## 2 Materials and Methods
### EMG, Kinematic and Kinetic Data during Heel-Raise Exercise  
The measurements were performed with a Noraxon myoSYNC(tm) synchronization system synchronized with a full HD and infrared-camera (30 Hz, 138-2, Noraxon, Scottsdale, AZ, USA) integrated video analysis system (Noraxon, Scottsdale, AZ, USA) and a 60 \(\times\) 50 cm force platform (9260 AA, Kistler Group, Winterthur, Switzerland) connected to the MP100 system. The locations of the reflective markers used in ankle kinematics analyses have been described in a previous study [6]. They were placed and fixed on the upper part of the posterior calcaneal tuberosity, lateral aspect of the 5 th metatarsal head, lateral malleolus, fibular head, femoral epicondyle, and thigh at 50% of the distance between the greater trochanter of the femur and the lateral tibiofemoral joint line of the tested leg of each participant [6,20] (Figure 1). The positions of the markers were used to calculate the sagittal plane knee and ankle joint angles. For example, the 0-degree or neutral position of the ankle is determined by a 90-degree angle between the fifth metatarsal and the fibula. Each participant stood on his or her single tested leg with the forefoot positioned in the middle of the edge of the step to allow full dorsiflexion to be reached (Figure 1). The given participant was allowed to touch the wall with an index finger at the shoulder level to maintain a steady one-leg standing position. The participant was then instructed to perform two sets of exercise tasks, with each set consisting of three cycles of full-weight-bearing ankle concentric (raising the heel to the peak ankle plantar flexion angle) and eccentric (lowering to the peak ankle dorsiflexion angle) exercises, with the participant's weight borne on the knee at a 0\({}^{\circ}\) extension, without loss of balance. The pace of the ankle movements was guided by a metronome set at 60 beats per minute giving four beats for a full cycle of plantarflexion and dorsiflexion. The concentric and eccentric phases were identified from the sagittal ankle joint angles through a video analysis system that determined, respectively, the elapsed time of dorsiflexion (flexion at the ankle, so that the foot points more superiorly) and plantarflexion (extension at the ankle, so that the foot points inferiorly). The simultaneous EMG, kinematic and kinetic recordings were averaged among the second and third consecutive cycles in each of the two exercise sets. The recordings were discarded and the measurement restarted if the given participant could not keep pace with the metronome, keep his or her trunk and knee straight (knee flexion 0-5 degrees as shown in the video analysis system), or if he or she lost his/her balance. The analyses included analyses of the RMS EMG amplitudes of the muscles, the RMS amplitudes of the ground reaction force (GRF), and mechanical work of heel lifting, all of which were quantified corresponding to the concentric and eccentric phases in the second and third full movement cycles. The mechanical work of the heel lifting was defined as the amplitude of the GRF in the \(z\)-axis multiplied by the lifting distance. The EMG signals were amplified (gain =500, CMRR > 100 dB) and filtered with bandwidths of 10-500 Hz. Furthermore, only the vertical component (Fz) of the GRF (determined using a 4 th order Butterworth low-pass filter with a cutoff frequency of 5 Hz) normalized with respect to body weight was utilized for kinetic analysis. The RMS EMG amplitudes (mV) of the muscles were averaged and normalized based on the value measured during the MVIC. The kinematics and kinetics data including the ankle joint angle, angular velocity, normalized GRF and the mechanical work were recorded and compared for the injured and non-injured legs at every relative 5 percentage points of the duration of the concentric and eccentric phases of the exercise cycle after time normalization (linear length normalization) (Figure 2a-d).