Rest Issue

 So I'm training for a 1/2 marathon (although I'm only scheduled for a 10 miler right now), I run 4x a week and do upper body and core the other two days.  Now I've started riding again which means I"m often running in the morning and riding horses in the evening (or vice versa).  Since riding is low impact I'm wondering if it's ok that I'm working my legs this much?  Should I dial back the running to 3x a week or should this be ok?

My legs are still too weak for me to do more than 30-40min. of riding but as I build of strength it will probably go to about an hour.  Am I setting myself up for an injury here?  Both of these things are very important to me and I don't want to give up either!

Riding horses actually works your hams and glutes as well as core... so that is probably why it is so tiring, particularly if you go above a walk.
I'll have to let the pros answer about rest etc as that is an issue for me, knowing when I "need" to rest and when my whiny mind is just "wanting" to rest

 I am printing this for my teen equestrian daughter.  Thanks!  She gets so sick of everyone telling her riding horses is just like sitting in a chair.   A boy recently told her riding isn't a sport.  She replied, "jumping and dressage are in the Olympics, unlike football"   lol.    

 And it's the only Olympic sport where women and men compete against eachother on equal footing!  The problem is, if you do it right it looks effortless.  but alas it certainly isn't as my abs and hips can tell you!

The fastest way to dissuade folks of that notion is to take them riding, lol.  Seated trot without stirrups followed by posting without stirrups is the toughest exercise I've ever done in or out of the gym.  I had an equitation instructor  who would put most drill seargents much less personal trainers to shame. 

 NO kidding!  I tried to do a posting without stirrups the other day and thought I might die.  As a child my trainer would have us do entire lessons (including jumping) with no stirrups and I did it.  I think one time around the indoor now and I'm done.  Hell my abs have a hard time coping with just a canter right now. 

I have my first dressage lesson on my new horse (leased not owned) on Sunday. I figure I will be in a world of hurt on Monday.

My advice would be listen to your body.   There really are no rules where cardio is concerned other than stretch first, stay hydrated and don't push to injury.

There are days I go for a 4 mile run and then do something else-but I do know when to say when.