
My Canon indoor sports lens recommendations ...
Canon EF 200mm f/2.0 L IS USM Lens
(large, expensive, awesome image quality)
Canon EF 135mm f/2.0 L USM Lens 
Canon EF 100mm f/2.0 USM Lens
(great value)
Canon EF 85mm f/1.8 USM Lens
(great value)
Canon EF 35mm f/1.4 USM Lens 
Canon EF 85mm f/1.2 L II USM Lens
(slower AF, wider aperture)
Canon EF 70-200mm f/2.8 L IS USM Lens 
Canon EF 70-200mm f/2.8 L USM Lens 
Canon EF 24-70mm f/2.8 L USM Lens 
Canon EF-S 17-55mm f/2.8 IS USM Lens
(EF-S mount only)
Basketball, volleyball, soccer, gymnastics, wrestling ...
At these events, the indoor available light action sports photographer encounters some really tough photography situations.
The lighting at best is usually dim.
The photographer is often committed to be at one location - and the participants move around.
And they usually don't move slowly.
An indoor sports lens needs to have a very wide aperture and it often needs to focus very quickly.
A fixed focal length (or prime) lens is often a good choice.
Select between the recommended fixed focal length lenses based on the focal length you need and your available budget.
The 85 f/1.2 L II does not focus as fast as the rest, but it has a wider aperture than the others.
It is one of my favorite lenses.
And if you can use 200mm of focal length, the Canon EF 200mm f/2.0 L IS USM Lens is simply awesome.
A fixed focal length lens has the obvious disadvantage of not being able to change focal lengths.
Even if the photographer knows where their position will be or is able to adjust to the optimal location,
the participants are often moving over a large area.
For this reason, a zoom lens has a big advantage.
The results will require less cropping - leaving more resolution in the final image.
The disadvantage a zoom lens has in an indoor action situation is the maximum aperture - f/2.8 is the widest Canon zoom lens currently made.
Because of the typically-poor indoor gym light levels, expect to need ISO 1600 or 3200 to get minimally acceptable shutter speeds (1/500 or higher) in all but the best-lit venues.
High ISO of course means more noise in your results.
The higher price tag is another frequent disadvantage for the zoom.
Of course, versatility cannot be ignored.
The Canon EF 70-200mm f/2.8 L IS USM Lens
and the Canon EF 70-200mm f/2.8 L USM Lens
are two of the best indoor sports lenses available.
They make excellent general purpose telephoto zoom lenses and can be used for outdoor sports as well.
The Canon EF 24-70mm f/2.8 L USM Lens and
Canon EF-S 17-55mm f/2.8 IS USM Lens (EF-S mount only)
are excellent indoor sports lens choices when shorter focal lengths are needed.
If you have court-side access, you may need these wider angle focal lengths.
Check my full reviews to see which lens(es) are best for you.