Normally, I wouldn’t draw attention to this first paper but it draws an interesting thought:  “That long term sustained loading is better for longitudinal bone growth, whereas short term intense loading is better for bone quality.”  This could be due to hydrostatic pressure being good for stimulating a cartilagenous(and thus a pro growth plate micro-environment) whereas rapid changes in fluid flow as induced by short term dynamic loading(like jumping) are better for changes in bone quality.  So I will be changing the way I will be performing LSJL, rather focusing on clamping as hard as possible I will not be clamping as hard but doing longer more sustained clamps.

Enhancement of bone quality and longitudinal growth due to free-fall motion in growing rats

“[We] investigate the synchronous phenomena between bone quality and longitudinal length in a same subject affected by landing exercise. Physical exercise on the ground induces external loading to human body due to resistance from ground which can activate bone generation or remodeling. Especially, when the impact stimulation is applied to bone, it may improve bone quality and lengthening.
6-week-old male Wistar rats were randomly allocated to one of two conditions: free fall from 40 cm-height (I40; n = 7), and control (IC; n = 7). The impact stimulations were administered to the free fall groups, 10 times/day, and 5 days/week for 8 weeks. Structural parameters and longitudinal length of tibia were measured to quantitatively evaluate the variation in morphological characteristics and bone length with maturing.
The landing impact seems to be commonly effective on the enhancement of bone quality as well as longitudinal growth. However, the extent of enhancement may be more dominant in bone quality than longitudinal growth. On the other hand, the ratio of longitudinal growth seems to be dependent on the duration of stimuli whereas the enhancement of bone quality does not.
This study verified that free-falls exercise can be effective on the enhancement of bone qualities and promotion of vertical growth in long bones. We expect that it might be possible for the moderate impact stimulation to be proposed as an aid for prevention of bone loss and promotion of bone lengthening.”

” Bone cells accommodate to a customary mechanical loading environment, making
them less responsive to routine loading “<-thus possibly needing to cycle on and off a method of bone stimulus.  Although our goal is to target stem cells to form new growth plates and not necessarily bone cells.

“In comparison between two groups, there is no significant [differnece] at 4 week, whereas the values in I40 group exhibited slightly but significantly higher than that in IC at 8 weeks”  So there was a change in limb length but it took 8 weeks to notice a difference.  It would be interesting to see if impact loading could have an impact on animals without functioning growth plates.  If it could increase longitudinal bone growth in some other way.

“the ratio of longitudinal growth seems to be dependent on the duration of stimuli whereas the enhancement of bone quality does not.”<-this is interesting maybe it’s more important to clamp for a long period of time than intensity of clamping.  This could a lot of sense if longitudinal growth is driven by fluid whereas bone mechanical parameters are driven by stimulation of osteocytes and bone cells.  Longitudinal bone growth could be driven by sustained hydrostatic pressure whereas bone quality could be driven by rapid changes in interstitial fluid flow.

Another study found “. observed significantly greater increase in bone length compared to the sedentary rats when they implemented the similar training 100 times/day in 5 days/week
on Fisher 344 rats of 3-month-old and 6-month-old for 8 weeks”

Here’s that other study:

Effects of Jump Training on Bone Hypertrophy in Young and Old Rats

“The effects of jump training on bone hypertrophy were investigated in 3, 6, 12, 20 and 27 month-old female Fischer 344 rats. The rats of all age groups were divided into jump training
(height: 40 cm, 100 times/day, 5 days/wkfor 8wks), run training (speed: 30 m/min, 1 h/day, 5 days/wk for 8wk) or sedentary group. Fat-free dry weights (FFW) of the femur and the tibia were significantly greater in the jump-trained rats than in the runtrained rats, and were significantly greater in the run-trained rats than in the sedentary rats. jump training significantly increased FNV of the femur and the tibia not only in young rats but also in old rats, while run training did not increase FFW significantly in old rats. In young rats, both jump training and run training significantly increased the length of the femur and the tibia and the diameter of the femur. The diameter of the tibia was greater in the jump-trained rats than in the sedentary and the run-trained rats in all age groups. The results of the present study indicate that jump training was a more effective training mode than run training for bone hypertrophy and that the effects were not limited by age. ”

According to the chart, Jump training increased length of the tibia and femur on rats younger than 12 months but actually decreased tibia and femur length on rats older than that.  So the compressive force actually denatured the tibia and femur such that it was shorter.

But in the study they do say ” In the 3 and 6 month-old rats, both jump training
and run training increased the length of the femur and the tibia and the diameter of the femur.”<-which is contrary to what the graph says.