EN
We show that in a super-reflexive Banach space, the conditionality constants $k_{N}(ℬ)$ of a quasi-greedy basis ℬ grow at most like $O((log N)^{1-ε})$ for some 0 < ε < 1. This extends results by the third-named author and Wojtaszczyk (2014), where this property was shown for quasi-greedy bases in $L_{p}$ for 1 < p < ∞. We also give an example of a quasi-greedy basis ℬ in a reflexive Banach space with $k_{N}(ℬ) ≈ log N$.