The aim of this study was to examine the maturity status according to PHV and physical fitness (i.e., vertical jump performance, linear sprint and CoD speed) of young male and female badminton players. Our main results indicate that boys presented better CMJ and linear sprint (5–10 m) and COD performances (M505 test) than girls. No significant sex-related differences were found for training volume and the on-court COD test. Our results indicate that Pre-PHV players presented lower jump (CMJ), linear sprint (5–10 m), and COD performance (both modified 5-0-5 and the on-court test) compared with the Post-PHV players. In addition, compared with Circa-PHV, Pre-PHV players also demonstrated lower performance levels in both, 10-m linear sprint and COD speed. Regarding the CODD%, no statistically significant differences were found between the maturity groups. Finally, when analyzing sex-by-maturity interactions, results showed significant interactions only for the Pre-PHV group, with higher training volume in boys than girls. In addition, sex-related performance differences were large for most measures, except for CODD%.
Regarding the observed sex-related differences, our results can be interpreted as an enhanced neuromuscular performance of boys compared with girls. It is likely that this difference is primarily caused by the higher strength capacity of boys (rather than a sex-mediated effect) (24). It seems that absolute sex-related performance differences disappeared when subjects are strength-matched, as recently reported in a study that compared “absolute” and “relative” maximum strength performance between male and female youth athletes (10). The results of this investigation suggest that these variations are caused by distinct strength values (rather than a biological consequence induced by sex). In other words, girls could show similar performance levels as boys if the strength capacity were similar between sexes. Future research could test this hypothesis to determine whether the decreased neuromuscular performance (i.e., jump performance, linear sprint and COD speed) in girls are a direct result of the lower strength levels.
During the early stages of long-term athlete development, players spend a great amount of training time mastering their individual badminton-specific skills, with technical and tactical sessions constituting an important part of the training week. In this regard, the information about training volume in young badminton players is scarce. Only few studies are available and researchers reported weekly training volumes ranging between 16-20 h hours at ages below 13 years old, with training volume increases up to 25 h per week in competitive players aged 13-15 years (25,26). Our results showed that the analyzed sample is far from this training volume, which highlights the recreational character of our study sample. Furthermore, when analyzing training volumes, there were no differences between boys and girls, although boys presented better performance levels in several fitness tests (i.e., CMJ, linear sprint and CoD performances), which could be related to a bias is directed towards a sport-specific activity at the expense of fitness training Thus, the inclusion of training programs that incorporate a variety of essential motor skills (i.e., locomotion, stabilization, strength) seems a worthwhile strategy to maximize motor skill proficiency, and reduce the risk of sustaining acute and overuse injuries in youth athletes (27). In addition, daily training practices of young badminton players is often characterized by co-education with boys and girls grouped according to chronological age. In this regard, it is well-known that large interindividual biological differences can exist within sexes and in individuals of the same chronological age (3), suggesting that chronological age is not a good indicator to use for training programming. Thus, a practical approach to design individualized training programs, and to organize training groups that are related to certain periods of trainability during the process of maturation is the use of an athlete’s PHV (28). The rationale for PHV usage is that maturity has a large impact on physical fitness qualities such as linear sprint and CoD speed, and jump performance. For example, were able to show significant differences in body height and mass according to the maturity status. Pre-PHV players were significantly shorter (>12%) and had less body mass (>20%) than Circa-PHV and Post-PHV players. Previous researchers reported that biological maturity leads to significant increases in body height and mass (3), which, in some cases, may disrupt motor coordination in complex motor coordination tasks (i.e., “adolescent awkwardness”) (29). From a practical point of view, although these alterations are not an absolute expectation, they may temporarily compromise the regulation of the lower extremity joint stiffness and lead to impairments in the individual’s ability to control multi-joint movements (30).
Regarding the linear sprint and jumping ability, the use of linear sprint tests, or the CMJ as a valid tests for general assessments of lower limbs neuromuscular function are well accepted in the literature (31), and seems to be relevant to describe its development during different stages of maturation (32). For linear sprint speed, Pre-PHV players were significantly slower than Post-PHV (~10-12%) players, and although non-significant, there is a tendency to be slower than their Circa-PHV (~5%) peers. Moreover, Circa-PHV players were also significantly slower than the Post-PHV counterparts (~8%) in the 5-m sprint, and although non-significant, ~6% slower in the 10 m. To the best of our knowledge, there is no previous study available that analyzed these physical qualities in a similar youth badminton cohort. Therefore, between study comparisons are not possible. However, our results are in agreement with previous research conducted with young athletes from other sports (14,33,34), showing that Pre-PHV players presented lower levels (~10-20%) of jump and sprint performance than their Post-PHV peers. The period around PHV seems to be a key point in which the ability to develop vertical power and the speed accelerate (29,35), which continue to increase, although not significantly, until the Post-PHV stage. Although physiological measures were not taken in this study, it is possible that factors such as increases in muscle size, limb length or tendon stiffness are related to the observed between group differences (36–38).
In badminton, players must frequently change direction towards the center of the court and then towards the opponents’ return (39), highlighting the crucial importance of CoD for this sport. Accordingly, previous researchers reported a significant relationship between CoD speed and the winning percentage in national-level players (40), highlighting this physical quality as one of the most important athletic skills needed to be a successful badminton player at any level. Consequently, the assessment of CoD should be included within badminton players’ test batteries. In the present study, we included a simple CoD test plus a badminton-specific test, which was previously shown to be highly sensitive to discriminate between athletes from different age groups and expertise levels (20). Our results showed that boys outperformed girls in the M505 test, but there were no differences in the CODD%. Thus, faster players in linear sprint performance did not present higher CoD deficits, which is in line with a recent study in young tennis players (17). However, these results are also contrary to previous studies in team-sport athletes (both professional and youth players), showing that faster and more powerful subjects tend to present higher CoD deficits (when compared with their slower and weaker peers) (41,42). Since badminton players are required to make a great number of directional changes during rallies, with a very short distance covered on each stroke, and rarely reach maximum speed, we can suggest that this group of players tend to be more efficient in this specific task (e.g., modified 505 test). Since the distance covered in a 505 test seem not enough to achieve considerable velocity, badminton players analyzed here seem to have the ability to handle and tolerate the higher approach velocities throughout this measurement.
Results regarding the on-court CoD test showed that comparing maturation groups, Pre-PHV presented lower levels of performance (~15-20%) compared to their Circa and Post-PHV peers. These results are in line with a previous study reporting that this test showed differences of large magnitude between U17 and U19 players (20), and reinforcing the idea that the test is highly sensitive to discriminate between players of different levels. Interestingly, when comparing genders, results of the on-court CoD test showed no differences between boys and girls, although performance levels were trivial in girls (~6%; ES: 0.34) compared to the boys. Although girls showed lower performance levels overall, there were more number in the Circa and Post-PHV stages. Thus, we could hypothesize that together with similar training volume between genders, girls seem to be more efficient in a sport-specific displacement. However, we need more research to confirm this hypothesis.
Practical applications of key findings
This study has important implications for daily exercise practice and future research. Considering that daily training practices of young badminton players usually involves co-education (i.e., girls and boys), the use of maturity status (i.e., PHV) instead of chronological age could be more appropriate when designing training programs. This strategy may be especially useful when youth players are training and competing in chronological age-based environments in which they may be more susceptible to maturation bias, particularly the immature individuals (3). Moreover, performance of boys and girls is different, especially in the first periods of sports development (i.e., Pre-PHV). Therefore, coaches should not only be aware of these differences, but also provide efficient training stimuli to avoid possible fitness deficits. From a practical perspective, it seems that girls benefit most from strength and conditioning programs that are incorporated into training before the onset of puberty (43), This could improve performance through enhanced neuromuscular activation and it may minimize the risk of sustaining injuries.
Findings of this study suggest the need to include specific training strategies related to the different maturation stages. In this regard, badminton training centres or schools can take advantage of using the online available PHV calculation equations (i.e., https://wwwapps.usask.ca/kin-growthutility/phv_ui.php), every 2–3 weeks, to design optimal training groups and plan the consequent training loads. Thus, players around PHV can benefit from neuromuscular training programs (44), including foundational strength and movement skills, which could be beneficial for developing their neuromuscular qualities (45). However, with the onset of puberty, circulating anabolic hormones (i.e., testosterone) provide an adequate foundation to build muscle mass through heavy resistance strength exercises. (46).
Limitations
A number of study limitations are worth mentioning, such as its cross-sectional design and the inclusion of bigger samples, including pre, around and post-PHV players organized by their competitive levels (regional, national), that would help to avoid potential selection bias. Furthermore, a more detailed analysis of the training volume at the different maturation stages, including specific volume for strength, endurance, and/or other qualities, would help to clarify if performance differences are also mediated by training. Finally, the lack of strength/power related measurements could help to determine whether the differences found herein are mediated by differences in the strength levels.