I used to train with a group that ranged from mile runners to marathon runners, all at a similar competitive level. For long periods of fall and winter, we could all train together in some approximation of harmony. But during track sessions, tensions sometimes ran high. Mile runners would begin to pause marathon runners for shorter intervals, and in retaliation, marathon runners would boost recovery jogs to prevent mile runners from catching their breath before the next rep. It was a good illustration of different methods and mindsets about recovery.
A new study from researchers in Spain delves into this culture shock, comparing active (jogging) and passive (standing) recovery between reps during interval training. It is the latest in a long series of such studies, which have generally produced a confusing and contradictory body of research. It doesn’t offer any final answers, but it can help clarify which questions are worth asking.
the study was published in the European Journal of Applied Physiology (where it is free to read online) by a research team led by Eliseo Iglesias-Soler of the University of A Coruña in Spain. He had 11 well-trained distance runners who did a 4 x 2:00 workout at their maximum aerobic speed, with 2:00 rest or jogging between intervals. They did the workouts on an outdoor track, with a bike clocking them at prescribed speeds (even during the jog break, which was at 80 percent speed). second ventilatory threshold). They also did five double-footed jumps immediately after each rep, which was supposed to assess their neuromuscular function, but seems like an odd thing to insert in the middle of a workout when you’re trying to understand recovery dynamics.
Here is the key data from one of the runners, showing his oxygen use (VO2) as the training progressed:
You can see that he uses more oxygen when he is running hard and less when he is recovering. You can also see that you use more oxygen during jogging recoveries (black lines) than complete rests (red lines). The interesting part is the spikes. The main purpose of interval training, according to one school of thought, is to allow you to spend more time in the extreme zone, shown here as dotted lines between 90 and 100 percent of VO2max, compared to just going out and running as hard as you can until you pass out. The rest between repetitions allows you to suffer plus rather than less.
In this case, the red spikes are higher than the black ones: complete rest allows this runner to spend more time in the extreme zone. In general, the average results are ambiguous, although the complete rest appear (with borderline statistical significance) to allow the runners to spend more time at VO2 max. On the other hand, the perceived exertion measured immediately after each hard repetition is lower with complete rest. As a result, the researchers conclude that complete rest is preferable for this type of training: You get similar cardiorespiratory benefits but it feels easier.
However, there are some caveats. One is that identical speeds were prescribed for repetitions. Perhaps the slightly lower VO2 values with active recovery means that if the speeds were freely chosen, you would actually do a faster workout with jogging breaks. This is, after all, one of the main arguments used to justify jogging recoveries: Low-intensity exercise keeps the blood flowing, which removes metabolic waste products like lactate and protons more quickly, and thus allowing you to go faster on the next interval. . (The idea that lactate Causes muscular fatigue has fallen out of favor, but it is still plausible that lactate levels are correlated with performance-impairing metabolites).
In this study, lactate levels were only measured after training ended and were, in fact, significantly higher (6.93 vs. 6.24 mmol/L) in the fully rested condition. But a 2014 study tracked them every 45 seconds for a three-minute recovery period after a total interval of 30 seconds. Lactate levels were initially identical for complete rest and easy cycling, but began to diverge after about two minutes. This suggests that the physiological benefits of active recovery begin at this time.
But all of this, in turn, raises a deeper physiological (or perhaps philosophical) question: Is it better to make training harder or easier? You could argue that standing completely still is the best option because your muscles will be drenched in lactate and you’ll be practicing running in those conditions. Or you could argue that jogging is better, because you’ll be training your body to remove lactate from the bloodstream more quickly and allowing your legs to run faster. The only real way to resolve this debate is to forget about physiological measures and do a training study: get a group of people together, train half with jogging recoveries, the other half with full rest, and see who makes the biggest improvements. . It would be a very difficult study to do.
In reality, there is unlikely to be a single best answer for how to recover between intervals. Instead, understanding the physiology of recovery gives you some tools to decide what is appropriate for a given session with given goals. If your goal is simply to run the workout as fast as possible, then it’s probably best to walk the recovery or stay still if the recovery is short, say a minute or less. That’s because complete rest helps restore phosphocreatine, which is the instantaneous energy that fuels sprints and the opening seconds of longer runs. If you take a couple of minutes or more, then a light jog is likely to help you run faster, thanks to the improved blood flow that cleans up lactate and other metabolites.
Then there is the mental dimension. In once a runner, Quenton Cassidy crouches exhausted after winning the Millrose Games. His mentor walks over to scold him: “Don’t grab your knees, boy… Here’s your sweatshirts, put them on. But don’t grab those knees because you have to run some of that. You just became the champion of Wanamaker Mile and you have to let them to know…”
I only started running recoveries after college, and it was a big adjustment at first. It’s a mental challenge to finish a hard interval and then force yourself to keep jogging, which I suspect is why effort ratings were slightly higher in the new Spanish study. But once you get over that hump, you realize that it’s actually not physically more difficult. And there’s something intangible about finishing a tough interval with a training group and seeing half of them crouch in anguish as you jog calmly forward. I’m not saying you should be competitive with your training partners, but if running is the goal, then it doesn’t hurt to let them (and yourself) subtly to know…
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