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Author ORCID Identifier

https://orcid.org/0009-0004-7450-4292

Date Available

4-28-2026

Year of Publication

2026

Document Type

Doctoral Dissertation

Degree Name

Doctor of Philosophy (PhD)

College

Education

Department/School/Program

Kinesiology and Health Promotion

Faculty

Fan Gao

Faculty

Haley Bergstrom

Abstract

Chronic nonspecific low back pain (CNLBP) is the leading cause of years lived with disability worldwide and represents a complex, multifactorial, and heterogeneous condition. It is characterized by substantial interindividual variability in muscle activation patterns, lumbo-pelvic coordination, and movement strategies. Although exercise is widely recommended as a first-line intervention and its clinical benefits are well established, the biomechanical mechanisms underlying functional improvement remain fragmented in the literature and are rarely synthesized quantitatively.

This dissertation conducted a systematic review with meta-analysis to investigate the biomechanical effects of exercise-based interventions in individuals with CNLBP. A total of 39 studies were included and evaluated for methodological quality using the Downs and Black appraisal tool. When appropriate, meta-analyses were performed using random-effects models, accompanied by evaluation of heterogeneity, exploratory subgroup analyses, and meta-regressions.

The results confirmed the beneficial clinical effects of exercise on pain and functional disability. Among the biomechanical outcomes that could be quantitatively synthesized, a consistent effect was observed in trunk muscle endurance, whereas findings of maximum isometric strength of the trunk extensors were inconclusive. Subgroup analyses and metaregressions did not identify moderators that substantially explained the between-study variability, reflecting considerable methodological and conceptual heterogeneity.

Narrative synthesis further expanded these findings by indicating that the most common adaptations associated with exercise involve functional reorganization of movement. These adaptations include changes in motor control, intersegmental coordination, muscle activation patterns, and dynamic stability during functional tasks. The absence of a uniform biomechanical response pattern suggests that exercise does not necessarily promote the "normalization" of a single parameter, but rather facilitates contextdependent adaptations and individualized motor strategies.

Overall, the findings suggest that the benefits of exercise in CNLBP are more strongly associated with functional and neuromuscular adaptations than with isolated structural changes. The substantial heterogeneity observed across studies should be interpreted not only as a methodological limitation, but also as a reflection of the inherent variability in motor strategies within this population. This dissertation contributes to a more integrated understanding of the biomechanical effects of exercise and highlights the need for greater conceptual and methodological standardization in future research.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2026.142

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