Journal of Sports Science and Medicine
Journal of Sports Science and Medicine
ISSN: 1303 - 2968   
Ios-APP Journal of Sports Science and Medicine
Androit-APP Journal of Sports Science and Medicine
©Journal of Sports Science and Medicine (2018) 17, 188 - 196

Research article
Structural and Biomechanical Adaptations to Free-Fall Landing in Hindlimb Cortical Bone of Growing Female Rats
Hsin-Shih Lin1,2, Ho-Seng Wang2, Hung-Ta Chiu1, Kuang-You B. Cheng1, Ar-Tyan Hsu3, Tsang-Hai Huang1, 
Author Information
1 Institute of Physical Education, Health and Leisure Studies, National Cheng Kung University, Tainan, Taiwan
2 Department of Physical Education, National Taiwan Normal University, Taipei, Taiwan
3 Department of Physical Therapy, National Cheng Kung University, Tainan, Taiwan

Tsang-Hai Huang
‚úČ Institute of Physical Education, Health and Leisure Studies, National Cheng-Kung University, No. 1, University Rd. 701, Tainan, Taiwan
Publish Date
Received: 07-09-2017
Accepted: 10-02-2018
Published (online): 14-05-2018
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The purpose of the study was to investigate the adaptation process of hindlimb cortical bone subjected to free-fall landing training. Female Wistar rats (7 weeks old) were randomly assigned to four landing (L) groups and four age-matched control (C) groups (n = 12 per group): L1, L2, L4 L8, C1, C2, C4 and C8. Animals in the L1, L2, L4 and L8 groups were respectively subjected to 1, 2, 4 and 8 weeks of free-fall-landing training (40 cm height, 30 times/day and 5 days/week) while the C1, C2, C4 and C8 groups served as age-matched control groups. The tibiae of the L8 group were higher in cortical bone mineral content (BMC) than those in the C8 group (p < 0.05). Except for the higher bone mineralization over bone surface ratio (MS/BS, %) shown in the tibiae of the L1 group (p < 0.05), dynamic histomorphometry in the tibial and femoral cortical bone showed no difference between landing groups and their age-matched control groups. In the femora, the L1 group was lower than the C1 group in cortical bone area (Ct.Ar) and cortical thickness (Ct.Th) (p < 0.05); however, the L4 group was higher than the C4 group in Ct.Ar and Ct.Th (p <0 .05). In the tibiae, the moment of inertia about the antero-posterior axis (Iap), Ct.Ar and Ct.Th was significantly higher in the L8 group than in the C8 group (p < 0.05). In biomechanical testing, fracture load (FL) of femora was lower in the L1 group than in the C1 group (p < 0.05). Conversely, yield load (YL), FL and yield load energy (YE) of femora, as well as FL of tibiae were all significantly higher in the L8 group than in the C8 group (p < 0.05). Free-fall landing training may initially compromise bone material. However, over time, the current free-fall landing training induced improvements in biomechanical properties and/or the structure of growing bones.

Key words: Mechanical loading, exercise, bone strength, animal model

           Key Points
  • An 8-week landing training from a height of 40 cm improved cortical bone structure and strength in the hindlimbs of growing Wistar female rats.
  • Tibiae and femora showed different patterns of adaptive responses to the 8-week free-fall landing training.
  • Free-fall landing training may cause a slight and temporary compromise in bone material properties, but eventually induces an improvement in biomechanical properties and structures of growing bones.
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