Intramuscular pressure in the Erector Spinae and intra-abdominal pressure related to posture and load

Study Design. Intramuscular pressures in both Erectors Spinae and intra-abdominal pressures were measured during different holding tasks. Objectives. To investigate the potential for using intramuscular pressure measurements in both Erectors Spinae to better quantitate the role of muscles during different lifting tasks in vivo. Summary of Background Data. Intramuscular pressure and intra-abdominal pressure were measured previously under isometric and dynamic conditions. However, no previous study systematically has addressed the relation between intramuscular and intra-abdominal pressures and different loads, tasks, and postures. Methods. Intramuscular and intra-abdominal were measured simultaneously with microtip pressure transducers in 10 healthy volunteers performing 24 different static holding tasks. Tasks included different weights (10 kg and 20 kg), postures (squat or back lift), and position of the weight. Results. Intramuscular pressures were dependent on posture. Kyphotic back posture produced intramuscular pressures of 120-130 mm Hg, compared with the 10-25 mm Hg produced when volunteers were in the erect position (P < 0.001). Holding a 10-kg weight at the thighs close to the body produced significantly (P < 0.001) lower intramuscular pressures (25-32 mm Hg) than that produced by holding it 25 cm in front of the body (47-56 mm Hg). In all tasks, intramuscular pressures were significantly higher with the 20-kg weight than with the 10-kg weight (P < 0.001). Highest values (> 300 mm Hg) were measured when the 20-kg weight was held in the kyphotic posture above the floor and 25 cm away from the body. Conclusions. Intramuscular pressure measurements in the erector spinae seem to be a valuable tool fro quantitating the role of back muscles during different lifting tasks.