Yoghurt has a very very low glycemic index, so it hardly raises insuline levels. Post workout drink/meal should elevate insuline levels, so the nutritients are transported to your muscle cells. A great post workout drink would be 1 scoop of AST VP2 (hydrolyzed whey peptides) with 50 grams of dextrose mixed in water. Or you could drink Surge by Biotest. Surge is designed to be the perfect post workout drink. Haven't tried Surge though.
Koen