He is doing squats to train his quadriceps femoris muscle.

He is doing squats to train his biceps femoris muscle.

The splenius capitis muscle is a part of the neck muscles, helping to tilt the head backwards.

The semispinalis capitis muscle is a part of the neck muscles, helping to tilt the head backwards.

The obliquus capitis superior muscle is part of the neck muscles, helping to tilt the head.

The obliquus capitis inferior muscle is a part of the neck muscles, helping to tilt the head.

The rectus capitis lateralis muscle is part of the neck muscles, and it helps to move the head sideways.

He is doing a special exercise to train his occipitofrontalis muscle.

He is doing a special exercise to strengthen his temporoparietalis muscle.

The crescent moon is floating in the sky, it's very beautiful.