Weightlifting can help improve muscle strength, and many people think it can actually help make the muscles around the SI joint stronger, so they can offer more support. This may be true, but you would need to strengthen these muscles before you suffer from an SI joint problem. Once the SI joint is not functioning properly, it’s too late to strengthen the muscles.
The strain from the weight can make the SI joint dysfunction worse and even cause severe problems. It can take several months to recover from an SI joint injury caused or aggravated by heavy weight lifting. The body uses a lot of muscles and ligaments to life weights, including those in the lower back.
Even if you are focused on your arms and legs, you may be using the lower back muscles without realizing it. This can easily aggravate the SI joint and make any existing conditions much worse.