Hello, everybody. My name is Mortada Najim, and I'm a second year osteopathic medical student at the University of New England, and today I'm presenting to you my project on deep lumbar muscle activation during core stabilization exercises in healthy subjects. Low back pain is a very common condition that affects a large percentage of the population. It's often due to atrophy or damage to the multifidus, which is a deep muscle that sinks along our vertebral column. The multifidus is composed of superficial fibers that span up to five segments, and those are thought to function as spinal extensors, as well as deep fibers that span up to two segments, and those function as intervertebral stabilizers. And it's the deep fibers that are most prone to undergoing atrophy and fatty infiltration in individuals with low back pain. Rehabilitative exercises are commonly prescribed to re-strengthen and activate the multifidus in individuals with low back pain. However, there's a lack of studies that investigate the independent activation of these fiber types in any individual. Therefore, the purpose of this study was to determine which exercises might preferentially activate the superficial and deep multifidus, as well as to determine whether adding load can alter the activation patterns of these fibers. Figure 1 on the bottom here depicts the superficial fibers of the multifidus in panel A and the deep fibers in panel B. For our methods, we used electromyography to measure muscle activity. Indwelling electrodes were inserted into the superficial and deep fibers at the level of L4, and that was done using ultrasound guidance, and the needle insertion is depicted in this yellow box here in this representative ultrasound image. The activity of the lumbar erector spinae was also measured, and that was done using surface electrodes at the level of L1 and L2. Once those were in place, participants performed a maximum voluntary isometric contraction, and that involved performing two sets of a six-second hold of prone trunk extension, and this served as our baseline for maximum muscle activation. Participants then performed a treadmill warm-up, and then they performed three isometric exercises. The reverse hyperextension, which is shown in figures 3 and 4, involved the participants stabilizing their trunk and swinging their legs up and back, and holding that position for five seconds, and repeating that for a total of five reps. The body weight trunk extension is shown in figures 5 and 6, and that involved stabilizing the lower body and raising the trunk and holding that position, and for the weighted trunk extension, that was identically the same as figures 5 and 6, except participants strapped a load to their chest, and because our lower body weighs more than our trunk, the amount of load added was adjusted to match the weight of the lower body. Following each of these exercises, participants performed or filled out a rate of perceived exertion, with 1 being minimal exertion and 10 being maximal exertion. Table 1 down here shows the demographics of the study. There were 17 subjects that were included in the study, 11 males and 6 females, who were in their mid-20s, and their weights and heights are listed here as well. Figure 7 shows the muscle activity calculations. Panel A shows the activity of the superficial and deep multifidus. The deep multifidus was most activated by the weighted trunk extension, as compared to the body weight trunk extension, and there were no significant changes for the activation of the superficial multifidus for any of the exercises tested. Panel B shows the activation of the lumbar erector spinae, and those were most activated by the weighted trunk extension. And in panel C, the rates of perceived exertion were highest for the weighted trunk extension, and when compared to the body weight trunk extension, they were nearly twice as high. What these results show is that when performing a trunk extension exercise, which primarily activates extensor muscle groups, seem to have also engaged spinal stabilizers when a challenging load was added and holding that position, and that was an interesting and novel finding. There were no significant changes for the superficial multifidus amongst the tested exercises, and that may indicate that those fibers may reach a saturation point, after which the lumbar erector spinae are recruited to accommodate higher loads. And all these results suggest that it may be necessary to apply a challenging external load to activate and subsequently strengthen deeper trunk musculature. Our references are listed down here, and that's my presentation for you. Thank you so much for listening.

lumbar muscle activation

core stabilization exercises

multifidus muscle

electromyography

low back pain rehabilitation