The mechanistic mysteries of foam rolling

As the popularity of foam rollers escalates, researchers are scrambling to document the therapy’s effects and tease out the possible underlying mechanisms, which now appear to be more complicated than the earliest investigators had hypothesized.

By Cary Groner

Foam rollers are beginning to seem a bit like Star Trek’s tribbles: inert and nonthreatening, but extremely successful at reproduction. In gyms and on athletic fields everywhere, people are half-lying on the colorful, worm-like cylinders and rolling slowly forward and back. Given how ubiquitous foam rollers have become, however, a surprising number of questions remain about what they do for us and how.

“In our research, we’ve found that foam rolling tends to offer similar increases in range of motion as static stretching, but without the typical impairment associated with stretching,” said David Behm, PhD, a research professor in the School of Human Kinetics and Recreation at the Memorial University of Newfoundland (MUN) in St. John’s, Canada. In one of those quirks of scientific curiosity, where investigators with similar interests tend to congregate at certain institutions, MUN has become a hotbed of research into foam rolling and its sister therapy, roller massage.

Some claims about foam rolling may not hold up, as it turns out, and Behm and his colleagues have published a number of studies in an attempt to winnow wheat from chaff. Other researchers are getting on board, and the recent American College of Sports Medicine (ACSM) conference offered a slew of papers on the subject. For that matter, a new article from Behm’s team, accepted for publication in BMC Musculoskeletal Disorders, offers insights into the approach’s mechanism of action that may upend much of what clinicians and trainers thought they knew.

The basics

Essentially, people use their own weight on the rollers to exert both direct and sweeping pressure on soft tissue, typically the calves, hamstrings, iliotibial band, quadriceps, or gluteals.¹ Researchers and trainers are interested in foam rolling’s effects in two primary conditions: athletic performance (particularly range of motion [ROM]), and recovery from intense athletic activities that create sore muscles. Much of the current research into both of these has come from the labs at MUN.

“How does it work?” asked Behm. “Some people describe it as self-myofascial release, but that suggests that it’s actually breaking up adhesions, having an effect on trigger points.”

Behm said that whereas foam rolling may exert enough pressure to help release fascial tissue due to the body weight involved, using a roller massager—typically a smaller, handheld device with an undulant surface—probably doesn’t generate adequate forces, given how tough fascia is.

Such issues are critical in sports medicine because, when fascia becomes restricted—typically due to injury, disease, inactivity, or inflammation—it can lose its elasticity and bind around injured areas, causing fibrous adhesions. These, in turn, often lead to pain and abnormal muscle mechanics that affect joint range of motion, strength, endurance, coordination, and other factors.² While massage and stretching sometimes help address such matters, they have recognized downsides; massage requires a therapist or trainer, while stretching runs the risk of weakening muscle tissue.³

A brief look at current research into foam rolling helps clarify where things stand and provides context for the new sheaf of papers.

Existing research

In a 2013 paper in the Journal of Strength and Conditioning Research (JSCR), for example, MUN investigators had participants perform two one-minute trials of foam rolling on their quadriceps; they measured parameters including knee joint ROM and muscle force beforehand, then at two and 10 minutes afterward.² Despite the brevity of the foam rolling, knee joint ROM increased by 12.7% and 10.3% (10° and 8°) at two and 10 minutes, respectively, without negative effects on voluntary muscle activation, force, or evoked contractile properties.

Another 2013 study from MUN had participants do a sit-and-reach ROM test before and after using a handheld roller massager on their hamstrings in four variations (one set for five seconds, one for 10 seconds, two sets for five seconds, two for 10 seconds).⁴ The authors reported a 4.3% ROM increase and noted the longer rolling durations tended to increase ROM more than the shorter ones.

A paper from Iowa researchers published in the Journal of Sport Rehabilitation last year looked at passive hip-flexion ROM before and immediately after static stretching, foam rolling plus static stretching, foam rolling alone, or no intervention (control) over the course of six daily sessions.⁵ They found that, although all approaches were associated with a significant change in ROM, participants who did the combined intervention improved more than those in any other group.

Then, in a paper published earlier this year, the MUN team had individuals perform two randomized applications of a handheld roller massager to their quadriceps; as a control condition, the participants sat quietly for the average time it took to complete the two roller-massage applications.⁶ Participants did five repetitions of 20 or 60 seconds per repetition, separated by 24 to 48 hours, then performed a lunge. Knee joint ROM was 10% and 16% greater in the 20- and 60-second conditions, respectively, than in controls; the roller massage was also associated with increased neuromuscular efficiency during the lunge.

As noted, one of foam rolling’s attractions is that it seems to increase ROM without introducing the performance deficits sometimes associated with static stretching. For example, a paper presented at the 2014 ACSM meeting in Orlando compared the effects of foam rolling and static stretching on the recovery of quadriceps and hamstring force production after intensive exercise.⁷ The authors found that foam rolling helped preserve muscle force versus stretching, particularly in knee extension (94% vs 84% of baseline) and knee flexion (98% vs 88%, respectively). Another study reported an increase in maximal voluntary contraction (MVC) of the plantar flexors at 10 minutes following roller massage versus static stretching, which decreased maximal force.⁸

Although researchers aren’t sure why foam rolling might preserve or increase muscle force, theories include elevated muscle temperature due to friction from the roller, myofascial release, and other factors, possibly in combination. It’s also conceivable that foam rolling may pressure tissue into a more gel-like state, improving the fascia’s viscoelastic properties without affecting muscles.¹

“So is foam rolling better than stretching?” asked Behm. “Magnusson says that you get an increase in range of motion because you have an increased tolerance to stretch.⁹ There’s definitely a neural component to this, and I think foam rolling taps into that increased stretch tolerance and the associated decrease in pain.”

As noted, research has also shed light on the use of foam rolling to help athletes recover from muscle damage and the associated soreness and swelling. For example, a 2014 study reported that individuals who did 20 minutes of foam rolling had less muscle soreness after a fatiguing squat protocol than controls, and also demonstrated improved vertical jump height, muscle activation, and both passive and dynamic ROM.¹⁰ And MUN research published earlier this year found that foam rolling after a similar squat protocol was associated with reduced delayed-onset muscle soreness (DOMS) and improved power, sprint time, and dynamic strength for one to three days after application.¹¹

“In that study, using the foam roller increased neuromuscular efficiency,” Behm said. “Once they were damaged—they had DOMS—they had to use more EMG activity to do those things. But if they used the foam roller, the increased effort was brought back to almost normal. I can’t say it’s equivalent to massage, because there are no studies directly comparing massage to foam rolling. But I would point out that you’re going to pay for your massage, so after an injury or a heavy workout, foam rollers would be helpful and similar to massage without the expense.”

New findings

As noted earlier, 2015 has been a big year for research into foam rolling.

In one study out of Austria, for example, researchers compared foam rolling to proprioceptive neuromuscular facilitation (PNF stretching, done with a partner to contract and relax muscles in a stretch) and found both methods about equally effective for increasing hamstring flexibility.¹³ Another paper reported that foam rolling plus stretching was superior to foam rolling alone for increasing ROM.¹⁴

Several papers presented at this year’s ACSM conference in San Diego addressed questions around foam rolling, as well. In one case, researchers reported that after foam rolling, participants showed significantly increased joint flexion in the hips and knees during the landing phase of a maximum vertical jump; jump height wasn’t affected.¹⁵ They noted that because such increased flexion is associated with lower injury risk, foam rolling could decrease injury rates without affecting performance.

In another paper, presented in poster form, researchers from the University of Minnesota in Minneapolis studied the effect of foam rolling on soreness and running performance compared with sham tights (placebo) in eight runners (four women).¹⁶ They found that foam rolling decreased leg muscle soreness compared with the placebo condition but did not affect running performance.

The lead author, Emma Lee, MS, a doctoral student in exercise physiology at the university, told LER she’s been a competitive distance runner for many years and wanted to study the rollers in a mixed-gender cohort of trained runners, given that most studies have been conducted in people who were only recreationally active or in strength-trained men.

“We had them do pre- and post-testing that included a running economy test—two stages of submaximal running, then a three-kilometer time trial, with economy measured by the volume of oxygen consumed per kilogram of body weight per minute,” she explained. “In the middle they did a downhill run on a treadmill for thirty minutes, which introduced muscle soreness. Immediately after the downhill run, they either foam rolled for eight minutes on each leg—quads, IT band, hamstrings, and glutes—or received the placebo treatment; we told them they were compression tights, though they weren’t.”

Lee found that in the placebo (sham tights) condition, time trials were significantly slower after the downhill run, whereas participants who’d done foam rolling had no drop-off in times. Soreness was much worse in those who didn’t foam roll, too.

“I’d recommend foam rolling after a workout that is potentially soreness-inducing,” she said. “In a trail run, or a race with a large downhill component, it could be beneficial to attenuate muscle soreness and possible declines in performance. I would especially urge people to foam roll if they have a competitive situation coming up soon after muscle-damaging exercise.”

In another ACSM poster, researchers studied the effects of six weeks of foam rolling on functional movement, which they described as an indirect way to assess fascial health.¹⁷ They found the treatment was associated with significant improvements in a variety of measures, including deep squats, hurdle steps, leg raises, and trunk and rotary stability.

“We did six different foam rolling exercises—calves, hamstrings, gluteals, IT band, quadriceps, then lower and upper back,” said lead author Briana Felton, BA, who will begin a doctoral program in exercise science at St. Catherine University in Minneapolis this fall. “I think this shows that you can have your athletes and clients use foam rolling rather than having to come in and have someone else do myofascial release on them.”

In a paper published this year in JSCR, investigators at the University of Oregon in Eugene examined the duration of effectiveness of foam rolling on hip extension angles in a dynamic lunge, done twice in each of three sessions a week apart.¹⁸ The intervention group performed foam rolling on their quadriceps between each of two lunges in sessions one and two, and five times in the week between those two sessions. They didn’t use the rollers between sessions two and three, or during session three.

The researchers reported that foam rolling was associated with increased hip extension during the lunge in the intervention group, but noted that these were within-group differences only; the change in hip extension angle did not differ significantly between the control and intervention groups. They speculated that this may have been due to individual variability within the study population, and to the testing of extension angles in a dynamic position. Moreover, extension angles in session three did not differ significantly from baseline in either group, suggesting that any effect wore off after a week without rolling.

Lead author Jenn Bushell, MS, ATC, who is now an athletic therapist at the University of Ottawa and works with the Canadian National Women’s Basketball Team, told LER that she was looking for alternatives to stretching, given the associated risk of strength reduction in highly trained athletes.

“The whole reason we’re doing foam rolling is for some kind of functional activity, but do we want it as a warm-up or as a cool-down?” she said. “I wanted to see what effect it might have if done consistently.”

Bushell noted that she and her colleagues did, in fact, find differences in hip extension angles between the groups, but that these hadn’t reached statistical significance. She added that although she’s more comfortable recommending foam rolling to her athletes than static stretching, there are still issues to be addressed.

“If people foam roll too much, they can get sore and end up feeling like they can’t do their workout,” she said. “I don’t think it actually gets deep enough into the muscle to damage it, but if you do it too long you can cause pain, and that poses an injury risk because it changes how your muscle fires when you’re active.”

In another study published this year, researchers at Oklahoma State University in Stillwater used a crossover study design to compare a single bout of foam rolling to a dynamic stretching protocol in college football linemen.¹⁹ Analysis revealed no pre- to post-test differences in the groups for a number of strength and power variables; however, hip ROM improved significantly in both groups. The authors concluded that the modalities were essentially equivalent.

“We looked at power, velocity, maximum torque, and range of motion in the hip flexors,“ said coauthor Bert Jacobson, EdD, FACSM, a regents’ professor and Seretean Professor in Wellness at the university. “We used a roller with a knobby surface, and in men that weigh between two hundred eighty and three hundred twenty pounds, that’s a lot of pressure; we thought it might detract from power and velocity, but it didn’t.”

As a former football player himself, Jacobson was particularly interested in the results in this study population.

“These guys are so well trained, but many of them don’t have a lot of range of motion,” he said. “The fascia, the tendons, the connective tissue can begin to shrink. That’s why athletes like a massage after a hard workout; it relaxes the muscle, loosens up the fascia, and helps prevent the formation of trigger points. The problem with having trainers do those massages is that you’ve got up to ninety athletes—twenty six starters—and there aren’t enough people on the training staff to handle that. I see foam rolling as complementary to a postpractice regime. All of the players agreed that it hurt like hell when they did it, but when they were done, they felt much better.”

New frontiers

Back at the Memorial University of Newfoundland, David Behm describes the startling results of his team’s new study (accepted for publication). Researchers treated individuals with exercise-induced sore calves (n = 75, in 15-person groups) using one of five interventions. Once they’d identified which calf was more painful, they used foam rolling (to 7 on a 10-point visual analog pain scale) on both the tender calf and the contralateral calf. They also used a sham treatment (foam rolling, but so softly it was unlikely to have therapeutic benefit), tender calf massage, and a control (no massage). Foam rolling on the contralateral calf had a similar effect on pain threshold as rolling the tender calf, unlike sham treatment.

“It turned out that it didn’t matter whether you treated the leg that was sore or the other leg; you had the same decrease in the pain-pressure threshold,” Behm said. “That tells us that even though there may be a myofascial release of some kind, there’s obviously a neural component to this.”

The researchers are still sorting out the implications of this, but Behm said it’s within current neurological thinking. One possible explanation is the “diffuse noxious inhibitory control theory,” which notes that, for example, if you stub your toe, you can stick your hand in very cold water and decrease the pain in your toe.

“The nociceptors in your hands send signals up to neurons in the central nervous system that take in all the information and inhibit afferent information from other parts of the body,” he said. “So if we cause some pain in the opposite calf, and both signals are going up to the brain, one signal may selectively inhibit the other.”

Behm noted, however, that such intriguing results don’t negate the obvious practical advantages of foam rolling, regardless of how well or poorly we understand them.

“One way roller massagers might be really effective is on second-string players,” he noted. “You’ve done a nice warm-up, then you go and sit on the bench, and you don’t know when the coach is going to call you. You could use a roller during that time and maintain your range of motion while you’re waiting to get into the game.”

However they’re used—and however they work—it seems apparent that foam rollers’ advantages far outweigh their minimal drawbacks. Athletes and their trainers can expect to see more of those tribbles as time goes on.

Cary Groner is a freelance writer in the San Francisco Bay Area.