The capacity of growing bone, muscle, ligament, connective tissue, and all other soft tissues to adapt to use history is well known, while the physiologic mechanisms that operate to effect the adaptations remain under investigation. Scientists are using new imaging technologies to observe tissue microstructure and to appreciate changes under various conditions or use. [1,2]
Movement-Related Bone and Joint Modeling
The mechanisms of change in developing bone and joint design are related to use history primarily during the first 7 years of life. The bones of the newborn infant are made mostly of cartilage that is filled with water. These very young bones change shape when they endure external forces imposed by gravity and muscle actions such as weight bearing, pull by the muscles, and torque (rotation) forces. Bones also adapt in thickness to the nature of typical loading forces. 
Bone and joint modeling normally occur in the context of full-term gestation followed by a typical course of acquisition of postural control in all positions and upon which movement skills emerge.
Daily life spent in compensatory postures and movement strategies fosters a progression of deformities and muscle imbalances. Growing bones and joints endure altered loads and adapt to them in the presence of altered weight loading, balancing, and movement skills. Common examples: hip subluxation; femoral and tibio-fibular torsion (twist) excesses or deficits; and knee joint malalignments – varum (bowed) or valgum (“knocked”).
Changes to the physical, biological, biochemical, and functional characteristics of muscles and associated connective-tissues and nerves are also seen. Muscle anatomy and physiology adapt to history-of-use. For example, children with compromised trunk control commonly recruit limb muscles in tonic (holding) patterns to maintain balance in functioning positions. Those muscles and accompanying connective tissues, vessels, nerves, and skin all shorten over time, and the child can develop contractures as a result.
TheraTogs’ Role in Physiologic Adaptation
Early Intervention: Prevention via early intervention is the first line of defense against pathologic adaptations in bone and soft tissues. We advocate using TheraTogs Wunzi systems for young infants without seizures or bradycardia who show evidence of a delay or difficulty in achieving the early, fundamental, symmetrical postures in supine and prone lying that are typical by age 4 months.
The judicious use of TheraTogs Wunzi garments and straps can:
- Deliver abundant somatosensory information
- Assist in aligning the spine, rib cage, and pelvis
- Assist in directing body weight loads to age-appropriate segments of the trunk and pelvis
- Assist in positioning the limbs for easy use in play.
caption: Ideal symmetry and limb position at age 4 months.
caption: Amelia at 8 months without and with the Wunzi and strappnig for symmetrical trunk and antigravity flexion assist.
Early intervention to promote sensorimotor development follows the course of postural and movement skill acquisition that is well illustrated and detailed by Lois Bly, PhD, PT. 
A key element of bone and joint development is the ability to manage body weight effectively in a variety of play postures.
Childhood Intervention: Use history is created by massed practice and thousands of repetitions of routine movements on a daily basis. Bone and joint changes are adaptations to that use history. Because the pliability of growing bones and joints diminishes during childhood, so does the opportunity to influence bone modeling. The potential for TheraTogs to affect growing bones by improving functioning joint alignment throughout the day is related to the maturity of the bones – the younger the child, the more responsive the bones are to modeling forces – and to the nature of daily movement activity.
Clinicians use specific clinical and radiologic assessments to document use-history-related bone shape and changes that reflect the effects of interventions such as TheraTogs – especially when combined with optimized foot and ankle support and postural retraining.
Contracture Reduction: Siracusa et al (2004) obtained findings regarding hamstring and hip adductor muscle extensibility – via joint range of motion assessments – before and after using customized Theratogs systems for 8 weeks – the average minimum study period – with 3 children with diplegic CP. 
No other aspect of their therapy program or use of orthoses changed during the wear period. All 3 children wore strapping that promoted lateral hip rotation and abdominal stability, with added straps targeted to individual issues.
- TH, an eight year old male who walks with posterior walker and who underwent a selective posterior dorsal rhizotomy at age 3 years, showed gains in hamstring muscle length of 11o on the left (L) and 25o on the right (R).
- AZ, a 3 year old female, who walks independently showed gains in hip abduction of 23° (L) and 15° (R); and in hamstring length of 19°(L) and 24° (R).
These findings suggest that by improving somatosensory input and functioning joint alignment, the necessity to recruit the shortened muscles that were used tonically for balance diminished, and they responded by elongating toward a more normal length.
- Bly L. 2011. Components of Typical and Atypical Motor Development. Laguna Beach, CA; Neurodevelopmental Treatment Association; www.ndta.org
- Legs & Feet: A Review of Musculoskeletal Assessments – a DVD of Beverly Cusick demonstrating 30 musculoskeletal assessment procedures- is available at www.gaitways.com.
- Siracusa C, Taynor M, Geletka B, Overby A. 2005. Effectiveness of a biomechanical intervention in children with spastic diplegia. Pediatr Physl Ther. 17(1): 83.