Kelley, K.K., Aaron, D., Hynds, K., Machado, E., Wolff, M.: The effects of a therapeutic Yoga program on postural control, mobility, and gait speed in community-dwelling older adults. Ülger, Ö., Yağlı, N.V.: Effects of Yoga on balance and gait properties in women with musculoskeletal problems: a pilot study. Subramaniam, S., Bhatt, T.: Effect of Yoga practice on reducing cognitive-motor interference for improving dynamic balance control in healthy adults. When both groups were combined, the synergy coordination index for Natarajasana was smaller than for Vrksasana, indicating that Natarajasana requires a larger synergy space and is a more challenging task. For the Natarajasana, Yoga practitioners showed higher average hip-flexion angle and hip-flexion torque but no differences in synergy parameters. They also used fewer muscle synergies than controls, which correlated positively with the center of pressure rambling trajectory variability, suggesting decreased control complexity. The Yoga group adopted a more abducted hip at the support leg associated with a higher lumbar bending in the Vrksasana posture. An additional analysis was performed using the synergy-coordination-index estimation from a minimum global set of eight synergies selected using a similarity index. The required number of synergies to reconstruct the original signal was estimated using a variability-threshold criterion. Muscle synergies were extracted from the EMG signals using nonnegative matrix factorization.

Inverse kinematics and dynamics analyses were performed using an OpenSim multibody model. Thirty-three reflective markers’ trajectories, ground-reaction forces, and EMGs from eleven muscles were registered. This paper compares ten regular Yoga practitioners with ten nonpractitioners while performing two single-leg support Yoga postures: Vrksasana (tree posture) and Natarajasana (dancer posture).

Muscle synergy variability