periodization principles. The same concepts governing strength training periodization apply to energy system development: progressive overload, specificity, and planned variation. Remembering back to the topic of speed reserve, not included below is the speed development component to training—sprinting stays a critical factor throughout the year.

Phase 1: Aerobic Base Development (Weeks 1-4)

• Primary Focus: Aerobic system capacity building

• Methods: Extensive tempo and long HIIT at 85-95% MAS

• Volume: High (longer sessions, where accumulation is the goal)

• Intensity: Moderate to high aerobic zones

• Recovery: Complete between sessions

Phase 2: Mixed System Integration (Weeks 5-8)

• Primary Focus: Aerobic and anaerobic system coordination

• Methods: Short HIIT, modified repeat sprint training (more aerobic)

• Volume: Moderate (balanced work and recovery)

• Intensity: Mixed aerobic and anaerobic zones

• Recovery: Planned incomplete recovery protocols

Phase 3: Competition Preparation (Weeks 9-12)

• Primary Focus: Sport-specific energy system demands

• Methods: Repeat sprint training, supramaximal HIIT methods to capitalize on lactate exposure

• Volume: Lower (high intensity, reduced volume)

• Intensity: Competition-specific demands

• Recovery: Mimics sport rest periods

Individual Programming Modifications:

Speed Profile Athletes:

• Extend Phase 1 duration (additional aerobic base building)

• Emphasize incomplete recovery protocols in Phase 2

• Focus on repeat sprint ability in Phase 3

Aerobic Profile Athletes:

• Accelerate progression through Phase 1

• Emphasize anaerobic development in Phase 2 and 3

• Include more explosive, short-duration efforts

Real-World Application: The Ithaca College Field Hockey Model

During my time at Ithaca College, I implemented this systematic approach with the field hockey team, creating an individualized energy system development program that demonstrated the power of MAS-based conditioning. Using Yo-Yo Intermittent Recovery Test scores, I calculated each athlete's MAS and subsequently categorized players into three groups: Gold, Blue, and White buckets.

Each bucket received individualized prescriptions for total yardage based on the time interval being targeted. For example, during 4-minute aerobic intervals at 90% MAS, Gold athletes (higher MAS) would cover significantly more distance than White athletes (lower MAS), but both groups would experience the same physiological stimulus. This approach ensured that every athlete had semi-individualized and attainable goals that pushed them toward their potential without leaving anyone behind.

The results were remarkable. Instead of watching some athletes struggle to complete sessions while others barely broke a sweat, every player was appropriately challenged. More importantly, athletes understood why they were running different distances—it wasn't about ability or effort, but about individual physiology and systematic progression.

Practical Implementation: MAS-Based Programming

Building on this real-world application, the following provides specific programming examples using MAS-based prescription:

MAS Calculation Example: Athlete completes Yo-Yo IR1 Test, reaching Level 17.4 MAS = 8.1 + (Level × 0.25) = 8.1 + (17.4 × 0.25) = 12.5 mph

Training Zone Calculations:

• 70% MAS = 8.5ish mph (Extensive Tempo)

• 85% MAS = 10ish mph (Intensive Tempo)

• 90-100% MAS = 11ish mph (Aerobic HIIT)

• 120+% MAS = 14ish mph (Anaerobic HIIT)

Sample Session Designs:

Aerobic Power Session (Long HIIT):

• Warm-up: 15 minutes progressive build to 80% MAS

• Main Set: 5 × 3 minutes at 90-95% MAS, with 1:1 W:R ratio.

• Purpose: Maximize VO₂max stimulation.

Repeat Sprint Session:

• Warm-up: Dynamic preparation + progressive speed build-ups

• Main Set: 3 sets of 4:00 minutes × 30s Rolling clock × 7s:23s W:R at 100% effort with 1-2 minute rest between sets.

• Purpose: Develop RSA under progressive fatigue

Vector-Integrated Session:

• Warm-up: Multi-directional movement preparation

• Main Set: Multi-directional Short Intervals- 3 X 4:00 min, 10s:20s W: R at 110% of MAS with 1 -2 minutes rest between sets.

  • Station 1: Continuous 10 yds down + back (180-degree cuts).

  • Station 2: Cross field zig-zag runs (135-degree cuts)

  • Station 3: Continuous Box cuts (90-degree cuts).

• Purpose: Energy system development with movement specificity

Monitoring and Assessment

Systematic conditioning requires ongoing monitoring to ensure appropriate adaptations and prevent overreaching. Multiple assessment strategies provide comprehensive feedback:

Weekly Monitoring:

• Session RPE using 1-10 scale for internal load quantification

• Heart rate response during standardized submaximal efforts

• Movement quality assessment during conditioning sessions

• Subjective wellness questionnaires

Monthly Testing:

• Repeat MAS testing to track aerobic improvements

• Maximum speed assessment for ASR calculation

• Sport-specific repeat sprint protocols

• Reassessment of Speed Reserve Ratio for program adjustment

Seasonal Evaluation:

• Comprehensive fitness testing battery

• Sport-specific performance markers

• Training load analysis and adaptation verification

• Program effectiveness evaluation and modification

Common Implementation Errors

Despite sophisticated understanding, several common errors limit conditioning effectiveness:

Error 1: Intensity Prescription Without Individual Reference Using arbitrary percentages or generic protocols instead of MAS-based prescription results in inappropriate training stimuli. Solution: Always base conditioning intensities on individual MAS values.

Error 2: Ignoring Speed Reserve Profiles Applying identical protocols to athletes with different Speed Reserve Ratios produces variable and often suboptimal responses. Solution: Modify training methods based on individual Speed Reserve characteristics.

Error 3: Confusing Speed Development with Conditioning Using incomplete recovery during maximum speed training or excessive volume during power development compromises both qualities. Solution: Clearly distinguish training purposes and apply appropriate protocols.

Error 4: Linear Movement Bias Exclusive use of straight-line running fails to prepare athletes for sport movement demands. Solution: Integrate multi-directional patterns throughout conditioning programs.

Error 5: Inadequate Recovery Prescription

Inappropriate work-to-rest ratios compromise training adaptations and increase injury risk. Solution: Match recovery periods to training objectives and energy system targets.

Conclusion: Precision Over Tradition

The strength and conditioning field stands at a critical juncture. We can continue applying outdated conditioning methods based on tradition and subjective assessment, or we can embrace the same systematic, evidence-based approaches that have revolutionized strength training.

The science is clear. Individual assessment protocols exist. Programming methodologies are established. The tools for sophisticated conditioning are readily available.

What's required now is educational commitment. Coaches must invest the same energy in understanding energy system development that they've devoted to strength training principles. This means studying exercise physiology, implementing assessment protocols, and programming with scientific precision.

The athletes we serve deserve nothing less. They deserve conditioning programs built on the same evidence-based foundation that guides everything else we do. They deserve individual assessment, systematic progression, and methods that actually prepare them for sport demands.

The choice is clear: continue relying on generic protocols and hoping for the best, or start treating conditioning with the sophistication it demands and the results it can deliver.

Your athletes' fourth-quarter performance depends on which path you choose.

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References:

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2. Daniels J, Scardina N. Interval training and performance. Sports Med. 1984;1(4):327-334.

3. Laursen PB, Jenkins DG. The scientific basis for high-intensity interval training. Sports Med. 2002;32(1):53-73.

4. Bangsbo J, et al. The Yo-Yo intermittent recovery test. Sports Med. 2008;38(1):37-51.

5. Buchheit M. The 30-15 intermittent fitness test: accuracy for individualizing interval training of young intermittent sport players. J Strength Cond Res. 2008;22(2):365-374.

6. Sandford GN, et al. Anaerobic speed reserve: a key component of elite male 800-m running. Int J Sports Physiol Perform. 2019;14(4):501-508.

7. Francis C. Training for Speed. Ottawa: Charlie Francis; 1997.

8. Heaney N. Maximal aerobic speed vs. Tempo: Which is optimal for team sport aerobic fitness? Sportsmith. 2024.

9. Laursen PB, Buchheit M. Science and application of high-intensity interval training. Champaign: Human Kinetics; 2019.

10. Bishop D, et al. Repeated-sprint ability - part II: recommendations for training. Sports Med. 2011;41(9):741-756.

11. Nimphius S, et al. Change of direction deficit: A more isolated measure of change of direction performance than total 505 times. J Strength Cond Res. 2016;30(11):3024-3032.

12. McArdle WD, et al. Exercise physiology: Nutrition, energy, and human performance. 8th ed. Philadelphia: Wolters Kluwer; 2015.

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