How do you know that? To what extent does training increase IGF-1? What type of training increases IGF-1 levels the most? I read through this very well put together study titled "Resistance exercise alters MRF and IGF-I mRNA content in human skeletal muscle" http://jap.physiology.org/cgi/content/full/95/3/1038 and it did not even seem to give these answers. If you do have the answers though, please share.
It did say though that
MRFs are a family of skeletal muscle-specific transcription factors that regulate the expression of several skeletal muscle genes
The study didn't give much in the way of recommendations relating to training style or recovery period to optimize the hormones responsible for hypertrophy. They did give this nice little graph though which shows hormonal levels at different points in time, but it doesn't tell me much:
So do you have the answers I was unable to find? If so please share them.