Interval Training – What Ratio Is Best?

Avatar for Hadyn Luke Hadyn Luke posted this on Wednesday 15th of December 2021 Hadyn Luke 15/12/2021


Interval Training – What Ratio Is Best?

In previous blogs we have investigated How a personal trainer can use interval trainingInterval training to motivate a client and progress fitness and Fat-burning zone – marvel or myth?. In this week’s blog we are looking at interval training ratios.


Interval training is used within personal training and gym programmes to improve results for anyone from regular gym goers to those participating in sports and athletics at a high level.

It involves a period of work followed by an active or passive rest period.

High-Intensity Interval Training (HIIT) is particularly popular at the moment and has remained in the top three of the Worldwide Survey of Fitness Trends released by the American College of Sports Medicine (ACSM) ever since it first appeared on the list in 2014 (see our blog on Results of the 2017 Worldwide Survey of Fitness Trends).

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    Interval training can be used to target all three primary energy systems: creatine phosphate, aerobic and lactic acid.


    Ratio: the aerobic ratio is: 1:1 to 1:0.5. This is to suggest you would start at the highest ratio (1:1) and over time progress on to the harder ratio (1:0.5)

    This equates to: four minutes of work followed by four minutes of rest, repeat x desired number of reps. Or 4 minutes work followed by 2 mins rest, repeat x desired reps.

    Minimum work duration: to ensure that the energy system used is aerobic and not lactic acid, the minimum work duration should be two minutes.

    Maximum work duration: depends on the individual’s goals. If they are training for a marathon, they might carry out 1 or 2 mile intervals. These could be four-minute miles to 15-minute miles, depending on their ability and fitness levels. For recreational use, a two-minute interval would be more appropriate.


    Ratio: the lactic acid ratio is: 1:4, 1:3 or 1:2. It is recommended you start on the highest ratio (1:4) and progress down the ratio’s as your lactic acid tolerance and lactic acid removal pathways improve.

    This equates to: one minute of work followed by a four-minute rest; or 30 seconds of work followed by a 90-second rest; or 30 seconds of work followed by a 60-second rest. Each protocol would be repeated for the desried number of reps.

    Minimum work duration: 15 seconds, in order to promote the use of the lactic acid system rather than the ATP/CP system (creatine phosphate).

    Maximum work duration: this will vary depending on fitness level and lactic acid tolerance. For example, a highly trained athlete will be able to maintain a higher output for longer, resulting in higher lactic acid levels. Generally, you wont be able to maintain a high (lactic acid generating) output for longer than 2-3 minutes.

    Please note, recent research suggests that shorter or inverse ratios, such as 2:1 (20 seconds on followed by 10 seconds rest), also known as Tabata training, has been shown to bring excellent benefits. Research conducted by Dr Tabata showed that individuals who performed 20 seconds maximal effort followed by 10 seconds passive recovery, repeated 8 times, resulted in greater anaerboic fitness, greater aerobic fitness, less body fat % and an increase in muscle mass when compared to individuals who exercised at 70% for 60mins.

    Creatine phosphate (ATP/CP) ratios

    Ratio: 1:6 or higher, up to 1:50 (or higher)

    This equates to: 10 seconds of work followed by 60 seconds of rest, or even five seconds of work followed by 250 seconds (4 mins 10 seconds) recovery.

    Minimum and maximum work duration: this will depend on the type of explosive fitness required by each individual. For example, Usain Bolt requires a large ratio to ensure that every time he works, he is training as fast as possible with no fatigue. Whereas an everyday gym-goer may be happy to work on a rower for 10 seconds, followed by 60 seconds of rest, to help develop their energy system.

    It is worth noting that no matter what type of interval training you use, the result will always lead to an improvement in your cardiovascular fitness. A 2001 study – “Energy system contribution during 200- to 1500-m running in highly trained athletes” (MR Spencer & PB Gastin) – showed that the aerobic energy contribution during running events was:

    • 29% for 200m
    • 43% for 400m
    • 66% for 800m
    • 84% for 1500m

    The results indicated that the aerobic energy system contributed more during high intensity activities than had been previously thought.


    It’s worth noting that an overarching benefit of interval training is that a majority of energy systems will be utilised and overloaded. This promotes a strong stimulus for the development of clients’ aerobic, lactic acid and ATP/CP energy systems. As always, the key is specificty to a clients level of fitness, goals etc and how you will promote overload to ensure progression.

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