The solution is to uncomment the MPM config include in httpd.conf
# Server-pool management (MPM specific)
Include conf/extra/httpd-mpm.conf
Then locate the mpm_winnt_module
and change the thread count from the current value to whatever you want.
<IfModule mpm_winnt_module>
ThreadsPerChild 1000
MaxRequestsPerChild 0
</IfModule>