Sagittal plane deformity can be defined as a deviation from the normal curvature of the spine in the sagittal plane. This deformity can distort the natural shape of the spine and cause posture problems. In recent years, effects such as reduced activity in daily life, increased time spent in front of computers and mobile phones, and inactivity during the recent pandemic have also led to a significant increase in sagittal plane deformity. In this study, 16 healthy adolescents and 16 adolescents with sagittal plane deformity participated. Surface EMG (sEMG) recordings were obtained from thoracal kyphosis subjects and lumbar lordosis subjects, commonly seen in patients with sagittal plane deformity (SPD), and from healthy subjects. After filtering the raw sEMG data, wavelet packet transform analysis was performed. The energy values of the wavelet packets corresponding to the low and high frequency components have been calculated. These energy values were statistically analysed using the Mann-Whitney U test to determine muscle differences between SPD subjects and healthy subjects. This statistical analysis identified the channels with significant differences between SPD subjects and healthy subjects. Channels with a statistical significance level of p<0.05 were included. When the muscle activation of these channels was compared, higher activity was found in SPD subjects, while in some movements activation was found in different channels in SPD subjects and healthy subjects. SPD subjects showed more muscle activity than healthy subjects and spent more energy to increase the quality of movements and to perform them with the correct muscle dynamics. It has been observed that SPD subjects develop compensations from different muscle regions in order to perform movements correctly due to postural changes. In healthy subjects, it was observed that movements were completed in accordance with the kinematics of the movement and that maximum movement quality was observed with less energy.