POST request getting converted to GET when URL rewriting is done in apache httpd

I have an apache web server that acts as a reverse proxy to internal app servers. I have used ProxyPass and ProxyPassReverse to achieve this. I have multiple context roots mapping to different applications. I am trying to remove the context root from the domain name for one context so that users can access the website directly as https://mydomain.com instead of https://mydomain.com/contextRoot. I have added the following rewrite rules instead of the proxypass and proxypassreverse configurations for this context.

# redirecting old URL to new URL RewriteRule ^/contextRoot(.*)$ https://mydomain.com$1 [L,R=301] # proxying to internal app servers RewriteCond % !^(/anotherContextRoot1.*)$ RewriteCond % !^(/anotherContextRoot2.*)$ RewriteRule .* http://10.1.0.1:8080/contextRoot% [L,P] 

This configuration works well for all http GET requests. For POST requests, the redirect happens, but the subsequent call becomes a GET. Please help me understand why this happens and how can I correct this. I also want to understand is there any more rewrite rule configuration that I have add to do what proxypassreverse used to do in the previous configuration.