## 1 Introduction  
Supramaximal running velocity has been used in sprint training in order to increase stride frequency [1]. Tow-training has been employed for sprinters to assist supramaximal running velocity. Running velocity is determined by stride frequency and stride length. In maximal sprinting, stride frequency plays a more decisive role than stride length does [1]. In addition, the large negative power of the knee flexors (hamstrings) and the large positive power of the hip extensor contribute to high stride frequency, enabling the sprinter to run at higher speeds [2, 3]. The mechanical power exerted by the hamstrings, which function in hip extension and knee flexion, becomes greater in the swing phase than it is when running at maximal speed [2, 4]. To improve running performance, it is necessary to follow a particular program to acquire higher stride frequency by exerting great power in the bi-articular muscles of the hamstrings, which cross both the hip and the knee joints [5]. Repeated supramaximal running can result in high stride frequency [1]. In supramaximal running, sprinters can sprint at a supramaximal level [6]. Further, tow-training, a method of supramaximal running, can result in a high level of neuromuscular performance [1]. Therefore, supramaximal running is suggested for specific sprint training programs [5] for its possible effects in increasing stride frequency in sprinters. Supramaximal running is used to improve sprinting performance through enhanced stride frequency [1, 6]. In supramaximal running, runners sprint for a certain period of time while maintaining a supramaximal speed [6]. Supramaximal training often uses tow-training with an elastic cord or a rope and pulley [6, 7]. Although innovations and improvements in towing systems have been available, the tow-training method has not been considered favored in the training context [7]. The first reason is that, as [PERSON] [7] reports, in most studies stride length increases, and stride frequency decreases or remains steady in supramaximal running. Even in research using a towing device that may offer precise control of assistance compared with other modes of overspeed training, a significant increase was observed in stride length but not stride frequency [8]. This may suggest that supramaximal running may not provide a transfer any greater than that provided by standard maximal running [9]. The second reason is that hamstring injuries tend to occur during tow-training [7; 10]. In an experimental study, [PERSON] et al. [10] reported that one of nine male sprinters suffered severe injury to the hamstring during supramaximal running. Researchers and coaches have highlighted issues related to hamstring injuries [7; 10; 11; 12]. As [PERSON] [13] suggested, there are risk factors leading to an injury, and some factors may be more predictive than others. [PERSON] [14] reported that most hamstring injuries occur while running or sprinting. He also listed several possible etiological factors that relate to the occurrence of a hamstring injury, such as inadequate flexibility of the muscles, inadequate muscle strength, and dyssysnergic muscle contraction. According to [PERSON] et al. [15], for sprinters with high sprint performance, not only strength deficits but also the lack of neuromuscular control and flexibility contributes to the occurrence of hamstring injuries. How strength, agility, and flexibility training induces the occurrence of hamstring injuries in sprinters has not been studied. If strength, agility, and flexibility do not function at a high-enough level to allow running velocities that well exceed 10 m/sec [16; 17; 18; 5; 6; 15; 10], the risk of hamstring injury in tow-training involving repeated episodes of supramaximal running increases. To develop a prevention program for hamstring injury during supramaximal running, we described a systematic preventive method involving multiple factors that have a causal relationship and in the light of which it is necessary to evaluate the effectiveness of the intervention program.