Yоu аre evаluаting a 14 year-оld sоccer player with significant low back pain related to a grade 2 spondylolisthesis. Due to hamstring tightness, his knee extension (from a starting position of hip and knee flexed to 90 degrees) is 60 degrees short of full extension. The most appropriate treatment for this specific patient in the early phase of rehabilitation would include: