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Exercise of young thoroughbred horses increases impact strength of the third metacarpal bone
Author(s) -
Reilly G. C.,
Currey J. D.,
Goodship A. E.
Publication year - 1997
Publication title -
journal of orthopaedic research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.041
H-Index - 155
eISSN - 1554-527X
pISSN - 0736-0266
DOI - 10.1002/jor.1100150611
Subject(s) - diaphysis , cortical bone , medicine , materials science , treadmill , orthodontics , dentistry , anatomy , surgery , physical therapy , femur
Exercise can have a profound effect on bone mass but little is known of its effect on bone's material properties. In this experiment, our hypothesis was that a large difference in the training regimen of young thoroughbreds would produce a measurable difference in the mechanical properties of their bone material. When they were about 19 months old, eight thoroughbred racehorses were given one of two exercise regimens that lasted for 19 weeks: four horses (controls) were walked for 40 minutes a day but had no other exercise, and the remaining four (exercised) were additionally trotted for 20 minutes a day and given progressively intensive exercise on a treadmill. Mechanical testing to failure was performed on longitudinal beam specimens of the mid‐diaphysis of the metacarpal. There was no difference in Young's modulus or bending strength between the two groups, although these properties varied somewhat depending on the position within the cortex from which the specimens had come. The specimensfrm the exercised horses had a slightly higher toughness, as measured by work (area under the load‐deformation curve). They had a considerably higher impact strength. The impact strength of specimens from, the outer coitex was also higher than that of those from the inner cortex in both groups. Impact strength correlated positively with the amount of micro‐cracking produced during testing. Microcracking is related to structural and microstructural features in the bone. Increased loading caused the bone to respond in a way lhat enhanced its ability to microcrack and hence its toughness.