Analysis of Electromyographic Activities of Ankle Muscles at Different Levels of Instability of Unstable Surfaces

Abstract

Abstract.[Purpose] The purpose of the present study was to examine differences in ankle joint muscles' electromyographic activities at different instability levels of unstable surfaces in order to provide a scientific basis for unstable surface training. [Subjects and Method] Sixty healthy adult males and females participated in the present study, and they were equally and randomly assigned to a 2.0 psi group, a 1.5 psi group, and a 1.0 psi group. The subjects were instructed to take a standing posture on a 13 inch diameter rubber air disc inflated at different air pressure for 15 seconds. While the participants maintained their standing posture, the EMG signals of the tibialis anterior, the peroneus longus, and the medial gastrocnemius of the dominant lower limb were recorded to assess the muscle activities.[Results] The muscle activity of the tibialis anterior was the highest at 1.0 psi and showed significant differences from its muscle activities at 1.5 psi and 2.0 psi. The muscle activities of the peroneus longus and the medial gastrocnemius were highest at 1.0 psi and showed significant differences from the muscle activities at 2.0 psi. At all the pressures, the muscle activity of the tibialis anterior was the highest and that of the medial gastrocnemius was the lowest, although the differences were not statistically significant. [Conclusion] The results of the present study show that to trigger the co-contraction of all muscles involved in ankle joint stability, 1.0 psi or lower instability should be provided.

Does Heel Height Cause Imbalance during Sit-to-Stand Task: Surface EMG Perspective

“…Hence, it seems that the high heel can beneficially increase the VM activation. We consider the reason behind the enhanced activity of the VM for elevated HHS is the fact that STS and STSR tasks make maintaining ankle joint positions difficult, so that more effort is required to maintain posture (Kang and Hyong, 2012 ; Hyong and Kang, 2013 ). This is in agreement with Hertel et al ( 2005 ) who stated that lateral and medial orthotics increases EMG activity in VM and decreased EMG activity in VL.…”

Effects of visibility and types of the ground surface on the muscle activities of the vastus medialis oblique and vastus lateralis

“…In a study by Kang and Hyong, the activity ratio of the VMO and VL was significantly different as the ground surface became more unstable 6 ) . This result is similar to that of our present study, which detected the biggest difference on the UGS, with vision blocked.…”

“…To detect the activity of the VL, a surface electrode was attached at 2/3 the distance between the lateral part of the knee bone and the anterior superior iliac spine are connected. To assess the activity of the VMO, a surface electrode was attached at the 4/5 the distance between the upper inner part of the knee bone and the anterior superior iliac spine 6 ) . The electrode for the VMO was 45 degrees from the shaft of the femur, and that for the VL was 15 degrees from the shaft of the femur.…”

“…Among closed kinetic chain exercises, squats are known to selectively strengthen the VMO 5 ) . Various types of squats have been described, and squats on an unstable ground surface (UGS) induce muscle activation because they increase joint movement and proprioceptive feedback 6 ) .…”

Force production during squats performed with a rotational resistance device under stable versus unstable conditions

“…Unstable surfaces create pressure and tension around the ankle joint stimulating the mechanoreceptors, thus generating afferent stimuli and reflexive motor responses which increase joint stability. Surfaces such as the Pielaster may beideal for stimulating these mechanoreceptors and may help in the prevention of (or recovery from) a range of joint injuries 25 ) . To activate the vastus medialis oblique, and to enhance the vastus medialis oblique/vastus lateralis ratio in order to prevent or mitigate knee joint dysfunction (the patellofemoral pain syndrome) highly unstable surfaces should be selected 26 ) .…”