Muscle synergies for the control of single-limb stance with and without visual information in young individuals

Abstract

Purpose Single-limb stance is a demanding postural task featuring a high number of daily living and sporting activities. Thus, it is widely used for training and rehabilitation, as well as for balance assessment. Muscle activations around single joints have been previously described, however, it is not known which are the muscle synergies used to control posture and how they change between conditions of normal and lack of visual information. Methods Twenty-two healthy young participants were asked to perform a 30 s single-limb stance task in open-eyes and closed-eyes condition while standing on a force platform with the dominant limb. Muscle synergies were extracted from the electromyographical recordings of 13 muscles of the lower limb, hip, and back. The optimal number of synergies, together with the average recruitment level and balance control strategies were analyzed and compared between the open- and the closed-eyes condition. Results Four major muscle synergies, two ankle-dominant synergies, one knee-dominant synergy, and one hip/back-dominant synergy were found. No differences between open- and closed-eyes conditions were found for the recruitment level, except for the hip/back synergy, which significantly decreased (p = 0.02) in the closed-eyes compared to the open-eyes condition. A significant increase (p = 0.03) of the ankle balance strategy was found in the closed-eyes compared to the open-eyes condition. Conclusion In healthy young individuals, single-limb stance is featured by four major synergies, both in open- and closed-eyes condition. Future studies should investigate muscle synergies in participants with other age groups, as well as pathological conditions.

Different Effects of Single-leg Stance Exercise and Bridging Exercise with Core Stability Exercise on Older Adults Balance

“…In addition, these exercises can activate nerves to improve proprioception so that they are considered effective in improving balance and functional walking. Leg muscles are important in maintaining postural balance and joint stability in addition to core muscles [20,21]. This statement is supported by Kusnanto et al, in Malasari et al, who stated that balance training could increase muscle fibre (hypertrophy).…”

The Influence of Knee Extensor and Ankle Plantar Flexor Strength on Single-Leg Standing Balance in Older Women

“…During the single-leg stance, the APs were primarily responsible for controlling the movement of the body’s center of mass in the anterior–posterior direction [ 17 , 40 , 41 ]. A previous study has shown that the first muscle synergy can primarily be attributed to an ankle control strategy, while the second muscle synergy is associated with a knee control strategy [ 16 ]. The result of this study found that three major muscle synergies were involved in the single-limb stance, two of which were ankle-dominant, and one was knee-dominant.…”

“…While both the AP strength and the KE strength are important for maintaining single-leg balance in older individuals, this study suggests that the AP strength may be more important. The biomechanical explanation for this finding is that the APs are more directly involved in controlling the movement of the body’s center of mass during the single-leg stance, whereas the KEs play a more supportive role in this process [ 16 ]. When the body experiences a balance perturbation, such as an unexpected push or slip, the ankle muscles are among the initial muscles to be activated in order to restore balance [ 42 ].…”

“…In the event of a balance loss, it is crucial to rapidly halt the body’s momentum and keep the center of mass within the limits of the base of support. During single-leg standing, the knee and ankle muscles work together to maintain balance [ 16 ]. Knee extensor (KE) and ankle plantar flexor (AP) muscle strengths are important for standing balance as they are responsible for maintaining upright posture and pushing the body forward and upward [ 17 , 18 , 19 , 20 ].…”

Characteristics of the postural stability of the lower limb in different visual states of undergraduate students with moderate myopia

“…When vision is impaired, the sensory input of visually impaired individuals appears as the vestibular and proprioception compensative mechanism ( Schwesig et al, 2011 ). Labanca et al (2021) compared with eyes-opened, the ankle muscle group co-activation and ankle strategy of young people were more obvious when the posture was unstable, the neuromuscular system could improve the stability by regulating the activity of the ankle muscle group in the eyes-closed state. However, it is unclear whether myopia affects muscle activation.…”