Changes in Spinal Muscle Oxygenation and Perfusion During the Biering-Sørensen Test: Preliminary Results of a Study Employing NIRS-Based Muscle Oximetry.

Low back pain (LBP) is suggested to be related to deconditioning of back muscles by a decreased capacity for hyperemia in exercising muscles. However, only inconsistent evidence exists regarding back muscle perfusion and oxygen saturation in healthy subjects and patients suffering from (chronic) LBP. Aim: We measured muscle perfusion in healthy subjects during the Biering-Sorensen (BS) test (the gold standard for evaluating back muscle endurance) using a commercial near-infrared spectroscopy (NIRS) device. We analysed data sets of five female healthy subjects (age: 34 +/- 15 years) who reached the maximum of 4 min during the BS test. Muscle oxygenation (SmO2) and perfusion ([tHb]) were measured using the Moxy NIRS device (Fortiori Design LLC, Hutchinson, USA). Probes were set unilaterally on M. longissimus, M. iliocostalis and M. multifidus. Additionally, mean arterial blood pressure (MAP), pulse pressure (PP), heart rate (HR), arterial oxygen saturation (SpO(2)) and lactate (pre, task, post) were measured. We observed (i) a large inter-subject variability in the SmO2 and [tHb] responses in the three muscles (i. e., SmO2 desaturations in the in M. longissimus across subjects during the task ranging from 1.1% to-56.6%), and (ii) a consistent response of the systemic signals in all subjects (i.e., increase in MAP, PP and HR). Lactate changes (post task minus task period) correlated with changes in PP and SmO2 of the multifidus muscle. Our preliminary results showed that during the BS test the response in the peripheral muscles was more variable than the central systemic response. A goal for future investigations is to explain this variability in the periphery by considering, for example, subject-specific changes in systemic cardiovascular activity, lactate and in the microvascular perfusion of muscle tissue.