Low Muscle Tone in Arms (Hypotonia)
The short answer
Low muscle tone in the arms means your baby's arms may feel floppy or offer less resistance than expected when you move them. While some babies naturally have lower muscle tone that improves with time and practice, significant or persistent low tone in the arms can affect reaching, grasping, and tummy time skills. Your pediatrician can assess whether your baby's tone is within the normal range or whether a referral for physical or occupational therapy would be helpful.
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By Age
What to expect by age
0-3 months
Newborns typically hold their arms in a flexed position close to their body and offer some resistance when you gently extend their limbs. A baby with low arm tone may let their arms rest loosely at their sides and offer little resistance when moved. Some degree of variation is normal, and premature babies often have lower tone initially. If your baby's arms seem significantly floppy and they have difficulty with feeding or show very little arm movement, bring this to your pediatrician's attention.
3-6 months
By this age, babies should be reaching for objects, bringing their hands together at midline, and starting to bear weight on their forearms during tummy time. Low arm tone can make these activities more difficult. You may notice your baby tires quickly during tummy time, has trouble reaching for and holding toys, or seems to use their arms less than expected. Physical therapy can be very effective at this stage to build strength.
6-12 months
Babies are now transferring objects between hands, feeding themselves finger foods, and bearing weight through their arms for crawling. Low arm tone may slow progress in these areas. Your baby may crawl with a modified pattern or prefer to scoot rather than bear weight through their arms. An evaluation can help determine the best approach to support your baby's upper body development.
1-3 years
Toddlers with low arm tone may have difficulty with activities like throwing a ball, climbing playground equipment, pushing riding toys, or using utensils. They may tire more quickly during activities that require arm strength. Occupational therapy can help build functional arm strength through play-based activities. Many children with mild low tone make excellent progress with consistent support.
What Should You Do?
When to take action
- Your baby has slightly lower tone than other babies but is meeting developmental milestones within the expected timeframes.
- Your premature baby has lower arm tone that is gradually improving as they grow.
- Your baby's arms feel a bit relaxed, but they are actively reaching for objects, bearing weight during tummy time, and using their hands appropriately for their age.
- There is a family history of being very flexible or "double-jointed," and your baby is otherwise developing well.
- Your baby's arms feel notably floppy and they have difficulty bearing weight on their arms during tummy time by 4 months.
- Your baby seems to avoid using their arms for reaching, grasping, or weight bearing, and this is affecting their development.
- You notice that your baby's arm tone is significantly different on one side compared to the other.
- Your baby's arms have become progressively floppier over time rather than getting stronger, or your baby has lost arm movement they previously had.
- Your baby has severely floppy arms combined with difficulty feeding, breathing problems, or overall low alertness.
Sources
Related Resources
Trust your instincts. If something feels wrong, reach out to your pediatrician.
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Related Physical Concerns
My Baby Seems to Use One Side More Than the Other
Babies should use both sides of their body fairly equally during the first 18 months of life. While slight preferences can be normal, a consistent pattern of favoring one side - using one arm much more than the other, crawling with one leg dragging, or turning the head predominantly one way - should always be discussed with your pediatrician. Early identification of asymmetry leads to the best outcomes.
My Baby Only Army Crawls
Army crawling (also called commando crawling) is a completely valid and normal way for babies to move. Many babies army crawl for weeks or even months before transitioning to hands-and-knees crawling, and some skip hands-and-knees crawling entirely. What matters is that your baby is independently mobile and exploring their environment.
One Side of My Baby's Body Moves Differently
Babies should generally use both sides of their body equally. If one side consistently moves differently, is weaker, stiffer, or less coordinated, this warrants evaluation. Asymmetric movement can indicate hemiplegia (cerebral palsy affecting one side), brachial plexus injury, or other neurological conditions that benefit from early therapy.
My Baby Crawls Unevenly
While some variation in crawling patterns is normal, consistently favoring one side or dragging one limb while crawling warrants attention. Babies should use both arms and both legs relatively equally when crawling. Persistent asymmetry could indicate muscle tone differences, hip issues, or neurological concerns that benefit from early evaluation.
My Baby Still Has the Fencing Reflex (Persistent ATNR)
The asymmetric tonic neck reflex (ATNR, also called the fencing reflex) causes your baby to extend the arm on the side they are looking toward. It should integrate between 4-6 months. If the ATNR persists strongly beyond 6 months, it can interfere with bringing hands to midline, bilateral hand use, and rolling. Evaluation is recommended.
Signs of Ataxia in Babies and Toddlers
Ataxia refers to wobbly, uncoordinated movements that result from problems with the cerebellum (the brain's coordination center). Signs include an unsteady, wide-based gait, difficulty with precise hand movements, and intention tremor (shaking that worsens when reaching for something). If you notice these signs, evaluation by a pediatric neurologist is important.