The pirformis is a small triangular muscle that passes over the sciatic nerve.
Why It's Important: If tight it can cause radicular or shooting symptoms into the legs. This muscle can also contribute to low back pain.
Psoas and iliacus are you deep hip flexors.
Why It's Important: Both biking and running are movements that require repetitive hip flexion. Biking+Running = ANGRY psoas. If this muscle is too tight, it can actually can alter you low back posture to look like the photo on the right:
The ITB is fibrous band that attaches below the outside of your knee.
Why It's Important: Any serious runner or triathlete knows how nagging an ITB issue can be. With running and biking we tend to move in planes and move our knee at angles that causes more friction of the band along the femoral condyles. Friction of ITB=sharp lateral knee pain.
While A.R.T. is effective for injury prevention and treatment, one must look at the macro perspective. What caused the tightness, pain, problem in the first place? I would consult your friendly local physical therapist to help you permanently fix those flexibility/strength issues.
What is your A.R.T. "money move" that gets you through your triathlon season?