## 1 Introduction  
The'static body-weight wall-squat' (SBWS) exercise is frequently included in lower-limb rehabilitation programmes [1; 2; 3; 4]. It also provides a practical, reliable, and well-tolerated clinical test for the assessment of the quadriceps muscle endurance [5; 6]. Given the isometric execution and support provided by the wall, this exercise requires less balance and stability than the common squat exercise. For this reason, the SBWS can be readily included in the early stage of rehabilitation interventions, as soon as the patient can tolerate weight-bearing [1]. The correct SBWS execution requires the subject to hold a partial squat position with the back flat against a vertical wall, spine in a neutral position, arms relaxed along the body, knee in proper alignment (i.e., neutral knee varus/valgus and internal/external rotation) and feet about shoulder-width apart. The knee flexion angle (\(\theta\)) and the horizontal distance (\(d\)) of the ankles from the wall constitute the main exercise variables. These two parameters completely determine the configuration of the body, including the hip and ankle angle, when the subject's anthropometry is known. Besides its popularity, information about the muscle contribution to the SBWS performance is lacking. [PERSON] [7] recorded electromyographic (EMG) signals during a dynamic version of the body-weight wall squat (wall slide). The participants were required to perform five consecutive exercise repetitions up to 60\({}^{\circ}\) of knee flexion meanwhile the feet were aligned with the hip or 50 cm forward and the posterior support was at the hip or scapular level. The author used surface EMG sensors to record the activity of the gluteus maximus, semitendinosus, vastus lateralis, and soleus muscles. The EMG data were used to quantify the _mean_ EMG activity among three consecutive repetitions. Critically, this information has limited impact on the management of the early subacute phase of lower limb rehabilitation, where fine control of muscle activity, joint torques, and joint reaction forces is needed in different phases of the exercise throughout the range of motion (ROM). For example, it is known that quadriceps contraction yields patterns of mechanical loading on the knee joint that change considerably over the range of knee motion and among the different knee joint structures [8; 9; 10; 11; 12; 13]. To gain a deeper insight into the biomechanics of static wall squat, [PERSON] et al. [14] have recently provided a quantitative analysis of this exercise combining biomechanical modelling and force plate measurements. In that study, the lower limb joint torques, and the shear and compressive components of the tibofemoral reaction force, were determined analytically as a function of \(\theta\) and \(d\) considering two additional exercise variants: (1) progressive shift between the scapular and the gluteal zone of the centre of pressure C\({}_{\text{wall}}\) of the supporting force exerted by the wall on the back; (2) progressive shift between the rearfoot and forefoot of the centre of pressure C\({}_{\text{GR}}\) of the ground reaction force. Both variants had an important impact on the joint torques and joint reaction forces in the whole domain of the \(\theta\) and \(d\) variables. To complete the biomechanical analysis of the SBWS, the EMG activity of relevant muscles involved in the exercise (hip, knee, and ankle extensors, erector spiane, and tibialis anterior) should be mapped in the whole domain of the four variables \(\theta\), \(d\), \(x_{\text{GR}}\) (the location of C\({}_{\text{GR}}\) on the ground, between rearfoot and forefoot) and \(y_{\text{wall}}\) (the location of C\({}_{\text{GR}}\) on the wall, between the scapular and the pelvic zone). However, this requires massive experimental activity. In this research, we provide the first set of such EMG measurements, selecting values of the four variables that are easily reproducible in clinical settings and of primary interest in rehabilitation applications.