Upper-Limb Strength Shifts Its Role as Young Female Tennis Players Mature
In junior tennis, strength is not a single trait. It changes shape as players grow, train, and learn to express force through the racket and the kinetic chain.
A comparative study in female tennis players under 12 and under 14 found that on-court performance, measured with the International Tennis Number (ITN) test, rose alongside stronger upper-limb profiles in the older group. The pattern was not uniform across ages. In the younger players, performance lined up more closely with general strength measures, while in the older players it tracked more strongly with joint-specific upper-limb strength and neuromuscular characteristics.
Age, Maturation, and Why Strength Does Not Mean the Same Thing at 11 and 13
The study examined 33 players and paired tennis performance testing with several strength assessments: handgrip strength, flexed arm hang, tennis-ball throw, isometric upper-limb muscle strength, and sense of force. This mix matters because tennis does not ask the arm to do one job. It demands grip stability, shoulder and elbow control, racket acceleration, and the ability to repeat forceful strokes without losing precision.
In younger athletes, general strength can act as a broad marker of readiness. A child with better whole-body strength often moves more efficiently, stabilizes the trunk more effectively, and transfers force more reliably into strokes. As players enter the U14 range, the body is farther along in neuromuscular organization, and the relationship becomes more specific: strength around individual joints and the control of force at those joints appear to matter more for tennis performance than raw, generalized force production.
Growth also complicates the picture. Between ages 10 and 14, girls experience marked changes in muscle mass and neuromuscular coordination, and this developmental window is especially relevant to junior tennis. The study’s comparison between U12 and U14 players fits that biology. The older group had higher ITN scores and greater muscle strength, but the authors tie those differences to body size and training experience rather than to a single isolated capacity.
The On-Court Test Matched the Developmental Divide
The ITN on-court test offered a practical performance frame because it captures tennis behavior rather than a laboratory abstraction. In that setting, the age-specific correlations tell a clinically useful story for coaches and performance staff: the same player may not need the same physical priority at age 11 as at age 13.
For U12 players, ITN scores were associated primarily with general strength measures. For U14 players, the stronger links emerged with joint-specific upper-limb strength and neuromuscular features. Sense of force did not differ between groups, yet its relationship with ITN changed by age and by joint function. The result suggests that force perception may remain relatively stable across these age bands while its practical relevance to court performance becomes more context dependent as the athlete matures.
One sentence captures the practical divide: younger players appear to benefit most from building broad physical capacity first, while older players rely more on refined upper-limb strength expression.
Why This Matters for Junior Training Design
The findings support a more age-sensitive approach to training. In preadolescent girls, coaches may get more value from programs that strengthen the overall motor base and general force production. As athletes approach adolescence, the emphasis can shift toward tennis-specific strength qualities, especially those tied to upper-limb joints and the neuromuscular precision needed to support stroke production.
That progression fits tennis physiology. Stroke execution depends on force generation and force transmission through the kinetic chain, but the racket arm must still control angle, timing, and stability at the shoulder, elbow, and wrist. If maturation improves general power first, then later allows finer joint-level control, the training emphasis should evolve accordingly. A one-size-fits-all program risks missing the stage-specific needs of the athlete.
The study also reinforces the importance of looking beyond a single strength test. Handgrip strength alone cannot explain the full profile of a junior tennis player, and neither can one explosive movement. The use of several measures provides a more believable picture of how physical development aligns with on-court performance. It also reflects the reality that tennis performance is built from multiple mechanical layers, not one dominant trait.
What the Sample Can and Cannot Support
The study included 33 players, which is enough to reveal an interesting developmental pattern but not enough to turn the findings into a universal rule for all junior tennis populations. The sample was limited to female U12 and U14 players, so the results should be read as age- and sex-specific observations within this group, not as a blanket model for all youth tennis.
Even so, the internal logic is strong. The older players were stronger and scored better on the ITN test, and the strength-performance links changed with age in a way that matches known maturation patterns. The absence of a difference in sense of force between groups also offers a useful caution: not every neuromuscular trait changes at the same pace, and not every performance marker is driven by the same mechanism at every developmental stage.
The report does not settle how these relationships evolve across a longer timeline or whether the same patterns would hold in boys, in larger cohorts, or in players exposed to different training systems. What it does provide is a concise developmental map: early junior performance depends more on broad physical readiness, while later junior performance depends more on joint-specific upper-limb strength and neuromuscular detail.
Tennis Development Is Not Just About More Strength
For youth tennis, the lesson is not simply to make players stronger. It is to make them stronger in the right way, at the right stage of development, and with the correct emphasis on the muscles and joints that shape stroke quality.
The study published in PLoS One adds a measurable framework to that idea by linking ITN performance with upper-limb strength profiles in U12 and U14 girls. The data point toward progression, not replacement: general strength matters early, then joint-specific force control becomes increasingly relevant as maturation advances and technical demands intensify. Coaches who ignore that sequence may train the athlete as if all developmental stages were the same. They are not.