If you don't tighten your abdomen to protect the lumbar spine when squatting and lifting your legs, it may make the erector spinae of the lumbar spine excessively tense, make the muscles stiff and compress the lumbar nerves.

Just find someone to massage erector spinae on the waist, and massage the strip muscles on both sides of the spine with your thumb.

In the future, you can use a weightlifting belt to protect the lumbar spine, which is equivalent to tightening the abdominal muscles.