*2.1. Participants*

Patients with AIS were recruited through the outpatient clinic specializing in the treatment of scoliosis. The inclusion criteria were: (1) diagnosed as AIS; (2) 10–18 years old with Risser sign ranged from 0 to 5; (3) Cobb angle between 20◦~50◦ ; and (4) experienced in the Schroth exercise (i.e., received the Schroth exercise training for at least three times previously) to control and ensure a good exercise performance among the participants. A sample size of 21 subjects was calculated (assuming that the effect size (d) = 0.5; statistical power (1 − β) = 0.8; level of significance (α) = 0.05 used for 2-tailed T-test). Patients with severe back pain, spinal surgery history and other neurological symptoms were excluded from this study. All participants gave their written informed consent to participate in the study.

#### *2.2. Assessment Procedure*

A Noraxon EMG assessment system with wireless electromyography sensors (Noraxon Inc., Scottsdale, AZ, USA) was used for data collection. The sampling rate of the EMG Sensor System was 1500 Hz with ±24,000 µV EMG input range. The baseline noise was less than 1 µV. The selectable low-pass cut-off and high-pass cut-off were at 500/1000/1500 Hz and 5/10/20 Hz, respectively. The CMRR of EMG preamplifier was more than 100 dB.
