Low Back Pain, Physical Activity, and Muscle-Strengthening Activity Among Saudi Adults: A Cross-Sectional Study

Background/Objectives: Physical activity (PA) and muscle-strengthening activity (MSA) are recommended for health, but their association with low back pain (LBP) is inconsistent and has rarely been examined against guideline thresholds in Saudi adults. This study examined whether meeting aerobic PA thresholds and the MSA frequency threshold was associated with chronic LBP (≥3 months). Methods: In this cross-sectional online survey (September 2025 to April 2026), 449 Saudi adults were analyzed. Exposures were meeting the thresholds for combined moderate-to-vigorous PA (≥150 moderate-equivalent minutes/week, walking not counted), moderate-intensity PA (≥150 min/week), vigorous-intensity PA (≥75 min/week), and MSA frequency (≥2 days/week; also modeled as 0, 1, and ≥2 days/week). Logistic regression adjusted for age, sex, and body mass index estimated adjusted odds ratios (aORs). Results: Chronic LBP was reported by 239 participants (53.2%). No statistically significant association was detected for combined PA (aOR = 0.904; 95% CI, 0.599–1.364), moderate-intensity PA (aOR = 0.813; 95% CI, 0.532–1.244), or vigorous-intensity PA (aOR = 0.935; 95% CI, 0.618–1.416). Meeting the MSA frequency threshold was associated with lower odds of LBP (aOR = 0.606; 95% CI, 0.385–0.954; p = 0.031). In the three-level model, 1 day/week did not differ significantly from no MSA (aOR = 0.949; 95% CI, 0.515–1.748) or from ≥2 days/week. Conclusions: There was no clear evidence of an association between aerobic PA thresholds and chronic LBP, although power may have been limited. Meeting the MSA frequency threshold was associated with lower odds of LBP, but the estimate is statistically borderline and the data do not show a frequency threshold. Given the cross-sectional design and self-selected sample, this finding is preliminary and needs longitudinal confirmation.