Are you asking for your own learning? If it's a general practitioner 'how effective?' question it ought to be in the standard forum ... I have responded on that basis, but clarify if it is for your own study.

A google search reveals quite a few research articles, most far too scholarly for me, but a couple took my eye.
www.sussex.ac.uk/informa...reports/csrp/csrp595.pdf and
http://www.ncbi.nlm.nih....pmc/articles/PMC1470479/ who were not impressed I think.

I merely glanced at these, but would bear in mind the question: 'effective compared to what?', as research also shows many traditional forms of training are not that effective either. And compared to no training at all . . .

I have used elearning as part of a H&S training strategy which had other strands to it. There are also different qualities of such products - I had my favourite, but even that had limitations. I regard elearning on the same level as structured reading, with the added benefit of recording who reads what, when etc.

You mention manual handling - might be worth searching the HSE site for their research on the effectiveness (not) of most MH training - done before elearning took off.