Pomodoro technique involves 25 minutes of focused work, and then 5 minutes of rest.
Preventing burnout for programmers
Karolis Ramanauskas

Most of the Pomodoro apps out there allow you to set whatever pomodoro duration suits you. When following 25mn pomodoros at the office, the dev guys around would very often skip one or two breaks because they were focused and needed to stay in their concentration tunnel more than 25mn. We eventually decided to go for 50mn pomodoros with 10mn breaks and left it to anyone to join the breaks at their will. What also works very well to relax your brain and trigger different areas is playing! Setup a ping pong net on a meeting room table, introduce a tiny rugby ball in the open space (careful where you throw it :P)… breaks are also fundamental to take some quality time with your teammates. And if you work solo, indeed a series of quick physical exercises is a great way to relax the tension in both brain and body.