Changes in agonist-antagonist EMG, muscle CSA, and force during strength training in middle-aged and older people. - Häkkinen,K.; Kallinen,M.; Izquierdo,M.; Jokelainen,K.; Lassila,H.; Mälkiä,E.; Kraemer,W.J.; Newton,R.U.; Alen,M. (J Appl Physiol, 1998)