Try Sprint Interval Training To Improve Your Running Performance

You have been hitting the trails, logging miles and doing everything that you are supposed to in order to improve your endurance and power.  Maybe you have a race coming up in a few weeks or you just want the personal accomplishment of getting through your regular run a little bit faster.  If you are finding that despite all your worthwhile efforts your performance has not changed in a meaningful way perhaps it is time to consider integrating sprint interval training into your program.

This week we take a look at an interesting study that shows a way for well trained individuals to really move the needle on their running performance with a minimal amount of time spent training.  As we go through the study keep in mind three things.  First, this study was conducted with subjects who were already well trained athletes.  We would expect to see positive changes in studies that take subjects who aren’t active and put them on aerobic/endurance/power based training plans.  If you are starting from a low level of fitness and get on a regular, supervised program most people will see a change for the better.  Taking a group of well trained athletes and coaxing a meaningful change in their performance is much more difficult and demonstrates the power of the training intervention.

Second, this study was done in a real world setting, not in a laboratory.  Often the changes that can be achieved in a very controlled setting working on a treadmill or cycle ergometer cannot be replicated in quite the same way in a real world setting.  If you cannot go out to the track, trail, road or gym and achieve the benefit of the specific plan studied then it might not matter all that much that it can produce an effect in the laboratory.

Third, this study achieved meaningful results with just a two week intervention.  Often we need data over much longer periods of time, weeks, months, even years to determine the impact of a particular intervention.  In the case of this study part of what was so interesting is that the trained athletes used as subjects achieved the beneficial effects of the sprint interval training program in just two weeks.  Who doesn’t want to do something that will improve their performance in such a short period of time?

The Study

In this study running performance was measured with a 3,000 meter time trial and a run timed to exhaustion at 90% of maximal aerobic speed (MAS).  The training program consisted of three workouts per week for two weeks.  In each workout the sprint intervals were 30 second all-out shuttle runs followed by 4 minutes of rest.  The subjects performed 4 rounds in their first workout, 5 rounds in their second, 6 rounds in their third and fourth workout, 7 rounds in their fifth workout and dropped down to 4 rounds in their sixth workout.

The total sprinting time over the two weeks totaled 16 minutes.  The entire 6 sessions only took 110 minutes including the rest time.  The shortest workout was 14 minutes and the longest was only 27.5 minutes.

To conduct the actual sprints, cones were placed every 5 meters for a 30 meter distance.  During the sprints the subjects would run to the 5m cone and back, then the 10m cone and back and so on until they reached the 30m distance.  They would continue running at full speed until the 30 seconds were up.

Three additional variables were also measured for each session.  1) The subjects peak power, which was considered the longest distance they ran in a 30-second period.  2) Mean power which was the total distance they ran for the session divided by the number of sets they ran that workout.  3) Fatigue index was considered the difference between the longest sprint they ran in any given workout and the shortest sprint they ran in the same workout.


Maximal aerobic speed saw a 2.8% increase.  This was significant though the effect size was small.  For the timed run at 90% of maximal aerobic speed there was a 42% improvement (158.9 seconds) which was considered a large effect size.  The timed 3,000 meter run saw a decrease of 50.4 seconds which is a 5.7% improvement in time.  The effect size is considered small-to-medium.

Peak power had a 2.4% improvement (3.06 m), significant but a small-to-medium effect size.  Mean power had a significant 2.9% improvement (13.9 m) for a medium effect size.  The fatigue index showed a positive trend with a medium effect size thought it did not reach a level of statistical significance.

Putting It All Together

So what does this all mean for most runners out there?  First and most importantly it shows that a very short 2-week low volume program can produce significant improvements in performance.  Most competitive runners already have fairly lengthy training programs and a schedule of competitions to plan around.  Even if you are not a competitive runner odds are that you still have a limited amount of time to train and are still interested in improving your performance.  A simple low volume, high-intensity program like this can quickly make positive improvements in both endurance and anaerobic performance.  Additionally this study demonstrates that the improvements are not limited to untrained subjects that will respond to just about any regular training protocol, already highly trained subjects can make significant improvements with this type of training.

Secondly a program like this does not require any special equipment.  A few cones make it look pretty but some water bottles, t-shirts, a big rock all work equally as well.  It is always nice to have a new training technique that doesn’t require you to open your wallet.  This study clearly showed that the results can be achieved in a real world setting without highly calibrated expensive laboratory equipment.

Third, all you need is a clear 30 meter space to run your sprints.  This means it can be done almost anywhere.  Even if you don’t have a full 30 meters you could still follow the program and simply limit the longest available distance to 20 or 25 meters.  Even if you have to train indoors because of weather it is still simple to perform a program like this.

Fourth, it is easy for multiple athletes to perform this program at the same time.  Individuals can set up right next to each other.  This makes it ideal for those working with teams to put everyone through the program together.  There is the added benefit that running against others often motivates people to push even harder.

A program similar to this can also be used as a tapering plan allowing for high intensities and low volumes to be programmed as you get closer to competition.

So why does such a short duration, low volume program produce such good results?  The leading theory is that this high intensity training technique leads to increases in enzymatic activity in both the aerobic and anaerobic energy systems.  It is also possible that this approach improved neuromuscular capacity which can result in improved running economy.

The use of shuttle runs was an interesting choice of the authors.  It allowed for high intensity training while ensuring that the improvements seen in the actual tests were not the result of skill acquisition but due to physiological adaptations.  As previously mentioned it also allowed for a small space to be utilized and a competitive atmosphere to be established between subjects.    This leads to the question of if another form of sprint interval training could produce similar results?  There is probably nothing magical about the use of shuttle runs in and of themselves.  The high intensity that they stimulate is most likely the key factor so it would not be reaching too far to assume that if the same intensity can be maintained for a full 30 seconds on a longer sprint, similar results would probably be achievable.  This eliminates the advantage of only needing a small space along with some of the mental variety that shuttle runs introduce but coaches shouldn’t feel limited to only using that one approach to including high intensity sprint intervals.

It would be interesting to compare the results of this study to slightly different training protocols. What would happen if you used a time different then 30 seconds for the sprints?  Do you need to go all the way up to 7 sets or can similar results be achieved if the volume is kept lower and only 4 or 5 intervals are used?  Would more intervals produce greater results or what happens if the program if followed for more than 2 weeks?  Like all studies, this one could had to choose a particular set of variables to use but the positive outcomes they produced makes you want to explore how those variables can be tweaked to produce even greater outcomes or optimize the time actually committed to the program.

There you go.  If you are looking for a way to improve running performance but do not have hours to commit over a prolonged period of time now you have a technique that will allow you to turbo-charge your training with a simple to perform, short duration low volume sprint interval plan.  Who doesn’t want to see a 42% improvement in their paced running and a 5.7% improvement in their race time for such a small amount of training?

Koral, J., Oranchuk, D., Herrera, R. and Millet, G. (2018) Six Sessions Of Sprint Interval Training Improves Running Performance In Trained Athletes.  Journal of Strength and Conditioning Research. 32(3): 617-623.

Burn Fat and Improve Endurance by 70%. Now in Pill Form.

What if I told you there was a way to increase your endurance by 70%?  People would be lining up and asking if we have it in pill form, and we almost do.  Most people are familiar with the idea of “hitting the wall”.  That moment when you are doing some sort of endurFance based activity and you just reach a point where you can’t go on.  Maybe your thinking gets cloudy.  Your muscles don’t seem to work anymore.  Your coordination has suddenly evaporated.  That image of the Ironman triathlete, just yards away from the finish line stumbling around.  So close to the end but unable to even coordinate those last few steps to get across the finish line.

Generally this is the effect of not having enough glucose in the blood stream to supply the brain with sufficient amounts to meet its energy demands.  No matter how badly you want to go, when blood glucose drops too low the brain just says no.  Like an automobile engine running out of gas.  So the longer you can maintain a higher blood glucose level, the longer you can go before hitting that proverbial wall.

Normally regular endurance exercise has three primary affects that spare blood glucose.  1) The transformation of muscle fibers to types with more oxidative capacity, which equals more energy production out of every gram of glucose used as fuel.  2) An increase in the number and activity of mitochondria, the powerhouses of cells where aerobic metabolism occurs. 3) The improved utilization of fatty acid as a fuel source, sparing the use of blood glucose and our stored carbohydrates in the form of liver and muscle glycogen.  Who doesn’t want to use more fat as fuel source.

Of course these changes take a great deal of hard work over a prolonged period of time.  As any new runner or average person struggling to lose body fat will tell you, change is difficult, comes slowly and is often hard to notice at all.

Well thanks to a nifty little molecule called peroxisome proliferator-activated receptor delta (PPARδ) we may be able to hack into our normal metabolic processes and accelerate our fat burning capabilities.  For the performance athlete this means sparing precious blood glucose and carbohydrate stores which will push the proverbial wall out further, enabling significantly longer, and greater achievements.  For the rest of the population the implications are just as significant.  Individuals dealing with obesity and other metabolic diseases may have a tool that helps them manage their conditions and make major improvements in their health.

PPARδ is what is known as a nuclear receptor and under normal circumstances it helps kick off the process of the transformation of muscle fibers to more oxidative types along with increasing the use of fatty acids as a fuel source in skeletal muscle.  It increases this switch to using fat as fuel through its interaction with two mitochondrial proteins, Cpt1b and Pdk4.  Carnitine palmitoyl-transferase 1b (Cpt1b) is an enzyme that limits the rate at which fatty acids are transported into mitochondria.  If you enable more fatty acid to enter, you are able to use more of it as fuel.  Pyruvate dehydrogenase kinase isozyme 4 (Pdk4) is involved in regulating the use of pyruvate.  Pyruvate is a byproduct of the metabolism of carbohydrates and it is then used in another metabolic pathway known as the citric acid cycle (also known as the TCA cycle or Krebs cycle) to produce even more energy.  You don’t need to be a molecular biologist to realize that impacting these two gatekeeper molecules can have a major effect on metabolism.  And now we know that PPARδ seems to be the key to impacting these two key proteins.

In experiments in which mice are manipulated to have more PPARδ, the mice are able to run twice as long as control subjects (Wang et at., 2004).  When the mice are manipulated to not have PPARδ they have problems with the generation of mitochondria and the determination of muscle fiber type (Schuler et al., 2006).  If a drug is introduced that activates PPARδ a cascade of positive metabolic and performance benefits are seen.

PPARδ stimulation increases fatty acid metabolism and improves performance

A recent study by Fan et al. (2017) took a closer look at the role of PPARδ and how its manipulation can impact metabolism and performance.  This study was conducted in mice but keep in mind we use mice for early experiments because their physiology is very close to humans and the results we see serve as successful stepping stones to studies and interventions in humans.  And yes, PPARδ is found and active in humans.

When the authors compared normal mice to ones without PPARδ they found the normal mice showed changes in fuel use from glucose to fatty acid after 4 weeks of running while the mice without PPARδ did not show these same metabolic shifts.  Metabolic activity related to the genes impacted by the two gatekeeper proteins, Cpt1b and Pdk4, which are affected by PPARδ were either reduced by 50% or completely absent.  Performance wise, the mice missing PPARδ were only able to run half as long as the normal mice.  While the shift to fat burning occurred, the mice without PPARδ who ran still saw a change in muscle fiber type and an increase in mitochondria.  Clearly it was the fuel source metabolic change that accounted for the increase in performance.

When the authors treated the mice with a drug that activates PPARδ for 8 weeks they found metabolic changes that indicate a significant shift towards increased fatty acid metabolism.  There was a strong increase in the expression of the two mitochondrial gatekeeper genes Cpt1b and Pdk4 and a decrease in anaerobic glycolysis (carbohydrate fueled metabolism).  When the drug was given to the mine manipulated to not have PPARδ none of the changes that are normally expected occurred indicating that all the metabolic and physiological changes we are concerned with are dependent on muscle PPARδ.  Performance wise, the mice given the PPARδ stimulating drug were able to run for 1.5 hours longer then the mice without it.

Increased endurance via blood glucose sparing

The authors theorized that the reason for the increased performance in the drug treated mice was that the increased fatty acid metabolism stimulated via PPARδ spared blood glucose levels.  Both drug treated and non-drug treated mice stop running and often pass out once they hit a blood glucose level below 70 mg/dL.  In control mice blood glucose levels begin to drop between 90-120 min.  In the drug treated mice, blood glucose levels were able to be maintained for extended periods of time and often did not even begin to drop until after 180 minutes.  These types of glucose sparing improvements are the same that are seen with exercise training.  This switch from glucose to fat fueled metabolism maintains blood glucose levels high enough to continue supporting the needs of the brain and other tissues allowing for the significant increases in performance.

In addition to all of this there was also an up-regulation of 492 genes and a down-regulation of 483 genes within the quadriceps of the tested mice.  These included genes that have roles in carbohydrate and fat metabolisms and insulin activity.

So there you have it.  PPARδ turns out to be the main regulator of changes in energy substrate use in muscles.  Increase its activation and you stimulate muscle cells to use more fat based energy sources, sparing blood glucose and extending performance.  The first question you should be asking now is can we take the drug that was used in this study and achieve the same results in humans.  The version used in mice is unfortunately not safe for humans however a company has already been set up and is in the process of developing a version that is safe for human consumption.  While how to address drugs like this in competitive sport performance is an entirely different problem there is no question it could have significant impacts on a range of metabolically related diseases.  So while you are waiting for your PPARδ stimulator in pill form, get out and do some endurance work and stimulate some fat burning/glucose sparing metabolic changes along with enhancing oxidative capacity of muscle fibers and stimulating the growth of additional mitochondria the old fashioned way, by breaking a sweat and doing some work.

Works Cited:

Fan, W., Waizenegger, W., Lin, C.S., Sorrentino, V., He, M., Wall, C., Li, H., Liddle, C., Yu, R., Atkins, A., Auwerx, J., Downes, M., and Evans, R. (2017) PPARδ Promotes Running Endurance by Preserving Glucose. Cell Metabolism 25, 1186-1192

 Schuler, M., Ali, F., Chambon, C., Duteil, D., Bornet, J.M., Tardivel, A., Desvergne, B., Wahli, W., Chambon, P., and Metzger, D. (2006). PGC1alpha expression is controlled in skeletal muscles by PPARbeta, whose ablation results in fiber-type switch, obesity, and type 2 diabetes. Cell Betab. 4, 407-414.

Wang, Y.X., Zhang, C.L., Yu, R.T., Cho, H.K., Nelson, M.C., Bayuga-Ocampo, C.R., Ham, J., Kang, H., and Evans, R.M. (2004) Regulation of muscle fiber type and running endurance by PPARdelta. PLoS Biol. 2, e294.