If you wanted to get an estimate of how fast you'd need to be moving in order to lift yourself with air deflection from running, you need to establish a couple of important parameters:
1. Body weight $p$
2. Torso angle $\theta$ (defined such that $0^\circ$ would be running upright)
3. Speed $s$
4. Torso length $\ell$
5. 229
Torso width $w$
6. Air density $\rho$
Afterwards, all you need to do is a little bit of fluid mechanical force balancing. You can estimate that your torso deflects all of the incoming air you come into contact with straight downwards, which is only a decent approximation if your torso angle is high, in which case the lift force you would feel is simply the change in vertical momentum of the air coming at you in your frame of reference:
$$ \begin{align} L &= v_{\text{down}} \dot{m}{\text{down}} \[5px] &= v{\text{down}} \dot{m}{\text{front}} \[5px] &= v{\text{down}} \left(s w \ell \cos{\left(\theta\right)} \, \rho \right) \[5px] &= \left(s\frac{\cos{\theta}}{\sin{\theta}}\right) \left(s w \ell \cos{\theta} \right) \[5px] &= s^2 \cot{\theta} \, \cos{\theta} \, w \ell \rho \end{align} $$
You can see that the approximation is bad for small torso angles since it predicts that you'd shoot off into space if you ran normally $\left(\theta = 0^\circ \right) ;$ that's because air would most certainly not deflect downwards if you ran this way.
To get liftoff, you want this lift to be equal to your body weight:
$$L = pg$$
Let's plug in some numbers. If you weigh $p = 175$ pounds, are running with a torso angle of $\theta = 45^\circ$, have a torso length and width of $\ell = 0.5$ meters and $w = 0.4$ meters respectively, you can plug this in along with an air density of $\rho = 1.225$ kilograms per meter cubed and $g = 9.81$ meters per second squared to find what minimum speed you need to run at:
$$s^2 \, \cot{\theta} \, \cos{\theta} \, w\ell\rho = pg$$
$$s^2 \times \frac{\left(0.2 \times 1.225\right)}{\sqrt{2}} \frac{\mathrm{kg}}{\mathrm{m}} = 778.45\ \mathrm{N}$$
$$s = 67.0332 \frac{\mathrm{m}}{\mathrm{s}} \approx 150\ \text{mph}$$
There are a great deal of things I haven't considered here, like the amount of body weight your feet are holding up by virtue of running, pressure changes along the vicinity of your body, etcetera. But you can always just slap on some safety factors and run three or four times as fast, since your speed would reduce back to the liftoff value (if not less) if your feet were lifted off the ground. 707