The Hemodynamic Research Of Peripheral Muscles During Different Modes Of Exercise, Oxygen Concentration And Postures

IntroductionAlthough enough attentions have been paid to the relationship between the changes of blood flow in erector spinae muscle and the low back pain, rare is known about the correlation of low back pain and the different posture of lumbar spine and corresponding load during exercise. Near infrared spectroscopy (NIRS) is one kind of non-invasive measurement and has been used to measure the change of hemodynamic in skeletal muscle over the last decade, which is achieved by measuring the signal with the laser probe on the surface of muscle and the hemodynamic of muscle hence is determined by the change of blood flow and its oxygenation. Although NIRS can not be used to measure the blood flow directly, researchers can acquire the change of blood flow and real-time oxygenation. Since oxygenated hemoglobin and deoxygenated hemoglobin have different absorption coefficient at specific wavelength, i.e 780, 810 and 830nm, their concentration can be determined by the corresponding coefficient and the value of total hemoglobin. In terms of the relationship of low back pain and the change of blood flow in erector spinae muscle, most of the studies are focusing on the flexion of lumbar spine.Moderate altitude is usually used to treat exercise the athlete to stimulate the hypoxia of trained muscles. However, there are seldom researches focused on muscle metabolism. In addition, the hypoxic condition in moderate and high attitude has been used to improve the training effect of some athletes by the sports physicians and researchers, however, there is some inconvenience to evaluate some sports tests in high attitude and we can not illustrate the metabolic state at both states such as normal oxygen pressure and hypoxia simultaneously. Some researchers introduced a device with which sports tests can be performed in a simulated high attitude with hypoxic state. Currently, seldom studies are associated with the application of such hypoxic room to assess the muscle metabolism during exercise.ObjectivesOur purpose of this study was to evaluate the changes of blood flow in erector spinae muscle during different postures and loads and their possible relation to low back pain. Also, the current study was designed to determine the effect of hypoxic environment in laboratory on resistance of vastus lateralis and erector spinae muscle during bicycling.Materials and MethodsFor the experiment one, twelve volunteers were recruited to join our research, they were asked to sign a consent document. Two machines of near infrared spectroscopy (NIRS) were used to evaluate the changes of blood flow of erector spinae muscle in 7 different lumbar postures and during exercise with or without load. The following postures were included: standing, lumbar flexion at 90 degrees, maximal extension, maximal left and right lateral bending, sitting and supine position. All the postures were assessed in a random order. We also assessed the changes of blood flow when the anticipants were asked to flex their lumbar spine with 10 Kg dynamic or static load. Namely, the blood flow and oxygenation of erector spinae muscle were recorded before, during and after the exercise including sitting, standing, exercise, post-exercise standing and sitting. All data were collected and input into the machine simultaneously and transferred into the accessorized laptop computer by the Excel file. The average 30-second data during standing were regarded as the baseline values, then all other data were recorded as the percentage to the baseline value expressed as% oxygenated hemoglobin,% deoxygenated hemoglobin and % total hemoglobin.Another twenty volunteers were asked to perform the following protocol on a bicycle. Firstly, they rested on the bicycle for 3 minutes, then ride the bicycle for another 3 minutes with 10W load at the rate of 50～60 times per minute, and then the load increased every 10 seconds at a rate of 10W until 200W, finally, the anticipants continued to ride the bicycle for the last 3 minutes with 10W at the same speed. 3 days later, they repeated the same experiment in a special room designed to have a hypoxic environment within it. The oxygen concentration inside is 14.4%, which exactly is the same concentration at 3000-meter altitude. The near infrared spectroscopy was used to measure the change of muscle oxygenation during exercise. The changes of oxygen saturation and heart rate were also recorded. The variation of oxygenated hemoglobin, deoxygenated hemoglobin and total hemoglobin was expressed as the percentage to the value during rest. All data were analysed with paired student t test with StatView software.Results%oxygenated hemoglobin and %total hemoglobin showed the maximal extent of decrease during 90-degree flexion. During the maximal lateral bending, the extent of decrease in %oxygenated hemoglobin was significantly greater in the contralateral muscle than the ipsilateral one. During the dynamic and static lumbar flexion with 10 Kg load, the blood flow of erector spinae muscle in lumbar spine decrease significantly with the dynamic exercise having the maximal decrease, while the blood flow in thoracic spine didn't show any statistical change. During exercise, the relative value of oxygenated hemoglobin decreased significantly than rest (p＜0.01), while the value in hypoxic room was especially lower than in the normal oxygen state (p＜0.001). The oxygen saturation didn't show significant change before and after bicycling, while its value decreased significantly when the volunteers entered the hypoxic room with heart rate increased (p＜0.05). There was no change of blood flow in erector spinae muscle during exercise.ConclusionsThe use of two near infrared spectroscopy makes us evaluate the hemodynamics of erector spinae muscle at both sides simultaneously. Our results demonstrated that asymmetric posture will result in the asymmetric distribution of blood flow. During lumbar flexion, the stretched muscle presented less blood flow and oxygenated state, which was much more distinguished in exercise with some load. Our results indicated that asymmetric posture and/or load with or without exercise might lead to the fatigue of erector spinae muscle and to induce the possible occurrence of low back pain. Some detrimental postures and exercise should be avoided during work time. Simulated hypoxic state can produce the similar effect on the training results as moderate altitude. Blood flow and muscle oxygenation in working muscle will change significantly during bicycling in normal oxygen state and hypoxic state. The decrease of oxygenation in vastus lateralis in different oxygen pressure indicated we can implement hypoxic training in laboratory instead of on mountain at the higher attitude.