HIIT Reverses Aging At a Cellular Level. Should We All Be Adding It To Our Exercise Programs and Turning Back The Clock?

High intensity interval training (HIIT) is one of today’s most talked about forms of exercise.  While the approach has been floating around gyms for a long time it has only been in the last few years that our colleagues in the research community have really begun to increase the amount of research being done in this area.  In 2012 when I attended the American College of Sports Medicine annual conference there was a session on HIIT research and the general attitude was that they had suddenly stumbled across an amazing new technique and were just starting to learn how it works.  This is the general flow of almost everything in the world of fitness and training.  A few coaches and trainers begin utilizing an approach, it theoretically makes sense and people seem to be making improvements and before you know it practitioner after practitioner are jumping on board and creating their own versions of it (many trying to sell their formula).  Once a certain critical mass is reached the research community begins to take notice and starts looking into the effectiveness of the approach.  They either quickly debunk it and move on or they find there is something to it and continue to do more and more research.  In the case of HIIT their early research was strongly in support of the approach and as the years have gone by the body of literature on the subject has grow quickly.  A scan of published studies on PubMed using the search term “high intensity interval training” comes up with 1,235 citations. Just in the first three months of 2017 there are 94 new studies and for 2016 there were 263.  I can promise you that if I tweaked the search terms a little or looked on another site for citations that we could increase those numbers.   Clearly there are far too many studies to do one simple deep dive into the research and draw a full understanding of it so with that thought in mind, I present to you the first installment of High Intensity Interval Training research.  I will do my best to curate the literature and pull out the pieces that are most relevant to front line coaches and trainers as well as everyday exercisers looking to maximize their health and fitness improvements.

The most recent HIIT study that has been getting considerable coverage from the mainstream media has the very digestible title “Enhanced Protein Translation Underlies Improved Metabolic and Physical Adaptations to Different Exercise Training Modes in Young and Old Humans”.  Sounds very exciting doesn’t it?  Well that is exactly the type of attention grabbing headline you expect from that newsstand favorite, Cell Metabolism.  Now the headlines that most popular media are using for this article tend to be along the lines of “HIIT Training, The Fountain of Youth”.  While that may be a bit of hyperbole, that title is far more along the lines of what this study actually suggests is happening at the cellular level.

Robinson et al.(2017) examined and compared a variety of responses to high intensity interval training, more traditional strength training and a combination of the two (both performed at a lower intensity and volume then the individual test groups).  The authors went one step farther in that they used both a young group of subjects (18-30 years) and an older group (65-80).

Subjects in the HIIT group trained 3 days per week on a cycling ergometer for 4 x 4 min at greater than 90% of peak oxygen consumption (VO2  peak) with 3 minutes pedaling at no load in between sets.  They then walked on a treadmill 2 days a week for 45 min at 70% of VO2 peak.  The resistance training (RT) group per formed 4 sets of 8-12 repetitions of a series of both upper and lower body exercises twice a week.  The combined training (CT) group underwent a 12-week sedentary period followed by 12 weeks of cycling 5 days a week for 30 minutes at 70% of VO2 peak and resistance training 4 days per week with less repetitions then the RT group used.

Cardio Respiratory Fitness, Muscle Mass and Insulin

Let’s begin reviewing the results with the easy and to be expected outcomes.  The youngsters saw significant increases in absolute VO2 peak for all three training approaches, the greatest results with HITT leading the way followed by CT and then RT.  For relative VO2 peak the young group saw an approximate increase of 28% with HITT, 17% with CT and no statistically significant change with RT.  The older subjects saw absolute VO2 peak increases for both the HITT and CT group.  They did see improvements with RT but the results were not statistically significant.  Absolute VO2 peak increased 17% for HITT and 21% with CT.  There were no significant changes for RT.  For the non-science geeks, remember VO2 peak refers to the top rate at which your body utilizes oxygen and a bigger number is better, so big props to the older group for such significant changes.

All three training groups for both age cohorts saw increases in fat free mass (that means added muscle mass).  As expected resistance training had the greatest impact and more so for the younger group but the results were positive for everyone in all conditions.  Leg strength increased for the RT and CT groups in both age categories but not the HITT group.  This could be to the specificity of training for the cycling group.

It is well known that insulin sensitivity is improved with exercise.  This means the body does a better job of responding to the presence of insulin and moving glucose from the blood stream into storage as glycogen.  The younger group of subjects saw improvements in insulin sensitivity for all three training categories.  The older subjects saw improvements for both HIIT and RT but not the combined training.

Mitochondrial changes

Let’s start by remembering that mitochondria are the power factories in your cells.  The more you have and the better they work the more ATP (ATP = energy molecules) you can produce and the more work you can do.  Also keep in mind that mitochondria are primarily associated with aerobic metabolism (with oxygen = cardiorespiratory fitness).  It is common for people to have reduced mitochondrial content and function with age and while this study is not looking at the causes for these declines with age, it’s fairly safe to say it is both a simple function of aging and also a result of a function of detraining for most individuals.  And while we are not touching on this subject today, do note that mitochondria are exceptionally complex structures that do far more than just produce ATP.

The authors found that with HITT the younger subjects had a 49% increase in mitochondrial respiration and the older subjects had an outstanding 69% increase.  Yes you read that correct, a 69% increase in their ability to produce energy, pretty amazing.  With the CT group the younger subjects saw a 38% increase but the older subjects did not.  Neither group saw improvements with RT suggesting that people need some form of cardiorespiratory stimulus different from resistance training to achieve these benefits.  Both HITT and RT resulted in increased in mitochondrial protein content for older adults explaining some of the improvements that they experienced.  It would be interesting to see a similar study conducted that used high intensity intervals done with various resistance training exercises to determine if those movements could generate similar mitochondrial changes as well as how different types and volumes of HITT influenced results.

Exercise effects on skeletal muscle gene expression

A gene is a set of instructions encoded on our DNA.  On its own it doesn’t do anything but if it is “expressed” it is turned on in such a way that a copy of those instructions are made and sent to other parts of the cell for its function to be carried out, usually the creation of a protein or other molecule that has a particular job in the cell.  Remember that not every gene expression and function they impact is positive and some can be involved in issues like cellular death or uncontrolled reproduction (cancer) so in some instances we want to see certain genes down-regulated while would like an increase in activity of others resulting in positive impacts on the cell and general body.

The authors refer to particular gene sequences that are turned on or off as gene transcripts.  Looking at transcription in skeletal muscle related to mitochondria, muscle hypertrophy (growth) and insulin sensitivity before training, the older subjects had 267 gene transcripts lower and 166 higher than the younger group.  That represents quite a significant difference in gene activity with age.  Following training the largest numbers of genes were turned on with HITT in both young and old subjects.  Compared to HITT, RT and CT increased 35% and 28% fewer genes in the younger subjects.  In the older subjects 70% and 84% fewer genes were expressed compared to HITT.  Score another one for older adults performing HITT.

In young subjects 274 unique genes were increased by HITT, 74 by RT and 170 by CT.  Older exercisers had 396 genes increased by HITT, 33 by RT and 19 by CT.  Both age groups clearly show the most gene activity as the result of HITT and this does not even count genes that were affected by more than one training mode.

The next question was how many of the genes affected are impacted in both the young and older group and how many are specific to age.  Of the total 553 genes affected by HITT in older subjects (157 had some overlap with RT/CT so 157 + 396 unique HIIT genes = 553), one –third (181) were also shared with the younger HITT group and the young RT and CT groups shared 114 of these genes. A full third of the older HITT genes (186 of 553) were unique to the older group suggesting that a large number of the genes impacted by HITT are age specific.

Impact of training on skeletal muscle proteins

When someone says protein most of us conjure up images of steaks and chicken breasts and post workout shakes, thinking of the macronutrient we all eat to survive.  Yes protein is something we eat and we all know that our bodies use it to produce muscle but at the cellular level a variety of proteins are being constantly produced and they have an assortment of functions, acting as catalysts, signal receptors, switches, motors and more.  As we previously mentioned, many of the gene transcripts that the researchers examined are turned on by different types of exercise and when they are expressed, many of them instruct the cell to build a particular type of protein depending on the gene.

The younger subjects in this study saw increases in protein abundance for 265 proteins following resistance training.  They saw 114 proteins increase following HIIT.  Only 35 of the proteins that increased were affected by both the RT and HIIT.  In the older subjects 147 proteins increased in abundance following RT and 227 increased following HIIT.  Only 38 were shared between the two types of training.  This suggests both significant impacts of the different types of training as well as the very large impact that HIIT has on older adults.

Looking at only mitochondrial proteins, the younger subjects had 141 increases with RT and only 25 with HITT while the older subjects increased 53 mitochondrial proteins with RT and 169 with HIIT.  Again very high rates for both types of training for older adults, especially with HIIT.

Study limitations

This was a very well conducted study but like all research, there are limitations.  There were a limited number of subjects and after they were broken down into three different training protocols for each age group that resulted in a fairly small number of subjects in each group.  The depth of cellular testing that was done was significant and produced meaningful results that do suggest these benefits can be achieved by the broader population but there is always a limit to how far we can extrapolate the results with a small study population.  There was also a fairly strict exclusion criterion so the individuals who were ultimately selected were extremely healthy to begin with.  That leads to the immediate question of how individuals with an assortment of medical conditions would respond to the same training protocols.

There are also issues regarding the training protocols used.  For the resistance training group, they were given what seems to be a very traditional basic plan that isn’t necessarily reflective of the type of training most people are doing in gyms today.  No low rep heavy work.  No resistance training based intervals or combinations that are designed to raise heart rate and present a metabolic challenge.  It would be interesting to see how more modern resistance training techniques fared.  The current trend for “metabolic” training and short rest times could produce results more similar to what we consider pure cardio intervals like biking and running.

For the HIIT intervals, what affect do different time intervals have?  Thirty seconds versus a minute versus the four minute bouts used in this study.  What about different volumes? Surely there has to be differences when those variables are changed.  How many intervals do we need to maximize benefits and what is the optimal time of those intervals?  Also, what about different types of stimulus, running or rowing as opposed to biking?  And what happens at lower levels of intensity?  Certainly not everyone can get out and start working at 90% VO2 peak and many people will never be able to train at that level for a variety of reasons.

Obviously no one study can answer everything but this study clearly adds to the body of literature that says HIIT really does something different in the body as compared to other forms of exercise and is worth continuing to ask these questions and investigate these issues.

So there you have it, HIIT increases VO2 peak, insulin sensitivity, mitochondrial respiration, muscle mass and strength in both young and old subjects with really remarkable improvements in older adults.  And while resistance training is great, it doesn’t impact the cardiovascular related elements in nearly as meaningful a way.  Not only does HIIT have those affects, on the cellular level it greatly increases gene expression and positively impacts regulation of muscle growth, mitochondrial pathways and protein synthesis.  Now get out there and start adding some HIIT training to your programs and keep thinking about all those amazing changes that are happening at the cellular level as a result.

Works Cited

Robinson, M., Dasari, S., Konopka, A., Johnson, M., Manjunatha, S., Esponda, R., Carter, R., Lanza, I., Nair, K.S., (2017). Enhanced Protein Translation Underlies Improved Metabolic and Physical Adaptations to Different Exercise Training Modes in Young and Old Humans. Cell Metabolism 25, 581-592.

Foam Rolling and Self-Myofascial Release, A Deep Dive. Do they really work?

Walk into any gym or training facility today and you will undoubtedly see a pile of foam rollers.  They may be lined up against a wall, neatly stored in a rack or strewn about throughout the facility.   Staring at you like a lonely girl at a high school dance.  “I’m here for a reason, come discover what wonders I hold”.  Like bunnies, if you leave two of them together you are likely to come back and find more magically appeared overnight.  Often a hybrid of their parents, now showing a new combination of colors and ridges and bumps.  Evil offspring mutating in countless variations.  There seems to be no end to the proliferation of rollers on the market, and the floors of your local gym.  Not to mention the three rollers cohabitating with me in my living room.  I’ll get off the sofa and roll on you while we watch Netflix, I promise.

With so many rollers invading our gyms and homes there must be something to them, right?  They are not just the latest fad hoisted upon us by money grubbing fitness manufacturers eager to separate us from our hard earned dollars and embraced by uneducated trainers whose idea of continuing education is Jonny Daredevil’s latest YouTube video showing how he can balance, one footed on an exercise ball while doing heavy kettlebell swings.

The good news is there really is something to them and yes, you should be using one.  And this is going to be the first of many articles looking at self-myofascial release (SMFR), foam rollers, what they do, how they really work on the body and what you should be doing with them.

Today we are talking about the effect of foam rollers on range of motion (ROM).  The first issue to get out of the way is the difference between flexibility, mobility and ROM.  For many people all three are considered the same thing.  In the olden days, say before 2010, flexibility was considered the ability of a joint to move through a full range of motion.  More recently you will find many professionals referring to flexibility being the ability of a muscle to lengthen.  Only one factor that can impact the ability of a joint to move through a full range of motion.

Neurological factors, joint capsules, ligaments, bone and other soft tissues can all be elements that limit the ability of a joint to move.  When all taken together, along with the capacity of muscles to lengthen, you get mobility, the ability of a joint to move through a range of motion.

So what’s different then between mobility and ROM?  In my humble opinion, nothing really.  Range of motion is just more of a clinical term that you see used in research and medical/rehabilitation settings describing the measurement of the motion of joint, the degree of angular motion.  Mobility is more of an applied term talking about the ability of the joint to move through a functional range of motion in everyday life and activity.  Of course this is open to endless debate and a bunch of drunken trainers sitting around a bar at night during a convention will argue how wrong I am and distinctly different the terms are.  What will it mean to you the exerciser, the trainer, the coach, absolutely nothing.

What does matter is how effective foam rollers and self-myofascial release (SMFR) are on increasing mobility/ROM/Flexibility/that warm fuzzy feeling you get when you can actually touch your toes.  So let’s take a look at what the research is really telling us.

The Research

Su et al. (2016) compared the effects of foam rolling, static stretching and dynamic stretching on ROM and peak torque for a knee extension and a knee flexion movement.  They used a Thomas test to measure quadriceps flexibility and a sit and reach test to measure hamstrings flexibility.  To test peak torque they used an isokinetic device at 60°/per second.  What this means to the non-research geek is they used a machine that allowed the subject to extend or flex their leg at the knee at a constant speed of 60°/per second, as hard as they could.  So what did they find?  Flexibility improved significantly more with the foam rolling as compared to the static or dynamic stretching.  Score one for foam rolling.  As for muscle strength the foam rolling and dynamic stretching groups improved on the knee extension.  This did not happen for the static stretching group and none of the groups saw improvement or a decrease in flexion performance after the intervention.  Why does this matter?  It says that foam rolling before activity does not reduce strength and performance afterwards, making it a beneficial warm up/prep activity.

Halperin et al. (2014) looked at range of motion and force production at the ankle and compared foam rolling to static stretching.  They used three 30 second bouts of either a hand held foam roller massager or static stretching.  There were flexibility improvements in both groups immediately after the intervention as well as ten minutes later.  Similar to the previous study there was an improvement in peak force in the foam roller group while the static stretching group saw a decrease.  This difference was significant 10 minutes later.  Again suggesting that foam rolling improves ROM while preserving or improving strength.

One of the interesting aspects of static stretching is that there is a measurable effect in the limb that was not stretched.  This is called a cross-over effect.  Kelly and Beardsley (2016) performed a study to determine if SMFR via foam rolling would create the same sort of cross-over effect as static stretching does.  They measured dorsiflexion (think pulling your foot and toes back towards your shin) on 26 subjects and had half of them perform 3 bouts of 30 seconds of foam rolling on their planter flexors (think calf muscles that make you point your foot down, like stepping on the gas or going up on your toes) on their dominant leg.  They took repeat measurements at 5, 10, 15 and 20 minutes after the subjects either performed the rolling or rested.  Significant increases in ROM were seen for at least 20 minutes in the leg on which SMFR was performed and up to 10 minutes on the uninvolved leg.  While the changes were not large they were statistically significant and suggest that a cross-over effect does exist.  This could mean that when a limb is injured/restricted, some positive impact can be had upon it through rolling the uninjured side.

Murray et al. (2016) looked at the effect of a single, 60 second bout of foam rolling on flexibility, muscle contractility and temperature.  The authors did find a statistically significant improvement in flexibility following foam rolling but they felt that the change was small enough as to not be of much practical relevance.  They did not find any changes in muscle contractility or temperature.

While the research up to now how shown a ROM benefit to using foam rollers for SMFR not all studies are in agreement.  Couture et al. (2015) found no improvements.  They used both short sets of rolling for 10 seconds as well as multiple longer 30 second bouts.  As we will discuss, the type of roller, amount of pressure, length of time and how ROM was measured can all be factors why this study found different results then other research.  They were one of the only studies to perform a pure knee extension measurement independent of contributions of the low back or other joints to hamstring flexibility.

Vigotsky et al. (2015) examined the effect of foam rolling on knee flexion and hip extension along with rectus femoris length during a modified Thomas test.  The authors did find changes in hip extension but not in knee flexion or muscle length.  Although they did find a statistically significant change in hip extension they did not feel comfortable concluding that foam rolling was responsible for the change.  The lack of change of muscle length suggested to the authors that the measured improvements in hip extension were more likely due to changes in stretch tolerance instead of changes in tissue length.  It was also noted that there was considerable variation between test subjects.  Some experienced hip extension increases, some didn’t and some had decreases.  This is complicated by variable changes in knee flexion.  Again some subjects had an increase while others saw decrease or no change which posed the question, were changes in knee flexion responsible for changes in hip extension (did reducing knee flexion allow for greater hip extension).  The type of force that was applied could also account for variations between this study and others. In the Thomas test it is only the weight of the subjects leg that was used to elicit a measurement, no outside force was applied by the examiner.  There was also a lengthy warm up period that could have impacted the results. The variation in warm up from study to study could be a major factor in difference in results.

Behara and Jacobson (2015) were the first researches to use the Rumble Roller as the SMFR tool.  The Rumble Roller has raised nodules that are designed to stimulate deeper layers of muscle tissue and stretch muscle and fascia is multiple directions.  It can be a more intense rolling experience for individuals new to foam rolling.  The authors found significant increases in ROM of 15.6%, similar to the results they found in subjects using dynamic stretching.  They did not find any significant changes or reductions in muscle force or power, similar to other studies.

Up to now the studies reviewed have looked at the acute effects of SMFR.  Junker and Stoggl (2015) looked at the impact of a four week foam rolling program as compared to contract-relax PNF (CRPNF) and a control group.  They found that a treatment dose of 3 times per week for 3 bouts of 30-40 seconds of rolling produced long term improvements in hamstring flexibility.  The results were similar for subjects who performed CRPNF.  This suggests a longer term cumulative flexibility benefit to incorporating foam rolling as a regular part of a training program.

Skarabot and Beardsley (2015) compared foam rolling to foam rolling in combination with static stretching and static stretching alone in resistance trained adolescent swimmers with at least six months experience foam rolling.  While a variety of different subject pools have been used in other studies this was the first to use individuals experienced in foam rolling.  The greatest improvements in flexibility were found in the foam rolling in addition to static stretching group.  The benefits of all test groups were found to only be significant immediately following treatment.  At ten minutes there were no differences from the baseline measurements.  This study raises the question of if a combination treatment approach with a reduced volume of static stretching could be used to maximize flexibility improvements while limiting the performance decreases seen with static stretching.

Bushell et al. (2015) looked at the effect of foam rolling on hip extension when there is a stretch placed on the rest of the frontal plane, meaning when the subject is in a dynamic lunge position.  While it is great to see improvements in ROM in passive stretch positions, the impact on flexibility interventions on actual dynamic movement, when multiple muscle groups and their associated firing patterns are in play is far more impactful in real life and activity.  After an initial treatment and measurement day the experimental group rolled for five days before retesting.  There was no long term benefits from rolling but at the second testing date the rolling subjects did show improvement in their second measured lunge immediately after rolling. This supported the idea that the benefits of rolling are limited to the short term.  The increased immediate improvement from the first day of testing to the second day of testing suggests that a week of rolling in between allowed the subjects to get used to the discomfort of rolling and this allowed them to achieve greater immediate benefits from rolling at the second session.  The test group also reported positive feelings

Peacock et al. (2015) were the first to compare different foam rolling techniques.  They had half their subjects roll along the mediolateral axis (sagital plane; low back, medial glutes, hamstrings, posterior calf, pecs and quads) and half their subjects roll along the anteroposterior axis (frontal plane; lats, obliques, lateral hip, iliotibial band, lateral calf and adductors).  Subjects were then tested in a serious of performance drills similar to the NFL combine (vertical jump, broad jump, shuttle run, bench press) as well as the sit and reach test.  They did not see any significant differences in any of the performance tests.  There was a difference in the sit and reach test with the mediolateral axis subjects showing more improvement.  While this study did not determine if foam rolling improved testing performance it did suggest that the approach towards rolling may not make any difference and subjects can roll whatever axis/plane they prefer.

The difference between five rounds of 20 second repetitions of rolling and five rounds of 60 second repetitions of rolling was investigated by Bradbury-Squires et at. (2015). The authors used a roller massager as opposed to a foam roller.  They found their subjects had 10% and 16% greater ranges of motion at the knee in the 20 second and 60 second groups as compared to a control group, suggesting that longer periods of rolling may elicit greater immediate improvements in ROM.  EMG activity was also measured during a lunge after the rolling and muscle activation levels were lower in both then 20 and 6o seconds groups as compared to the control subjects. The authors interpreted this as increased neuromuscular efficiency with the 60 second roller group showing greater changes then the 20 second group.  While this is a very interesting and useful study, the biggest problem I find with it, as in many of the other studies is that in the real world very few individuals do multiple rounds of rolling.  You may be able to program someone to do 6o seconds instead of 20 seconds but rarely will individuals follow directions to do multiple rounds of rolling on the same body part.  I am left asking what would the results be with just a single round of rolling?

Halperin et al. (2014) looked at ankle ROM and force production when a hand held roller massager was used.  They compared static stretching to the roller massage and found that while both improved ROM at 1 min after treatment there was a statistically significant improvement between the two approaches at 10 min with the roller group showing greater ankle ROM. They also found that the roller group had significantly improved force production at 10 minutes as compared to the static stretch group.  This study used three sets of 30 seconds with a 10 second rest in between.

Mohr et al. (2014) looked at passive hip flexion when comparing static stretching, foam rolling, both performed together and a control group.  Their subjects performed the interventions daily over the course of six days.  All three of their test groups saw significant improvements with the combined rolling and static stretching group showing the greatest change.  What was particularly interesting about their subject population was they had less than 90° of passive hip flexion prior to the study.  This raises the question of the impact of rolling and other interventions on individuals who are showing deficiencies before treatment as opposed to well trained individuals who have more optimal ranges of motions.  Perhaps the amount of benefit someone sees from SMFR may have to do with their individual state and the trained, flexible athlete should expect a smaller overall improvement then the inflexible average person who is new to training and self care.

One of the common uses of foam rolling is to reduce muscle soreness and improve function after activity, especially in the days that follow an intense bout of exercise.  Macdonald ET at. (2014) explored this notion of foam rolling as recovery tool.  After a 10×10 squat protocol designed to create exercise-induced muscle damage test subjects performed a foam rolling protocol immediately after, at 24 hours and at 48 hours.  They found that foam rolling significantly reduced muscle soreness/pain at all time points along with improving ROM.  The authors also found improvements in tests of power and muscle activation in the FR group as compared to their control group.  They concluded the improvements were achieved primarily through the impact of the rolling on connective tissue along with neural responses.

Pearcey et al. (2015) also looked at the effect of foam rolling on exercise induced muscle soreness.  Also utilizing a 10×10 squat protocol to induce muscle damage, the authors had subjects perform 20 minutes of foam rolling of the lower extremity after the squat session and at 24, 48 and 72 hours.  The subjects also retested on a measure of pain, sprint speed, power, change of direction speed and dynamic strength endurance before each foam rolling session.  Improvements in pressure-induced pain were found at all time points for the foam rolling group.  Subjects also saw increased performance measures in all tests except for change of direction speed.  While retesting each measure at each time marker seems to be a bit overkill to see if foam rolling improved recovery the results do strongly show that at all times there are benefits to rolling.

In another study MacDonald et al. (2013) measured knee ROM and quadriceps muscle performance.  At 2 minutes post intervention they found 10.6° improvements in ROM and at 10 minutes there were still 8.8°improvements.  Those values represent a 12.7% and 10.2% improvement.  Individual results varied from a minimum of 4° to almost 20°.  They also found no decreases in any of their measures of muscle power and performance.  This study utilized two 1-minute bouts of rolling.

One of the biggest questions regarding utilizing rollers is how long should one roll?  Most studies have utilized multiple bouts of 30 or 60 seconds in their studies.  While this is fine in a research setting, in reality most people are not going to do 3 to 5 sets of rolling of the same body part.  Sullivan et al. (2013) attempted to answer some of this question in their study utilizing either one or two sets of 5 or 10 seconds of rolling with a hand held roller-massager.  They found ROM improvements of 4.3% with a trend towards the 10 second bouts having a greater effect.  To the casual reader 4.3% may not sound like a lot but it is a significant change and to achieve it with only 10 seconds of rolling suggests a real world intervention that is quick, easy to do and effective.

Most foam rolling studies that examine performance measures compare the rolling group to a static stretching group.  Healey et al. (2014) compared the a foam rolling group to a planking group and then measured vertical jump height and power, isometric force and agility along with muscle soreness, fatigue and perceived exertion.  There were no improvements in athletic performance in the foam rolling group as compared to the planking group.  This continues to support the notion that while rolling may not improve performance, unlike static stretching it will not decrease performance.  This study did not look at range of motion improvements so if that is an objective of the individual rolling this study in combination with those that did measure ROM supports utilizing SMFR to avoid negative impacts on performance.  The rolling subjects in this study did report lower perceived fatigue after their testing which could allow for extended workout times and volumes leading to more performance enhancements over time.

In an entirely different physiological arena, Okamoto et al. (2014) looked at the impact of foam rolling on arterial function.  Stiff arteries are associated with increased cardiovascular risks.    They contribute to elevated systolic blood pressure and left ventricular hypertrophy.  The researchers examined if SMFR with a foam roller would have any effect on arterial stiffness and vascular endothelial function, a related measure that impacts stiffness and can be accessed through plasma nitric oxide (NO) concentrations.  Measurements taken after a 15 minutes roller session showed significant decreases in arterial stiffness and increases in plasma NO concentrations (a good thing).  These results suggest a meaningful beneficial impact of foam rolling on cardiovascular function.  In theory long term benefits from rolling could improve baseline arterial stiffness though longer term studies need to be conducted to determine this.  This study also utilized young healthy subjects so the impact of rolling on other populations also needs to be examined before to broad of an interpretation of the results is made.

Limitations of the research:

While the overall trend in the research shows that foam rolling clearly has benefits there are many factors which limit the extent to which we can interpret the results from the research.  Most of the studies are done with a fairly small number of subjects.  There are enough to find statistically significant results but there are limitations to how powerful the results are from a study with 10-20 subjects as compared to one with hundreds of subjects.  While these studies have lower subject numbers, the consistent results across a number of studies helps balance this limitation and suggest that the results are valid.

There may also be issues with the gender of subjects.  Studies done on one gender may not have the same results on the other gender and studies done with a mix of genders may not have enough subjects of any one gender to have enough power to be generalized to all individuals.

Most of these studies are done on younger subjects who are fitter and have less history of injury.  The results of a study on adolescents or young adults may not be the same with older adults.  There are also issues of the level of training/fitness in the subjects as well as previous experience with foam rolling.  Fit, athletic individuals, who are usually subjects, can respond quite differently then out of shape, untrained individuals.

Then there are issues pertaining to the specific variables of the study.  How many sets of rolling were done and for how long?  If a study used three sets of rolling but in real life someone is only doing one set will they see the same results?  How long did the subjects in the study roll?  Are the results transferable to shorter times?  Are the benefits greater for longer rolling periods?  Some studies did show benefits from very short duration interventions which is quite promising but there are limits to how far those results can be extrapolated.  There are questions regarding the amount of force used in the rolling, the amount of rest time between sets, the pace of rolling, length of rolling (short strokes over part of the muscle vs. long strokes the length of the muscle), the type of roller used and the particular muscles rolled.

While it wasn’t discussed in this article, most of the studies had subjects perform some form of warm up prior to rolling.  Many of the benefits of rolling are also seen in various warm ups and we need to ask if particular warm ups prior to rolling impact its effectiveness or if a warm up should even be done prior to rolling or after.  And if warm ups are a factor the type and duration of warm up needs to be considered.

Then the issue of what type of measurement is being taken and if it accurately reflects the results of rolling.  For the same joint and muscle groups more than one measurement technique can be used and different studies used these different measurements.  Are some more appropriate than others?  While a measurement technique may have previously been shown to be valid, showing a result in that particular type of measurement doesn’t necessarily mean an improvement in mobility during dynamic training activity will be found.  Some medications can be shown to lower blood pressure but they do not lower the risk and rate of heart attack and stroke.  Some rolling techniques and measurements may show positive results in the lab but that doesn’t mean they have the same benefit during actual training.

There are also questions regarding the long term results of a rolling intervention.  Immediate changes were well measured as were a number of time intervals after the intervention but there is very little material regarding the long term permanent benefits.  Does a regular rolling program over a period of weeks result in lasting changes in mobility or are the results only applicable in the shorter term and should be viewed primarily as pre-event activity.  Some of the research did start to look at longer term recovery factors and the results are positive but there still needs to be a good deal of investigation of the impact of rolling on recovery and how it should be used post activity.

Now after asking all those questions about the research you are probably sitting there saying, “Did I just waste my time reading all of the summaries?  There are so many issues not answered in the research”.   Yes there are a lot of questions left to answer but there are always are.  The general trend in a fairly sizeable body of literature suggests that foam rolling is the real deal and worth considering as part of a well rounded training program.  Does it mean you should stop doing other types of mobility, warm up and recovery work?  No, there are still benefits to other interventions but you can’t ignore that rolling has a place and in some instances may be a better choice than other activities.

How it works:

If your eyes aren’t glazed over from reading everything up to now you may find yourself asking, “Seth, I get it, foam rolling works but how does it work?”  Well, I’ll take a long pause here while you prepare to hit your head against the wall, we aren’t entirely sure.  There are a number of different theories as to what mechanisms are at work that seem to be physiologically sensible and it would be a safe bet to say that a combination of the following mechanisms are behind the benefits but we cannot say for certainty which mechanism is really responsible.

Mechanisms of action are primarily broken down into either mechanical or neurophysiological.

Mechanical actions

The first explanation has to do with the material nature of fascia.  A simple explanation is that fascia consists of collagen and elastin fibers along with ground substance which acts as a lubricant around the other fibers.  Ground substance is a viscous material that can go from a very fluid state to a firmer more jelly like character.  When tissues are injured, little used or often just old the ground substance can become a harder, more solid like gel and even dry up, limiting motion.  When heat or pressure is applied to tissue, specifically ground substance, it can make it less dense and more fluid like.  This process is called thixotrophy and a roller is a mechanism through which the necessary heat and pressure can be applied to create this affect.

Foam rollers also act on the tissues by compressing them like you would squeeze a sponge, allowing them to rehydrate as the force is taken off of a location.  The roller can also mechanically create motion between layers of fascia, break collagen bonds through mechanical force, break down fascial adhesions, release fascial trigger points and increase blood and lymph flow.

Neurophysiological actions

The pressure applied from a roller can influence various neural receptors.  Through a process known as autogenic inhibition the roller can stimulate Golgi tendon organ receptors which will inhibit signals from the muscle spindles, resulting in a decrease in muscle tension.  Rolling can also stimulate other neural receptors resulting in a reduction of pain and a relaxation of muscle tissues.  Rolling appears to improve stretch tolerance similar to static stretching allowing for greater ranges of motion.

Improvements in performance are suggested through decreases in neural inhibition as well as better communication from afferent receptors found in connective tissue.  The phosphorylation of myosin regulatory light chains has also been suggested as an explanation for improvements in performance.  This means an increase in the rate of engagement of cross bridges resulting in increased force development and contraction magnitudes on subsequent contractions.  Essentially an increased contractile response.

While we cannot pinpoint the exact mechanism for change with rolling for any given individual, our understanding of these various tissues, receptors and mechanisms of action allow us to say with a fair degree of confidence that some combination of these factors are responsible for the benefits we see with SMFR and rolling.

So there you go.  A pile of research strongly suggesting self myofascial release and foam rolling are beneficial activities to add to your training programs.  Now go out and explore that ever growing pile of rollers in your local gym or training center.  There is no reason to be afraid of them and you just may find yourself feeling and moving better.

Works Cited:

Behara B, Jacobson BH. (2015). The Acute Effects of Deep Tissue Foam Rolling and Dynamic Stretching on Muscular Strength, Power, and Flexibility in Division I Linemen. J Strength Cond Res. 2015 Jun 24.

Bradbury-Squires DJ, Noftall JC, Sullivan KM, Behm DG, Power KE, Button DC. (2015). Roller-massager application to the quadriceps and knee-joint range of motion and neuromuscular efficiency during a lunge. J Athl Train. Feb;50(2):133-40.

Bushell JE, Dawson SM, Webster MM. (2015)Clinical Relevance of Foam Rolling on Hip Extension Angle in a Functional Lunge Position. J Strength Cond Res. Sep;29(9):2397-403.

Couture G, Karlik D, Glass SC, Hatzel BM. (2015). The Effect of Foam Rolling Duration on Hamstring Range of Motion. Open Orthop J. Oct 2;9:450-5.

Halperin I, Aboodarda S.J., Button D,  Andersen L, Behm D. (2014). Roller Massager Improves Range of Motion of Plantar Flexor Muscules Without Subsequent Decreases in Force Parameters. Int J Sports Phys Ther. Feb;9(1): 92-102.

Healey KC, Hatfield DL, Blanpied P, Dorfman LR, Riebe D. (2014). The effects of myofascial release with foam rolling on performance. J Strength Cond Res. Jan;28(1):61-8.

Junker DH, Stöggl TL. (2015). The Foam Roll as a Tool to Improve Hamstring Flexibility.  J Strength Cond Res. Dec:29(12):3480-5

Kelly S, Beardsley C. (2016). Specific and Cross-Over Effects of Foam Rolling on Ankle Dorsiflexion Range of Motion. Int J Sports Phys Ther. 2016 Aug;11(4):544-51.

Macdonald GZ, Button DC, Drinkwater EJ, Behm DG. (2014). Foam rolling as a recovery tool after an intense bout of physical activity. Med Sci Sports Exerc. Jan;46(1):131-42.

MacDonald GZ, Penney MD, Mullaley ME, Cuconato AL, Drake CD, Behm DG, Button DC. (2013). An acute bout of self-myofascial release increases range of motion without a subsequent decrease in muscle activation or force. J Strength Cond Res. Mar;27(3):812-21.

Mohr AR, Long BC, Goad CL. (2014). Effect of foam rolling and static stretching on passive hip-flexion range of motion. J Sport Rehabil. Nov;23(4):296-9.

Okamoto T, Masuhara M, Ikuta K. (2014). Acute effects of self-myofascial release using a foam roller on arterial function. J Strength Cond Res. Jan;28(1):69-73.

Peacock CA, Krein DD, Antonio J, Sanders GJ, Silver TA, Colas M. (2015). Comparing Acute Bouts of Sagittal Plane Progression Foam Rolling vs. Frontal Plane Progression Foam Rolling. J Strength Cond Res. Aug;29(8):2310-5.

Pearcey GE, Bradbury-Squires DJ, Kawamoto JE, Drinkwater EJ, Behm DG, Button DC. (2015). Foam rolling for delayed-onset muscle soreness and recovery of dynamic performance measures. J Athl Train. Jan;50(1):5-13.

Škarabot J, Beardsley C, Štirn I. (2015). Comparing the effects of self-myofascial release with static stretching on ankle range-of-motion in adolescent athletes. Int J Sports Phys Ther. Apr;10(2):203-12.

Su H, Chang NJ, Wu WL, Guo LY, Chu IH. (2016). Acute Effects of Foam Rolling, Static Stretching and Dynamic Stretching During Warm-Ups on Muscular Felxibility and Strength in Young Adults. J Sport Rehabil. Oct 13:1-24.

Sullivan KM, Silvey DB, Button DC, Behm DG. (2013). Roller-massager application to the hamstrings increases sit-and-reach range of motion within five to ten seconds without performance impairments. Int J Sports Phys Ther. Jun;8(3):228-36.
Vigotsky AD, Lehman GJ, Contreras B, Beardsley C, Chung B, Feser EH. (2015). Acute effects of anterior thigh foam rolling on hip angle, knee angle, and rectus femoris length in the modified Thomas test. PeerJ. 2015 Sep 24;3.