Introduction
Almost all types of strength training involve resistance exercises that require eccentric and concentric muscle contractions in order to stimulate strength gains (Fox, Bowers, & Foss, 1993), muscle hypertrophy (Fox et al., 1993; Tesch, 1988; Lüthi et al., 1986), neural adaptation (Sale, 1988), and metabolic adaptations (MacDougall, 1985) within the targeted muscle. It is the eccentric component of an exercise that is believed to cause the greatest amount of morphological change within the worked muscle (Armstrong, 1984; Clarkson & Tremblay, 1988; Fritz & Stauber, 1988; Stauber, Clarkson, Fritz, & Evans, 1990), strength loss (Fridén, Sjöström, & Ekblom, 1983; Newham, Jones, & Clarkson, 1987; Rödenburg, Bär, & De Boer, 1993) and muscle soreness (Abraham, 1977; Newham, 1988). These changes are believed to be due to muscle damage that is non-permanent and repairable (Fridén, 1984). In addition, muscle tissue has shown that an adaptation to this type of stress takes place during as well as after recovery that results in less damage and soreness in the targeted muscle after subsequent exercise bouts (Byrnes, Clarkson, White, and Frykman, 1985; Clarkson & Tremblay, 1988; Ebbeling & Clarkson, 1990).
