Research Review Corner: October 2012

The effect of walking in high- and low-heeled shoes on erector spinae activity and pelvis kinematics during gait

BACKGROUND INFORMATION

“Is wearing high heels bad for my back?”

This is a question many of us confront in our offices almost every day.  When your patients ask, what do you say? Many of us immediately dispense advice to avoid wearing such footwear for long periods of time, perhaps offering an eloquent explanation including some sort of ‘compensation’ (everyone’s favourite), muscle fatigue or ‘calf’ tightness, and even spinal alignment or pelvic tilting issues.  Sound familiar?  Is this correct? What does the research say?

Women have been wearing high-heeled shoes since the 17^th century in both social and work settings.  In many cultures, such footwear is very common.  Recent data indicates that 59 per cent of women wear high-heeled shoes for one to eight hours per day!¹ It may not be surprising then, that footwear with increased heel height has been linked to low back (although cause and effect has not been firmly established)².  By placing the foot in a plantar-flexed position, it is obvious that wearing high-heeled footwear alters foot loading patterns, which could logically alter muscle activation, pelvic tilt, gait parameters, and so on.

The purpose of this study was to evaluate the changes in electromyographic (EMG) activity of the spinal erectors and pelvic kinematics during gait while wearing low- and high-heeled shoes.  This study differs from previous work in two important ways:

1)   The authors utilized a comprehensive approach, looking at both low- and high-heeled shoes conditions (as well as no shoes) using EMG and biomechanical techniques; and

2)   They addressed the effect of age on potential changes from wearing high-heeled shoes by incorporating younger and middle-aged subjects.

PERTINENT RESULTS

·       There were no significant differences in height or body weight between the younger and middle-aged women.

·       Overall, the erector spinae exhibited an increased EMG recording (higher activity) with increasing heel height (P < 0.05).

·       More specifically, in the younger women: both low and high-heeled shoes resulted in significant differences in lumbar erector spinae EMG activity during gait at initial ground contact as well as in toe off among the three conditions, with an increasing amount of EMG activity being observed in association with increased heel height (the difference between EMG activation with low vs. high-heels was not significant).

·       In middle-aged women, significantly higher lumbar erector spinae EMG activity was noted during gait with high-heeled shoes compared with gait without shoes (the differences between the low-heeled shoes and no shoes conditions were not significant in this age group).

 Biomechanical Variables:

·       No differences in gait velocity were noted between study groups, or among the three shoe conditions within the two patient groups.

·       Interestingly, no relationship was noted between wearing high-heels and pelvic tilt angles (P > 0.05).

·       Younger women exhibited an increase in pelvic range of motion in the sagittal plane during high-heeled gait compared with low-heeled gait and walking without shoes (P < 0.05). This compensatory response was not observed in middle-aged women.

·       There was no significant effect of heel height on pelvic ROM in young or middle-aged women in the frontal (P > 0.05) or transverse planes (P > 0.05).  However, it should be noted that ROM in these two planes was significantly lower in the middle-aged women compared to the younger women (P < 0.05).

·       There was no significant effect of heel height on pelvic alignment in young or middle-aged women in the sagittal, frontal, or transverse planes during the initial contact and toe-off phases of gait (P < 0.05).

CONCLUSIONS AND PRACTICAL APPLICATIONS

The most important finding from this study is that wearing a stiletto-type heel (10 cm) significantly increases lumbar spinae EMG during gait in both younger and middle-aged women.  This effect of wearing high-heeled footwear may have clinical consequences, including increasing general or muscular fatigue, creating swelling or limited movement, raising the possibility of cumulative strain, promoting fibrosis in the paraspinal musculature, altering joint loading profiles…this list could go on and all these factors could be both consequences and causes of LBP. 

Another interesting observation was that sagittal pelvic ROM seems to increase in younger women while wearing high-heels, but such adaptations were not observed in the middle-aged women.  This may indicate that over time, women adapt their mechanics to accommodate wearing footwear with higher heels.  It could also reflect general age-related changes in body structure, soft tissue characteristics, joint mechanics, and so on.  Further research is required to clarify this issue. 

This study could not answer all our questions on the effects wearing of high-heels, but it does provide some useful information that we can incorporate into our discussions with our patients.  This is what evidence-informed practice is all about!

STUDY METHODS, STRENGTHS AND WEAKNESSES

Thirty-one young women (20-25 y.o.a.) and 15 middle-aged women (45-55 y.o.a.) participated in this study. Subjects were excluded if they had a previous history of LBP or orthopedic limitations of the lower limb in the six months before the study.  All subjects reported wearing high-heeled shoes occasionally but not more frequently than once a month.  In order to better familiarize the subjects with high-heeled ambulation, subjects were asked to use stiletto type shoes one hour per day during the week before participating in the study. All testing was conducted during a single laboratory session, utilizing a repeated-measures design.  In this session, each subject ambulated in one of three conditions: 1) without footwear, 2) in shoes with four centimeter heels (low heels), and 3) in shoes with a height of 10 centimeters (high heels). The heels of both the low- and high-heeled shoes were of the stiletto-heeled type with a base of one centimeter.

Muscle EMG and pelvic kinematics were measured during a 10 second stance and during gait on a flat surface at a self-selected, natural speed along a sixmeter walkway.  A total of six trials were performed in each condition (in each trial, three full strides were recorded – the middle stride in each trial was used for data analysis).  The average of the six trials was taken for each measure.

Surface EMG recordings were taken from the lumbar erector spinae (bilateral) and pelvic kinematics were measured via reflective markers using a six-camera BTS Motion-Capture System (BTS Bioengineering). 

From this kinematic data, the following outcome variables were derived:

1)   Pelvic tilt angle: Pelvis alignment in the sagittal plane was used to measure the angle of pelvic tilt (degrees) during a resting bilateral standing position.

2)   Pelvic ROM: Pelvic ROM in the sagittal, frontal, and transverse planes (degrees) on pelvic angular displacement in the gait cycle. The maximum and minimum angular positions were estimated, and ROM was calculated as maximum angular position minus minimum angular position.

Pelvic alignment angle: Data of the gait cycle initial contact and toe-off events for each gait trial and side were used to calculate the angular value of pelvic alignment in the sagittal, frontal, and transverse planes (degrees).

Study Strengths:

·       The inclusion of young and middle-aged subjects.

·       Comparison of two different heel heights as well as a no shoes condition.

Weaknesses:

·       The study population consisted of healthy subjects without low back pain, so these findings cannot be extrapolated to this clinical population.

·       Subjects in this study only wore high-heels occasionally – further research could include subjects who wear such footwear more frequently.

·       No kinetic data was collected, so the authors’ conclusions were based on EMG and kinematic data alone.

ADDITIONAL REFERENCES

1)   Hsue BJ, Su FC: Kinematics and kinetics of the lower extremities of young and elder women during stairs ascent while wearing low and high-heeled shoes. J Electromyogr Kinesiol 2009; 19: 1071-8.

2)   Lee CM, Jeong EH, Freivalds A. Biomechanical effects of wearing high-heeled shoes. Int J Indust Ergonom 2001; 28: 321-6.

3)   Bird AR, Bendrups AP, Payne CB. The effect of foot wedging on electromyographic activity in the erector spine and gluteus medius muscles during walking. Gait Posture 2003; 18: 81-91.

4)   Cowley EE, Chevalier TL, Chockalingam N: The effect of heel height on gait and posture: A review of the literature. J Am Podiatr Med Assoc 2009; 99: 512-8.

In addition to practising full time in Toronto, Dr. Shawn Thistle is founder and president of Research Review Service Inc., an online, subscription-based service designed to help busy practitioners integrate current, relevant scientific evidence into their practice (www.researchreviewservice.com). Shawn also recently launched The Epicurean Scholar, which offers continuing education seminars combined with gourmet food and wine events (www.epicureanscholar.com).  Dr. Thistle graduated from CMCC (where he lectures in the Orthopedics Department) and holds an Honours Degree in Kinesiology from McMaster University. He also holds a certificate in Contemporary Medical Acupuncture from McMaster University, and is a Certified Active Release Techniques (ART®) Provider and Functional Range Release®/Functional Anatomical Palpation® instructor and provider.