The below paper adds to the evidence that it’s possible to increase the length of certain bones. If the mechanism by which the bones increase in length is not related to the growth plate then it is possible to increase the length of bones post puberty. Tennis involves vibration, inversion/eversion of the bone against gravity, and torsion all of which I am currently testing and have gotten slow but steady results from in length. This is not a great paper but it adds to the evidence that loading in the right manner can increase bone length. It is cited in Susan Pfeiffers paper who showed that it is possible to increase arm bone length post skeletal maturity.

Unilateral Activity and Bone and Muscle Development in the Forearm

“Tennis players exercise one arm almost exclusively and mere inspection shows that they develop one arm more than the other. A comparison was made of the arms of tennis players to evaluate alterations in muscular development and bony structure associated with extensive unilateral activity. In order to assess whether differences between arms of tennis players were larger than for normal young males (non-tennis players), a group of soldiers was also studied.”

“seven nationally ranked tennis players from the Minnesota-Wisconsin-Iowa area and 11 soldiers from Fort Lee, Virginia, were used as test subjects”

“All of the tennis players had played tennis regularly winter and summer for at least the last seven years. None of the soldiers had engaged in any type of extensive unilateral activity.”
“Hand area, third-finger length, wrist width and the forearm circumference measurements differed between the arms of the tennis players but not between the arms of the soldiers.”

“Ulna length proved to be significantly different in both groups, but a slightly more significant difference was noted between arms of tennis players than soldiers. Radius length differed only in tennis players”

You can see that the tennis players had greater length asymmetry than the soldiers. The third finger length asymmetry was pretty much the same which is interesting.

“Contralateral arm movement is necessary to elevate the ball for the service as well as to steady the racket prior to hitting the ball during the volley and when hitting ground strokes.”<-So rapid inversion/eversion of the arm. Torsional loading to grip the racket. And vibration when the ball hits the racket.

“Bony lengths were increased in the dominant forearm of tennis players, indicating an alteration in the osseous “growth apparatus””

“Hand area, hand width, third-finger length, wrist width, and forearm circumference (relaxed and contracted) differed significantly between the dominant and other arm of tennis players, but only hand width, wrist width and forearm circumference (contracted) differed between arms of soldiers.
Radius and ulna length and distal ulna width were different between the arms of tennis players but only ulna length differed between arms of soldiers.”

“small changes in radius and ulna length could be associated with participation in this vigorous unilateral activity.”

It should be noted that soldiers also engage in unilateral activities with their dominant arm. So it is likely that the types of loads that occur in tennis are the kinds of loads that induce growth in length and we should attempt to apply those loads to the legs.