Interval sessions for Endurance Athletes

Interval sessions for Endurance Athletes

How you recover could be more important than how you work...

Intervals are common place in the training plans of the vast majority of athletes, irrespective of sport type. An interval session is simply one in which a work period (usually higher intensity) is interspersed with a rest period (allowing recovery). When training is done in this manner it typically allows for a greater total workload than would be achievable through continuous exercise.


Within endurance sport, the dominant energy system is the aerobic one and so the primary goals of interval sessions include improving aerobic capacity and power. Anaerobic workloads are less commonly prescribed, can also be useful but won’t be discussed here. When athletes look at interval workouts they typically fixate on the work periods and how hard or easy they are likely to be. In this short blog I’d like to be an advocate for the importance of the RECOVERY PERIOD!


The purpose of the recovery period is to allow sufficient down time for the next work interval to be achievable. Simple! The quality of the work interval is maintained through adequate recovery. Anything above that is not necessary and may actually change the nature of the session and the resulting outcome. In brief, when we slow down to recover, our heart rate and respiration rates fall, our perception of effort falls and our focus can wander, cellular enzymes can be replenished and lactate cleared.  Crucially, recovery does n it have to full it just has to be sufficient! Allowing greater recovery than needed and therefore greater freshness for the next work period may not in fact be the best option.

Basic Rules of Recovery Intervals:

  • Take as little as needed to perform the next work interval successfully. When analysing threshold swim workouts I first look at whether the short recovery time was kept consistent before looking at the pace achieved during the swim. For example, a threshold swim of 10x150m with 15s recovery should be disciplined in both the upper aerobic pace of the swimming and the strict ‘off the wall’ time ion order for the session to be effective.
  • Research (Dr, Stephen Seiler) suggests 2mins recovery may be the minimal effective dose for hard aerobic interval workouts. For example, VO2 max intervals of 6x3mins with 3mins recovery is a common session. Consider progressing this by reducing the recovery to 2.5 and then 2mins while maintaining the same power and/or HR (which is the key to these sets).
  • Typical recovery periods for threshold sessions are based on a 4:1 ratio of work: rest. So 8mins on and 2 off for example. While I wouldn’t shorten this recovery any further typically, I would consider raising the effort level during the recovery for some athletes. Remember the goal of this type of interval session is to elevate ‘sustainable aerobic power or pace’ and therefore we don’t want to overly rely on the anaerobic system during these sessions. Some athletes do this naturally and their aerobic development may be hindered by a very strong anaerobic system. How do we prevent this? I consider simply asking them to remain a little under target effort at all times during the work period and then also maintain a decent lower aerobic effort during the recovery periods to prevent them from restoring their anaerobic energy supply Then when they hit the next interval it should be fuelled more aerobically. Examples would include run recoveries at a ‘float’ pace rather than passive rest, walk or easy jog. On the bike the power target would be mid zone 2 (65%) rather than typical zone 1 (<50%).


In summary, don’t always view GOING HARDER as the goal, keep your discipline and work in the target zone. Then consider progressing through manipulation of the recovery interval not the work interval. It may take a little experimentation and you’ll need to allow for day to day and week to week variation too but please give it a go….


Phil Ellison

Senior Triathlon Coach at Total Tri Training

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