Curved soles 'no better than flats' for back pain

"Shoes with curved unstable soles are no better than traditional trainers for reducing lower back pain," BBC News reports, after a small but well-designed study found no significant benefit in people wearing "rocker sole" shoes.

The study involved 115 adults with chronic lower back pain who were randomised into two groups: rocker sole trainers or normal trainers. They were asked to wear these trainers for at least two hours a day over the course of a year. They were also asked to exercise once a week for four weeks and wear their trainers to these sessions.

The good news was that in all groups back pain improved to some degree. However, the rocker sole-style footwear was no better (or no worse) than flat sole trainers in reducing disability or pain scores.

For a number of measures the rockers actually fared worse than their flat sole counterparts, including satisfaction with the trainers and a clinically important reduction in self-reported disability.

The study had many strengths, including its randomised design and realistic treatment conditions, which involved prescribing shoes plus exercise rather than just shoes.

However, a general limitation of the study is that it only recruited people with chronic lower back pain, so the effect of the rocker shoes on other musculoskeletal conditions was not tested.

Larger studies assessing pain and disability over a longer period of time would be able to confirm or refute these findings, but initially – and in light of the strengths mentioned above – they appear reliable. 

Where did the story come from?

The study was carried out by researchers from UK-based hospitals and universities in collaboration with international partners.

It was funded by Masai GB Ltd, a footwear manufacturer specialising in rocker sole ranges. Because of the largely neutral findings of the study, it is clear the funders had no influence on the study design or reporting.

The study was published in the peer-reviewed medical journal, Spine.

The BBC coverage of the study was balanced and factually accurate.

What kind of research was this?

This was a multicentre, assessor-blind randomised control trial comparing the effectiveness of rocker sole footwear with traditional flat sole footwear for people with chronic lower back pain.

The researchers reported that over the past decade, persistent advertising has claimed that footwear constructed with a rocker sole will reduce lower back pain. Shoes with an unstable curved sole are often marketed as being able to help increase muscle activity, reduce lower back pain and improve posture and balance when walking and standing.

However, as the authors noted, there is no robust evidence to support these claims. The present study aimed to provide robust evidence on whether rocker sole shoes helped lower back pain.

A randomised control trial is the best study design for comparing the effectiveness of two treatments, such as two different types of footwear that could be recommended as part of lower back pain management.

It is not possible for such a trial to be double blind, as participants would know what shoes they were wearing, but the fact that the assessors were blind to treatment allocation (single blind) is a strength.

What did the research involve?

The study recruited 115 adults with chronic lower back pain (three months duration or longer) who were randomised to wear either rocker sole shoes or flat sole shoes while standing and walking for a minimum of two hours each day.

The researchers excluded people with a diagnosed medical cause for their back pain and those for whom a prescription of rocker shoes and exercise would be inappropriate, for example, people with neurological conditions, a history of falls, or severe cardiovascular disease.

Participants were assessed after six weeks, six months and one year using a disability questionnaire called the Roland Morris Disability Questionnaire (RMDQ).

Importantly, participants' disabilities were assessed by an assessor who did not know which shoes the participants had been wearing, making the study single blinded.

Measures of pain, health-related quality of life and the time participants had spent in their shoes were also recorded at each of the time points.

As well as wearing the shoes, all participants attended an exercise and education programme once a week for four weeks and wore their assigned shoes during these sessions.

Analysis was by an intention-to-treat method, meaning all participants initially randomised were analysed in the final results, including those who dropped out of the study later on. This is the best way of analysing results from studies such as this, as it captures all the participants.

What were the basic results?

The main results were as follows:

• Both footwear groups reported reductions in disability at each time point when compared with baseline.
• There were no differences between the groups in disability reduction at any follow-up point (six weeks, six months and one year).
• A greater proportion of participants allocated to wear flat sole shoes (53%) reported a minimal clinically important improvement (greater than or equal to a four-point improvement in the RMDQ) at six months than those allocated to the rocker sole group (31%). There were no differences between the groups at six weeks or 12 months.
• Flat sole shoe wearers who reported pain while standing and walking showed a greater improvement in disability at six weeks and 12 months than the rocker sole shoe wearers.
• There was no difference seen at any time point in the subgroup of participants who did not report pain while standing and walking.
• Both groups reported reductions in ratings of pain intensity at each time point when compared with baseline. The pain reductions were similar at the 12-month time point.
• There were no differences between the groups at any follow-up point for secondary outcomes investigating fear of movement, spinal impairment, days off work, health-related quality of life, patient-specific functional activity, and anxiety and depression.
• At six and 12 months, participants in the flat sole shoe group were more satisfied with the shoe they received than participants in the rocker sole shoe group (at six months, 62% and 37% respectively, and at 12 months, 73% and 46% respectively, were very or extremely satisfied).

How did the researchers interpret the results?

The researchers drew four main conclusions from their research findings:

• Rocker sole shoes seem to be no more beneficial than flat sole shoes in affecting disability and pain outcomes in people with chronic lower back pain.
• If a person's chronic lower back pain is predominately aggravated by standing or walking, it may be more beneficial to wear flat sole shoes than rocker sole shoes.
• A greater proportion of participants who wore the flat sole shoes reported a clinically important change in self-reported disability at six months.
• At both six and 12 months, participants in the flat sole shoe group were more satisfied with the shoe they received than the participants in the rocker sole shoe group.

Conclusion

This study indicates that rocker sole-style footwear is no more beneficial than flat sole trainers in reducing disability and pain outcomes in adult chronic lower back pain sufferers. For a number of measures, such as satisfaction with the trainers and a clinically important reduction in self-reported disability, the rockers fared worse than their flat sole counterparts.

The study had many strengths, including its randomised and single blind design, realistic intervention conditions (prescribing shoes plus exercise rather than just shoes) and having an appropriate number of people in their study. Taken together, the study appears reliable and its results robust.

A general limitation is that the study only recruited chronic back pain sufferers, so the effect of the shoes in people with shorter term lower back pain (less than three months), or other muscular conditions where the shoes might be considered beneficial, was not tested. However, chronic back pain sufferers are the group most likely to try the shoes, so this was a realistic approach to take.

Larger studies assessing pain and disability over a longer period of time would be able to confirm or refute these findings.