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Can Micro-Bursts on Endurance Rides Improve Performance?

Sprints will usually take place at some point on nearly every group despite what may have started off as a steady state endurance ride. However, there's now some very interesting data to support a training strategy that includes 3-4 hr endurance rides with micro-bursts somewhere within it. But what's the benefit? What Micro Sprints Do To Your Body

Shortness of breath, muscle burn, increased fatigue, etc. All of these are markers of a workout’s effectiveness, but none actually demonstrate what a workout is doing to your body. Researchers from Norway recently dug into the details of this and discovered the long-term, ergogenic effects of this type of workout. Twelve elite cyclists (VO2max 73.4±4) were put through two separate workouts, one of 4 hours of cycling at 50% VO2max and another with 4 hours of cycling at 50% VO2max with three sets of 3 x 30sec sprints, one per hour after the first. I’d argue that these are a bit long for sprints, but they do match the group ride lead-out & sprint style that we’re familiar with. After the workouts, they took muscle biopsies and blood samples, then dug into the data to see what happened.

The goal was to see if the sprints created greater gains while keeping recovery time equal, and they did indeed. I’ll break them down by category.

What Didn’t Change

There’s a long list of things that didn’t change, but here are the highlights:

  • Time to recovery stayed the same.

  • Short sprints didn’t seem to change how quickly the legs came back.

  • Hormone levels

  • There were very few differences in hormone levels, indicating essentially no difference here.

  • Training effect

  • There was no difference in the markers of fatigue used by the study

There were essentially no differences in these areas, but that doesn’t mean the exercise was ineffective.

What Sprint Efforts Did Change

Genetics The sprint efforts made many genetic and gene expression differences, indicating that the body was responding to the different effort and adapting to it. Genetics are often misunderstood in exercise science, so here’s a quick breakdown:

Gene sequences are innate and unchangeable. These are the differences between you and a top athlete. Their genetic sequences are always going to push them ahead with the same amount of work (or even less).

Gene expression, on the other hand, changes all the time. Gene expression changes in response to hunger, thirst, exercise, stress, and more. Gene expression is the amount of protein synthesis your body does at each gene. For example, when you exercise a lot, you’ll need more proteins associated with strength and cardiac endurance, so your body will express those genes more often. This is what changed in the study.

Specifically, the gene expression that changed in this study was related to angiogenesis, ion transport, mitochondrial function, metabolism, and protein synthesis. The scientists saw this through mRNA differences in the blood samples they took.

Here’s a quick breakdown of the changes:

  • The sprint group had greater angiogenesis gene expression, indicating that their bodies were building and repairing more blood vessels, a huge part of exercise endurance.

  • Ion transport expression increased in the sprint group as well, another essential element of exercise. Ion transport is needed to cause muscles to contract and relax and send nerve impulses throughout the body. Increasing ion transportation could lead to an increase in recovery capability and muscle contraction force.

  • Myostatin expression decreased in the sprint group as well. This is great news for muscle development. Myostatin is a protein that inhibits muscle growth, so lowering its expression increases the amount of muscle synthesis performed after a workout.

  • Lastly, fat metabolism gene expression increased in the sprint group, indicating that their bodies were switching to more fats for fuel, an essential part of endurance athletics ability.

Why You Should Sprint in Endurance Rides

As a quick summary, sprints in the midst of long endurance rides don’t increase the amount of recovery required, do increase angiogenesis, ion transport, muscle grown, and fat metabolism. This simple addition to your endurance rides can have huge effects that researchers are just now digging into. In the words of the authors:

Inclusion of sprints to prolonged LIT exercises might thus be an efficient training strategy for elite athletes, potentially leading to beneficial adaptations in skeletal muscle without affecting muscle performance on consecutive days.

I have a number of clients that are adding protocol to their endurance rides on a regular basis. The sprints don’t have to be perfectly programmed to get the same effects, so feel free to adjust as needed. If you have a few small hills, sprint up those instead of rolling them easily, that’s all you need to get these ergogenic boosts. I would suggest that if you are a sprinter type, keep the sprint efforts to the first part of the endurance ride - when glycogen stores are full. If you are more of an endurance rider, these efforts will be of more benefit if spread across the duration of the ride. Sprints in the later half of the ride will stimulate the VO2 system as a pose to the glycolytic system.

The information used in this article comes from: Almquist, N. W., Ellefsen, S., Sandbakk, Ø., & Rønnestad, B. R. (n.d.). Effects of including sprints during prolonged cycling on hormonal and muscular responses and recovery in elite cyclists. Scandinavian Journal of Medicine & Science in Sports, n/a(n/a).

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