Badminton is a racket sport characterized by intermittent actions, jumping, changes of direction and rapid arm movements with a high demand on aerobic power, alactic anaerobic and to a lesser extent lactic anaerobic metabolic systems (Cabello Manrique & González-Badillo, 2003). Achieving high levels of physical performance is essential for success, given the sport's intense physiological requirements (Phomsoupha & Laffaye, 2015). Torres-Luque et al. (2019) investigating both male and female high-level adult badminton players across group and elimination phases of international competitions, recorded notable differences in match characteristics as championships progressed. Similarly, in a study focusing on Olympic-level male singles (Chiminazzo et al., 2018), observed that point duration and strokes per point increased from the group phase to the elimination phase, particularly in the third set. In competitive badminton, athletes often face multiple matches in a single day, especially during tournaments. While the physical toll of such match schedules has been acknowledged, there is limited research addressing how the cumulative demands of several matches affect young athletes’ performance during real competitions. Existing studies have primarily focused on isolated matches or simulated conditions, in many cases with adult athletes (Birdsey et al., 2019; Ojala & Häkkinen, 2013), whereas Moreno-Perez et al. (2020) did examine junior players, underscoring the need for research on how multiple matches within a single day affect fatigue and recovery in developmental-aged badminton athletes under real competitive conditions.

Monitoring athlete response to fatigue or physical performance during competition is a common approach that reveals the competition requirements, facilitating preparation and guiding athletes and coaches towards practices that can lead to increased athletic performance (Abián-Vicén et al., 2014; Faude et al., 2007; Gomes et al., 2014; Maraga et al., 2018; Ojala & Häkkinen, 2013). Understanding the progression of fatigue during competition is essential for coaches and athletes to optimize performance and recovery strategies. Monitoring tools like the rate of perceived exertion (RPE), session RPE (sRPE), and the Muscle Fatigue Visual Analog Scale (MFVAS) offer practical, subjective methods to assess internal load (Foster et al., 2001; Kenttä & Hassmén, 1998). Meanwhile, objective measures such as countermovement jump peak height (CMJh) provide insights into neuromuscular fatigue, although their sensitivity in racket sports remains debated (Heishman et al., 2020; Abián-Vicén et al., 2012).

In relation to the perceived load and the characteristics of the matches, it has been reported that after two accumulated matches in a real competition, no significant differences are seen in perceived exertion sRPE, muscle pain or lower limb strength determined by CMJh - suggesting that the muscular performance of the lower limbs is not negatively affected by the accumulation of matches. Moreno-Perez et al. (2020) and Abián-Vicén et al. (2014) found that although a single match did not lead to a reduction in CMJh in a real competition, the accumulation of competitive rounds during competition did lead to a reduction in relation to the post-match vertical jump of previous rounds. Moreover, CMJh was not only not negatively affected after a singles badminton match, but the peak jump height was greater post-match versus pre-match, suggesting a lack of muscle fatigue caused by the match (Abián-Vicén et al., 2012). The absence of negative effects on CMJh would agree with the results obtained in tennis (López-Samanes et al., 2018; Maraga et al., 2018; Ojala & Häkkinen, 2013) and in accordance with other authors (Bishop et al., 2023) indicating the lack of sensitivity of CMJh as a neuromuscular fatigue monitoring metric. Thus, to date, the data found in the scientific literature are controversial and inconsistent.

Many studies have examined a simulated competitive situation or analyzed the effect of one or two badminton matches on jumping ability, vertical strength or RPE of elite senior athletes (Abián-Vicén et al., 2012, 2014; Lin et al., 2023), though no studies to date have analyzed the cumulative effect of more than two matches during a real competition on the same day in young athletes.

To address this gap, the present study aimed to investigate the evolution of fatigue across five consecutive matches during a single-day U17 national badminton tournament. A combination of subjective -RPE, sRPE, MFVAS, total quality recovery test (TQR)- and objective -CMJh, drop jump peak height (DJh), reactive strength index (RSI)- measures was employed to examine changes in internal and neuromuscular load. These tools were selected based on their frequent use in monitoring fatigue and recovery in athletic populations, although their sensitivity in youth badminton contexts remains unclear. Rather than offering generalizable claims, this study seeks to provide context-specific insights that may assist coaches and practitioners in understanding the fatigue profiles of youth athletes and selecting practical monitoring tools in real-world competition.

This study explores how fatigue evolves throughout a single-day national badminton tournament involving five consecutive matches, by examining subjective and objective metrics. We also aim to identify practical, cost-effective monitoring strategies that coaches and organizations with limited resources can implement. Our main findings indicate that match time,: (i) match time, RPE, sRPE and MFVAS (pre- and post-match) increased as the competition evolved, while DJh (pre- and post-match) decreased; (ii) the first match of the day was physically more demanding than the second and even the third in terms of match time, points played, RPE, sRPE and post-match MFVAS and; (iii) a positive stable relationship was present between sRPE and the number of points and sets played in a match, as well as its duration. This would suggest that the accumulation of 5 matches in the same day in a national U-17 8* badminton competition would lead to an increase in physical demands as the competition progresses, with RPE, sRPE, MFVAS and DJh being metrics more sensitive to such fatigue than CMJh, RSI and TQR.

Our results evidenced a clear increase in the demands imposed by the matches as the competition progressed, with an increase in match time and a slight increase in the number of sets played. The mean match duration of 27.9±9.3 minutes was shorter than that recorded in other studies analyzing Spanish badminton championships, with a mean duration of 34.6±8.4 and 41.3±15.9 minutes in the second round and quarterfinals, respectively (Abián-Vicén et al., 2014). These differences in terms of match duration with respect to the data provided by the study of Abián-Vicén et al. (2014) may be due to the fact that the competitive level of the athletes was higher in their study (an absolute category tournament versus U17 in our work). Despite this, our results are in agreement with the findings of other authors in which a mean match duration of 27.1±5.6 was reported in the "XI Spanish Junior International" (Moreno-Perez et al., 2020).

To gain a more insightful overview of match demands as the competitive round progresses, we observed changes in match duration, rest time and in the RPE, sRPE, DJh and MFVAS scores. Authors such as Moreno-Pérez et al. (2020) did not find significant differences between daytime sRPE values (148.6±66.0 versus 156.6±74.8 AU) or in post-match MFVAS scores (28±24 versus 32±21 mm) between two matches performed on the same day in 21 badminton players in an international junior competition. This suggests that two matches may not induce sufficient cumulative fatigue, whereas five matches provide a clearer picture of accumulated physical demands. In our study, the increased demands were accompanied by an increase in RPE and a reduction in DJh as the competition progressed. This would make sense given the structure and organization of the competition, where those athletes with the highest-level move from round to round so that in each round the confrontation proves more demanding than the previous one, resulting in an increase in points played per match, match time and rest time within the match due to the high demands and more similar levels between players. Our data are consistent with those reported by Torres-Luque et al. (2019) and Abián-Vicén et al. (2014), who found an increase in the demands of each match as the competition progressed. When comparing the demands and characteristics between the matches analyzed in this study and those found in other high-level competitions, it becomes evident that our athletes are in a process of development as badminton players.

Our findings regarding MFVAS are in accordance with those of Lin et al., (2023), who also found a significant increase between pre- and post- singles simulated 1-h matches, supporting the observation of the neuromuscular fatigue caused by a single match. Although MFVAS reflects accumulated fatigue in the lower body, this fatigue affected performance in DJh, but not CMJh or RSI. The absence of CMJh jump reduction would coincide with the observations of Moreno-Pérez et al. (2020) and Abián-Vicén et al. (2012) in several badminton matches on the same day, while differing with those of Abián-Vicén et al. (2014). In our study, the lack of CMJh sensitivity as a metric of lower limb neuromuscular fatigue, likewise reported by RPE, sRPE, MFVAS and DJh after several matches is in accordance with Bishop et al. (2023), which supports the theory that CMJ neuromuscular fatigue sensitive metrics are time-based and not output based. To our knowledge, no studies have evaluated RSI or DJh as a reliable metric of lower body neuromuscular fatigue in an official racquet sports competition involving 5 matches on the same day.

In our study, we also observed that the requirements of the first match were greater than in the second match for RPE, sRPE, points played and game duration, and even greater than in match 3 for RPE, sRPE, post-match MFVAS and game duration. Such findings are consistent with those of Maraga et al. (2018), who found the first match to be more demanding than the second match, and with the second match in turn being less demanding than the third match in junior athletes during a simulated tennis competition with three singles matches on the same day. This could be due to the psychological difficulty for athletes to solve the first match of the day and thus start the tournament, though the difference in the level of the players is even greater than in the later matches. In contrast, Gallo-Salazar et al. (2019) documented an increase in total match duration, point duration, rest duration and RPE in the second match with respect to the first match during a simulated competition with two tennis matches on the same day (one in the morning and the other in the afternoon). The comparison of our results with those of other studies is difficult, to the best of our knowledge, no other studies have analyzed 5 or more matches on the same day in a real badminton competition in this age group, and the evidence is still inconsistent.

Regarding the relationships between the match characteristics and physical performance, we found a clear correlation between the number of sets, the number of points, match time and sRPE. As match duration and points played increase, so does effort, which directly influences sRPE calculations (Foster et al., 2001), These associations align with expectations for cumulative fatigue markers. Likewise, RPE was also positively related to match time, indicating that the longer the match time, the greater the athlete perception of effort. Moreover, our match characteristics were also associated - albeit punctually - to the physical performance variables, which would indicate the lack of a stable association between the two. These findings may be indicative of the complex nature of a badminton match and competition where several factors, in addition to those contemplated in our study, may influence cumulative fatigue - thus making it difficult to identify a more stable association between match-specific demands and the physiological response of the badminton player.

This study has some limitations that should be addressed. On one hand, the public health situation caused by Covid-19 forced paralyzing training of the athletes while they advanced in category during that time. This produced a mismatch in the national ranking, due to which the level of the athletes in the category was not faithfully represented by their position in the ranking and therefore the seeded athletes in the competition. On the other hand, the organizational health and safety procedures that had to be adopted, added to the natural rhythm of the competition, did not allow the participation of a greater volume of athletes. Thus, future research should focus on clarifying the relationship between objective and subjective variables with respect to their sensitivity to fatigue, as well as the SSC mechanisms most affected by fatigue in a badminton competition with several matches on the same day in a more stable national ranking situation and with a larger volume of subjects.