-tai-chi: i have just read a systematic review and meta-analysis:

Objective It remains unclear whether Tai Chi is effective for preventing falls in older adults. We undertook this  systematic review to evaluate the preventive effect of Tai Chi by updating the latest trial evidence.
Systematic review and meta-analysis: Tai Chi for preventing falls in older adults.
http://bmjopen.bmj.com/content/7/2/e013661

-but i have read at least three more papers last 2016:

Health benefits of tai chi. What is the evidence?
http://www.misericordia.mb.ca/files/TheBenefitsofTaiChi.pdf
The Effect of Tai Chi on Reducing the Risk of Falling: A Systematic Review and Meta-Analysis.
https://www.ncbi.nlm.nih.gov/pubmed/27430918
Tai Chi as an intervention to reduce  falls and improve balance function in the elderly: A meta-analysis of  randomized controlled trials 
http://www.sciencedirect.com/science/article/pii/S209577181630024X

-thanks goodness all agree: tai-chi is good for preventing falls in the elderly

-but, how many systematic review and meta-analysis are enough?

-un saludo juan gérvas @JuanGrvas