Exhaustion

The mechs couldn't fight much longer at this pace.

Each of the mechs had been moving around a lot, which meant that they used their energy reserves at a much higher rate than was sustainable.

Normal mechs could keep going like this for quite a while, but tournaments usually restricted the amount of energy that mechs could have in order to prevent them from stalling matches for hours at a time.

The matches of the Twin Weapons Tournament obviously weren't meant to last that long, so the rules had been rather heavy-handed about limiting their maximum energy reserves.

The mech pilots participating in this tournament were all aware of these limitations. Even if they used their best possible means to reduce the amount of energy they were expending, their mechs were still moving closer to exhaustion with each exertion they made.