Tag: sprint interval training

Sprint Interval Training Leads To Improved Results With A Five-Fold Lower Amount Of Time And Volume

You can’t turn on your computer or glance at your phone these days without seeing an article about how high Intensity interval training (HIIT) is the activity you must be doing to get fitter. We’ve covered some of the benefits in previous posts and pretty much every fitness professional worth their weight in protein powder is preaching HIIT. The problem has been for all the data that has accumulated recently regarding the benefits of interval training, very little research has directly compared it’s impacts against more traditional approaches towards exercise.

The reason why, this research is complicated and time consuming to conduct and there are only so many resources that are allocated to the topic. Today we have a study that shows for some important measures of cardiometabolic heath, interval training can provide similar benefits to longer duration moderate intensity cardiovascular training in 20% of the time.

Considering that lack of time is one of the major factors that people site for not meeting their exercise goals an approach that provides meaningful benefits in a short period of time could be an optimal solution for some. The exercise guidelines of 150 minutes of moderate intensity or 75 minutes of vigorous intensity aerobic activity a week are well established and accepted. If you can cut those numbers back considerably while still maintaining meaningful cardiometabolic changes then there may be a large segment of the population that can benefit while overcoming their time restraint barriers.

The Study

Sprint interval training (SIT) is a version of HIIT that involves very brief bursts of all-out intensity followed by longer periods of low-intensity recovery exercise. Compared to HIIT, the intervals are generally shorter and harder and the recovery periods longer. In this study SIT was compared to moderate intensity continuous training (MICT), think jogging or riding the bike for a longer period of time at a comfortable but slightly strenuous pace.

The SIT group performed a 2-minute cycling warm up followed by three 20 second all-out cycling intervals. Each interval was followed by a 2-minute low-intensity recovery effort. The final recovery interval was a 3-minute cool down. The total time spent on the bike was 10 minutes per session and only 1 minute of it was full intensity sprint work.

The MICT group cycled for 45 continuous minutes at approximately 70% of the maximum heart rate. They had an additional 2 minute warm up and 3-minute cool down for a total of 50 minutes of work per session. There was also a control group that did not exercise.

In the first week of the study the subjects exercised 1 time. In the second week they exercised twice and for the following 10 weeks they exercised 3 times per week. At week 7 and at the conclusion of the 12 weeks they were assed.

Cardiorespiratory Fitness

Both the SIT group and the MICT group experienced a 19% improvement in their VO2peak over the course of the 12 weeks. At 6 weeks both groups had already achieved a 12% increase. That is a significant improvement in a relatively short period of time and similar achievement between both the SIT and MICT suggests both the time saving effect of the SIT approach but also the value of the MICT for individuals who may not be able to train at the intensity levels necessary for SIT.

Glycemic Control

The more insulin sensitive someone is, the better job their cells do of removing sugars from the blood stream. Poor insulin sensitivity can lead to high blood sugar levels and ultimately type 2 diabetes. It has been well accepted that physical activity is an effective means to improve insulin sensitivity over time. In this study the SIT group saw a 53% improvement in their insulin sensitivity over 12 weeks. The MICT group also saw an impressive 34% improvement. While both results are outstanding clearly the SIT intervention was superior.

Skeletal Muscle Mitochondrial Content

Mitochondria are the powerhouses of our cells and the more we have, the more energy we can produce. It is widely accepted that mitochondria production increases with physical activity, specifically exercise that is aerobic in nature, including high-intensity interval training. Measuring the activity level of the enzyme citrate synthase is a method of determining the mitochondrial content of skeletal muscle. Over the 12 weeks the SIT group in this study saw a 48% increase in maximal activity of citrate synthase while the MICT group had a 27% increase.

Putting it all together

The body of research demonstrating the effectiveness of various interval training techniques continues to grow. This study very clearly demonstrates that SIT is as effective as MICT in improving cardiorespiratory fitness, insulin sensitivity and skeletal muscle mitochondrial content. The SIT actually showed better results then more traditional training. The most interesting aspect of all of this is that the SIT protocol required a five-fold lower volume and time of exercise to achieve the same results. Just 1 minute of peak work within a 10-minute period, 3 times a week was enough to match 3 sessions of 50 minutes of MICT per week.

Now don’t think that you can just suddenly start training hard for very short periods of time regardless of your training status and objectives. This study showed positive changes with that approach and when we are talking about improving health measures the improvement is significant. If you are a higher-level athlete pushing your fitness levels toward peak levels you will still require more training, but for most average people, the lower volumes are exceptionally interesting. The higher-level athlete still can look at higher intensity training techniques, but they will be applied differently. For weight loss, both groups in this study saw a positive change in body composition but the purpose of the study was not to examine optimum approaches to body fat loss. We will cover that in other posts.

There is also the issue of how many individuals can train at SIT levels of intensity. Individuals new to exercise, older individuals and those with various physical limitations or disease states may not be able to perform SIT. For some it is a physical issue, for others a motivational one. More traditional moderate-intensity training is still valid and appropriate for many populations but for those who are looking for a shorter time commitment, SIT might just be the ideal intervention to improve their health and fitness.

 

Gillen, J., Martin, B., MacInnis, M., Skelly, L., Tarnopolsky, M. and Gibala, M. (2016) Twelve Weeks of Sprint Interval Training Improves Indices of Cardiometabolic Health Similar to Traditional Endurance Training despite a Five-Fold Lower Exercise Volume and Time Commitment. PLOSOne: April 26. doi.org/10.1371/journal.pone.0154075

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.

Results

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.