BACKGROUND CONTEXTChronic low back pain (CLBP) is a significant global health burden, primarily affecting the middle-aged and older; However, there is a lack of clear, evidence-based guidelines for leisure-time physical activity aimed at preventing CLBP. PURPOSEThis study sought to delineate the association between aerobic physical activity (APA) and muscle strengthening activities (MSA) and the prevalence of CLBP. STUDY DESIGNThis was a population-based study conducted across the United States. PATIENT SAMPLEThis nationwide study utilizes deidentified data from 22 consecutive rounds of the National Health Interview Survey (NHIS) from 1997 to 2018. OUTCOME MEASURESThe primary outcome was self-reported CLBP. METHODSWe analyzed the prevalence of CLBP in a representative sample of 324,793 middle-aged and older people. Among 263,871 individuals, we used multiple logistic regression to investigate individual and joint association between the amount of APA and MSA with CLBP. RESULTSIn total, 263,871 participants (mean age, 59.0 years; SD, 9.7) were included in the final analysis. From 1997 to 2018, the prevalence of CLBP was approximately 32%, with an annual increase. Engaging in APA for 75 to 150 minutes weekly was associated with a modest reduction in CLBP risk (OR [95% CI] = 0.97 [0.97–0.98]). Similar benefits were seen with 150 to 225, 225 to 300, and >300 minutes. Engaging in MSA 2 to 3 times and 4 to 5 times weekly also reduced CLBP risk (0.98 [0.98–0.99] and 0.98 [0.97–0.99], respectively). Optimal reductions of CLBP risk may be associated with balanced levels of APA and MSA, with recommended amounts being 225 to 300 min/w of APA and 4 to 5 times/w of MSA (0.92 [0.89–0.95]). CONCLUSIONSThe study found engaging in over 75 minutes of APA and 2 to 5 weekly MSA sessions is associated with a reduced risk of CLBP. Furthermore, a balanced combination of APA and MSA may correspond to the greatest reduction in CLBP risk.