This study investigated the effects of traditional free sprint training (FST) and speed, agility, and quickness training (SAQT) on reaction time and lower limb muscle activation during a crouch start in healthy college students. SAQT led to improved activation of the rectus femoris after 6 weeks, with further enhancements observed in both the rectus femoris and biceps femoris after 12 weeks. However, no significant differences were found in crouch start reaction time or in the activation of other muscle groups (e.g., the peroneus longus) between groups or across time points.

In this study, the measured crouch start reaction time was the combined duration of central processing time and peripheral muscular execution time, encompassing both cognitive information processing speed and neuromuscular contraction efficiency (Mero and Komi 1990; Zhang et al. 2013). Although improvements in reaction time were observed following the intervention, the changes did not reach statistical significance as hypothesized. One possible explanation is that the crouch start reaction represents a very brief, simple reaction task, where movement is initiated immediately upon hearing an auditory stimulus—leaving little room for measurable improvement. Previous studies have used acceleration training methods, such as resisted sprint training or plyometrics to enhance explosive muscle output (Lockie et al. 2012). Additionally, the fluidity and coordination of movement during the crouch start are critical. Research suggests that crouch start reaction time is closely linked to the coordination of rapid arm and leg movements (Borysiuk et al. 2018). Because participants in this study were not trained sprinters and likely lacked technical proficiency in the crouch start, this may have limited their capacity for reaction time improvements. Moreover, participants’ baseline reaction times may have already approached normative values for healthy individuals, leaving limited potential for further enhancement. These factors may collectively explain the lack of significant changes in reaction time.

During sprint starts, multiple-joint muscles are activated spontaneously, and muscle force generation depends on various factors, including the total motor units available for contraction, the excitability of motor neurons, and the surface area of contracting muscles. The faster the muscle electrical signals are generated, the quicker the muscles reach their maximum activation. Leg extensor muscles contribute significantly to generating maximum horizontal velocity during the sprint star (Borysiuk et al. 2018; Mero and Komi 1990).

The FST group showed improved activation of the right biceps femoris after 6 weeks. Previous research has shown that SAQT enhances lower limb strength and explosive power with interventions of 6 weeks or more, particularly in athletes like soccer player (Kumar 2018). SAQT also improves neuromuscular development, leading to better speed, agility, and flexibility (Azmi and Kusnanik 2018; Gill 2019). Similarly, FST has been shown to enhance short sprint performance and horizontal power (Lockie et al. 2012; Luteberget et al. 2015; West et al. 2013).

In this study, the SAQT group demonstrated significant increases in rectus femoris and biceps femoris activation over time, whereas other muscles did not show notable changes. This is partially consistent with our hypothesis and likely reflects the biomechanical demands of the crouch start and the specificity of the SAQT protocol. The crouch start requires powerful and coordinated hip and knee extension to generate maximal force against the starting blocks. The rectus femoris, functioning as a primary knee extensor and hip flexor, and the biceps femoris, serving as a hip extensor and knee flexor, play pivotal roles during the initial propulsion phase. The SAQT program, which emphasizes quick acceleration, rapid direction changes, and neuromuscular coordination, likely provided a specific stimulus enhancing the activation of these major muscle groups involved in forceful lower limb extension. In contrast, muscles such as the peroneus longus, which primarily contribute to ankle stabilization and lateral control, may not have been sufficiently challenged by the SAQT activities to induce significant neuromuscular adaptations. Consequently, improvements in muscle activation were more localized to those muscles most directly responsible for explosive sprinting movements.

Both SAQT and FST involve the stretch-shortening cycle (SSC), which enhances muscle performance by improving strength and neuromuscular coordination during training (Markovic et al. 2007; Brown and Ferrigno 2014). This mechanism likely contributed to the observed improvements in biceps femoris activation in both groups during the mid-test. However, SAQT yielded greater lower limb muscle activation in the post-test, suggesting superior improvements in muscle coordination and neuromuscular efficiency. During the sprint start, the muscle activation between the legs, with studies identifying the rectus femoris, biceps femoris, and peroneus longus as the most engaged two-joint muscles (Pain and Hibbs 2007).

Sprinting start is a complex whole-body movement, and the push-off during the initial phase is the primary force generating forward force. When muscles contract across multiple joints, the greater the tension during knee extension and leg push-off, the greater the activation of the gluteus maximus, adductor magnus, rectus femoris, and biceps femoris muscles on the lateral and medial sides of the thigh. This explosive movement allows the body to accelerate to the maximum extent and effectively coordinate the limbs (Alkner et al. 2000; Slawinski et al. 2010). The significant activation of these muscles after SAQT training in this study aligns with prior findings, indicating that the muscles of the thigh contribute more force to the sprinting start. However, no significant differences in the peroneus longus were observed after SAQT or FST training in the present study. Bezodis et al. reported that the anterior leg accounts for 66–76% of the total horizontal impulse force during sprint starts, with contact time on the starting block 1.9–2.4 times longer than the posterior leg, producing greater propulsive force (Bezodis et al. 2019). However, in our study, there was no difference in the activation of the peroneus longus muscles between the left and right legs. This discrepancy may stem from the participants being general university students rather than professional athletes, resulting in limited familiarity with the crouch start technique and insufficient neuromuscular coordination and strength to optimize peroneus longus muscle activation.

Previous research has demonstrated that neuromuscular coordination in professional athletes before and after the start significantly influences performance. Proper activation of lower limb muscles, particularly through explosive force generated by the gluteal, knee extensor, and ankle extensor muscles, is critical for maximizing sprint performance (Markovic et al. 2007; Piechota et al. 2019). However, among non-athletes, sprint start effectiveness depends more on the readiness, strength, and speed of the body’s movements. These findings underscore the importance of combining technical and physical training to improve sprint start efficiency. Future studies should explore how skill-based interventions can bridge the gap between general and elite-level sprinting performance.

This study has several limitations. First, participants were general university students with no prior sprint training, which may limit generalizability to trained or professional athletes. Nonetheless, the results offer a valuable foundation for future research in both professional and student athlete populations. Second, although participants did not report regular exercise habits, it is possible they engaged in physical education classes or irregular physical activity during the study period. Third, we did not instruct participants to abstain from caffeine or stimulants before testing, which may have affected reaction time outcomes.

In summary, SAQT resulted in greater lower limb muscle activation compared to FST; however, it did not significantly improve reaction time. This may be attributed to the brief nature of reaction time, which relies more on motor coordination than on muscular adaptation. Participants’ limited experience with crouch starts likely also contributed to the lack of measurable gains in reaction time. These findings highlight the need for further studies involving skilled athletes and incorporating skill-based training to improve technical aspects of the sprint start. Future research should assess the long-term effects of SAQT and its application across different athletic populations.