I was doing butterfly chest excercise with machine as shown here
But, my trainer said I am doing it wrong as my hands should be straight when coming to front. While earlier, my elbow was bent when I bring my hands together. I was able to do 110 pounds with my prior technique. However, with the technique told by trainer I was hardly able to do 60 pound. So, if the trainer told me the correct form, which I think he did, which muscle was I training earlier? He told me it was shoulders, but, I have my doubts. Can someone clarify proper method of butterfly fly on this machine?