Keywords: junior tennis, biological maturation, peak height velocity, injury prevention, youth athletes
This blog provides a summary of our recent study published in the British Journal of Sports Medicine [1].
Why is this study important?
Junior tennis players are not simply “small adults”. During adolescence, athletes experience rapid changes in height, body composition, muscle strength, flexibility and coordination [2]. These changes can affect how the body responds to tennis training and competition [3].
In many youth sports, injury prevention is still often based on chronological age, such as under-12, under-14, under-16, or under-18 categories [4]. However, two athletes of the same chronological age may be at very different stages of biological maturation [5]. One player may be in the middle of a growth spurt, while another may already be several years past it.
This is especially important in tennis, where young athletes are exposed to repeated sprinting, stopping, changing direction, trunk rotation and high-volume hitting [6]. Despite this, little has been known about how biological maturation relates to injury risk in junior tennis players. We wanted to better understand when young tennis athletes may be most vulnerable to injury and whether these vulnerable periods differ between boys and girls.
How did the study go about this?
We retrospectively analyzed 15 competitive seasons of data from a tennis academy in Japan. The study included 100 junior tennis athletes, with 50 boys and 50 girls.
We estimated each athlete’s biological maturation using age at peak height velocity (APHV), which is calculated from the longitudinal height data. APHV refers to the age when an athlete reaches their fastest rate of height growth during adolescence (Figure 1).
Figure 1: An example of a growth velocity curve showing the identification of peak height velocity (PHV) and age at peak height velocity (APHV).
This is a useful marker because it allows us to look at injury risk in relation to each athlete’s own growth timing, rather than simply using chronological age [7].
Each athlete’s development was divided into five maturity phases:
- more than 18 months before APHV
- 18 to 6 months before APHV
- around APHV
- 6 to 18 months after APHV
- more than 18 months after APHV
We then examined injury incidence and injury burden across these phases. Injury incidence tells us how often injuries occurred, while injury burden also considers severity by including the number of days lost from sport [7].
What did the study find?
We found large individual differences in maturation timing. In both boys and girls, the difference between the earliest and latest maturing athletes was approximately 4.5 years (Figure 2). This means that athletes of the same chronological age may have very different maturation status.
We also found clear sex-based differences. Boys reached APHV at approximately 13.2 years of age, whereas girls reached APHV at approximately 11.5 years of age. Boys also had a higher peak height velocity than girls (Figure 2).
Figure 2: Growth velocity curves for boys (A) and girls (B)
APHV: age at peak height velocity; PHV: peak height velocity. Boys: n=50, Girls: n=50. *Significant sex difference (p < 0.05)
A total of 256 injuries were recorded over the study period. Lower limb injuries were the most common in both boys and girls, followed by upper limb and trunk injuries. Tendon injuries were the most frequent injury type in both sexes, contrasting with the predominance of muscle injuries often reported in adult tennis players. This finding may reflect the unique mechanical demands placed on the developing musculoskeletal system [8].
The timing of highest injury risk differed between boys and girls. In boys, injury incidence and injury burden were highest around APHV (Figure 2 and Figure 3). This suggests that the period of rapid growth may be a key window of vulnerability for boy tennis players. In girls, the highest injury incidence and injury burden occurred after APHV (Figure 2 and Figure 3). This suggests that injury prevention in girl tennis players may need to continue beyond the growth-spurt period, especially as training exposure and sport-specific demands increase.
Figure 3 Injury incidence (number of injuries per year) plots for boys (A) and girls (B). Boys: n=114 injuries and girls: n=142 injuries. *p=0.016, **p=0.004, ***p=0.003, ****p=0.002, *****p<0.001. Error bars indicate 95% CIs.
Figure 4 Injury burden (days absence per year) plots for boys (A) and girls (B). Boys: n=114 injuries and girls: n=142 injuries. *p=0.038, **p=0.036. Error bars indicate 95% CIs.
What are the key take-home points?
Our study suggests that junior tennis injury prevention should consider biological maturation, not just chronological age.
For boys, the period around APHV may be a particularly important time to monitor training load, flexibility, trunk function and growth-related symptoms. For girls, clinicians and coaches should remain alert to injury risk after APHV, when tennis-specific exposure and physical demands may continue to increase.
A practical message is that growth should be tracked routinely. Regular height measurements can help identify when an athlete is approaching or passing through their growth spurt. This information can support more individualized decisions about training volume, recovery, conditioning and injury prevention.
The main message is simple: in junior tennis players, injury risk changes with maturation, and the timing of risk differs between boys and girls. To protect young athletes and support long-term development, clinicians, coaches and parents should look beyond age categories and pay attention to each athlete’s biological growth stage.
Authors information: Dr Yoshimasa Saigo and Daichi Morikawa, Department of Orthopaedics, Faculty of medicine, Juntendo University, Tokyo, Japan.
References:
- 1. Saigo, Y., et al., Injury risk and its relationship with biological maturation among 100 junior tennis athletes: a 15-year retrospective analysis. Br J Sports Med, 2026.
- Terry A. Adirim, T.L.C., Overview of Injuries in the Young Athlete. Sports Med, 2003. 33: p. 75-81.
- DiFiori, J.P., et al., Overuse injuries and burnout in youth sports: a position statement from the American Medical Society for Sports Medicine. Br J Sports Med, 2014. 48(4): p. 287-8.
- Rice, R.P., et al., Age and Gender Differences in Injuries and Risk Factors in Elite Junior and Professional Tennis Players. Sports Health, 2022. 14(4): p. 466-477.
- Katsunori Fujii, S.D., Jinzaburou Matsuzawa, Optimum Onset Period for Training Based on Maximum Peak Velocity of Height by Wavelet Interpolation Method in Japanese High School Athletes. J Physiol Anthropol Appl Human Sci, 2005. 24: p. 15-22.
- Hjelm N, W.S., Renstrom P. , Injury profile in junior tennis players: a prospective two year study. Knee Surg Sports Traumatol Arthrosc., 2010. 6: p. 845-50.
- Monasterio, X., et al., The burden of injuries according to maturity status and timing: A two-decade study with 110 growth curves in an elite football academy. Eur J Sport Sci, 2023. 23(2): p. 267-277.
- Pluim, B.M., et al., Tennis injuries: occurrence, aetiology, and prevention. Br J Sports Med, 2006. 40(5): p. 415-23.
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