# Acute Effects of Static Stretching on Submaximal Force Control of the Ankle
## 1 Introduction  
Static stretching (SS) involves extending a particular muscle or muscle group to its end range and maintaining that position for a prescribed time with the goal of enhancing flexibility and increasing joint mobility. It is widely utilized in sports and rehabilitation settings [1, 2, 3]. In the context of sports performance, SS has traditionally been incorporated into warm-up routines to prepare the muscles for subsequent physical activity by optimizing muscle extensibility and joint mobility. Moreover, SS contributes to the prevention of acute musculoskeletal injuries, particularly in sports involving rapid or repetitive muscle lengthening [4]. However, despite its common use, the acute physiological effects of SS on neuromuscular function, particularly in relation to force production and motor control, remain under ongoing investigation. SS is known to decrease the stiffness of the muscle-tendon complex [5] and reduce the sensitivity of muscle spindles [6]. Reduced muscle spindle sensitivity may compromise proprioceptive input and reflex activity. These SS-induced alterations, including changesin muscle-tendon compliance, length-tension relationship, and central neural drive, may modulate the nervous system to finely regulate muscle force output [5; 7; 8; 9; 10]. Taken together, these findings suggest that SS can acutely influence neuromuscular function and potentially affect the precision of force modulation. Many daily tasks demand precise adjustment of the force output and accurate modulation of muscle force in accordance with environmental and task-specific demands is essential for motor control [11]. When such modulations are effective, it can facilitate smooth movement and lead to joint stability [12; 13]. On the other hand, impaired force modulation may result in excessive or insufficient force production, leading to movement inefficiency and compromised postural control [14; 15]. Maximal muscle strength is a common performance outcome in sports. However, sports such as football and basketball require rapid movement transitions and fine motor adjustments, necessitating the ability to exert force at the appropriate timing and magnitude. Thus, an impaired ability to finely adjust muscle force can lead to inefficient movement strategies, increased energy expenditure, and reduced movement accuracy or stability, which may hinder functional performance in both daily life and sports [16; 17]. Conversely, appropriate modulation of muscle activity may contribute to smoother coordination, more successful task performance, and lower risk of injury. Therefore, assessment of force control at submaximal intensities is considered important. Force control is defined as the ability to generate muscle contraction with precision and stability under static or dynamic conditions [18]. Previous studies have suggested that the SS negatively affects this ability. For instance, SS consisting of three sets of 60 s applied to the knee extensor muscles significantly decreased force steadiness at 5% and 20% maximal voluntary isometric contraction (MVIC) [19]. Similarly, five sets of 60 s of SS applied to the ankle plantar flexors resulted in a significant decline in force steadiness at 20% MVIC [20]. However, these studies primarily assessed force steadiness using isometric contractions with a constant target torque. The effects of SS on force control under dynamic conditions involving force fluctuations are unclear. In real-world movements, force is not exerted at a fixed level but is dynamically adjusted to match the demands of the tasks. Moreover, many of these real-world tasks are preceded by SS as part of warm-up or rehabilitation protocols. Therefore, understanding how SS affects the ability to modulate submaximal force under dynamic conditions is important. Understanding how SS affects submaximal force control may help clarify the mechanisms underlying SS impact on performance, thereby supporting its more effective application in sports and rehabilitation settings.