# The Effect of Bodyweight Support and Incline Running on Triceps Surae Electromyographic Activity
## 1 Introduction  
The lower body is an essential component in performance in most sports; however, the calf is the most injured part of the lower body [1; 2], and Achilles Tendon rupture cases seem to keep increasing despite enhancements in knowledge and research [3]. Based on injury prevention and rehabilitation recommendations, the training load should be increased progressively while working with longer contractions to lead to better tendinous adaptations [4]. Along with rehabilitation recommendations, IR allows the longer contraction of the triceps surae due to an increased amplitude of movement. In addition, IR leads to a lesser reduction in the ankle range of motion compared to level running and can reduce the risk of tendinopathy [5; 6]. At the same time, as the passive eccentric and active concentric phases of the muscle are amplified during IR, with the increases in the slope, muscle work is increased [7; 8]. Finally, as EMGA depends on contraction intensity, increasing IR increases EMGA [9]. EMGA is increased by greater motor drive and motor unit recruitment. Asa result, it optimizes contractions by creating more tension on the muscle fiber and can, therefore, improve the rehabilitation process. However, tendinopathy can also occur with repeated overloading on the tendinous-muscular system [5]. As IR increases the intensity of contraction, noticeable by the increase in EMGA of the lower limb, it could potentially cause repetitive overload. Nevertheless, IR is not easily accessible at an early stage of rehabilitation, and it is well established that early mobilization of the injured limb is crucial for a quick and successful rehabilitation program [10; 11]. It is necessary to find a way to allow injured athletes to run on an incline slope as soon as possible. Therefore, the use of BWS in IR is a way to prevent injury. Among the methods/types of equipment that are commonly used among physiotherapists and rehabilitation trainers during a rehabilitation program for the lower limbs are BWS treadmills, which are capable of reducing the active body weight of the patients during a rehabilitation program; thus, they help to unload lower extremities while the patient is walking or running on a treadmill. This type of training is mainly used in non-healthy populations, like Spastic Paretic [12] or Post-Stroke patients [13; 14; 15], or in patients with Spinal Cord Injury [16; 17] or even with Parkinson's disease [18]. However, BWS seems to favor rehabilitation, even in athletic populations. Indeed, even if walking and running are essential stimuli during athletes' rehabilitation programs, they can also traumatic joints and muscles because injured athletes show greater vertical impact and impact loading, with the latter being one of the principal components that may affect the success or failure of a lower-limb rehabilitation program [19]. Thus, BWS reduces the ground forces the injured athlete produces during running and avoids exacerbating the injury [20]. However, until now, the data about the effectiveness of BWS have been controversial. It seems that BWS does not reduce the total rehabilitation time significantly but allowed patients to run 2 weeks before a control group in Achilles tendon rehabilitation [21]. Also, for anterior cruciate ligament reconstruction rehabilitation, using BWS is significantly more efficient than standard rehabilitation at 12 weeks follow-up but not at 24 weeks [22]. Moreover, after a 6-week speed-training program, no differences were found between standard training and BWS training; only a decrease in injury was found for BWS training (66% against 8%) [23]. Furthermore, during a BWS running training program, EMGA decreased [17; 24]. With body support ranging between 10% and 40% of the patient's body weight, a decreased EMGA of the triceps surae was observed [24], a reduction which seemed to be more pronounced in the GM and GL than SOL [25], which may lead to the variable effectiveness of BWS.