Interval Training

This lesson covers interval training as required by the OCR GCSE PE specification (J587). In the OCR specification, interval training is a broad training method that encompasses several sub-types, including HIIT. Understanding the concept of work:rest ratios is central to this topic, and you must be able to explain how interval training can be adapted for different sports and fitness goals.

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What Is Interval Training?

Definition: A training method that involves alternating periods of high-intensity work with periods of rest or low-intensity recovery.

The defining feature of interval training is the structured alternation between work and rest. Unlike fartlek training (which is flexible and unstructured), interval training follows a pre-planned pattern.

Key Features

Feature	Detail
Work periods	Intense exercise targeting a specific energy system
Rest periods	Recovery between work periods — can be complete rest or active recovery (e.g. walking, light jogging)
Work:rest ratio	The relationship between work time and rest time
Repetitions (reps)	The number of work periods in a set
Sets	Groups of repetitions
Energy systems	Can target aerobic or anaerobic systems depending on work:rest ratios and intensity

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Work:Rest Ratios

The work:rest ratio determines the nature of the training and the energy system targeted:

Goal	Work:Rest Ratio	Example
Aerobic endurance	1:0.5 or 1:1	3 minutes running at 70% max HR, followed by 1.5–3 minutes recovery
Anaerobic endurance	1:2 to 1:3	30 seconds at 90% max effort, followed by 60–90 seconds recovery
Speed / power	1:5 to 1:10	6-second maximal sprint, followed by 30–60 seconds recovery

graph LR
    A["Work Period<br>(high intensity)"] --> B["Rest Period<br>(recovery)"]
    B --> C["Work Period<br>(high intensity)"]
    C --> D["Rest Period<br>(recovery)"]
    D --> E["...Repeat"]

    style A fill:#e74c3c,color:#fff
    style B fill:#2ecc71,color:#fff
    style C fill:#e74c3c,color:#fff
    style D fill:#2ecc71,color:#fff

Why Work:Rest Ratios Matter

• Short rest (relative to work) = the aerobic system is trained because the body does not fully recover between efforts, forcing the heart and lungs to work continuously.
• Long rest (relative to work) = the anaerobic system is trained because the body recovers enough to perform maximally in each work period, targeting speed and power.

Exam Tip: OCR examiners frequently ask you to "suggest an appropriate work:rest ratio" for a named sport or fitness goal. Always justify your choice — e.g., "A 1:3 ratio would be appropriate for a sprinter because the long rest allows full recovery of the ATP-PC system, enabling maximum-intensity efforts in each work period."

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HIIT (High-Intensity Interval Training)

HIIT is a sub-type of interval training characterised by very short bursts of maximal or near-maximal effort followed by brief recovery periods.

Key Features of HIIT

Feature	Detail
Work intensity	85–100% of maximum effort
Work duration	Typically 20–60 seconds
Rest duration	Typically 10–60 seconds
Session length	Usually 15–30 minutes in total
Energy systems	Primarily anaerobic, but also improves aerobic capacity

Example HIIT Session

Exercise	Work	Rest
Burpees	30 seconds	15 seconds
Squat jumps	30 seconds	15 seconds
Mountain climbers	30 seconds	15 seconds
Tuck jumps	30 seconds	15 seconds
Repeat circuit 3–4 times	—	2-minute rest between circuits

Advantages of HIIT

• Time-efficient — significant fitness gains in short sessions.
• Improves both aerobic and anaerobic fitness.
• Increases metabolic rate for hours after the session ("afterburn effect").
• Can be done with minimal or no equipment (bodyweight exercises).
• Addresses tedium — the short, intense bursts keep the session engaging.

Disadvantages of HIIT

• Very demanding — not suitable for beginners or those with health conditions without careful modification.
• High risk of injury if technique deteriorates during maximal efforts.
• Requires adequate recovery between sessions (typically 48 hours).
• Difficult to maintain motivation for repeated maximal efforts.

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Applying Interval Training to Different Sports

Sport	Interval Training Design	Justification
100 m sprint	6 × 60 m sprints, 1:8 work:rest ratio	Mimics the maximal effort and ATP-PC energy system demands of the event
Football	10 × 30-second runs at 85% max HR, 1:2 ratio	Replicates the repeated high-intensity running with brief recovery seen in a match
800 m running	5 × 400 m at race pace, 1:1 ratio	Develops anaerobic endurance and lactate tolerance specific to the event
Swimming (100 m)	8 × 50 m at 90% effort, 1:3 ratio	Specific to the distance, environment, and muscle groups used
Netball	15 × 20-second sprints with direction changes, 1:2 ratio	Mimics the repeated short sprints and rest periods in the game

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Advantages and Disadvantages of Interval Training (General)

Advantages	Disadvantages
Highly adaptable — work:rest ratios can be adjusted for any sport or fitness goal	Can be mentally demanding — repeated high-intensity efforts require strong motivation
Can target aerobic or anaerobic systems	Requires careful planning — work:rest ratios, sets, and reps must be calculated correctly
Can be made sport-specific by including sport-related movements	Risk of injury increases at higher intensities
Allows precise control of training intensity	Requires adequate recovery time between sessions
Time-efficient compared to continuous training	May require a track, timer, or other equipment for accurate measurement

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How Overload Is Applied in Interval Training

FITT Variable	How to Apply
Frequency	Add more sessions per week
Intensity	Increase the speed or effort during work periods
Time	Increase the number of reps or sets; reduce rest periods
Type	Change the exercises or movements used in the intervals

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Common Exam Mistakes

• Not understanding work:rest ratios. If the question says the work period is 30 seconds and the ratio is 1:3, the rest period is 90 seconds (30 × 3). Students often get this calculation wrong.
• Confusing interval training and fartlek training. Interval training is structured with planned work and rest periods. Fartlek is flexible and unstructured.
• Suggesting interval training is only anaerobic. Interval training can target the aerobic system if longer work periods with shorter rest periods are used.
• Ignoring the sport-specific element. When asked about a specific sport, the intervals should mimic the demands of that sport — sprinters need short maximal efforts, midfielders need repeated moderate-to-high intensity efforts.

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Summary