Surface electromyography of the foot: A protocol for sensor placement

Plantar intrinsic foot muscle activation during functional exercises compared to isolated foot exercises in younger adults

BACKGROUND

Training the plantar intrinsic foot muscles (PIFMs) has the potential to benefit patients with lower extremity musculoskeletal conditions as well as the aged population. Isolated foot exercises, often standard in clinical practice, are difficult to perform, whereas functional exercises are much easier to accomplish. However, it is unclear whether functional exercises are comparable to isolated foot exercises in activating the PIFMs.

OBJECTIVE

This study aims to compare the activation of PIFMs between functional exercises versus isolated foot exercises.

METHODS

Using surface electromyography (EMG), muscle activation of three PIFMs was measured in four functional exercises (i.e. normal/unstable toe stance, toe walking, and hopping) versus a muscle-specific isolated foot exercise in 29 younger adults, resulting in 12 comparisons.

RESULTS

Functional exercises showed larger mean EMG amplitudes than the isolated foot exercises in 25% of the 12 comparisons, while there was no difference in the remaining 75%.

CONCLUSION

Functional exercises provoked comparable or even more activation of the PIFMs than isolated foot exercises. Given that functional exercises are easier to perform, this finding indicates the need to further investigate the effectiveness of functional exercises in physical therapy to improve muscle function and functional task performance in populations that suffer from PIFM weakness or dysfunction.

Comparison of EMG signal of the flexor hallucis longus recorded using surface and intramuscular electrodes during walking

The purpose of this study was to compare the use of intramuscular (iEMG) and surface (sEMG) electromyography electrodes to record flexor hallucis longus (FHL) muscle activity during walking, and describe the role of the FHL. Muscle activity was recorded in 12 participants using sEMG and iEMG during treadmill and overground walking. Inter-tester reliability for visual detection of onset and offset of muscle activity was high (ICC = 1.00). During the loading period, the number of bursts of muscle activity was statistically significantly greater using iEMG compared to sEMG when treadmill walking (p = 0.016), and the duration of muscle activity was significantly greater for iEMG (p = 0.01) on both walking surfaces. There were no differences for peak and mean root mean squared (p ≥ 0.07). The FHL activity observed during the loading period (heel strike to forefoot strike) supports the function of the FHL to act as a dynamic ankle stabiliser of the rearfoot, as well as contributing to propulsion during the latter part of stance. The choice of electrodes to detect FHL activity should be dependent on whether the loading and propulsive periods are of interest, and whether treadmill or overground walking will be examined.