What are the three energy systems in HSC PDHPE?

The ATP-PC (alactacid) system uses creatine phosphate for roughly 10 to 12 seconds of maximal effort with no fatiguing by-product. The lactic acid system uses carbohydrate anaerobically for roughly 30 seconds to 3 minutes, fatiguing through hydrogen-ion accumulation. The aerobic system fully oxidises carbohydrate, fat and some protein for minutes to hours, fatiguing through glycogen depletion and dehydration. All three operate at once; the proportions shift with intensity and duration.

What are the principles of training?

Progressive overload, specificity, reversibility, variety, training thresholds, and warm-up and cool-down. Progressive overload is the gradual increase in stimulus over time. Specificity means adaptation matches the demand. Reversibility is the loss of adaptation when training stops. Variety sustains motivation and stimulus. Thresholds calibrate intensity. Warm-up and cool-down protect against injury. Exam questions almost always require you to apply them to a named athlete.

What physiological adaptations occur with aerobic training?

Resting heart rate falls as the left ventricle strengthens, stroke volume and maximal cardiac output rise, VO2 max increases through better oxygen delivery and extraction, capillary and mitochondrial density increase in slow-twitch fibres, and total haemoglobin mass rises. Lung capacity itself changes little; what improves is the efficiency of gas exchange and breathing pattern.

How does the inverted-U hypothesis describe arousal and performance?

Performance rises with arousal up to an optimal point, then declines as arousal continues to rise. The optimal level depends on the task: fine-motor skills such as golf putting need low arousal, while power and gross-motor skills such as sprinting or tackling need high arousal. Athletes manage toward their optimum using relaxation to lower arousal or self-talk and music to raise it.

What are the four psychological strategies in Core 2?

Concentration (attentional focus, pre-performance routines, cue words), mental rehearsal (visualising the performance in vivid sensory detail), relaxation techniques (diaphragmatic breathing, progressive muscle relaxation, calming imagery), and goal-setting (outcome, performance and process goals, often using the SMART framework). Strong answers use them in combination rather than as isolated tools.

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HSC PDHPE Core 2 Factors Affecting Performance: deep-dive 2026 guide

Deep-dive on HSC PDHPE Core 2 Factors Affecting Performance. The three energy systems, types of training, principles of training, physiological adaptations, sport psychology, nutrition and skill acquisition, with model extended responses and exam-style practice.

Generated by Claude Opus 4.718 min readNESA-PDHPE-CORE-2Updated 2026-05-24

Jump to a section

How Core 2 fits into HSC PDHPE
The three energy systems
Types of training
Principles of training
Physiological adaptations to training
Sport psychology
Nutrition and recovery
Worked example 1: an 8-mark analyse response
Worked example 2: a 5-mark applied response
Check your knowledge
Related guides

How Core 2 fits into HSC PDHPE

Core 2, Factors Affecting Performance, is the sport-science half of the course. It explains what makes an athlete fast, strong or skilled: how the body fuels movement, how training drives adaptation, how psychology shapes performance, and how nutrition and skill acquisition complete the picture. Core 2 underpins the Sports Medicine and Improving Performance options and appears in Sections I and II of the HSC exam.

Like Core 1, Core 2 is framework-driven, but here the frameworks are physiological. The energy systems, the principles of training and the stages of skill acquisition are the scaffolding for nearly every extended response. Markers reward precise terminology applied to a single carried-through example, usually one athlete or one sport.

The three energy systems

ATP (adenosine triphosphate) is the universal fuel for muscle contraction. Stored ATP lasts only a couple of seconds; everything else is the body resynthesising ATP through three routes.

ATP-PC (alactacid) system

Fuel source. Creatine phosphate stored in muscle.
Efficiency. The fastest resynthesis but a small total yield because stores are limited.
Duration. Roughly 10 to 12 seconds at maximal intensity.
Cause of fatigue. Depletion of creatine phosphate.
By-products. None that cause fatigue.
Recovery. Rapid, roughly 50 percent restored in 30 seconds and full restoration in 3 to 5 minutes.

Dominant in short explosive efforts: a 100m sprint, a maximal jump, a tennis serve.

Lactic acid system

Fuel source. Carbohydrates (muscle glycogen and blood glucose) broken down anaerobically.
Efficiency. Fast but inefficient, only 2 ATP per glucose molecule.
Duration. Roughly 30 seconds to 3 minutes at high intensity.
Cause of fatigue. Accumulation of hydrogen ions lowering muscle pH. Note that it is the hydrogen ions, not lactate itself, that cause fatigue; lactate is a useful fuel shuttled to other tissues.
By-products. Lactate and hydrogen ions.
Recovery. 20 to 60 minutes; active recovery clears lactate faster than passive recovery.

Dominant in the 400m run, 100m swim, and middle-distance finishing sprints.

Aerobic system

Fuel source. Carbohydrates, fats, and in long events some protein, fully oxidised in the mitochondria.
Efficiency. Slow resynthesis but a very high yield, 36 to 38 ATP per glucose molecule.
Duration. Minutes to hours, limited by fuel availability.
Cause of fatigue. Glycogen depletion, dehydration, electrolyte imbalance, hyperthermia.
By-products. Carbon dioxide and water, neither fatiguing.
Recovery. Glycogen restoration can take 24 to 48 hours after full depletion.

Dominant in the marathon, long-distance cycling, and the base running of team sports.

Types of training

Different sports demand different fitness components, and different methods build different components.

Aerobic training. Continuous (steady effort, 20-plus minutes at 60 to 80 percent maximum heart rate), fartlek (continuous with irregular bursts), aerobic interval (structured repeats near lactate threshold), and circuit (stations in sequence with limited rest).
Anaerobic training. Anaerobic interval training, in two forms: short intervals of 10 to 30 seconds targeting the ATP-PC system, and long intervals of 30 seconds to 2 minutes targeting the lactic acid system.
Flexibility training. Static (held at end range), ballistic (bouncing, higher injury risk), PNF (partner-assisted contract-relax, large gains), and dynamic (controlled sport-specific movement, now standard in warm-ups).
Strength training. Resistance training as the general category, including isotonic (muscle changes length, concentric and eccentric), isometric (force with no length change, such as a plank), and isokinetic (constant velocity, specialised equipment).

The right method depends on the sport's energy-system mix and dominant fitness components. A 100m sprinter prioritises short anaerobic intervals, heavy isotonic strength and dynamic flexibility; a marathon runner prioritises continuous training and aerobic intervals; a soccer player needs the full mix.

Principles of training

The syllabus names seven principles, and exam questions almost always require you to apply them to a named athlete.

Progressive overload. Gradual, systematic increase in stimulus, the practical rule being roughly 10 percent per week. Overload can come from intensity, volume, frequency or density.
Specificity. Adaptation matches the demand, across muscle group, energy system, movement pattern and speed of movement.
Reversibility. Adaptations are lost when training stops. Aerobic gains decline faster (within 2 to 3 weeks) than strength gains (4 to 6 weeks).
Variety. Novelty sustains motivation and stimulus, but within a structured program, not randomly.
Training thresholds. The aerobic threshold zone runs roughly 60 to 85 percent of maximum heart rate; the anaerobic threshold sits above roughly 85 percent. A useful estimate of maximum heart rate is the Tanaka formula:

HR_{max} \approx 208 - (0.7 \times \text{age})

A 17 year old has an estimated maximum heart rate of roughly $208 - (0.7 \times 17) = 196$ bpm, giving an aerobic zone of roughly 118 to 167 bpm.

Warm-up. Raises body temperature, blood flow and joint range, and primes the nervous system, reducing injury risk.
Cool-down. Gradually lowers heart rate, clears lactate, and prevents blood pooling, followed by static stretching.

Physiological adaptations to training

Training works because the body adapts. The syllabus expects these adaptations and the training that causes each.

Resting heart rate falls (from roughly 70 to 80 bpm toward the 40s in trained endurance athletes) because a stronger left ventricle pumps more blood per beat. Caused by aerobic training.
Stroke volume and cardiac output rise. Cardiac output equals heart rate multiplied by stroke volume:

\text{Cardiac output} = \text{Heart rate} \times \text{Stroke volume}

At rest, cardiac output is similar for everyone (around 5 L/min), but the trained athlete achieves it with a lower heart rate and higher stroke volume. At maximal effort, a trained endurance athlete can reach 30 to 40 L/min versus around 20 L/min untrained.

VO2 max (the maximum rate of oxygen uptake and use, in mL/kg/min) rises through better cardiac output, more capillaries and mitochondria, and improved respiratory efficiency.
Lung capacity itself changes little; what improves is gas-exchange efficiency and breathing pattern.
Haemoglobin mass rises, increasing oxygen-carrying capacity. Iron deficiency, more common in adolescent female endurance athletes, blunts this adaptation.
Muscle hypertrophy is the increase in fibre cross-sectional area from sustained mechanical loading, driven by resistance training. Early strength gains (first 2 to 3 weeks) come from improved neural recruitment, not growth.
Fibre adaptations. Slow-twitch (Type I) fibres adapt to aerobic training with more mitochondria and capillaries; fast-twitch (Type II) fibres adapt to anaerobic and strength training with greater size and glycolytic enzyme activity. The broad fibre-type ratio is largely genetic.

Sport psychology

Two athletes with identical physical preparation can perform very differently because psychology is the variable.

Motivation comes in four overlapping types: intrinsic (from within the activity), extrinsic (external rewards), positive (drawn toward a desired outcome) and negative (driven by fear of an undesired one). The most durable performers are primarily intrinsically and positively motivated.
Anxiety and arousal. Trait anxiety is a stable personality characteristic; state anxiety is situational and manageable. Arousal is physiological activation. The inverted-U hypothesis (Yerkes-Dodson) says performance rises with arousal to an optimum, then falls; fine-motor skills need low arousal, power skills need high arousal.
Psychological strategies. Concentration (pre-performance routines and cue words), mental rehearsal (vivid visualisation), relaxation (diaphragmatic breathing, progressive muscle relaxation, imagery), and goal-setting (outcome, performance and process goals). Strong answers combine them.

Nutrition and recovery

The syllabus splits nutrition into three timing windows. Pre-performance focuses on topping up muscle glycogen and arriving well-hydrated, including carbohydrate loading for endurance events over 90 minutes. During performance, the aim is to maintain blood glucose and replace fluid and electrolytes, scaling carbohydrate intake with event length. Post-performance follows the 3-R framework: refuel (carbohydrate), repair (protein) and rehydrate, with the first 30 to 60 minutes being the most receptive window. Of the supplement categories, caffeine and creatine have the strongest evidence; most well-fed athletes need few supplements.

Recovery strategies span physiological (cool-down, hydration, nutrition), neural (sleep, light activity), tissue damage (ice, compression, rest) and psychological (relaxation, debrief) approaches.

Worked example 1: an 8-mark analyse response

Worked example 1: analyse the energy systems in one sport

Prompt: "Analyse how the three energy systems contribute to performance in a sport of your choice. Refer to fuel source, duration and cause of fatigue." (8 marks)

Choose the 800m run, the canonical example because it uses all three systems substantially.

ATP-PC system: Fuel source: creatine phosphate stored in muscle. The explosive start and the accelerations on the curves draw almost entirely on ATP-PC. Duration: roughly 10 seconds at maximal intensity before stores deplete. Cause of fatigue: depletion of creatine phosphate.
Lactic acid system: Fuel source: muscle and blood glucose via anaerobic glycolysis. The fast first lap and the closing sprint draw heavily on this system. Duration: roughly 30 seconds to 3 minutes at high intensity. Cause of fatigue: accumulation of hydrogen ions lowering muscle pH and impairing contraction.
Aerobic system: Fuel source: carbohydrates and fats oxidised in the mitochondria. The middle of the race, and recovery between surges, draw on the aerobic system. Duration: sustainable for minutes to hours. Cause of fatigue: glycogen depletion and dehydration over longer efforts.
Analysis: The 800m blends all three: ATP-PC and lactic acid dominate the opening surge, the aerobic system supplies a large share through the body of the race, and the lactic acid system supplies the finishing kick despite mounting acidosis. The systems do not switch cleanly; they overlap continuously, which is why an 800m runner trains all three through interval, repetition and tempo work. Performance is best understood as the proportions shifting with pace, not as one system handing over to the next.

Worked example 2: a 5-mark applied response

Worked example 2: apply progressive overload and specificity

Prompt: "Apply the principles of progressive overload and specificity to a training program for an athlete of your choice." (5 marks)

Choose a 1500m runner.

Progressive overload is the gradual, systematic increase in training stimulus. For the 1500m runner this means increasing weekly mileage by no more than about 10 percent per week, increasing interval intensity across a training block (for example, working a set of 12 by 400m from a slower to a faster target pace over several weeks), and lengthening the long run as the base phase progresses. The athlete keeps adapting because the demand keeps growing, but only enough to provoke adaptation, not enough to cause injury.

Specificity is that adaptation matches the demand. The 1500m runner's training must reflect 1500m demands: aerobic capacity, lactate-threshold tolerance, and the ability to hold near-maximal pace for roughly four minutes. In practice this means most training is done running rather than cycling or swimming, interval work is done at and slightly faster than race pace, and tempo runs sit at lactate threshold. Specificity rules out spending hours on unrelated bike intervals or heavy strength work that does not transfer to running economy.

Together the principles explain why the program looks the way it does: progressively harder running work at running-specific intensities. They operate jointly, since overload without specificity wastes adaptation potential and specificity without overload produces a plateau.

Check your knowledge

A mix of definitional, explanation and exam-style questions covering Core 2. Answer under timed conditions, then check against the solutions block.

Name the three energy systems and state the fuel source and cause of fatigue for each. (6 marks)
Explain why the lactic acid system produces only 2 ATP per glucose molecule while the aerobic system produces 36 to 38. (3 marks)
Distinguish between continuous training and aerobic interval training, and name one athlete who would use each. (4 marks)
Define progressive overload and explain one risk of applying it incorrectly. (3 marks)
Using the formula for cardiac output, explain why a trained athlete has the same resting cardiac output as an untrained person despite a much lower resting heart rate. (4 marks)
Describe the inverted-U hypothesis and explain why a golfer and a powerlifter have different optimal arousal levels. (4 marks)
Describe how an athlete could combine all four psychological strategies before a major final. (6 marks)
Outline the three nutrition timing windows and state the main goal of each. (4 marks)

Solutions

Q1: ATP-PC: fuel is creatine phosphate, fatigue is depletion of creatine phosphate. Lactic acid: fuel is carbohydrate (glycogen and glucose) used anaerobically, fatigue is hydrogen-ion accumulation lowering muscle pH. Aerobic: fuel is carbohydrate, fat and some protein oxidised in the mitochondria, fatigue is glycogen depletion, dehydration and hyperthermia.
Q2: The lactic acid system breaks glucose down only as far as lactate, without oxygen, capturing just 2 ATP per glucose molecule. The aerobic system fully oxidises glucose through the Krebs cycle and electron transport chain in the mitochondria, releasing far more stored energy and yielding 36 to 38 ATP per molecule. Complete oxidation is slower but far more efficient per molecule of fuel.
Q3: Continuous training is sustained steady effort, typically 20-plus minutes at 60 to 80 percent maximum heart rate, building the aerobic base; a marathon runner uses it as the bulk of training. Aerobic interval training is structured repeats near lactate threshold with short defined rests, building VO2 max and threshold; a distance runner or rower uses it. Continuous training is steady, interval training is broken into hard efforts with rest.
Q4: Progressive overload is the gradual, systematic increase in training stimulus over time so the body keeps adapting. Applying it incorrectly, typically by increasing several variables at once or by more than about 10 percent per week, compounds risk and commonly causes overuse injury or burnout because the body is loaded faster than it can recover and adapt.
Q5: Cardiac output equals heart rate multiplied by stroke volume. At rest the body's oxygen demand is the same for everyone, so resting cardiac output is similar (around 5 L/min). The trained athlete has a much higher stroke volume from a stronger left ventricle, so the same cardiac output is achieved at a lower heart rate. The product stays constant because the rise in stroke volume offsets the fall in heart rate.
Q6: The inverted-U hypothesis states that performance rises with arousal to an optimal point, then declines as arousal continues to rise. A golfer performs a fine-motor, precision skill (putting), which is disrupted by even moderate arousal through tremor and concentration errors, so the optimum is low. A powerlifter performs a gross-motor, maximal-force skill, which benefits from high arousal and adrenaline-driven force production, so the optimum is high.
Q7: Goal-setting establishes process goals for the final ("control the first section, accelerate at the planned point"). Mental rehearsal is done daily beforehand, visualising the venue, opponents and race plan in vivid sensory detail. Relaxation techniques such as slow diaphragmatic breathing and progressive muscle relaxation are applied in the call room to bring spiking state anxiety down toward the optimum. Concentration is anchored by a consistent pre-performance routine and cue words at the start line. The strategies work together to bring the athlete to the start with arousal near optimum and attention on the next action.
Q8: Pre-performance: top up muscle glycogen and arrive well-hydrated, including carbohydrate loading for events over 90 minutes. During performance: maintain blood glucose and replace fluid and electrolytes, scaling carbohydrate with event length. Post-performance: restore glycogen, repair muscle and rehydrate (refuel, repair, rehydrate), with the first 30 to 60 minutes the most receptive window.