I think this comes down to different cultures due to scoring systems and should not be generalised.

In kickboxing, it is actively encouraged to keep your guard up at all times, including when throwing a kick. That is because you want to minimise risk as hits taken adding up to dizziness is what is to be avoided at all costs and depending on the rules, even light hits may count as a score against you.

In Muay Thai, on the other hand, a display of dominance is your main goal. Accordingly, fighters more often consciously let their guard down in order to show 'look, I don't even need to protect myself against this guy'. Also, if you are not actively trained to keep your hands in front and up, this is the more natural thing to do to keep your balance.

Thus, it comes down to slightly more power with the help of this counter-movement of the arm vs. slightly more defensive capabilities with a hand out ready for block/parry. I wouldn't say that these differences generally hold between these two sports though, as the emphasis on power or safety respectively isn't tied to the sport as such, beyond the mentioned cultural difference.

I think this comes down to different cultures due to scoring systems and should not be generalised.

In kickboxing, it is actively encouraged to keep your guard up at all times, including when throwing a kick. That is because you want to minimise risk as hits taken adding up to dizziness is what is to be avoided at all costs and depending on the rules, even light hits may count as a score against you.

In Muay Thai, on the other hand, a display of dominance is your main goal. Accordingly, fighters more often consciously let their guard down in order to show 'look, I don't even need to protect myself against this guy'. Also, if you are not actively trained to keep your hands in front and up, this is the more natural thing to do to keep your balance.

Thus, it comes down to slightly more power with the help of this counter-movement of the arm vs. slightly more defensive capabilities with a hand out ready for block/parry. I wouldn't say that these differences generally hold between these two sports though, as the emphasis on power or safety respectively isn't tied to the sport as such, beyond the mentioned cultural difference.

Accordingly, you will find both in pictures and technical descriptions of both sports, although Muay Thai that is explicitly trained in the context of MMA tends to have their guard/hand up as well, as goals and demands are similar to full contact kickboxing.

I think this comes down to different cultures due to scoring systems and should not be generalised.

In kickboxing, it is actively encouraged to keep your guard up at all times, including when throwing a kick. That is because you want to minimise risk as hits taken adding up to dizziness is what is to be avoided at all costs and depending on the rules, even light hits may count as a score against you.

In Muay Thai, on the other hand, a display of dominance is your main goal. Accordingly, fighters more often consciously let their guard down in order to show 'look, I don't even need to protect myself against this guy'.

Thus, it comes down to slightly more power with the help of this counter-movement of the arm vs. slightly more defensive capabilities with a hand out ready for block/parry. I wouldn't say that these differences generally hold between these two sports though, as the emphasis on power or safety respectively isn't tied to the sport as such, beyond the mentioned cultural difference.

I think this comes down to different cultures due to scoring systems and should not be generalised.

In kickboxing, it is actively encouraged to keep your guard up at all times, including when throwing a kick. That is because you want to minimise risk as hits taken adding up to dizziness is what is to be avoided at all costs and depending on the rules, even light hits may count as a score against you.

In Muay Thai, on the other hand, a display of dominance is your main goal. Accordingly, fighters more often consciously let their guard down in order to show 'look, I don't even need to protect myself against this guy'. Also, if you are not actively trained to keep your hands in front and up, this is the more natural thing to do to keep your balance.

Thus, it comes down to slightly more power with the help of this counter-movement of the arm vs. slightly more defensive capabilities with a hand out ready for block/parry. I wouldn't say that these differences generally hold between these two sports though, as the emphasis on power or safety respectively isn't tied to the sport as such, beyond the mentioned cultural difference.