## 2 Methods  
This study was approved by the ethical committee of the Center for Research Ethics, Sungshin Women's University. The investigation conforms to the Declaration of Helsinki. All subjects gave written, informed consent before participating in the study.  
1. Participants: This study was conducted from April 2019 to June 2020 in the Seoul Municipal CP welfare center in Korea. A total of 18 ambulant adults with CP were recruited for this study. 7 ambulant adults with CP were excluded because they did not achieve the criteria of maximal exercise. Thus, the data from 11 subjects (11 men) with CP were used for the analysis. The mean (\(\pm\)SD) age, height, weight, and BMI of the subjects were 37.00 \(\pm\) 12.72 years, 170.45 \(\pm\) 6.37 cm, 67.02 \(\pm\) 8.62 kg, and 23.09 \(\pm\) 2.78 kg/m\({}^{2}\), respectively.
2. Lower extremity muscle strength measurement (Isokinetic exercise test): To measure the muscle strength of HIP joint and KNEE joint in lower extremities, the variables of the isokinetic muscle strength and the muscular endurance were performed using the isokinetic equipment (Biodex Co, Shirley, NY, USA). The range of motion (ROM) of all joints was as follows: 0\({}^{\circ}\) of maximum extension was set as neutral, the range of flexion was set as 90\({}^{\circ}\) bent from the neutral position, and gravity compensation was performed in the state of flexion of about 15\({}^{\circ}\). For accurate measurement during the test, a dynamometer coincided in the motion axis of each test joint, and the subjects were given an accurate understanding of the test and practiced three times before the test. For the isokinetic muscle strength measurement of HIP joint, the 45\({}^{\circ}\)/s protocol indicated the muscle power and the 300\({}^{\circ}\)/s protocol indicating the muscle endurance were used. Additionally, the measurement of KNEE joint was performed once on the left and right side using the protocol of 60\({}^{\circ}\)/s, indicating the muscle power and 300\({}^{\circ}\)/s indicating the muscular endurance. Then, the results of peak torque % body weight (%) and Agon/Antag ratio (%) of the agonist and antagonist muscle, both in the left and right side, were analyzed using the average value.
3. Aerobic capacity measurement: Progressive exercise tests were conducted on the treadmill (Quinton model- 4500) using previously developed protocols targeting CPs [28,46]. The initial protocol speeds were 5 km/h\({}^{-1}\) and 2 km/h\({}^{-1}\) for the subjects who has been classified as GMFCS level I and II, respectively. There was a speed increase at a rate of 0.25 km/h\({}^{-1}\) every minute until it was terminated voluntarily. The subjects were verbally instructed to continue until they felt the exhaustion. Using a portable cardiopulmonary indirect breath-by-breath calorimetry system (MetaMax 3B; Cortex Biophysik, Leipzig, Germany), pulmonary ventilation (VE), respiratory exchange ratio (RER), and oxygen uptake (VO\({}_{2}\)) were persistently measured. A HR monitor (Polar Electro, Kempele, Finland polar Co. RS-800) was used to measure heart rate (HR). During the gait on the treadmill, peak VE (VE\({}_{\text{peak}}\)) and peak RER were defined as values measured when VO\({}_{\text{2 peak}}\) was detected. The subjects had the mission to accomplish two of the following three criteria for the results to be accepted with VO\({}_{\text{peak}}\): (1) RER value greater than 1.0, (2) The value of heart rate greater than the predicted heart rate ([220-age] \(\times\) 085), or (3) a plateau (increase of <150 mL \(\cdot\) min of oxygen) in O\({}_{2}\) with increasing work rates. To avoid the effect on the metabolic response and HR of the subjects, they were told to avoid excessive physical activity for 24 h before testing and to refrain from any stimulating substances (alcohol, coffee, tobacco, and so on) or any drugs which could interfere with the experiment. Subjects had their last meal 3 h prior to the initiation of the test.