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)