Hoffmann Reflex And Neuromuscular Fatigue Under Normoxic And Hypoxic Conditions

Objective: In the fields of Sports Science, the study of Sports fatigue plays a key role. But up till now, we can still find some controversies and unknown fields in the subject, such as the reason leads to muscular fatigue and how to monitoring it. One of the main reason which leads to sports fatigue is neuromuscular fatigue, but the key reason is the fatigue response of central and peripheral system. Hoffmann reflex is one of the basic monosynaptic reflexes in the spinal cord. It belongs to stretch reflex by electrical analog, which is a good way to study Neurobiological and every kind of reflex pathways and the relationship between them. In this paper, the methods based on neurophysiology and electrophysiology were used for establish the H reflex model which can be used to evaluate the neuromuscular fatigue of rat, and to explore the effects of the IHT on the monosynaptic pathway of H reflex in mankind and rats.Methods: In this study, the subjects were male SD rats and healthy volunteers. Homemade oxygen generating device was used in the study. First, a rat neuromuscular fatigue model was established which fit for the study of evoking H reflex. Interventions such as strychnine injection, treadmill training, IHT and so on are applied respectively to this model, in order to observe the changes of H reflex parameters before and after IHT and during the recovery of neuromuscular fatigue. Second, a model of human neuromuscular fatigue was established. Intervention studies of treadmill training and IHT were also applied in this model in order to observe the changes of H reflex parameters before and after neuromuscular fatigue and during the recovery of neuromuscular fatigue. In order to determine the relevant parameters of neuromuscular fatigue before and after the recovery process of H reflex, such as Hmax, Mmax, H-wave latency, M-wave latency and Hmax/Mmax ratio were tested and recorded to diagnose the neuromuscular fatigue, evaluate the extent of the occurrence and development of neuromuscular fatigue and reveal the mechanisms of neuromuscular fatigue and its recovery procedure. By the end of this experiment, we applied SPSS 13.0 statistical software to analysis the Data. Results. 1. We established a stable model of rat's neuromuscular fatigue in this study. This model is fit for the evoking of H reflex before and after fatigue. And the model is sensitive to the interfering studies of drugs and training methods. 2. The main sensitive parameter of H reflex changed in the half-time recovery procedure of neuromuscular fatigue was the amplitude of H-wave which showed decrease in the study. We can analysis quantitatively the H reflex by stabilizing or fixing M-wave in the future study. 3. Amplitude of H-wave in sprint athletes decreased after fatigue, and restored soon; but for distance athletes, H-wave was in low-status after fatigue and during the recovery procedure. 4. Hmax was suppressed for a long time before and after the neuromuscular fatigue was happened in those rats which under the two weeks of intermittent hypoxia training and which combined with intermittent hypoxia training and treadmill training. Before and after the neuromuscular fatigue, there was a long time suppression occurred in Hmax. It might be associated with the regulation of intermittent hypoxia training to the H reflex pathway in the spinal cord. 5. Hmax in sprinters increased first and then decreased during the recovery process after intermittent hypoxia training. The result might be an adaptive change arose from descending supspinal sources caused by intermittent hypoxia training. 6. Intermittent hypoxia training was useful for improving body balance, and the normoxia training combined with intermittent hypoxia training is helpful to improve neuromuscular response ability and simultaneously improve the simple reaction time.Conclusion: We established a stable neuromuscular fatigue models in this study, and had set up a system of H reflex parameters in evaluating the neuromuscular fatigue. H reflex was selected to be a biological probe of neuromuscular fatigue in this study, and through which revealed the principle of the H reflex changes during the fatigue in man and rat. The results also showed us that adaptive plasticity of the human nervous system associated with the H reflex pathway can be induced in response to intermittent hypoxic training or other interventions.