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Scott, R 
ORCID: https://orcid.org/0000-0001-7642-545X,
2024.
The quantification of mechanical loading and its association with bone adaptation.
PhD, Nottingham Trent University.
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Abstract
Weight-bearing exercise, and resultant high-impact loading, is known to cause positive bone adaptations. The optimal magnitude, frequency and duration of load required to produce an osteogenic response, however, remain unclear. Furthermore, there is a lack of applied research investigating if measurements of external load can be associated to bone adaptation. This thesis investigated: how bone responds to load; practitioner perceptions and use of mechanical loading as a method of estimating bone load; the association between mechanical load and bone characteristics in professional athletes, and the dose-response effect of drop jump height on bone adaptation in low active, young adults.
An in vitro model was developed to analyse the effects of intermittent and continuous load on osteoblast activity over 12 days. Bone formation markers alizarin red (ARS), alkaline phosphatase (ALP) and Procollagen I N-Terminal Propeptide (PINP) were assessed. Secondly, support staff (n=71) were questioned to understand how bone is monitored in sport and what methodologies are used. The perceptions were compared to research to investigate if there are similarities between the academic and applied knowledge. Experimentally, external load training characteristics and bone characteristics were assessed in academy footballers (n=15) over 14 weeks. Whole body measurements were determined using dual-energy x-ray absorptiometry (DXA) and global positioning systems (GPS) were used to measure external load. Additionally, external load and bone characteristics of fast bowlers (n=14) and footballers (n=11) were assessed to observe the contralateral effects of mechanical loading. Whole body DXA scans and Peripheral Quantitative Computed Tomography (pQCT) tibial bone characteristics were analysed. External load was measured using inertial measurement units (IMUs). Finally, young people performed 16 weeks of drop jumps from 60cm (n=11), 40cm (n=11), 0cm (n=11) or no jumps (n=11). Bone adaptations (DXA, pQCT) and external load (IMU, force plates, motion capture) were assessed at multiple time points (pre-intervention, week 6, week 12, post-intervention).
An increase in ALP was observed when rest periods were inserted between loading bouts, however, no changes were observed in PINP and ARS between loading conditions in vitro. Mechanical load can be used to promote bone adaptation, however, support staff shared they do not monitor external load as a method of estimating bone load due to a lack of knowledge, indicating there is a disconnect between research and the applied environment. In academy footballers, GPS-derived high metabolic load distance (HMLD), accelerations and decelerations were associated with increases in leg BMC (P=0.008). When measuring site-specific load using IMUs, cumulative load was associated with greater axial and polar tibial strength in professional fast bowlers (P=0.035). Low active, young adults performing 60cm diagonal drop jumps showed an increase in tibial axial strength compared to jumping from 0cm over 16 weeks. Diagonal drop jumps from 40cm, however, produced a greater increase in cortical density than jumping from 60cm. The findings suggest monitoring external load during interventions targeting bone accrual may advance our understanding of mechanical load experienced by individuals. The relationship between external load and bone adaptation may then be used to identify loading thresholds and optimise impact exercise for bone health.
| Item Type: | Thesis |
|---|---|
| Creators: | Scott, R. |
| Contributors: | Name Role NTU ID ORCID |
| Date: | September 2024 |
| Rights: | This work is the intellectual property of the author. You may copy up to 5% of this work for private study, or personal, non-commercial research. Any re-use of the information contained within this document should be fully referenced, quoting the author, title, university, degree level and pagination. Queries or requests for any other use, or if a more substantial copy is required, should be directed to the owner(s) of the Intellectual Property Rights. |
| Divisions: | Schools > School of Science and Technology |
| Record created by: | Melissa Cornwell |
| Date Added: | 14 Apr 2025 14:59 |
| Last Modified: | 14 Apr 2025 14:59 |
| URI: | https://irep.ntu.ac.uk/id/eprint/53404 |
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