Does Calf Botox Make Your Legs Weak When You Walk or Exercise?

In studies, calf botox did not noticeably change how people walked. Still, people who climb stairs often or enjoy hiking and running usually worry first: "What if my legs feel weak and I fall?" They also want to know how much the calf actually slims down, and who sees less of a change.

This article explains which muscle calf botox works on, what studies found about walking and balance, how much the circumference changes, and what to check before treatment.

Which muscle does calf botox target, and why do people worry about strength?

Which muscle does calf botox target, and why do people worry about strength?

Calf botox is usually injected into the gastrocnemius, the muscle that bulges at the upper back of the calf. Botox blocks the signal from the nerve to the muscle, so the muscle contracts less, and as it is used less over time, its volume shrinks. The gastrocnemius lifts the heel and pushes the body forward, so people naturally worry that weakening it will make walking harder.

Underneath the gastrocnemius sits a second muscle, the soleus. It also helps support the body when you stand or walk slowly. If only the gastrocnemius is injected, the soleus keeps working as usual.

The feeling of reduced muscle strength usually starts a few days after the injection, and calf volume shrinks later, over several weeks. That is why worries about leg strength tend to show up one to two weeks after treatment rather than right away. The connection between nerve and muscle returns over a few months, so both strength and volume gradually go back to how they were before.

Gastrocnemius: the two-headed muscle that bulges at the upper back of the calf. It stands out firmly when you rise onto your toes.

Which muscle does calf botox target, and why do people worry about strength?

How did walking and balance change in studies?

How did walking and balance change in studies?

In one study, 15 healthy women received botox in both gastrocnemius muscles, and their walking was measured at 1 and 3 months. Step length, number of steps and walking speed were the same as before treatment. There was, however, a small change in how quickly they shifted their center of gravity to keep balance. The researchers suggested taking this into account for people at high risk of falling.

Another study gave 40 Asian women one of two doses (160 units or 200 units) and saw no leg weakness or abnormal sensation. Both studies were small and followed people for only a few months.

The table shows little difference for walking on flat ground, but situations that demand more balance, such as high heels or hiking trails, have not been studied yet. So for the first few weeks after treatment, it is wise to be careful with high heels and rough paths. If you exercise regularly, tell the doctor at the consultation what kind of exercise you do and how much.

How much does the circumference shrink, and who sees less of a change?

How much does the circumference shrink, and who sees less of a change?

In a randomized trial of 20 people, each leg received either 60 units or 100 units. After 8 weeks, calf circumference went from 36.35 cm to 35.87 cm. A higher dose did not shrink it more. The lead researcher disclosed receiving clinical trial funding from a botulinum toxin manufacturer.

How much does the circumference shrink, and who sees less of a change?

Since the change is less than 1 cm, expecting your trousers to feel loose is likely to disappoint. What changes is less the circumference and more the shape of the muscle that pops up when you rise onto your toes.

The thickness of the calf fat layer also affected satisfaction. When 50 cases were grouped into thin, medium and thick fat layers, the medium group was less satisfied than the other two, and all three groups were not very satisfied with how much the overall circumference shrank. After the gastrocnemius was injected, the soleus and fat beneath it sometimes became thicker over time. In a study that split 34 people into a gastrocnemius-only group and a group that also had the soleus injected, injecting both reduced the soleus's tendency to thicken, but satisfaction was similar in both groups. Treating more muscles did not lead to a better result. If your calves look thick mainly because of fat rather than muscle, botox changes less.

How STON Clinic approaches calf botox consultations

How STON Clinic approaches calf botox consultations

First, we check whether your calves look thick because of muscle or fat. If the upper calf bulges firmly when you rise onto your toes, muscle is the bigger part; if the soft part you can pinch while relaxed is thick, fat plays a larger role. The calf is not a site for which the US FDA has approved botox, so you should also know that this is off-label use based on the doctor's judgment before deciding.

Pain, bruising or swelling at the injection site is a common reaction and usually settles within a few days. Contact us right away, without waiting, if you notice any of the following.

• Your legs feel so weak that climbing stairs or rising onto your toes is hard
• Swallowing becomes difficult or your speech becomes slurred
• Breathing feels tight (in this case, go to the emergency room first)

Calf botox is not given during pregnancy or breastfeeding, or to people with conditions that weaken the muscles. At the consultation, starting with "Does my calf look bigger because of muscle or fat?" makes it easier to estimate the change you can expect. When you contact the clinic, please send photos of the back of your calves both on tiptoe and relaxed, along with the exercise you usually do.