Between work intervals

What you do between work intervals can be as important as the work itself

You’re doing some tough intervals in the pool, on your bike, or at the track, and after each one you’re gasping for oxygen and hoping that the pain in your muscles will subside soon. You’ve read that it’s best to exercise lightly during your recovery intervals, but your body and mind are telling you to just grip the pool edge, stand down from your bike, or lean over and clutch your knees while your lungs heave to and fro. Does it really make a difference what you do between work intervals?
Research carried out recently in France answers that question with a resounding yes. The new study suggests that if you’re carrying out short, very intense work intervals, you’re far better off exercising lightly during your recovery intervals, compared to just resting.

In the just-published research, 10 fit (VO2max = 56), healthy male cyclists exercised at an ‘all-out’ intensity during six-second work intervals, with five-minute recoveries. Although such recoveries might seem unusually long to you, they are of a duration which is often recommended during intense training sessions. The principle behind such elongated recoveries is that they permit higher-quality work during subsequent work intervals.

After the initial six-second work interval and five-minute recovery, the cyclists completed a second six-second work interval with greater pedal resistance, recovered again, carried out a third six-second interval with even higher resistance, recovered, and continued in this manner until they reached ‘peak anaerobic power’ – the highest power they could possibly exert during the six-second exertions.

On one occasion, cyclists completed the session while recovering ‘passively’ (e.g., while sitting idly on their bikes or while standing around). On a second occasion, the athletes recovered ‘actively’ – while pedalling their exercise bikes at a moderate intensity of 32% VO2max (about 50 per cent of maximal heart rate), a work rate which some exercise physiologists have suggested is optimal during recovery periods. In both of these situations (passive and active recovery), the French scientists measured blood-lactate levels at the beginning and end of each recovery interval and charted actual power produced during successive work intervals. Of course, the whole idea was that if one recovery mode were better than the other, it would produce higher power production during the work intervals.

The focus on lactate levels during recovery made a lot of sense. After all, during short, very intense work intervals, most energy for muscle contractions is produced anaerobically (oxygen- independently). Anaerobic energy production is thwarted by high lactate levels, so the researchers reasoned that the recovery method which did the best job of attenuating lactate would also produce the best-quality work intervals.

So what happened? Well, of course heart rate was higher after the active recoveries, compared to the passive ones. That might seem like a bad thing, but it was actually good, since it meant that there was less ‘shock’ to the cardiovascular system (heart rate was required to rise less precipitously) during each subsequent work interval, and it also meant that the heart was doing a better job of pushing blood to the muscles after the active recoveries, too.

And lactate? It was significantly lower at the ends of the recovery periods when the recovery was active, rather than passive. How’s that? Greater activity led to lower lactate? Absolutely! You see, muscle cells – especially ‘slow-twitch’ muscle cells – actually use lactate as an important fuel. If the muscle cells are basically dormant, as they are during passive recovery, they ‘burn’ lactate at very low rates. If they’re moderately busy, as they were during the French active-recovery periods, they metabolise lactate at appreciably greater rates. This should lead to lower muscle-lactate levels and – most importantly – less interference with anaerobic energy production during subsequent work intervals.

For the bottom line was that the French cyclists actually produced more power during work intervals which followed active recoveries, compared to passive ones. Power output was about 5 to 15 per cent greater when the active recoveries were utilised.

So what’s the take-home message for you? If you’re conducting a high-quality interval session, it’s always wise to resist the temptation to be passive during your recoveries. Hanging on to the edge of the pool or leaning up against a fence by the track may SEEM like the right thing to do, but moving around at a slow but steady rate is the best way to prepare yourself for the next work interval. Active recoveries lead to better-quality work intervals, which ultimately produce higher fitness levels and improved competitive performances.

The practical French investigation also provided a second important message. As we said, lactate levels were lower following active recoveries, compared to passive ones. However, what we didn’t say is that in both cases lactate levels actually went up during the recoveries (they just rose less during active recoveries).

Now, the whole point of a long recovery-to-work time ratio has been to mollify lactates and therefore prepare athletes for high- quality work intervals. But note that a ratio of 5 minutes of recovery to six seconds of work, the one used in the French study, is about as long as this ratio EVER gets, yet lactate levels still rose during recoveries.

The message is that there’s no point in making your recovery interval ridiculously long in hopes of zeroing-out lactate. That troublesome fellow is actually going to go up during your recoveries. Instead of focusing on long, ‘perfect’ recoveries, you should remember that a key principle of training is to make your high-quality workouts as specific to the demands of your competitions as possible. During competitions, you don’t get extraordinarily long recoveries between bursts of energy; you must work at a high level continuously. Therefore, it makes sense to PROGRESS in your interval sessions from longer to shorter active recoveries over a period of several weeks. As long as the shortened recoveries don’t compromise how fast you can swim, cycle or run during your work intervals, your workout will be of higher specificity and quality and you’ll be better prepared for competitive situations.

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