Circuit run (sub-threshold run)

The “Circuit run” workout is the fastest type of endurance workouts you will do during the early stages of the Quantity (traditionally called the Base or Aerobic) phase. It teaches you to run at the fastest pace you can sustain without “huffing and puffing”, that is – by burning mainly fat and oxygen for fuel and incurring little or no oxygen debt.

This workout will allow you to run faster before you fatigue because oxygen-independent metabolism (anaerobic) sets in later. Scientifically, this pace is run close below the  “lactate threshold” but we prefer the more descriptive term “maximal steady state” used by Arthur Lydiard.

“We call the limit the maximum steady state; the level at which you are working to the limit of your ability to breathe in, transport and use oxygen. When you exercise beyond that maximum steady state, your running becomes anaerobic. Chemical changes occur in your body’s metabolism to supply the oxygen you need to supplement what you can breathe in, transport and use.” – Arthur Lydiard, Running with Lydiard



High-end endurance run.

  1. Choose a looped course that will take you between 10-25 minutes to complete (generally 3-5 km)
  2. Warm-up during the first lap
  3. Change into  a comfortably fast pace on the second lap
  4. Take your time after the first lap, run an easy lap and then another comfortably fast
  5. Compare the times from the first lap to the second
  6. If doing more laps than two, keep doing one lap easy and one comfortably fast
  7. If paced correctly you will slow very little or not at all from fast lap to fast lap – the average pace between your hard and easier laps should be roughly as set out in your plan
  8. This is one of the most difficult exercises for runners to pace correctly initially: take your time and treat each “Circuit run” as an opportunity to improve your pacing rather than just increasing pace blindly.
  9. Ensure the total amount of “harder running” never exceeds 60 minutes for this workout

Important points:

  • Attempt to run even pace (each fast lap about as fast as the first at the same effort)
  • Don’t run so hard that your slow laps become so slow that the average pace falls well below the target in your plan

Rate of perceived effort:


Experienced competitors/elites:

The value of this workout increases for experienced competitors and elites. The ability to increase VO2 max (maximum oxygen uptake) decreases over time whereas the lactate threshold remains very trainable and will allow experienced athletes to run at increasingly higher percentages of their VO2 max for longer periods of time. Even for an elite athlete the reduced fatigued from running more at sub-threshold than threshold benefits the overall weekly training effort and general health and well-being.

Lactate threshold pace will generally be around 10-15 seconds per mile slower than 5k race pace for elites whereas it is closer to 10k pace for less trained runners and slower than 10k pace for runners with 50-minute and slower 10k times. Go by intensity first and pace second. Remember that in these sub-threshold runs your pace and intensity is slower than 60-minute race pace (15k to 10 mile race pace for experienced runners) and you should not go beyond this intensity.


  • Fastest endurance pace
  • Lactate shuttle training (re-using lactate as fuel for endurance running)

“When the maximum steady state, the aerobic exercise upper level, is low, you can be running anaerobically at a comparatively low speed; as the maximum steady state is pushed upwards, the slower anaerobic speeds become aerobic (and economical). And, if training progresses on this principle – that aerobic exercise is 19 times more economical than anaerobic – then the possibilities of running farther and faster aerobically (and with economy) must increase.” – Arthur Lydiard, Running with Lydiard


  • Pacing
  • Rhythm
  • Knowing your recovery pace

Biggest mistakes:

  • Running the fast laps so hard you have to slow down to a trot during the slow laps
  • Running faster than your maximum steady state pace (roughly 15km race pace)
  • Starting out too fast and having to slow down.
  • Maintaining too high a heart rate to sustain your pace and becoming anaerobic (“huffing and puffing”)
  • Running too slowly at the beginning so that the split for the second half of the run is more than 10% faster than the first.


Circuit runs can be done on any looped trail, but we recommend picking a scenic road or trail loop with some undulations. When using this session during the cross-country season or as preparation for hill or mountain running, it should be done over hilly trail.


Out and Back: This variation of the “Circuit run” is the original trademark Lydiard-workout which we recommend in the later parts of the base (aerobic) phase. More information on it in the dedicated entry on “Out and Back“.

Lactate (aerobic) intervals and repetitions: similar in principle to standard intervals/repetitions, these are workouts where the fast repetitions are run at lactate threshold pace or slower. For maximum effect, these repetitions should be slightly longer (1 mile or upwards for experienced athletes, approx. 5-7 minute running time for less experienced runners). As you are not incurring oxygen debt in this type of interval training, you should keep your rests brief such as one minute easy jogging. Sample workouts include: 3-5 mile repetitions with 1 minute easy jog recovery or 2×2 miles with 2 minute easy jog recovery.

Super-threshold intervals and repetitions: as above, but your repetitions are slightly faster than your lactate threshold (you are “dipping your toes into anaerobic waters”) with slightly shorter recovery. Sample workouts include: 2 sets of 3x1km repetitions with 45 seconds recovery between repetitions and 2 minute recovery between sets. Recovery can be easy jogging, walking or total rest.

These two variations are useful for runners who are comfortable with their own pacing but wish to mix-up their training or maintain lactate threshold speed more consistently than they are currently able to do through continuous running.

Cruise-intervals: similar to progression runs but you can intersperse your maximal steady state running at any point of the workout depending on what you are trying to simulate. Do you expect to need a fast start and finish? In that case perhaps a session such as the following would be appropriate:

3km @ max. steady state pace + 5km aerobic running + 3km @ max steady state pace.

The term cruise-interval denotes any type of aerobic workout with maximal steady state repetitions inserted. An extreme example could be 20km run with every second kilometre being at maximal steady state. This may be a useful simulation for off-road runners and others who need to be able to handle undulating terrain and regular changes in intensity.


The idea for this workout was provided by Dr Keith Livingstone, coaching advisor to ChampionsEverywhere and has been used with success by some of Australia’s best youth squads.

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