Can biceps and triceps work at the same time?

Yes, biceps and triceps can work at the same time, especially during compound exercises that engage multiple muscle groups. For example, during a push-up or bench press, the triceps are primarily responsible for pushing, while the biceps stabilize the movement. However, they generally function in opposition—when one muscle group contracts, the other relaxes. In some exercises, like certain cable machines, both can be activated simultaneously to a degree.