  We consider the energy-supercritical harmonic map heat flow from
$\mathbb{R}^d$ into $\mathbb{S}^d$, under an additional assumption of
1-corotational symmetry. We are interested by the 7 dimensional case which is
the borderline between the Type I blowup regime. We construct for this problem
a stable finite time blowup solution under the condition of corotational
symmetry that blows up via concentration of the universal profile $$u(r,t) \sim
Q\left(\frac{r}{\lambda(t)}\right),$$ where $Q$ is the stationary solution of
the equation and the speed is given by the rate $$\lambda(t) \sim
\frac{\sqrt{(T-t)}}{|\log(T-t)|},$$ which corresponds to the speed predicted by
Biernat.
