When treating the achilles tendon, always consider the functional chain.
Huijing et al., 2003 as well as Stecco et al. has showed that between 30-40% (!!!!) of muscle force transmission occurs within fascial bonds. This ratio is so significant that we MUST look at the whole picture when treating muscular dysfunction.
Common causes of achilles tendon problems, are posterior pelvic tilt and toe gripping. Posterior pelvic tilt inhibits the lower back and thus also normal force transmission through the hamstrings and tricep surae. A subsequent cheat to help with plantar flexion, is toe gripping.
Thus, to solve the achilles issues, it will often not be sufficient to merely perform eccentric calf raise exercises. The present dysfunction is too high.
So, how to stimulate the achilles and triceps surae properly? Massage or dry needle the FDL, optimize pelvic posture, AND perform eccentric calf raises while focusing on not clenching the toes.
A recipe for success!