Most of the clinical trials behind yoga's back pain evidence ran their programs over 12 weeks, which is a reasonable real-world expectation for when to expect a meaningful, measurable difference.
What the trial timelines show
The Saper et al. 2017 trial compared 12 weeks of yoga classes against physical therapy and education, finding meaningful improvement in both intervention groups by the end of that window.
Short-term vs. long-term relief
Some people notice a subjective easing of tension or improved mobility within the first few sessions, while measurable, sustained functional improvement in research typically reflects weeks of consistent practice, not a single session.
Consistency matters more than intensity
Short, regular sessions (the kind a 5–12 minute daily program is built around) align better with how the underlying research was actually structured than occasional long, intense classes.
Is it normal to not feel different after the first week?
Yes — most of the research showing meaningful benefit reflects several weeks of consistent practice, so a lack of dramatic change in the first few days isn't a sign the approach isn't working.