Sports Science Fundamentals: Physiology, Testing, and Recovery

Posted on Nov 6, 2025 in Physical Activity and Sports Sciences

Energy Systems, Fitness Components, and Performance Testing

ATP and Energy Systems

  • ATP (Adenosine Triphosphate) – Molecule that provides energy for muscle contractions. Limited storage.

  • Aerobic – With oxygen.

  • Anaerobic – Without oxygen.

Three Main Energy Systems

  1. ATP–PCr System (Anaerobic)

    • Duration: ~5 seconds or less.

    • Very high intensity.

    • Uses stored creatine phosphate (CP).

    • Recharges ATP without oxygen.

  2. Glycolysis System (Anaerobic)

    • Duration: 30 seconds–3 minutes.

    • High intensity.

    • 2 ATP from glucose, 3 ATP from glycogen.

    • Occurs in the sarcoplasm.

  3. Oxidative System (Aerobic)

    • Low–moderate intensity, long duration.

    • Slowest but most efficient.

    • Occurs in mitochondria.

    • Uses carbohydrate oxidation or fat oxidation.

All three systems work together; dominance depends on intensity and duration.

Creatine Phosphate (PCr)

  • Stored in muscle in small amounts.

  • Used for very short, explosive efforts.

  • Anaerobic — no oxygen required.

Fitness Components and Performance Tests

Cardiorespiratory Endurance

  • Ability of heart and lungs to supply oxygen during sustained activity.

  • Tests: VO₂ max, Yo-Yo intermittent recovery, Queens College step test, Cooper 12-minute run.

Body Composition

  • Ratio of muscle, fat, bone, and other tissues.

  • Tests: Weight, DXA scan, skinfolds, bioelectrical impedance.

Muscular Strength

  • Maximum force a muscle can produce in one effort.

  • Tests: 1RM, handgrip dynamometer, isokinetic testing.

Muscular Endurance

  • Ability of muscles to perform without fatigue.

  • Tests: Push-ups, prone hold, wall sit, dead hang.

Flexibility

  • Range of motion at a joint.

  • Tests: Goniometry, sit-and-reach, Apley scratch.

Agility

  • Change position quickly and accurately.

  • Tests: Illinois agility, T-test, reactive agility test.

Coordination

  • Use senses and body parts together smoothly.

  • Tests: Agility T-test, Y-balance, hand-eye coordination, reaction time, sport-specific drills.

Balance

  • Maintain equilibrium (stationary or moving).

  • Tests: Quiet stance, single-leg stance.

Power

  • Rate of performing work.

  • Tests: Countermovement jump, horizontal jump, medicine ball throw, Wattbike 6-second test.

Speed

  • Perform a movement quickly.

  • Tests: Flying 30m sprint, 10m sprint, 20m sprint, 20m shuttle run.

Why Assess Performance?

  • Performance evaluation

  • Individualized training programs

  • Injury prevention

  • Progress monitoring

  • Talent identification and development

  • Research and scientific analysis

Test Principles

  • Specificity: Match test to sport’s movements and energy demands.

  • Validity: Measures what it’s supposed to measure.

  • Reliability: Consistency/repeatability.

  • Standardization: Consistent administration.


Research Methods and Data Analysis Fundamentals

The Scientific Method

  1. Ask a question

  2. Do background research

  3. Construct a hypothesis

  4. Test with an experiment

  5. Analyze data and draw conclusions

  6. Report results

Types of Research

  • Qualitative: Text-based data – interviews, focus groups, observations.

  • Quantitative: Number-based data – surveys/questionnaires, experiments, longitudinal, cross-sectional.

Research Variables

  • Independent Variable (IV): Factor manipulated/observed to predict an outcome.

  • Dependent Variable (DV): Measured outcome to assess IV’s effect.

Descriptive Statistics

Purpose: Summarize collected data without predictions.

Central Tendency:

  • Mean – Average.

  • Median – Middle value.

  • Mode – Most frequent value(s).

Spread:

  • Range – Maximum minus Minimum.

  • Standard Deviation (SD) – Average distance from mean.

  • Quartiles – Four equal parts of dataset.

Handling Outliers in Data

  • Identify: Box plots, statistical tests.

  • Analyze: Determine cause (error, natural variation, significant result).

  • Decide: Keep, transform, or remove.

  • Document: Rationale and method for transparency.

Confidence Intervals

  • Range likely to contain the true population mean.

  • Indicates reliability of estimate.

Skewness (Data Distribution)

  • 0: Symmetrical

  • >0: Positive skew → tail to higher end

Kurtosis (Peakness of Distribution)

  • 3: Normal (Mesokurtic)

  • >3: Peaked (Leptokurtic)


Recovery Methods and Sleep Science for Athletes

Selye’s General Adaptation Syndrome (GAS)

  • Framework describing:

    1. Imposed training stress →

    2. Acute fatigue response →

    3. Adaptation →

    4. New homeostasis

  • Key for understanding training load, recovery, and performance progression.

Effective Recovery Strategies

  • Purpose: Restore physical and mental well-being, reduce overtraining risk, maintain performance, prevent injuries, support long-term development.

  • Strategies:

    • Evidence-supported: Nutrition, hydration, sleep, water immersion, compression, massage.

    • Other: Fads with minimal evidence.

  • Recovery is essential for sustainable performance.

Defining Sleep

“A reversible, naturally occurring state of reduced responsiveness to external stimuli and relative inactivity, with distinct brain wave cycles essential for physical and mental recovery.”

The Importance of Adequate Sleep

Lack of sleep → Decreased vigilance, thinking, decision making, reaction time, mood, cognitive function.
Adequate sleep → opposite effects (enhanced performance and mood).

Stages of the Sleep Cycle

Two main phases in ~90 minute cycles:

  1. Light NREM Stage 1 — Drowsy, 1–7 minutes

  2. Light NREM Stage 2 — Memory consolidation, 10–25 minutes

  3. Deep NREM Stage 3 — Body repair and regeneration, 20–40 minutes

  4. REM Sleep — Vivid dreams, high brain activity, 10+ minutes

Regulation of Sleep

  • Circadian Rhythm

    • 24-hour internal body clock (SCN in hypothalamus).

    • Controlled by light/dark cycles.

    • Melatonin rises in evening, falls in morning.

  • Sleep Pressure (Homeostasis)

    • Builds with adenosine during wakefulness.

    • Cleared during sleep.

Methods for Measuring Sleep

  • Polysomnography — Lab gold standard.

  • Actigraphy — Wrist-worn movement monitoring.

  • Questionnaires and diaries.

  • Wearable trackers.

Key Sleep Metrics

  • Sleep latency — Time to fall asleep.

  • Sleep efficiency — Percentage of time in bed actually asleep.

  • Wake after sleep onset — Time spent awake during the night.

Sleep Regularity

  • Consistent sleep/wake timing equals better quality sleep and performance.

  • Stronger mortality predictor than total sleep duration.

Understanding Chronotype

  • Morning type — Peak alertness earlier.

  • Evening type — Peak later.

  • Intermediate — More flexible.

  • Match activities and recovery to natural rhythm:

    • Morning types: schedule high-focus tasks early.

    • Evening types: avoid early competitions without adjustment.

    • Travel/competition: shift schedule gradually in advance.

Applying Chronotype to Recovery

  • Time naps, contrast baths, mental training when least alert.

  • Schedule cognitive-demanding tasks in peak alertness zone.

Essential Sleep Hygiene Tips

  • Keep consistent bedtime/wake time.

  • Avoid caffeine/alcohol close to bed.

  • Reduce screen light before sleep.

  • Relax before bed (reading, meditation).

  • Keep bedroom cool, dark, quiet.

Sleep Extension

  • Intentionally increasing sleep beyond normal baseline can improve performance, reaction time, and recovery in athletes.


Nutrition for Health and Athletic Performance

1. Nutrition Basics

  • Nutrition = science of obtaining and using nutrients for growth, metabolism, health.

  • Nutrients: perform physiological/biochemical functions.

  • Energy Flow: Sun → plants → animals → humans (chemical energy → ATP).

2. Macronutrients

  • Carbohydrates (CHO): main muscle/brain fuel, stored as glycogen.

    • Simple (1–2 sugars) vs. Complex (3+ sugars + fiber)

    • 1 g CHO = 4 kcal.

  • Fats (Lipids): long-term energy, hormones, cell membranes, vitamin transport (A, D, E, K), brain/nerves.

    • Essential FAs: linoleic (Ω-6), α-linolenic (Ω-3)

    • 1 g fat = 9 kcal.

  • Protein: tissue structure, enzymes, hormones; 20 amino acids (9 essential).

    • 1 g protein = 4 kcal.

3. Micronutrients

  • Vitamins:

    • Fat-soluble: D, E, K, A

    • Water-soluble: B, C

  • Minerals: bone health, nerve signals, fluid balance, oxygen transport, enzyme activation.

4. Energy Systems and ATP

  • ATP = usable energy currency; limited stores.

  • Fuel sources: CHO, fat, protein.

  • 1 cal = 4.18 kJ.

5. Energy Expenditure (EE)

  • RMR (Resting Metabolic Rate): 60–80% EE sedentary / ~40% in athletes; increased muscle increases RMR.

  • TEE (Total Energy Expenditure) = RMR + TEF (food thermic effect) + AEE (activity)

    • AEE = ExEE + NEAT.

  • Low Energy Availability = intake < needs → decreased performance, increased health risk.

6. Dietary Analysis Methods

  • Prospective: log in real-time.

  • Retrospective: recall past intake.

7. Body Composition Metrics

  • FFM (Fat-Free Mass): muscle, bone, water, organs.

  • BMI (Body Mass Index): weight/height² (kg/m²) – cannot distinguish muscle vs. fat.

  • WHR (Waist-to-Hip Ratio): fat distribution risk (>0.9 men, >0.85 women).

  • Body Fat %: health/performance metric.

  • BIA (Bioelectrical Impedance Analysis): electrical resistance to measure composition.

8. Sports Nutrition Strategies

  • Pre-exercise fuel:

    • CHO focus (1–4 g/kg, 1–4 hours before)

    • Avoid high fat/fiber close to exercise.

  • During exercise:

    • For exercise lasting >60 minutes: Consume CHO (30–60 g/hr) and electrolytes.

  • Post-exercise recovery:

    • CHO + protein (3:1 ratio) within 30–60 minutes.

    • Rehydration: replace 150% of fluid lost.

  • Hydration guidelines:

    • Monitor urine color.

    • Avoid both dehydration and overhydration (hyponatremia).

  • Supplements:

    • Only if diet insufficient; evidence varies.

    • Common: creatine, caffeine, beta-alanine.