Effect of increased relative stiffness of the lumbar spine on hamstring muscle stretching in individuals with a history of low back pain suspected to have a clinical lumbar instability: A randomized crossover design

BackgroundTheoretically, lumbopelvic stabilization techniques during hamstring muscle stretching could increase lumbar stiffness relative to hamstring muscle in individuals with a history of low back pain and suspected clinical lumbar instability. However, evidence to support this theory is limited. This study aimed to 1) determine changes in lumbopelvic, lumbar, and hip motions, and hamstring muscle length after stretching exercises with lumbopelvic stiffening or relaxing techniques, and 2) compare those changes between techniques.MethodsThis study used a randomized crossover design. Thirty-two participants with a history of low back pain and bilateral hamstring muscle tightness were recruited. The order of the first technique was randomly assigned. After a 2-day washout, participants were crossed over to the second technique. Motion data during active forward trunk bending and bilateral hamstring muscle length during passive knee extension were collected pre- and post-intervention.FindingsSignificant increases (P < 0.05) were found in bilateral hamstring muscle length for both techniques. However, stiffening technique demonstrated a significant decrease in lumbar motion (P < 0.05) and increase in hip motion (P < 0.05), while relaxing technique demonstrated trends showing increases in lumbar and hip motions (P = 0.134 and 0.115, respectively). The findings showed significantly greater improvement (P < 0.05) in lumbar and hip motions with stiffening technique.InterpretationThe findings suggest increased relative stiffness of the lumbar spine during hamstring muscle stretching can specifically lengthen bilateral hamstring muscle and decrease excessive lumbar motion. This stiffening technique may prevent excessive movement of the lumbar spine, thereby reducing the risk of recurrent low back pain.