Here is a quick leg workout you can do without any equipment in as much or as little time as you have available. The goal is to do as many rounds as you can until you are burned out but if you only have ten minutes, then simply do it as many rounds as you can in ten minutes. The purpose of this is to give you a wonderful lower body and cardio workout with no excuses to get in your way.
Tabata: High Knees - A tabata is a specific type of interval training. You are working as hard as you can for 20 seconds, resting and catching your breath for 10 seconds and then repeating for a total of 8 rounds (4 minutes). If you are a beginner, you may just want to march in place with high knees but if you are more advanced, you should be running in place with high knees. Swinging the arms and trying to get the elbows up towards shoulder level will increase the intensity whether you are marching or running.
Squats - Place your feet about hip width apart. Bend your knees in an attempt to get your hips down to the same level as your knees. Try and make sure your knees don't buckle in towards each other and that they don't push forward over your toes. If you notice your knees buckling in, make a conscious effort to push them away from each other. If your knees are over your toes, try to sit your butt back as far as you can like there is a chair just barely out of your reach. Stand back up and repeat 19 more times!
Jump Squats - The movement is the same but you are adding a little jump as you stand back up. The best tip I can give you here is to land as quietly as possible. This will help protect your joints by landing softly instead of pounding down.
Lunges - If the jump squats were a lot for you cardiovascular then you can do these lunges stationary. In this case you would plant one foot about two feet in front of the other - this is very much based on height so I can't give you an exact measure - and then bend both knees towards a 90 degree angle and lift back up. Do twenty on one leg and then twenty on the other leg. If you aren't tuckered out from the squats then you can alternate legs. This increases the cardio component which will help you burn more calories. If you are alternating you just continually switching from a left leg lunge to a right leg lunge.
Burpees - If you need help with this, it is best to watch my YouTube video. I break it down step-by-step based on beginner to advanced.
Side Lunges - Again with these lunges, you could stay stationary doing one leg at a time if you are feeling winded or you can alternate if you want more of a challenge. When you step out wide to the right, bend your right knee as much as you can while you keep the left leg straight. Think about the same alignment as a squat on the right leg. You are trying to sit your hips back as low and far back as you can.
Single Leg Bridges - Finally! You get to lay down. Lay down on your back, bend both knees and place your feet on the mat with your arms by your sides. Lift your hips as high as you can and then extend one leg straight out. Try to "glue" the legs together by squeezing the inner thighs towards each other. Now with the leg extended, start to lower your hips back down to the mat and then bridge back up.
Repeat as many times as you can. When you do a workout as many rounds as possible it is called AMRAP for short. This is a great way to track your progress over time. For example you could do this leg workout every Wednesday and just put a little note in your calendar of how many rounds you completed. This will help keep you accountable and see your success. I think it takes us awhile to see results in the mirror so having other ways to track your fitness journey can be very motivating.