The most important thing in boxing is to keep things fresh. If you notice that you hit the punch bag with the same combos every time, there is a good chance that your opponent will also notice. 

If you act like a computer and exercise the same movements, again and again, your opponent will be able to drop you quickly. To be unpredictable. You can also buy the best punching bag (which is also called ‘ Achetez le Meilleur sac de boxe’ in French) from various online sources. 

Although defining any type of combo will take place by definition that makes it more unpredictable, there are some combos that can describe how to think unpredictably. 

Let watch the simple jab. Only one Jab is usually followed by a cross or hook; but why? Try mixing it with a cross jab, then across Jab, or maybe a cross Jab Jab. 

As long as the Jabs are fast and light, you can always maintain a good defense. Think about what these additional Jabs will throw your opponent from its timing and global game. 

Fast Jabs must make a pop sound on the punch bag, as opposed to a flat ball.

It's not just the number of Jabs that count – it's the timing between them. Try throwing three strokes in a second, pause for another second, then throw a jab. 

Or maybe continuous Jabs for a few seconds, followed by a break, followed by a single Jab, then across. 

The pause tells your opponent that you have tired (even if you do not have). The unique Jab makes your opponent think that you will repeat more Jabs and the cross comes like a complete surprise. 

Use a stopped clock or even a metronome next to the punching bag to test your speed and variation.