Everything depends on the lighting.
Without knowing that, we can't tell you what to do.
What exposure and camera settings are you using now? That will at least give us a starting point.
What you want and what you can do are two different things.
LOW light sports photography depends very much on having the right gear.
In LOW light, FAST glass wins.
Ditch the 100-400/4.5-5.6, and get closer with a FASTER lens. A 70-200/2.8 or a faster prime.
Your 70D maxes out at ISO 12800.
IMHO, that is not high enough for LOW light photography.
You probably need a camera with a higher max ISO of 25600, or higher.
A camera with a higher max ISO can only make up so much for a slow lens.
At some point, you may/will need BOTH, a high max ISO AND a FAST lens.
The body in profile (as you pic) is deeper than a body head-on.
You need more Depth of Field (DoF) for a body in profile.
A shorter lens at the same aperture will give you more DoF.
There are DoF calculators that you can use to see this.