Meaning: Stretching can make you stand, sit, and walk straighter.
Choice of Words: The verb "improve" suggests a positive change or enhancement. "Posture" refers to the way you hold your body when you stand, sit, or walk.
Alternative Expressions
Stretching makes your body straighter.
Meaning: This means that stretching can help your body stand or sit in a more upright position.
Choice of Words:Makes means to cause something to happen. Straighter means more upright or not bent.
If you stretch, you'll stand taller.
Meaning: This means that if you stretch your body, you may be able to stand taller because your body will be more upright.
Choice of Words:If means that something is dependent on something else happening. Stand means to be upright on your feet. Taller means higher in height.