## 1 Introduction
As same as [6], it also investigated LP45 by physioball and elastic band with submaximal loads on EMG amplitude and fatigue indices. Higher levels of CRMS (Coefficient of Root Mean Square) and Cf5 were noted for RF muscles, VL, and VM, respectively. It showed that both physioball and elastic band could be adopted to reduce excessive varus and valgus forces during leg press. It may increase quadriceps activation and improving the knee joint stabilization. In [6; 7], it sought to investigate the effect of performing leg press (LP) 45 degrees using a physioball and elastic band to reduce excessive varus and valgus forces, to increase quadriceps activation and improve knee joint stabilization. The use of surface electromyography is a widely accepted technique for measuring the electrical signals produced by muscle contractions and estimating the strength of muscle. It is suitable to apply in sports medicine research [8]. The surface electromyogram is a general technology that is used to measure muscle strength by measuring the electric signal of muscle contraction. It is also applied for sport medicine. Integrated Haptic Feedback (IHF) provided an over-ground gait training regimen for post-stroke ambulatory subjects. The effects of IHF system was trailed by six post-stroke ambulatory individuals in walking. It indicated that patients' body sway was not disturbed under the faster walking. Hence, IHF system was a valuable tool to assist physical therapist in gait rehabilitation of post-stroke individuals. Both using kinesthetic and tactile cues for the post-stroke gait rehabilitation is a novel concept. The symmetry, balance and muscle activation patterns imply that integration of haptic cuesmay benefit post-stroke gait rehabilitation to improve the symmetry and muscle activity simultaneously [9; 10]. At present, most of the clinical examination methods use palpation or X-ray image to diagnose the positions of the patella and femur as well as to determine the cause of patellar lateral subluxation, and then finally decide whether surgery or non-surgical treatment is to be adopted. Cases like patella dysplasia, defects of femoral sulcus and femoral condyle, may be based on surgical treatment, while non-surgical treatments mainly consider strengthening the VMO of the quadriceps femoris muscle and protecting the patella [11]. Understanding the VMO and VL muscle contraction patterns can improve rehabilitation actions and overall rehabilitation effects [12]. Medical research attempting to find an effective treatment for the patellofemoral malalignment has found that kicking forward action could trigger a higher VMO, and therefore it became an effective treatment that helps patients to alleviate their symptoms [13; 14]. Since the goosestep does not fit the ergonomics to hurt the brain due to the heel on the ground violently, the goosestep could not be used for patients. In order to compare the effects of the triggering time of VMO and VL on patellofemoral pain syndrome, observe the difference of muscle time under different movements and find the optimal relationship between VMO and VL, the study of [PERSON]. et al. showed that if the VMO nerve trigger time was reduced or was inappropriately five milliseconds later than that of the VL, it might result in significant lateral movement of the patella affecting the patella joint [15]. In [16], the presence of anterior knee pain (AKP) is a delay in the recruitment of VMO relative to VL. However, much fewer literature was regarding the recruitment of VMO within the AKP population. Both the systematic review and meta-analysis are only to examine the relative timing of onset for VMO and VL with AKP compared with the asymptomatic population. However, some patients with AKP may not have a VMO-VL dysfunction. Therefore, it is difficult for the clinical treatment. In [17], the temporal recruitment of VMO was compared with the one of VL during voluntary ankle movements and perturbed standing with patellofemoral pain. [PERSON] et al.