AK, combined or not, is a good bet to raise or re-raise, but it is useless to even an invitation or let alone a re-invitation. In poker, the ace-king is a hand that should be used in an aggressive manner, if not, better not use it at all. If the danger is great, lets the hand. Let a strong hand is not a sign of impotence, but rather a demonstration of wisdom as only the great players know what is the best time to play it. Above all, do not put at risk the whole tournament by one hand, nor with a combination AK unless you are not in short stack. You can afford to take a call if you are in a good position (in a position where you have to play before your opponent on the flop). Your advance allows you to test the blocking bet on the flop, with the aim of taking the enemy by surprise and anticipate making your bet before him. This can disturb and destabilize your opponent. In fact, you have every chance to win if the shooter rolls a pair of aces or kings, since you already have the best kicker.
AK (Ace-King combination, of the same suit, such as AK of hearts), has a force even more impressive, given that it can take up the color or the color of axes. It is clearly reasonable to play it, even if you have made a call before your preflop (indeed, this is true if the re-invitation is manageable).
The AK will be used in other ways, depending on the depth of your own stack:
Big Stack: Six big stack if you have a number of chips equal to 25 times the big blind. Suppose you are at the beginning of the tournament and you have enough chips: you can afford to get even a call, just to see what happens on the flop.
Middle stack: Six middle stack if you have a number of chips between 10 and 20 times the big blind. This is an intermediate situation, since the player does not have a stack high enough to scare others with his invitation, although not to worry too much for our stack. It is also true that if we raise, our gestures can be interpreted as a desperate attempt to take away the blind with the aim of improving the stack. Some of your opponents will be tempted to follow you out of curiosity. If the flop is not directly on your side and if it came up, a bet or call, do not insist. Minimize your losses and continue your game. Avoid unnecessary risk of experiencing in your situation. The middle stack is not large enough to impress and thus deter, or to point in preflop.
Short Stack: Six short stack if what you have available is equivalent to less than 10 times the big blind. To continue to participate in the tournament, you all-in. A player who has the combination AK, despite everything, a good chance to take away the pot. However you do not have enough time to wait for better cards.
Ultimately, AK is a beautiful combination whose potential deterrent force is very strong, but this does not mean that you should use it with caution. It is a good combination for: boost early in the game, even out at the end of the tour if the stake is not too high and the flop if you pull your pair of aces or kings and there is no danger (ie, not there are possible flush, straight or full on the table).