Can training your uninjured limb maintain flexibility in the injured limb?

A recent study published in The International Journal of Sports Physical Therapy found that foam rolling improves ankle dorsiflexion for at least 20 minutes on the limb that is rolled on and up to 10 minutes on the opposite limb that has not been foam rolled. (1) Researchers Shane Kelly and Chris Beardsley recruited 26 active university students (16 women, 10 men) for this study and randomly assigned to the foam rolling group or control group. Both groups warmed up by doing double-leg heel raises for ten reps, which is something previous studies on ankle flexibility have done.

Both groups performed a weight-bearing lunge test where subjects stood with their foot about 10 cm away from a wall perpendicularly. Then they look straight ahead and flex the knee until it reaches the wall with the heel still on the ground. Measurements were made between the big toe to the wall of the flexing leg when the knee touches the wall or reached the maximum end range of motion at the ankle.

Immediately after the measurements are made, the control group sat for two minutes while the foam rolling group rolled on the dominant leg for three bouts of 30 seconds with a 10-minute rest period between sets. All subjects’ dorsiflexion for both legs were measured, starting with the dominant leg.

While Kelly and Beardsley did not find any difference between the groups at the baseline, there was a difference between the groups when they were retested for dorsiflexion. The dominant leg that was foam rolled increased the dorsiflexion by an average of 1.12 cm immediately after foam rolling while the non-dominant leg increased by 0.72 cm. The control group barely had any increase of range of motion: 0.11 and 0.04 respectively.

As time went on, approaching 20 minutes, the dorsiflexion angle decreased almost by half for the dominant leg and over 80 percent for the non-dominant leg in the foam rolling group. Hardly any changes occurred in the control group.

When asked why this study was conducted, Kelly said that he had an interest in myofascial techniques. “Foam rolling is common yet not a huge amount known about it. Chris thought it would be a good idea to investigate the cross-over effect, as it hadn’t been explored with respect to foam rolling,” Kelly explained in an online interview with Massge & Fitness Magazine. “So next thing you know, it’s finished! I just randomly shot Chris an email.”  To Kelly’s knowledge, no published study has looked at the relationship between the cross-over effect and foam rolling or a self-myofascial technique.

Seems Kinda Small, Doesn’t It?

While gaining an average of 1.12 cm on the foam rolled leg may not seem very statistically significant, for patients, having an increase of range of motion — preferably without pain — would be very beneficial, a stepping stone to recovery.

“…in a rehabilitation setting, where ankle [dorsiflexion] ROM may be limited, small changes could be beneficial and so have a greater clinical relevance. Additionally, a longer intervention may provide greater improvements in ankle [dorsiflexion] ROM, a potential area for future research,” Kelly and Beardsley wrote.

Research about cross education for strength gains and minimizing strength and muscle mass loss on the injured and immobilized limb has been around since the late 19th century. (2) The mechanism of the cross education effects is unclear, but the researchers propose two plausible explanations of its effects. ​

Mechanical Model

“…it is theorized that the material properties of fascia are affected by the pressure exerted through SMFR, thereby altering its viscoelastic properties. Many possible mechanisms exist including thixotrophy, piezoelectricity, fascial adhesions, cellular responses, fluid flow, fascial inflammation, and myofascial trigger points.”

Neurophysiological Model

“…mechanical pressure from SMFR influences a state of tissue relaxation through afferent signal input to the central nervous system via stimulation of the Golgi reflex arc and other mechanoreceptors.”

“But it seems like you affect the mechanoreceptors at the local level stimulating a more global neural response, maybe as high up as the cortical level,” Kelly added. “No doubt there is a neural component involved but as to what level/depth I don’t know and more research is needed to clarify.”

Don’t Jump to Conclusions Yet

The authors admit that there are some problems with this study that warrant some caution when interpreting the research and applying it to the clinical setting. First, the testers weren’t blinded to who is doing the foam rolling or not, “which increases the risk of bias and type I error.”

Second, the sample size has a weak statistical power and is based on previous studies with small sample sizes. And third, the heel raise warm-up may affect the flexibility of the subjects, which may affect the results, as well as an increase of stretch tolerance.

Since the study was done with healthy, young adults, it is uncertain whether foam rolling has any significant benefits to patients with a leg or foot injury and older patients.

Nonetheless, this study in cross-education show evidence that foaming rolling on one leg increases the flexibility of the opposite ankle, which coincide with previous studies on strength and movement gains on the non-trained limb. As more studies on cross-education progresses, more will be revealed on how this mechanism works and how to apply it in the rehab and fitness settings.

“If you’re a clinician with a patient who has one limb/joint immobilized and you want to limit the loss in ROM, then there may be some benefit to rolling the contralateral limb,” Kelly said. “Again, more work is needed as the long-term benefits of the cross-over effect are yet to be determined and as mentioned in the study. Clinical relevance may be negligible.”

 

References

1. Kelly S, Beardsley C. Specific and Cross-over Effects of Roam Rolling on Ankle Dorsiflexion Range of Motion. International Journal of Sports Physical Therapy. 2016;11(4):544-551.

2. Barss TS, Pearcey GEP, Zehr EP. Cross-education of strength and skill: an old idea with applications in the aging nervous system. The Yale Journal of Biology and Medicine. 2016;89(1):81-86.