The biceps and the triceps are two major muscles in your arms. The biceps are the large muscles in the front of your upper arm, while the triceps are those at the back. Because both these muscles are in the arms, it's convenient and practical to work them out on the same day.
One Day Arm Workout
For most people, working out the biceps and triceps on the same day is a good idea. When you work out one part of your arm, you are often engaging other parts as well. After training a muscle, it needs to rest for at least a day, which is why many people train legs one day and arms the next. It's also important to train inverse muscles for balance, so if you are strengthening your biceps you will want to work out your triceps as well.
Strengthen or Tone
You can do separate exercises for triceps and biceps or combination moves that work out multiple parts of the arms. To increase muscle bulk, do fewer repetitions of heavier weights. To tone, do more repetitions of lighter weights, making sure the reps are still challenging. You can also work out your arms with your own body weight by doing exercises such as push-ups.