As the name implies ‘alternations’  is a workout that consists of alternating between two or more paces or intensity levels as part of a continuous running session.

Specifically, alternations consist of a faster segment followed by a slightly slower segment.

Alternations differ from ‘intervals’ or ‘repetitions’ because there is no ‘recovery intervals’ in between ‘hard repeats’ – both paces or intensities you alternate between are equally important to the workout. Alternations are closely related to Fartlek.

Because there is no recovery interval consisting of ‘easy’ running or passive rest, alternation session tend to be harder than interval sessions although this is not always the case (such as when you alternate between two paces that are not very fast).

This type of workout has a long history and you may have encountered them under different names. Coaches like Renato Canova refer to them as ‘runs with variation of speed’ or ‘lactate clearance workouts’ whereas an older name is ‘accordion runs’. The specific term ‘alternations’ was first used by Steve Magness in ‘Science of Running’ (as far as we know).

Alternations workouts should not generally be done early in training unless you are alternating very short fast sections with longer medium sections (such as 30 seconds FAST, 2:30 minutes steady).


    1. Start out with doing a good warm-up. This is the phase during which to develop and practice your own pre-race warm-up.
    2. Pick two paces that are related to your race: ideally one pace faster and one pace slower than your race pace (such as 3k and 10k pace when training for a 5k race)
    3. Alternate the first pace for the assigned time and then change to the second pace for the assigned time. Repeat as long as you can. (for instance, run 1 minute at 5 km pace then drop to half-marathon pace for 2 minutes)
    4. Slow-twitch runners (very endurant but not naturally fast) benefit most from alternating 10k to 10 mile pace type of work with steady (bit slower than MP) to Marathon Pace type work
    5. Fast-twitch runners (less endurant, more powerful) will generally do a very short and very fast segment followed by a medium effort segment (such as 200m @ 1 mile pace with 800m @ half-marathon pace)
    6. Fast-twitch runners can also benefit from splitting the workout into sets (i.e.two sets of 3x 400/200m at MP/5K pace with 3 min jog in between each set)

Stop the workout when:

  • You start to struggle to hold your pace in either side of the alternation
  • Your time starts to fall off
  • You cannot hold good form
  • Your workout is completed

Make sure you finish the workout with a good cool-down; minimum of 15 minutes easy trot. This will aid your recovery.

Important points:

  1. Never do this type of workout 2 days in a row.
  2. Always give yourself at least 48 hours to recover.
  3. Check your recovery indicators daily. Do not do another interval workout until you have recovered from the previous one.
  4. Never run alternations if you feel an infection coming on.

How to progress alternation training

To minimise risk of staleness and injury progress your alternation training through the following three phases (the workouts in our programmes automatically factor this transition in):

  1. General: During the Base Period alternations tend to have very short segments of fast running followed by steady running. This is a brilliant way to include a little bit of race-specific training very early on.
  2. Related: The race specific paces (or a bit faster) are now generally introduced in a short segment alternating with marathon pace or similar (such as 200m @ 5k pace with 800m @ marathon pace for a 10 km race)
  3. Specific: The faster segments now tends to become longer and sometimes more race specific (such as progressing the above session to 200m @ 5k pace with 600m @ 10k pace or 400m @ 10k pace with 600m @ marathon pace).

The possibilities are endless! If you cannot recover within 48 hours from the session your volume of faster work is too high – reduce it in the next workout!

Rate of perceived effort:

7-9 (90-98% VO2max)

Experienced competitors/elites:

Experienced competitors should be aware that this type of session is crucial in allowing them to speed up during races to above average pace and still recover late in the races: making them more tactically flexible.

More details on alternations can be found here.


  • Lactate and phosphocreatine recycling
  • Efficiency at faster paces


  • Ability to change paces in races
  • More accurate perception of subtle changes in pace

Biggest mistakes:

  • Converting your training times to predict race times. Your times will probably not correlate to race times as yet simply because you have not yet developed your speed to its maximum. The times are not important it is the physiological response of your body to the workout that matters.
  • Running the alternations too hard. While you never get full recovery in an alternation workout you can sabotage yourself if you run a workout that is alternating 5k and Marathon Pace by running either or both too hard (i.e. 3k alternating 1/2 marathon pace or 5k pace alternating with 10k pace)
  • Squeezing out one more set of alternations after the signs to quit are evident. This is counter-productive and will mess up your training for the rest of the week. Have the discipline to stop pouring when the glass is full.


Any terrain is suitable. If you operate with precise paces or track, then a level road or track will be best.

This workout is very suited for running on trails where you can alternate ‘efforts’ rather than ‘paces’ to account for harder or easier stretches of the trail (such as ‘4 min medium alternating 2 min hard over trail’.


Alternations of pace can be done in many ways. One standard run we employ is called ‘varied pace easy run’ (as opposed to the normal easy run). In such a run you make an effort to vary your pace as you feel (similar to Fartlek).

This will have some of the benefits of alternations but will not be quite as intense or precise. Unstructured varied pace runs is a good way to prepare for ‘real’ alternations. Another way to achieve this is to run over hilly ground and trails and to vary your effort slightly instead of trying to keep one steady effort throughout.

Parts of the workout descriptions are adapted from BreakThrough Running with permission.

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Director and coach at Borg Coaching Services
Rene Borg is the head coach of Glendalough AC and a passionate runner competing over all distances and terrains.

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