How A Personal Trainer Can Use Interval Training

Avatar for Hadyn Luke Hadyn Luke posted this on Tuesday 12th of September 2023 Hadyn Luke 12/09/2023


How A Personal Trainer Can Use Interval Training


Today’s personal training fitness blog looks at using interval training when setting cardiovascular training programmes. Many personal trainers and sports conditioners will learn about the use of interval training whilst studying towards their Level 3 personal training course, as it allows their clients to work at a higher intensity and achieve more targeted results.

Intervals comprise of a period of work, followed by a period of recovery, for a pre-planned period of time. The work period can be followed by either active rest, where there is still dynamic movement but at a reduced rate, or passive rest, where the client is essentially still and resting. It is typical that between 5-10 repetitions are completed, with the use of sets when applicable. 

For example- 5 reps of 45 seconds at 10kmph on a treadmill followed by 90 seconds of recovery walking at 5kmph on a treadmill. 3 sets with 4 minutes rest between each set. So the client will complete a total of 15 reps over 3 sets.

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    Types of Intervals

    Depending on the specific goal, a personal trainer will devise the appropriate interval training programme.  All three primary energy systems, Creatine Phosphate, Aerobic and Lactate can be targeted using interval training. 

    Creatine Phosphate Intervals

    • Objective: Boost explosive power.
    • Intensity: High (90-100% VO2max, RPE 9/10).
    • Duration: Brief (0-10 seconds).
    • Ideal For: Sprinters and short-distance track cyclists.

    Lactic Acid Intervals

    • Objective: Enhance the body’s ability to manage lactic acid build-up
    • Intensity: Moderate to high (70 – 90% VO2max, RPE 8-10)
    • Duration: Extended (1-3 minutes)

    Aerobic Intervals

    • Objective: Conditioning, calorie burn, and client enjoyment.
    • Intensity: Moderate (60-70% VO2max).
    • Duration: Varying (1-5 minutes).

    Aerobic intervals can also be used to taper intensity of a training programme and are often used as recovery sessions or as conditioning sessions for the de-conditioned.  They also allow for maximal enjoyment for the client with minimal boredom and discomfort while ensuring fitness progression, higher calorie burning and a sense of achievement.  These periods of work and rest are normally between 1-5 minutes and at an intensity of 60-70% VO2max.

    A personal trainer will devise an interval training programme depending on their client’s fitness: someone new to the gym will obviously follow a different regime from a professional athlete. Variables of interval programme design could include the targeted energy system, work and rest period ratios, intensities, reps and sets.

    Creatine Phosphate

    To improve a client’s creatine phosphate anaerobic energy system, a personal trainer will have them working maximally at 90-100% of their VO2Max for a duration of 5-15 seconds. As this involves working at high intensity, the ratio of recovery will need to be relatively high, for example 1:6. So a client might work for 10 seconds and recover for 60 seconds. In sports training, this is particularly effective for anyone competing over short distances, such as a 100m sprinter or a short-distance track cyclist.  Activities where maximal recruitment of fast twitch muscle fibres are needed for short periods of time will benefit from this method of training.

    Lactic Acid

    To create lactic acid the duration will need to be longer: anything from 30 seconds up to 2-3 minutes, depending on how well conditioned the client is. For a shorter work period, the intensity could be as high as 85-90% VO2Max; for an longer work duration it should be closer to 70-85% VO2Max.

    The ratio of work to rest should be from 1:2 up to 1:4. So a personal trainer will devise an interval training programme where the client works for one minute and recovers for four minutes.

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      Aerobic Fitness

      The final interval training ratio is for aerobic fitness, which facilitates aerobic endurance and stamina. Here, the client would work on a broader RPE scale depending on the length of training and fitness level of the client: anything from 3-4 up to 6-7. The ratio would be 1:1 or lower, so a one-minute run would be followed by a one-minute rest period.  The rest period could be half the time of the work period as the intensity should be more manageable targeting the aerobic system in the whole part.  Shorter rest period are required as there is a lack of lactate acid building up.


      To keep clients engaged and challenged, trainers can:

      • Increase reps or sets
      • Reduce work or rest interval times
      • Adjust work-to-rest ratios
      • Adjust the intensity of work or rest intervals via speed, incline resistance 

      For example, with lactic acid training at a ratio of 1:4, the client might work for one minute and recover for four minutes and then repeat that four times, making four reps in one set. In time, the trainer might increase the volume of reps in a set, so the client could carry out five reps for each set. The number of sets can then be increased for a higher volume of work.

      An alternative approach is to reduce the recovery period.  For example in the above example the rest period of four minutes could be reduced to 3.5 minutes altering the ratio of 1:4 to 1:3.5.  This allows for less recovery between work periods and increases the frequency of work demands on the cardio-vascular and muscular systems therefore increasing the intensity.

      A further option includes increasing of the work or rest intensity and completing the same reps / sets and ratio of work to rest.

      Different approaches will work better with differing clients of differing motivations and goals.  But it is fun to experiment.


      Personal trainers will generally recommend interval training rather than exercising at a steady rate (LSD / continous training). Interval training requires the body to generate more energy and therefore take in more oxygen to generate it.  When a body is unable to take in more oxygen, energy starts to be created through the lactate system. During the recovery periods, the heart rate remains high to continue to supply the body with oxygen to “neutralise” the lactic acid produced (the EPOC or Excessive Post-exercise Oxygen Consumption effect).  The overall effect of this training system is an increase in calories burnt in relation to LSD training for the same duration.

      If you would like more information on personal trainer courses, visit Level 3 Diploma in Personal Training.

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