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Active Recoveries in Interval Training

Posted on October 15th, 2016 by

We all have done interval sessions with full or active recoveries. In this week’s blog, we want to explore the concept of active recoveries a bit more.

Last week, I received an invite from Dr Matt Long to join his Facebook group ‘BUAC (Birmingham University Athletics Club) – Education & Resources’. Matt posted a short video showing BUAC athletes during their recoveries. Some were standing, others were jogging during their recoveries. Matt asked which athlete would you rather be? The athlete who is resting or the other one jogging during the recovery. Considering the amount of interval training sessions we have done I thought, this would be worthwhile a ‘Hare Brains’ blog post.

To better understand what is going on physiologically and psychologically within an interval session we have to revisit its parts and intended purpose before we can draw conclusions on what type of recoveries work best in which circumstances and how athletes can benefit from active recoveries.

Repetition vs. Interval Training

The terms repetition and interval training are often used interchangeably for anything speedwork related. However, there are subtle differences between both methods of training. Like most quality running sessions, a session consists of hard running (repetitions) for a set distance/time followed by jogging or a pause (interval). When referring to ‘repetition’, we mean the part of actively running, while the interval, is the pause between repetitions.

Depending on the training emphasis, interval and repetition training have different aims. During a repetition session bouts of fast running can be run faster at race pace for set distance or time. The focus is on what happens within the repetition, e.g. how fast to run. The time between repetitions can be several minutes or whatever time it takes to be able to run the next repeat at high intensity. For example, 4x 400m (800m Race Pace) [7’ Rest], 4 repetitions of 400m at 800m race pace followed by 7 minutes rest.

Interval training, on the other hand, focusses more on what happens in between the repetitions, while the pace/speed of the repetitions is less strict. Interval training is used with shorter repetitions to promote greater heart stroke volume.

An interval session 12x 400m (5k) [1’20’’ ’active jog recovery], 12 repetitions of 400m at 5k race pace followed by a jog for 1’20’’.

Important to remember that interval training is a kind of repetition training. However, not all forms of repetition training are interval training.

Active vs. Full/Rest Recoveries

During Thursday track sessions we have practiced active and full recoveries. For example, a lap of jogging after 4x 1km or a 45’’ full recovery after 400m. By full recovery, we mean rest, the athlete tries to speed up recovery by waiting between intervals and reduce the heart rate as quickly as possible towards 120 beats per minute (bpm).

An active, jogging recovery, once finished with a repetition the athlete would continue and jog during the recovery period. The heart rate reduces slowly, though will unlikely hit the same levels in comparison to the full recovery. While running at a lower heart rate during recovery, physiologically, the heart expands and pumps volumes of blood around and gets strengthened.

Lactate – Friend of foe?

When we train on the track and push hard throughout the session, we experience a sensation of exhaustion, tiredness, fatigue and soreness. In contrast, when we go for an easy run we finish with a feeling of being energised and able to run further. Depending on our pace, we have to fuel the body with energy. When running slow, we use glycogen stored in the muscle and fat. When going faster, we shift the fuel mix and increase the amount of muscle glycogen and lower the portion of fat as fuel.

When athletes get asked what is going on, often athletes refer to ‘lactic acid’ started to build, a burning sensation in their muscles, preventing them maintaining the pace. The common perception is that lactic acid is not good for you.

The truth is the human body does not produce ‘lactic acid’. As a by-product during running, the body produces only lactate and not the acid form. Lactate is a source of fuel (for muscles) and good for you. The amount of lactate created depends on the exercise intensity and running speed. When running slow, we produce small amounts of lactate, which the body recycles as fuel for the muscles. When running fast (i.e. min 80% of maximum heart rate), we produce more lactate. When lactate becomes available, it can be recycled and contrary to common belief can help to delay fatigue and serve as a fuel for muscles.

To take advantage of this fuel, when we start to produce lactate, we can recycle lactate into fuel when we shuttle the lactate around the legs and feed the muscles. To maximise performance, either improve the rate of recycling lactate or a reduce the production of lactate at higher speeds.

A new kind of Interval Training

The concept of active recoveries has been around for years. Initially, I came across when I read an article from Peter Thompson on the New Interval training, which explains the physiological side between classic and new interval training with active recoveries. Thompson refers to this form of training lactate dynamics training. Thompson suggests converting most traditional interval training sessions into a new interval session (aka lactate dynamics session). For example, 12x 400m (5k) (1’ Rest) becomes 12x 400m (5k) (200m Active Recovery Jog) or even better 3x 4x 400m (5k) (200m Active Recovery Jog)(400m Jog in between sets). By making the interval more active the heart rate will come down more slowly during the interval, though stays higher in comparison to full rest, body promotes the lactate shuttle and enables athletes to spend more time their maximum oxygen uptake.

While there is certain strength and training age required to make it through a 6k-8k training session with active recoveries, those new to sessions can incorporate walking recoveries, reduce the session volume and slowly progress their active recoveries over a few weeks.

Important, many runners run their repetition too hard and end up running the reps at their best race effort rather than their form on the day. In all sessions we do we refer to the most recent 3k, 5k or 10k pace, not your lifetime best pace for 4k, 5k or 10k. Further, we have to put the interval session into the wider context of the season. Fitness and form will progress and so will your training paces through consistent practice.

Isn’t this Fartlek?

The concept of bouts of fast running followed by relaxed running over varying distances is also known as Fartlek, Fartlek is a Swedish term for ‘fart’ (speed) and ‘lek’ (play), roughly ‘fartlek’ translates to ‘speed-play’. As the name suggests, a more playful, less rigid and structured approach to speed development.

Former Swedish decathlete and cross-country coach Göta Holmér introduced the Fartlek training method in 1937. At the time Paavo Nurmi dominated long distance running and Holmér had to find a new approach to improve the Sweden’s XC team performance against the ‘Flying Finns’. Developing speed endurance, through running short bouts at faster than race pace speeds with good running rhythm followed by easy running as part of a longer run proved to be effective. Fartlek training improves speed, stamina, running economy and endurance. Holmér most famous proteges were Gunder Hägg and Arne Andersson. Hägg was the first athlete to break 14 mins (13:58.2) for the 5,000m and his 4:01.4 for the mile was a world record at the time, which was broken 9 years later by Roger Bannister.

A typical fartlek session according to Holmér is 8-9 miles long which incorporates a 3 mile of fartlek in a natural setting. For example, for Hägg’s 4’01” mile (race pace), a (structured) fartlek session a la Holmér during his peak period could have been 24x 200m (mile pace) [200m active recovery], or time-based 24x 30” (mile pace) [~50” active recovery]. To get a full session, embed the fartlek in a 25′ warm-up and 25′ cool-down.

Something for you to try out on a Tuesday Night. Remember, a traditional Fartlek session is unstructured, and the athlete chooses intuitively, spontaneously for how long and how fast the bouts of intense and relaxed running are. The active recoveries in between the bouts of fast running will help to refuel the muscle with lactate. This session can be done on undulating terrain and can be run individually or in a group.

Physiological Dimension of Active Recoveries

One could do an experiment, run a session of 4x 1,200m [5k] (3’) with full and active recoveries by wearing the heart rate monitor. During full recoveries, well-trained athlete’s heart rate will quickly drop towards 120 bpm and even further. Typically, athletes spend the first 200m into the 1,200m repetition, bringing the heart rate quickly up towards 95% of their maximum HR and try to maintain the heart rate at that level for the duration of the repetition.

Full vs Active Recovery

Full vs Active Recovery

Figure 1: Full vs. Active Recovery

When applying active recoveries, the heart rate never drops to 120 bpm (more likely 140 bpm). As a consequence, when starting the first repetition, less time is required to reach 95% of maximum HR again. For example, athletes reach their effective heart rate sooner, already 50 meters into the session. If we add up the additional gain of training at 95% maximum heart rate for each repetition, we will end up with a total quality training time at 95% of max. HR, which could provide a greater training stimulus. If we all add up those gains for each repetition when applying active recoveries, then athletes can get more out of the session in comparison with an interval session based on full recoveries.

Psychological Dimension of Active Recovery

In an interview on BUAC, British coaching legend, Bud Baldaro made an interesting observation. In most races there is no walking involved, active recoveries mimic a race situation and keep the athlete engaged in the session. The focus remains on running. When standing still, the mind quickly fades, gets distracted, lose focus and concentration.


It is desirable to take advantage of the lactate shuttle and apply active recoveries during an interval session. However, as pointed out it depends on the training and biological age of the athletes. Those with a few years training age can handle the intensity and have the aerobic capacity to apply jog recoveries, while a beginner may struggle, though a walking recovery is a good alternative as well. Next time you train on the track, don’t beat yourself up when you have not hit your target pace, rather focus on the active recoveries and the training benefits it will have for you.

Urban Bettag coaches for the Mornington Chasers and leads the development of their track training and mentors their junior coaches. He blogs and shares his wisdom about running on the Hare Brain Blog every Friday.