NEAR-INFRARED MONITORING OF THE LUMBAR ERECTOR SPINAE MUSCLE IN HEALTHY MEN AND WOMEN DURING STATIC AND DYNAMIC ENDURANCE WORK

Understanding muscle hemodynamics using near-infrared spectroscopy is increasingly evident in the recent spinal disorders-related literature. However, none of these human studies addressed the issue of physiological limits for the lumbar muscle within the same participants during various exercise modes. The purpose of this study is to evaluate physiological limits for the lumbar muscle during dynamic and static endurance tests. On three separate days, 22 healthy men and women performed three endurance protocols (static prone trunk extension, arm cranking, and pushing–pulling) until volitional exhaustion. For each protocol, minimum and maximum oxygenation and blood volume responses from the right lumbar erector spinae were obtained using a continuous dual wavelength near-infrared spectroscopy (Micro-Runman, NIM Inc., PA, USA). Statistical analysis showed that greatest reduction in oxygenation (minimum) were obtained during dynamic exercises: pushing–pulling (2.1 times) and arm cranking (2.03 times) versus static test (P < 0.05). Physiological change (calculated as the difference between maximum during recovery and minimum at the point of volitional exhaustion) during static test was lower [(66–75% for oxygenation) and (34–46% for blood volume)] than dynamic exercises (P < 0.05). Contrary to the theory that sufficient occlusion of blood flow to the lumbar muscle is possible with static trunk extension, it was concluded that a dynamic protocol until volitional exhaustion might be a good alternative in establishing near-infrared spectroscopy-derived physiological limits to the lumbar muscle. Further research is essential to identify an optimal calibration procedure for establishing true hypoxic values for the human lumbar muscle.