Rhythmic arm swing enhances long latency facilitatory effect of transcranial magnetic stimulation on soleus motoneuron pool excitability.

The purpose of this study was to investigate whether rhythmic arm swing modulates the long latency effect of transcranial magnetic stimulation (TMS) on soleus motoneuron pool excitability. Ten healthy humans rhythmically swung the left arm back and forth in a sitting position. The soleus H-reflex was evoked when the arm was in the backward swing phase. Conditioning TMS was delivered over the motor cortex 8 ms before the soleus H-reflex was evoked. The soleus H-reflex amplitude in both legs was depressed by the rhythmic arm swing. In contrast, rhythmic arm swing enhanced the facilitatory effect of conditioning TMS over the motor cortex contralateral to the arm swing side on the soleus H-reflex ipsilateral to the arm swing side. This finding indicates that rhythmic arm swing enhances some polysynaptic facilitatory pathways from the motor cortex contralateral to the arm swing side to the soleus motoneuron pool ipsilateral to the arm swing side.

Preoperative quadriceps strength as a predictor of return to sports after anterior cruciate ligament reconstruction in competitive athletes.

OBJECTIVES: To determine whether preoperative quadriceps strength predicts the likelihood of return to sports (RTS) following anterior cruciate ligament reconstruction (ACLR) in competitive athletes. DESIGN: Case-control study. SETTING: Single-center. PARTICIPANTS: A total of 221 competitive athletes who underwent primary ACLR were followed and divided into RTS (n = 177) and non-RTS (n = 44) groups based on self-reported sports activities at one year postoperatively. MAIN OUTCOME MEASURES: Isokinetic quadriceps strength tests were performed preoperatively and at six months and one year postoperatively, and the quadriceps index (QI) was calculated. Functional performance was evaluated by the single-leg hop (SLH) test at six months postoperatively. RESULTS: Preoperative QI significantly predicted the likelihood of RTS (odds ratio, 1.68 per 10-unit increase; P < 0.001), with a preoperative QI cut-off of 66% (AUC: 0.74; sensitivity: 68.9%; specificity: 77.3%). Subjects with a preoperative QI < 66% had a significantly lower postoperative QI, SLH, and rates of RTS compared to those with a higher preoperative QI (P < 0.01). CONCLUSIONS: Preoperative quadriceps strength could predict the likelihood of RTS following ACLR, and a preoperative QI < 66% was associated with a greater risk of unsuccessful RTS at one year postoperatively. Preoperative QI should be evaluated as a predictor of RTS.