My new favorite dumbbell leg exercise - DUMBBELL SUMO SQUAT! If you try it, remember to stick your rear end out like a sumo wrestler so that you don’t put excessive pressure on your knees (no really - careful with your joints!)
Anyway, I added this to my lower body weight routine the other day and it seriously is a butt and thigh blaster. Add this to your low body weight day, and then when you do cardio (I do cardio 6 days a week, either by itself or interwoven into weights as intervals) do this exercise without dumbbells… FAST. Then, when your legs or butt starts to burn a little bit from lactic acid buildup, hold the squat position for 32 counts of the song you have on so you can get some isometric in there. Don’t give up early - it’s worth the payoff!
While you’re doing it, remember that active recovery is the best way to handle your muscles when you are working them out. Have you ever been super sore from a workout, and then you noticed that you got up and got moving around a lot and didn’t feel sore anymore? Active recovery! Your muscles need the nutrients in your blood to repair themselves so get it pumping.
Just don’t over-do it, and remember to eat good, healthy, appropriate food within 20 minutes of your exercise cool down (some carbs with a bit of protein! It will help restore your missing muscle glycogen that you just used… muscles won’t repair well without it and you’ll lose strength and endurance if you don’t replenish! If you have questions, feel free to ask, but I’m gonna tell you right now I either gag down a couple spoonfuls of small curd cottage cheese or drink chocolate milk and gag down a couple spoonfuls of low fat greek style yogurt (low fat has way more protein than normal greek yogurt). On a side note, if you put a couple spoonfuls of greek yogurt in with half a smooshed banana, it’s actually really good. I just barely discovered greek style yogurt, and it’s pretty versatile - you know - for yogurt.
[start rant]
On the topic of over-doing it, I just want to take this moment to point out that a high percentage of people that ‘exercise’ are chronically under-trained. It happens when people ‘exercise’ but they either don’t have the intensity or duration needed to actually do a real amount of good. Under-training CAN result in slight adaptations (tighter muscles or some muscle definition), but it doesn’t really add up to cardiovascular health, higher VO2max, higher lactate threshold, or weight loss. I’m sure you know these people. “I walk for two hours a day and I can’t lose any weight,” or “I get enough physical activity from yard work/house cleaning/wii sports/insert other lameass excuse here.”
Look, every single time I have gained weight in my life I know exactly why it happened. I lost lean muscle mass (due to a new desk job or chronic tiredness from pregnancy or playing WoW for six months…) and then my base metabolic rate (BMR) went DOWN. Suddenly, even though I wasn’t really eating more (excluding pregnancy… biscuits & gravy and pumpkin pie anyone? lol), I still gained weight. I struggled to get my pregnancy weight off and I realize now what I was doing wrong. I thought I could just do aerobics and I’d lose it. Well, not so much. I would have lost it… it would have just taken a long time. Bottom line is I needed to resistance train to increase my lean muscle mass, and do cardio as well. That’s how I lost it, too. That’s how you increase your BMR. Give your body WORK to do - trick it into thinking it NEEDS TONS of energy. In doing so, you’ll get your cardiovascular system healthy and a hot bod. 
[end rant]
SO YEAH. Dumbbell sumo squats on lower body days. Do it - you’ll thank yourself (your glutes will anyway). Sumo squats in cardio - keep it high tempo and keep your butt SQUEEZED lol. You can do ball exchanges. then ball leg curls, then do a set of 4-step side kicks, then front kicks to round off your set so that you can start again
Also, don’t breathe to the beat. LOL. I am SO guilty of doing this. Don’t hold your breath, but don’t pull a me and breathe with the beats (in out in out in out). This can lead to hyperventilation if you are listening to really fast tempo music (like I do), and just really isn’t a great habit to be into. It’s important to get enough O2 (surprisingly enough!). When you are lifting weights breathe out while you do the work (push, pull, whatever part of the lift is the grunty effort part), and inhale on the easier part. DO NOT HOLD YOUR BREATHE WHEN YOU LIFT.
OK I just totally went off on a coupla tangents and in the time it took to write this, I really should have been showering. EW. Final tip of the night - shower right after you workout. PEEYOO - you stink! 