Read Nicki Doane's response:
Lengthening the gluteal muscles and hamstrings would be highly beneficial for sacroiliac injuries. When it comes to muscle strength, I am a firm believer in the saying, "There is strength in length." When a muscle is long and lean, it has more ability to contract than when it is overdeveloped and short. When people have stiff and strong gluteals and hamstrings, the tendency to "recruit" flexibility is high—and that flexibility comes from the closest available joint, which is the sacroiliac joint. We tend to rely on the areas of our bodies that are already flexible, and we don't take the time to open the areas that need it. For example, in Virasana (Hero Pose), many people can sit between their feet with their bottom on the floor because of the flexibility in the knee joint. Well, that pose should not depend on knee flexibility but on hip flexibility and long quadriceps. The danger is in overstretching the knee joint and never opening the hips or thigh muscles. This is considered "recruiting." It is not a sustainable way of practicing and can result in injuries.
In terms of SI problems, people tend to overstretch that area instead of achieving the pose through long hamstrings and quadriceps. To protect the SI, care must be taken to lengthen the gluteals, hamstrings, and quadriceps.
When teaching a vinyasa class, it would be wise to begin to incorporate standing asanas such as Trikonasana (Triangle Pose), Parsvakonasana (Side Angle Pose), and Parsvottanasana (Intense Side Stretch Pose) into the sequence often, to lengthen the hamstrings and glutes. Then either do more repetitions of those poses or try holding them longer.
Anyone who's ever been in one of my classes knows that I think lunges and backbends are crucial poses as well. These poses help lengthen the psoas muscle, which runs along the front of the body. A stiff psoas is sometimes the culprit in back pain and sacroiliac problems.
I also ask you to consider telling those students with sacroiliac problems that a vinyasa-style class may not be the most appropriate for them. Vinyasa classes tend to contain a lot of forward bends, which can exacerbate an SI problem. Supta Padangusthasana (Reclining Big Toe Pose) is a much more appropriate pose, and the injured side should be held twice as long as the other side. Asymmetrical poses such as Trikonasana and Parsvakonasana are also recommended; they stretch the hamstrings without overstretching the SI.
Nicki Doane had a wanderlust that led her to India in 1991 to study yoga. She went to Mysore to meet Sri K Pattabhi Jois and immediately realized she had found her teacher. Nicki started teaching in 1992. She cites Pattabhi Jois, along with Eddie Modestini, Gabriella Giubilaro, and Tim Miller among her most influential teachers. She is an authorized teacher of Ashtanga Yoga. Although rooted in Ashtanga, Nicki's teaching goes beyond the traditional. Her classes combine asana, Pranayama, philosophy, and poetry. The emphasis is on awareness: creating integrity within each pose that can be carried beyond the mat into daily life. Nicki lives in Sebastopol, California with her husband, Eddie Modestini. Together, Eddie and Nicki co-direct Maya Yoga Studios in both California and Maui, Hawaii.