Upright bipedal exercise training improves intervertebral disc health: a systematic review and meta-analysis

INTRODUCTION & AIMS The structure and function of human tissue, such as bone, muscle and tendon, can be improved with targeted exercise training. However, the effects of exercise training on intervertebral disc tissue has received comparably less attention. With a scope to identify types of exercise training that improve intervertebral disc health, this study examined the impact of historical exercise, sport and/or physical activity on quantitative intervertebral disc outcomes. METHODS The protocol was prospectively registered with PROSPERO (CRD42022366391). Five databases (inception to 30th September 2022), 17 trial registries and reference lists and forwards/backwards citations were searched. Inclusion criteria followed the Participants (human), Exposure (exercise, sport or physical activity for greater than one week), Comparators (non-exercise, sport or physical activity control group), Outcomes (magnetic resonance imaging measures of lumbar intervertebral disc health on a continuous scale [e.g. T2, signal intensity, intervertebral disc height]) and Study design (any) framework. Pairwise random-effects restricted maximum likelihood meta-analysis estimated standardised mean difference (Hedges g). RESULTS From the search yield of 2,150 records, 12 reports representing 10 studies (participants: 874) were deemed eligible. When compared to any comparator, upright bipedal exposures (g [95%CI]: 0.31 [0.06, 0.55]; P=0.014; studies: 6; participants: 346; I2: 87%), were associated with greater intervertebral disc health. However, no physical loading exposure (g [95%CI]: 0.29 [-0.23, 0.82]; P=0.275; studies: 10; participants: 874), non-upright/non-contact exposures (g [95%CI]: 0.70 [1.25, 2.64]; P=0.336; studies: 5; participants: 260), extreme trunk range of motion exposures (g [95%CI]: -0.28 [-1.60, 1.04]; P=0.456; studies: 3; participants: 230) and aerobic-based exposures (g [95%CI]: 0.48 [0.08, 1.04]; P=0.094) were associated. Sensitivity analyses supported the robustness of primary and secondary effect estimates. CONCLUSION Greater intervertebral disc health associated with a prior history of upright bipedal physical loading indicates prospective interventions examining upright bipedal exercise effects on intervertebral disc health are warranted.