Single-leg balance in “instability” footwear
© Price et al; licensee BioMed Central Ltd. 2012
Published: 10 April 2012
The concept of instability footwear is to reduce stability, increase muscle activation and “tone”. Recently numerous brands have developed instability footwear for significant sales. Despite extensive marketing claims there are few empirical studies quantifying effects of instability footwear on muscle activity or motion in healthy individuals aside from Masai Barefoot Technology (MBTTM) [1, 2]. The aim of the study was to quantify instability in single-leg standing in a variety of commercially available instability sandals.
Fifteen female subjects participated (age: 29±6.7 years, mass: 62.6±6.9 kg, height: 167.1±4.2 cm). The protocol quantified Centre of Pressure (CoP) excursion (Kistler) and lower extremity integrated muscle activity (IEMG) (Noraxon) for three thirty second single-leg standing trials in four experimental conditions and one control (Earth FootwearTM). The instability footwear conditions were FitFlopTM, MBTTM, Reebok Easy-ToneTM and Skechers Tone-UpsTM. IEMG is presented normalised to control.
CoP and IEMG results for the footwear conditions.
CoP medial-lateral range (mm)
CoP anterior-posterior range (mm)
CoP medial-lateral velocity (mm.s-1)
CoP anterior-posterior velocity (mm.s-1)
Medial gastrocnemius IEMG (%)
Peroneals IEMG (%)
Increased anterior-posterior CoP range in MBT is expected due to the rocker profile . Other conditions have footbeds with intrinsic instability not an external feature, which may increase effectiveness in gait. IEMG increased in experimental conditions showing instability shoes increased total activation, however high variability masks statistical differences. Inter-subject differences forms part of on-going analysis. Limitations of single-leg balance mimicking gait are recognised; increased duration of muscle activation is claimed by brands and fixed-duration testing negates this.
The study was part-funded by FitFlop ltd.
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