Lucky you -- Crape myrtles happen to be one of the most easily renovated shrubs/trees.

They not only tolerate pruning, they actually respond best with serious cutting back, producing more flowers when new growth is encouraged.

Cut those crape myrtles back to four good main "trunks" each, cleaning up everything else -- all laterals, side branches, branchlets, skinny shoots, EVERYTHING.

As it puts out new growth in spring, watch for shoots going the wrong direction and snip them off and pinch to encourage shoots to go into the right directions.

All the new growth of spring will produce the flowers of sumer into fall.

Joe

Or you could train them into single-trunked trees. I like multiple trunks better, though.
Renee

Something important I forgot to mention...

Do this serious pruning in January-February. Not now.

Joe

guru1950 has some good advice, but I've found that merely shaping the crepe myrtle as you would a hedge, still gives a lush flowering. When my tree gets too tall for my 6' ladder, it should maintain it's nice shape atop four clean, straight trunks.
A crepe myrtle can get quite tall, given the opportunity. I hate to see these lovely, hardy trees near cut in half each spring. Many call it "crepe murder".
cora in Florida

Here in California, we take adavantage of crape myrtle's bloom-on-new-wood habit by encouraging as much new wood each spring as possible. Serious pruning helps that. My advice given previously refers to a one-time renovation; I'm not suggesting hacking back the crape myrtle EVERY year. But cutting out piddly growth each winter makes for a shaplier, more graceful tree.

Also here in California, most good gardeners frown on whacking small trees into balls, cones, hedges and such. We especially like the beautiful trunk structure and bark of crape myrtles and do what we can to show that off.

We're also fortunate to have access to a wide selection of crape myrtle cultivars -- some do get to be large trees (40 feet or so), some are small trees (15 to 20 feet or so) and some are even shrubs ("myrlettes"; under 6 feet).

Joe

Crepe myrtle are certainly tolerant of pruning, both good and bad. Part of the beauty of Crepe myrtle is the beautiful color and shape of the trunks. For most locations pruning to support multiple trunks is the most attractive. The amount of bloom for most species will be directly proportionate to the amount of sunshine they receive. They should not have to reach for the sun. Al

There are many hybrids which range from small ground cover to small to medium shrub, large shrub, small tree, etc. Mostly we just see the Tree size ones here and in the Nurseries. If you have a true shrub type it will top out at less than 5 feet, I have several which I can't see getting over 3 feet even without pruning.

What's the point... In my experience the shrub ones do not have the pretty bark, and so are better not pruned to show their legs so to speak...

I have dug some up (nasty chore as they have really thick strong roots which seem to go almost straight down) to move them (amazingly most have survived - did this in winter), and have had the roots I left in the ground re-sprout... talk about shovel pruning...

Chad