Rest insertion combined with high-frequency loading enhances osteogenesis

• Published in: Journal of applied physiology (1985) 2004-05, Vol.96 (5), p.1788-1793
• Main Authors: LaMothe, Jeremy M, Zernicke, Ronald F
• Format: Article
• Language: English
• Subjects: Adaptation, Physiological; Animals; Biological and medical sciences; Bones; Calcification, Physiologic; Exercise; Female; Fundamental and applied biological sciences. Psychology; Mice; Mice, Inbred C57BL; Osteogenesis - physiology; Periosteum - physiology; Rest - physiology; Skeletal system; Tibia - metabolism; Tibia - physiology; Time Factors; Weight-Bearing - physiology
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.01145.2003

McCaig Centre for Joint Injury and Arthritis Research, Faculties of 1 Kinesiology, 2 Medicine, and 3 Engineering, University of Calgary, Calgary, Alberta, Canada T2N 1N4 Submitted 22 October 2003 ; accepted in final form 2 January 2004 Mechanical loading can significantly affect skeletal adaptation. High-frequency loading can be a potent osteogenic stimulus. Additionally, insertion of rest periods between consecutive loading bouts can be a potent osteogenic stimulus. Thus we investigated whether the insertion of rest-periods between short-term high-frequency loading bouts would augment adaptation in the mature murine skeleton. Right tibiae of skeletally mature (16 wk) female C57BL/6 mice were loaded in cantilever bending at peak of 800 µ , 30 Hz, 5 days/wk for 3 wk. Left tibiae were the contralateral control condition. Mice were randomly assigned into one of two groups: continuous high-frequency (CT) stimulation for 100 s ( n = 9), or 1-s pulses of high-frequency stimuli followed by 10 s of rest (RI) for 100 s ( n = 9). Calcein labels were administered on days 1 and 21 ; label incorporation was used to histomorphometrically assess periosteal and endosteal indexes of adaptation. Periosteal surface referent bone formation rate (pBFR/BS) was significantly enhanced in CT (>88%) and RI (>126%) loaded tibiae, relative to control tibiae. Furthermore, RI tibiae had significantly greater pBFR/BS, relative to CT tibiae (>72%). The endosteal surface was not as sensitive to mechanical loading as the periosteal surface. Thus short-term high-frequency loading significantly elevated pBFR/BS, relative to control tibiae. Furthermore, despite the 10-fold reduction in cycle number, the insertion of rest periods between bouts of high-frequency stimuli significantly augmented pBFR/BS, relative to tibiae loaded continually. Optimization of osteogenesis in response to mechanical loading may underpin the development of nonpharmacological regiments designed to increase bone strength in individuals with compromised bone structures. mouse; bone adaptation; biomechanics Address for reprint requests and other correspondence: R. F. Zernicke, Faculty of Kinesiology, 2500 University Dr., NW, Calgary, Alberta, Canada T2N 1N4 (E-mail: zernicke{at}ucalgary.ca ).