Resistance training with instability is more effective than resistance training in improving spinal inhibitory mechanisms in Parkinson's disease

This study assessed 1) the effects of 12 wk of resistance training (RT) and resistance training with instability (RTI) on presynaptic inhibition (PSI) and disynaptic reciprocal inhibition (DRI) of patients with Parkinson's disease (PD); 2) the effectiveness of RT and RTI in moving PSI and DRI values of patients toward values of age-matched healthy controls (HC; Z-score analysis); and 3) associations between PSI and DRI changes and clinical outcomes changes previously published. Thirteen patients in RT group, 13 in RTI group, and 11 in a nonexercising control group completed the trial. While RT and RTI groups performed resistance exercises twice a week for 12 wk, only the RTI group used unstable devices. The soleus H reflex was used to evaluate resting PSI and DRI before and after the experimental protocol. The HC (n = 31) was assessed at pretest only. There were significant group X time interactions for PSI (P < 0.0001) and DRI (P < 0.0001). RTI was more effective than RT in increasing the levels of PSI (P = 0.0154) and DRI (P < 0.0001) at posttraining and in moving PSI [confidence interval (CI) 0.1-0.5] and DRI (CI 0.6 -1.1) levels to those observed in HC. There was association between DRI and quality of life changes (r = -0.69, P = 0.008) and a strong trend toward association between PSI and postural instability changes (r = 0.60, P = 0.051) after RTI. RTI increased PSI and DRI levels more than RT, reaching the average values of the HC. Thus RTI may cause plastic changes in PSI and DRI pathways that are associated with some PD clinical outcomes. NEW & NOTEWORTHY Patients with Parkinson's disease (PD) have motor dysfunction. Spinal inhibitory mechanisms are important for modulating both supraspinal motor commands and sensory feedback at the spinal level. Resistance training with instability was more effective than resistance training in increasing the levels of presynaptic inhibition and disynaptic reciprocal inhibition of lower limb at rest of the patients with PD, reaching the average values of the healthy controls.