tightens up

On the scan his Achilles is completely clear but as soon as he stays out for a while it tightens up and he has pain.

在扫描上，他的脚后跟完全没问题，但只要他出去站一会儿，他的脚后跟就发紧，他感受到疼痛。

Further testing with my music shows one clear advantage though, this amp really tightens up bass to deliver more kick and control.

不过再做测试还是发现有改进，低频控制力增强了，鼓点听起来更带劲。

This aluminum coats and tightens up the clearances of the parts, which creates a loss of power.

这些金属屑覆盖并使各部件间间隙变得更紧，这将导致动力损失。

He tightens up when he's flying.

他在飞行中绷得紧紧的。