Partitioning a Daily Mechanical Stimulus into Discrete Loading Bouts Improves the Osteogenic Response to Loading
Open Access
- 1 August 2000
- journal article
- research article
- Published by Oxford University Press (OUP) in Journal of Bone and Mineral Research
- Vol. 15 (8), 1596-1602
- https://doi.org/10.1359/jbmr.2000.15.8.1596
Abstract
A single 3‐minute bout of mechanical loading increases bone formation in the rat tibia. We hypothesized that more frequent, shorter loading bouts would elicit a greater osteogenic response than a single 3‐minute bout. The right tibias of 36 adult female Sprague‐Dawley rats were subjected to 360 bending cycles per day of a 54N force delivered in 1, 2, 4, or 6 bouts on each of the 3 loading days. Rats in the 6‐bouts/day group received 60 bending cycles per bout (60 × 6); rats in the 4‐bouts/day group received 90 bending cycles per bout (90 × 4); the 2‐ and 1‐bouts/day groups received 180 and 360 bending cycles per bout, respectively (180 × 2 and 360 × 1). A nonloaded, age‐matched control group (0 × 0) and two sham‐bending groups (60 × 6 and 360 × 1) also were included. Fluorochrome labeling revealed a 10‐fold increase in endocortical lamellar bone formation rate (BFR/bone surface [BS]) in the right tibia versus the left (nonloaded) side in the 60 × 6 bending group. Endocortical BFR/BS in the right tibia of the 4‐, 2‐, and 1‐bout bending groups exhibited 8‐, 4‐, and 4‐fold increases, respectively, over the control side. Relative (right minus left) values for endocortical BFR/BS, mineralizing surface (MS/BS), and mineral apposition rate (MAR) were 65–94% greater in the 90 × 4 and 60 × 6 bending groups compared to the 360 × 1 bending group. Sham‐bending tibias exhibited relative endocortical bone formation values similar to those collected from the control (0 × 0) group. The data show that 360 daily loading cycles applied at intervals of 60 × 6 or 90 × 4 represent a more osteogenic stimulus than 360 cycles applied all at once, and that mechanical loading is more osteogenic when divided into discrete loading bouts. Presumably, bone cells become increasingly “deaf” to the mechanical stimulus as loading cycles persist uninterrupted, and by allowing a rest period between loading bouts, the osteogenic effectiveness of subsequent cycles can be increased.Keywords
This publication has 23 references indexed in Scilit:
- Evaluation of a bone's in vivo 24‐hour loading history for physical exercise compared with background loadingJournal of Orthopaedic Research, 1998
- The response of rat tibiae to incremental bouts of mechanical loading: A quantum concept for bone formationBone, 1994
- Periosteal bone formation stimulated by externally induced bending strainsJournal of Bone and Mineral Research, 1994
- Bone response to alternate-day mechanical loading of the rat tibiaJournal of Bone and Mineral Research, 1994
- Mechanical loading thresholds for lamellar and woven bone formationJournal of Bone and Mineral Research, 1994
- Characterization of in vivo strain in the rat tibia during external application of a four-point bending loadJournal of Biomechanics, 1992
- A noninvasive, in vivo model for studying strain adaptive bone modelingBone, 1991
- Bone histomorphometry: Standardization of nomenclature, symbols, and units: Report of the asbmr histomorphometry nomenclature committeeJournal of Bone and Mineral Research, 1987
- Regulation of bone mass by mechanical strain magnitudeCalcified Tissue International, 1985
- The influence of strain rate on adaptive bone remodellingJournal of Biomechanics, 1982