Training Interference: Kicking It Down The Road

If you can't get in today's workout
should you kick it down the road?

"Why do today what you can put off until tomorrow?"  ~Anonymous

The variable of interference is an integral part of every endurance training plan.  In every day practice the concept helps to answer the question, "If I miss today's training unit should I push it to tomorrow?".  The answer is almost always "perhaps", but let's look at why.

In the programming of endurance sports training, interference implies that one training unit has the potential to impact another training unit.  The magnitude of this interaction almost always is directly related to the time proximity of the two training units.  That is to say, the closer the training units are stacked together with respect to time, the greater the potential for them to interact.  When training programs are designed, this relationship between training units is fairly precisely orchestrated.

For simplicity let's categorize interference three ways; maximal, potential, and minimal. An example of all three is depicted in the training log below.

Maximal Interference
When performed on the same day, two training units have great potential to interfere with each other.  The type, duration, and intensity of the training unit will determine the amount of time needed for recovery (complete or incomplete) and therefore the magnitude of interference exerted on the subsequent training unit.  In this example, a running-specific hill workout precedes a mobility/strength training unit.  Because this training cycle represents a specific preparation phase for an upcoming event (within 4-8 weeks), running is given priority over mobility and strength development.  When two training units are scheduled and performed on the same day it can be assumed that the first training unit will maximally interfere with the subsequent training unit.  Sometimes there is an attempt to avoid this interaction (as in the case of scheduling the running unit first), and sometimes the interaction is used purposefully (as in the case of pre-fatiguing the sport-specific soft-tissues with "doubles").

Potential Interference

A common program design philosophy includes microcycle variability.  This is seen as following "hard" days with "easy" days to give the body's adaptive mechanisms a chance to do their work.  When multiple hard efforts are scheduled in sequence, not only is there less time for important training adaptations to occur, but the risk of overreaching is considerably higher.  In the example above, Thursday's steady-state workout is scheduled forty-eight hours prior to Saturday's long run.  This design is described as "potential interference" in so much as there is likely to be some carried fatigue from Thursday without compromising Saturday's training unit.  This carried fatigue is both purposeful and potentially important with regard to sport-specific performance.  In other words, marathon and ultramarathon sports have both a strength endurance and metabolic endurance component.  Performing Saturday's long run on some carried fatigue helps to prepare the athlete for the physical and energetic demands later in races.

Minimal Interference

Lastly, there are times in which training units are scheduled to minimally interact with each other as in the case of these Saturday long runs.  Although often this more a function of time availability, it does end up serving an important design benefit.  Training units of two hours in duration or longer, place significant stress loads on the body.  This includes the structural components (ie. musculoskeletal system), bio energetic systems (ie. glycogen and fat), and immune system.  The ability to successfully complete these long training units is vital to sport-specific performance.  Therefore while some carried fatigue is beneficial (as in the potential interference example above), an excessive amount of carried fatigue not only potentially compromising the successful completion of the training unit, but is also significantly increases the risk of soft-tissue injuries and illness.

In summary, because most weekly training schedules often use all three forms of interference, be careful when you "kick a training unit down the road" by moving it to the next day.