The reticulospinal tracts (RSTs) primarily facilitate gross movements, such as shoulder abduction, with a flexion bias, potentially limiting their effectiveness in mediating movements requiring hand opening. Therefore, it is possible that when opening the hand, RST use will be suppressed. Using the startReact paradigm, we compared RST use during a shoulder abduction with and without hand opening. Seventeen right-handed neurologically intact participants performed these two motor tasks under varying shoulder abduction loads. Electromyography from shoulder abductors, wrist and finger flexors and extensors, and bilateral sternocleidomastoids were recorded. Our startReact findings indicated that with increasing load, there was a significant decrease in coactivation between shoulder abductors and wrist flexors during the simultaneous shoulder abduction and hand-opening task, compared to the shoulder abduction task alone. This decrease suggests a suppression of RST use to allow for hand opening, highlighting a control strategy that optimizes motor performance.