Of course, they're also still trying to recover their speed. They're a lot harder to hurt, but don't like that their lap times more than doubled overnight.
Considering how important speed is to a ninja, this has to had hit them pretty hard.
IIRC, part of the reason why turtles/tortoises are so slow, is because evolution itself never required them to
be fast.
Herbivores so they never had to chase their food – and in the case of omnivorous breeds, if the prey
does escape, they seldom bother giving chase – plus their shells (and ability to retract their limbs) made them armored enough to not
need to run away from predators.
Plus, their physiology is very much
not designed for speed – they have to plant one front and one hind leg as anchors, while lifting the other two stubby little limbs fully off the ground in order to take a single step. Incredibly dense muscles, as a direct result, however that same muscle density is also significantly taxing on their (highly limited, due to their slow metabolisms) energy reserves.
Honestly, probably the best solution for Gai and Lee right now, would be for Naruto to give them each a seal that boosts their metabolisms – bring it back up to human-standard, so that they have the energy to lug around all that extra natural weight.