Did you think that eccentric muscle actions were the only contraction types that could shift the optimum length (SOPL) of muscle (see picture)? Net effect longer and stronger muscles.
An interesting research finding in terms of SOPL of muscle is that of Guex et al (2013). They proposed that the training range of motion could be a stimulus just as important as eccentric muscle actions.
The researchers performed a single set of concentric contractions beyond optimal length (seated hip flexion at 80°). After the set at 80° of hip flexion, the optimal angle was shifted by ~15° in the direction of longer muscle length. However, a non-significant shift of 3° was found at 0°.
The take home is that training range of motion seems to be a relevant stimulus for SOPL to longer muscle lengths, which has interesting implications for injury prevention and performance.