This study examined whether verbal instruction emphasizing force exertion during the braking phase of rebound jumps can acutely enhance the reactive strength index (RSI), a key indicator of stretch–shortening cycle performance linked to sprinting and change-of-direction ability. Seventeen physically active men without plyometric training experience were randomly assigned to an intervention ( n = 8) or control group ( n = 9). Both groups performed repeated rebound jumps under standard instruction. The intervention group additionally received braking-phase–focused instruction. RSI significantly increased only in the intervention group ( p < 0.05), accompanied by greater soleus muscle preactivation before ground contact. These findings suggest that simple, targeted verbal instruction can acutely optimize neuromuscular strategies during plyometric tasks, offering coaches a practical tool for enhancing explosive performance without long-term training.