Being Taller by Increasing Bone Mass

CH Turner is one of the scientists involved in Lateral Synovial Joint Loading.  In this paper, he hypothesizes that bone does not grow by impact but rather by shear strain such as at induced by LSJL.  This means that traditional height increase routines like ankle weights and jumping may not increase height by increasing size in non-long bones such as the vertebrae.  Creating gap microfractures is still effective as that involves a gradual lengthening of bone like limb lengthening and does not involve inducing an anabolic growth in bone.

Exercises for improving bone strength.

"Bone tissue responds to dynamic rather than static loading.  As static loads (even those that produce fairly large stresses or strains)do not initiate osteogenesis, stress or strain in the tissue cannot by itself be the primary stimulus for cellular response. Instead there must be something special about dynamic loading—for instance, dynamic loading creates fluid movement in bone’s lacunar-canalicular network, which in turn generates shear stresses on the plasma membranes of resident osteocytes, bone lining cells, and osteoblasts[stem cells and chondrocytes as well]. Bone cells are highly sensitive to fluid shear stresses, and respond by initiating a cascade of cellular events. High impact exercises that produce large rates of deformation of the bone matrix best drive fluid through the lacunar-canalicular network system[like LSJL]. Thus increasing loading rate is one step toward more effective application of mechanical forces to promote osteogenesis."

So jumping and ankle weights still might work as they drive fluid flow through the bone.  LSJL is the best however as it is the fluid flow that is the key to bone growth.  This fluid also drives stem cells into the hyaline cartilage growth plate line which can result in long bone growth. 

"Bone cells become desensitised to prolonged mechanical stimulation. Rats trained to jump many times a day increased the mass of their femora and tibiae, but the anabolic response became saturated after about 40 loading cycles; animals trained to jump 100 times a day did not improve their bone mass significantly over those trained to jump 40 times a day. Bone loses over 95% of its mechanosensitivity after only 20 loading cycles. Presumably bone cell mechanosensitivity will return after a period of no loading.
Rats were subjected to mediolateral bending of the tibia. All six groups of rats in the experiment received 360 cycles a day of the same loading stimulus, delivered as 90 continuous cycles, four times a day. Some of the rats were allotted eight hours between each of the four daily bouts, others were given 4, 2, 1, 0.5, or 0 hours of rest between each of the four daily bouts. Load induced bone formation was improved by the rest periods, and as the rest (no loading) periods were lengthened, bone formation was enhanced further. With a rest period of four hours between loading bouts, loading induced bone formation was almost doubled. After 24 hours of rest, 98% of bone mechanosensitivity returns.  Osteogenic response to exercise can be enhanced by regimens that incorporate periods of rest between short vigorous skeletal loading sessions."

One can assume that the mechanosensitivity can be similar for stem cells and chondrocytes.  Therefore, the best way to perform LSJL is once every 24 hours.  Of course, this does not incorporate duration of the loading regime but our goal is to induce fluid shear stress.  If by loading longer we can push down the dumbell or the table clamp and generate more shear stress by a larger load then we should load until we can no longer generate a larger shear strain.  I found that takes about 30 seconds.

"Engaging in exercise during skeletal growth is unequivocally more osteogenic than exercise during skeletal maturity. During growth, the bone surfaces are covered with a greater proportion of active osteoblasts[and active chondrocytes] than after skeletal maturity. Periosteal expansion occurs predominantly during growth, and consequently the childhood and adolescent years provide a window of opportunity to significantly enhance periosteal growth with exercise[periosteal expansion can occur after growth too]. Periosteal growth determines the periosteal breadth of a bone, which is important in skeletal health for two main reasons. Firstly, addition of bone to the periosteal surface improves the bending and torsional strength of the bone most effectively. Secondly, resorption of bone from the periosteal surface is extremely rare in the adult[any height you gain from increasing periosteal width will stay]; usually it is the trabecular, endocortical, and Haversian bone surfaces that undergo remodelling. These observations indicate that the periosteal breadth of a bone will remain intact until senescence. Consequently, vigorous exercise during growth and young adulthood may well reduce fracture risk in later decades."

Developing individuals have more naturally active chondrocytes and osteoblasts.  More active cells means a greater response to mechanical stimuli.  Mechanical stimuli will naturally increase the number of active chondrocytes and osteoblasts so the loading effect of LSJL should become greater and greater as more osteoblasts and chondrocytes are activated.  It's unfortunate that CH Turner has written no such paper directly for chondrocytes so we have to infer what would happen to them.