Females suffer more ACL injuries than males and have a lower rate of return to sport while also a higher incidence of reinjury. Jessica Montgomery explains how neuromuscular electrical stimulation can level the playing field for post-ACLR female athletes. Anterior cruciate ligament (ACL) injuries occur two to eight times more often in females than males(1,2).... MORE
Rollin,’ rollin’, rolling!
The foam roller emerged on the therapeutic scene over five years ago, and has recently become one of the hottest fitness trends, making it into the ‘top 20’ in the United States for the last two years1. Touted for its effectiveness in decreasing muscle soreness and treating trigger points, health clubs even offer foam rolling classes. In today’s feature article, Andrew Hamilton explores whether the foam roller results live up to the hype.
With the proliferation of foam rollers now on the market, researchers from California State University tried to get a handle on which type of foam yields the best results. They randomly assigned 36 recreationally active adults to one of three groups using soft, medium, and hard density rollers. Each subject rolled their left quadriceps according to instructions provided in a video, for two minutes.
Does it really work?
The investigators measured knee flexion range of motion (ROM) and pressure pain threshold (PPT) before and immediately after rolling. Each intervention had a significant within group result for both ROM and PPT (see table 1). However, the between group analysis revealed a statistically similar result no matter how dense the foam roller used.
Table 1: Within group comparison before and after intervention
|Soft Density||Medium Density||Hard Density|
|Knee passive flexion range of motion change after rolling.||+ 7 degrees||+ 8 degrees||+ 8 degrees|
|PPT change after rolling (reported in kilopascals).||+ 175 kPa||+ 180 kPa||+ 151 kPa|
A team of Spanish scientists added vibration to their rolling protocol, hypothesizing that the vibration might further improve results. They selected 38 healthy adults to undergo a randomized controlled trial using a standard foam roller, a foam roller that also vibrates, and no rolling2. Each subject performed a rolling protocol to the calf muscles of their dominant leg, using one of the randomly assigned roller conditions, on three separate days. Ankle dorsiflexion ROM and maximal voluntary isometric contraction (MVIC) in plantar flexion and dorsiflexion was tested on both legs both before and immediately after each rolling session.
Both rolling scenarios resulted in significantly higher ankle dorsiflexion ROM in both legs compared to the control intervention. However, the addition of the vibration to the rolling did not significantly change the outcome compared to rolling alone. The MVIC of both legs remained the same after all testing conditions.
How does it work?
It appears that at least in the short term, rolling effectively increases range of motion and the PPT. The controversy in using this technique is in the how. These two recent (2018) studies may give clues to the mechanisms at work, and it’s not myofascial release.
The first is the observance of the increased PPT after rolling. Researchers theorize that pressure from the roller elicits a response from cutaneous and mechanoreceptors. The resulting nociceptive response triggers either the gate theory of pain pathway or the diffuse noxious inhibitory control theory pathway.
The other interesting clue from the Spanish study is the increase in ankle ROM in the contralateral untreated leg. This crossover result alludes to a central neural pathway or a more global neurophysiological response. The factor lacking in most studies, excluding one highlighted by Hamilton, is the carryover of the immediate effects of rolling. Therefore, rolling may be best utilized in a therapeutic setting where increased range of motion or pain control enables greater immediate participation in exercise and functional movement.
- Int J Sports Phys Ther. 2018 June;13(3):475
- J Musculoskelet Neuronal Interact. 2018;18(2):262