The pro??tein is an iso??form, or slight var??i??ant, of PGC-1 al??pha???an im??por??tant reg??u??la??tor of body me??tab??o??lism turned on by forms of ex??er??cise, such as run??ning, that in??crease mus??cle en??dur??ance rath??er than size. ???it is pret??ty amaz??ing that two pro??teins made by a sin??gle gene reg??u??late the ef??fects of both types of ex??er??cise,??? said Spiegel??man.