The purpose of this study was to capture changes in cerebral blood flow using near-infrared spectroscopy, investigate the effects of MP on flexibility, and examine the associated factors.
The subjects were 11 healthy young men (20.9 ± 0.7 years), with the target muscle for MP being the right hamstring. A random crossover study design was used, where subjects participated in both the MP group and a control group (resting). Prior to the experiment, subjective imagery ability was assessed using the Motor Imagery Questionnaire and the Kinesthetic and Visual Imagery Questionnaire (KVIQ). The experiment involved measuring flexibility measures before and after MP (or rest); and cerebral hemodynamics during MP (or rest). Flexibility evaluation indices included range of motion (ROM), passive torque and stiffness, calculated from torque-angle curves during passive extension of the knee joint using constant velocity exercise equipment. Functional Near-Infrared Spectroscopy was used to measure cerebral hemodynamics. The analysis of cerebral blood flow changes in this experiment used changes in oxygenated hemoglobin as the indicator. Probes were attached to the left and right premotor, supplementary motor and primary motor cortices. MP was encouraged with regard to imagining the sensation of a stretched right hamstring. Subjects were asked to imagine their right hamstring being stretched in a chair position for 60 seconds with their eyes closed.
ROM and passive torque exhibited a significant increase after MP. Passive torque also differed between groups. However, no significant differences were observed in stiffness. Cerebral hemodynamics exhibited a significant increase in the left supplementary motor cortex region during MP. In addition, a positive correlation was found between the rate of change in ROM before and after MP implementation, and scores on the KVIQ musculoskeletal imagery scale (r = 0.56).
The results of this study suggest that changes in cerebral blood flow within the motor cortex are associated with changes in flexibility in MP. The increase in ROM due to MP is thought to be associated with an increase in passive torque mediated by central nervous system factors. Furthermore, it was seen that the higher the KVIQ score, the more activated the brain activity became which, in turn, influenced the increase in flexibility.
MP can increase ROM and may help prevent ROM limitations in individuals who are immobilized due to injury, or who are unable to move their bodies for some other reason. Furthermore, the combined effect of MP and stretching is expected to further improve flexibility.
flexibility
functional near-infrared spectroscopy
