Preliminary Study On The Correlation Between Bioimpedance And Stress Fracture During Training

Military training is one of the major tasks of our army in peacetime, especially as the changing of international environment and increasing instability factors of security situation with our neighborhood. So, intensity of training in our army is increasing and incidence of military training injuries is increasing too which seriously affects training effect. Hence, prevention of these injuries has become a key point of research in military medical departments.The incidence of military training injuries in our troops is 30% to 40%. It is different from company to company. Stress fracture is one kind of the most common injuries during training. It's reported that incidence of stress fracture is 2% to 64%, and 90% of the stress fractures develop on tibias. Therefore, fundamental studies on the evaluation of stress fracture are significant to improve our troops'training efficiency and to reduce training injuries.Bioimpedance technique can provide human physiological and pathological information through measurement of electric property of tissues or organs. There are electrodes providing electric stimulation on object, and then electric information is recorded. It is noninvasive, harmless, cheap, continuous measurement, easy manipulation, and contains more information. It can easily accepted by doctors and patients, but low precision. The major implied fields are cellular measurements, volume changes, body composition, tissue classification, tissue monitoring and electrical impedance tomography. Bioimpedance contains rich information about tissues'physiological and pathological information. So, it has a promising future of implication in military training injuries.On the basis of other researches in this field, pathogenesis of stress fracture and symptom of muscle fatigue accompanying stress fracture, we used bioimpedance technique to monitor rabbits'shanks during rabbit training. We established the animal model of stress fracture and measured their bioimpedance every 3 days in order to evaluate training and to diagnose stress fracture using this technique.The present paper covers the following aspects.1. Investigation of military training injuries in basic troopsWe summarized incidence, position, kind and other data of stress fracture according to previous reports. We also summarized the predisposing factors and prevention of stress fracture.2. Establishment of rabbit's tibia stress fracture modelWe designed the stimulating devices and established animal stress fracture model. These devices can stimulate rabbits to jump through high voltage and low current flow with a certain frequency. Rabbits were diagnosed by SPECT and X-ray images during and after the experiment. This model can lead rabbits to stress fracture, but not complete fracture.3. Construction of the shank impedance spectroscopy measurement systemWe constructed an impedance spectroscopy measurement system based on 1260 Impedance/Gain-Phase Analyzer (Solartron Company, UK) in order to get consistent result. A four-terminal method was adopted with Ag/AgCl electrodes. The temperature and humidity were controlled.4. Extraction of bioimpedance characteristic parameters and realization of the related softwareWe extracted the characteristic parameters of bioimpedance by iterative least square fitting algorithm, and we designed and realized the software which could calculate these parameters automatically and analyze the results of the bioimpedance data.5. Study of bioimpedance change regularity during trainingWe grouped 8 rabbits into two groups, control group and experimental group. Rabbits in control group were feed in normal way and rabbits in experimental group did jump training every day. The experiment lasted 21 days. We measured bioimpedance of every shank every 3 days, and the data were saved in files.We calculated bioimpedance characteristic parameters and circuit model parameters. Some of them have significant change regularity. Parameters, such as x₀,α, R_e , R₀ , R_∝, R_i , have significantly decreased during training. Parameter C m has significantly increased during training. This implies that training can change electric property of tissues.6. Study of correlation between bioimpedance and stress fractureAll 8 rabbits in this experiment did jump training every day. The experiment lasted 21 days. The rabbits had been diagnosed by SPECT and X-ray images in the 10th day and the 21st day. Finally, there were 9 tibias suffering from stress fracture. We measured every shank's bioimpedance every 3 days. The bioimpedance data were saved in files.We grouped the bioimpedance data into two groups. Group 1 came from shanks which had suffered from stress fracture in the 21st day and group 2 came from shanks which had not suffered from stress fracture in the 21st day. We calculated those parameters and found that the change rate of parameters, such as x₀,α, R_e , R₀ , R_∝, R_i , C_m were significantly different in two groups. The rate in group 1 was higher than that in group 2. So, the bioimpedance parameters'changes may reflect one bone's liability to suffer from stress fracture, and according to the results, bone with quicker changes of these parameters during training is more likely to suffer from stress fracture. In addition, f₀'s change in two groups was more interesting. It had changed significantly only in group 1 and this change seemed earlier than SPECT result's change. This implies that bioimpedance technique may be used in early diagnosis of stress fracture.Although we have found some promising implication possibility of bioimpedance technique on training monitoring, there must be a long way to realize.