Flexing the brain
The amount of effort you can see is immense. This man is buffed, and his brain seems like it is flexing its biceps. Everything is flexed, his nerves, arms, and brain, and we don’t blame him. We can see his nerves because he is bald; if we didn’t have hair on our scalp, we might have a similar view on our heads. We’d just suggest he tone down the weights and let his brain rest.