The two men have apparently never heard the expression "weak abdominal muscles."

Low back pain can also be a problem, especially among skiers with weak abdominal muscles.

His right kneecap is misaligned because of a weak muscle.

Anastasia also had a weak muscle in her back.

The old have to move slowly because it's necessary to consider whether the stiff legs and weak muscles can manage obstacles.

This may shift the effort to weaker muscles that cannot handle the weight.

Some people are born with weak abdominal muscles and may be more likely to get a hernia.

The nerves may break down over time and cause you to have weak muscles again.

The fish here have weak muscles, soft skin and slimy bodies.

Her weaker feminine muscles could not compete with his.