Is bone's response to mechanical signals dominated by gravitational loading?

Area of Science:

• Bone biology and biomechanics
• Skeletal adaptation to mechanical stimuli

Background:

• Bone is subjected to gravitational and muscle loading during physical activity.
• The relative contribution of each loading type to bone adaptation is debated.
• Current paradigms often overemphasize muscle loading's role in bone morphology.

Purpose of the Study:

• To critically evaluate the prevailing paradigm that muscle loading is the primary determinant of bone morphology.
• To explore the potential role of gravitational loading and other mechanical signals in bone adaptation.
• To propose a more comprehensive model for bone's response to mechanical stimuli.

Main Methods:

• Literature review and critical analysis of existing research on bone loading and adaptation.
• Examination of inconsistencies in current muscle-loading-centric paradigms.
• Consideration of gravitational loading and high-frequency, low-magnitude signals.

Main Results:

• Little evidence supports large-magnitude muscle contractions as the dominant bone mechanosensory input.
• Inconsistencies in the literature suggest gravitational loading plays a significant role.
• Bone's response is activity-, location-, and weight-bearing status-dependent.

Conclusions:

• The prevailing paradigm may oversimplify bone's response to mechanical loading.
• Gravitational loading warrants greater consideration in determining bone mass and morphology.
• A comprehensive model must integrate gravitational, muscle, and subtle high-frequency loading signals for a complete understanding of bone adaptation.