“…the so-called ascending limb of the force-length relationship (Edman et al, 1978(Edman et al, , 1982Julian and Morgan, 1979b). Rather, force enhancement has been thought to occur only on the so-called descending limb of the force-length relationship, a region in which the active isometric force decreases with increasing muscle/fibre length (Abbott and Aubert, 1952;Edman et al, 1978Edman et al, , 1982Julian and Morgan, 1979b;Herzog and Leonard, 2000), and in which sarcomere lengths are assumed to be unstable (Hill, 1953) and nonuniform in length (Julian and Morgan, 1979b;Morgan, 1990Morgan, , 1994Allinger et al, 1996). Therefore, force enhancement has been associated frequently with the occurrence of instability and the associated non-uniformities in sarcomere lengths (Julian and Morgan, 1979a,b;Edman et al, 1982;Morgan, 1990Morgan, , 1994Edman and Tsuchiya, 1996;Morgan et al, 2000).…”