My daughter has the same problem (at 12m and 24m) as well, she is now 50m. She started swimming and hiking with me thereafter and is much better than before (she always infected by her classmate in the past) now.
We have consulted different doctors and the conclusion is that 抽筋 will be stopped at around 5-6. The most proper way to reduce the rate of 抽筋 is to improve her health by having more Vitamin C, more exercise and a better diet.
I swam with my daughter every week in last summer (27oC of indoor pool is still cool for my daughter, so only in summer) and she went hiking with me last week for 4 consequent hours (1 hour on my backpack) from Tsuen Wan to Sham Tseng.
Take care of your little child and do some exercise with him/her.