“Eccentric” muscle contractions are contractions while lengthening, also called braking contractions. Dr. Peter Malliaris:
“Can authors please stop using this phrase: ‘the current gold standard for the treatment of Achilles tendinopathies is eccentric exercises.’ If ‘gold standard’ means the best available, the evidence does not support this.”
I do not use “gold standard” in my Achilles tendinitis guide. What I do say is this: “If exercising eccentrically is actually useful in rehab, it is not clearly established yet.” And it’s unlikely to get there.