I'm just going to say it... this workout isn't for everyone.  You need 90 minutes, a wicked playlist, and the most motivated attitude you can dig up!  It's tough. 
You also need: a treadmill and some floor space or an area outdoors with a hill to run up and down.  The workout is written for a treadmill, modify it accordingly if going outdoors!

3 km run at 6.5, will take under 16 minutes.

100 lunges

10 minute run doing the following:
6.0 1 minute
7.5 1 minute
6.0 1 minute
7.5 1 minute
6.0 1 minute
7.0 1 minute
6.0 1 minute
7.0 1 minute
6.0 1 minute
7.5 1 minute

100 explosive calf jumps (think jumping rope but higher and a little slower!)

10 minute run of the following:
Incline of 6
4.0 1 minute
5.5 1 minute
4.0 1 minute
6.0 1 minute
4.0 1 minute
6.5 1 minute
4.0 1 minute
7.0 1 minute
4.0 1 minute
7.5 1 minute

100 push ups

5 minute run of the following:
Run at a steady state of 6.5 but alternate incline from 1 to 3, back and forth each minute.
5 minute run of the following:
3 incline, run alternating between 6.0 and 7.0 each minute

100 squats

3 km run at 6.5, should finish in under 16 minutes.

In total, it's an hour of running plus however long it takes to do the interval exercises.  

Take breaks when you need them!  You will feel like amazing when you are done!  It's worth it to push through and finish - because there's NO QUITTING!
 

I haven't worked out in 10 days due to Christmas coming early, getting sick and doing some travelling. It just never worked out - which is pretty rare for me, I do try to fit it in when I can.  Especially when you only need 15 minutes to get a solid workout in.

Back at it today though.  Definitely felt the first three minutes as my body remembered how to work.  I struggled with the push ups, which are a strength of mine.  

Let me know how it works for you!
TOTAL WORKOUT TIME:
27 minutes or
13.5 minutes per circuit


Circuit 1
30 second intervals with 10 seconds of rest.
1st round.  Do each exercise twice (back-to-back).  Then before you move on to the next exercise you do two rounds of skipping.  For the first round of skipping do regular skipping (for a calf workout), the second round do high knees.

2 frog jumps, then 2 push ups.  Add difficulty by bringing your elbows to your sides! (remember do this exercise for two intervals before moving on!)

2 rounds of skipping

Squat with weighted shoulder presses (hands at shoulders, press hands overhead towards the sky). Hands lower back to shoulders.  Squat.  Bring your weights down to floor while squatting down.  Come back to starting position.  Do this round twice!

2 rounds of skipping

Elevated Push Ups (feet on a stable raised object - such as a couch or chair).  Do two intervals!

2 rounds of skipping

Chair Knee Raises with Squats.  Stand on one side of a chair, step the leg closest to chair up onto chair.  Bring other knee up towards chest.  Step back down to ground.  Squat.  On the 2nd round do the other leg.

2 rounds of skipping

Lunge Jumps

2 rounds of skipping.

Circuit 2
30 second intervals with 10 seconds of rest.1st round.  Do each exercise twice (back-to-back).  Then before you move on to the next exercise you do two rounds of jumping jacks.  For the first round of jacks do touch the floor jacks, the second round - regular jacks.

Crab Push Ups.  Sit on your glutes, hands under shoulders, fingers towards toes.  Lift glutes, heels under knees.  Weight on 1 foot, flip your body into a plank position going that direction.  Do one, 1-legged push up.  Flip back.  Do other side.  Remember, same deal as last circuit - do this exercise for two intervals!

2 rounds of Jacks

180 degree Burpees!  A complete burpee but add a 180 degree squat jump at the end of each burpee.
Do this for two intervals!

2 rounds of Jacks

Isometric Plie Squat with Forward Raises.  Holding a plie squat (same as a sumo squat - feet are turned out 45 degrees, knees follow the middle toe), do forward raises.  2 rounds!

2 rounds of Jacks

2 push ups, roll, Jump up into a squat.  Feet together.  Hop as far as you can the same direction you just rolled from.  Side Lunge.  Hop back, feet together, side lunge.  Do this for two rounds!

2 rounds of Jacks

Isometric scissor crunches with hands raised.  Lie on your back.  Lift one leg six inches off the floor.  The other leg extends towards the ceiling.  Hands are by your hips, six inches off the floor, palms facing down.  Crunch your shoulders off the ground.  This is the position for the exercise!  Now the exercise is to simply pulse crunch in this position!  For the second round, switch your legs!

2 rounds of Jacks

And you are DONE!  

Got this workout from my fav workout guru!  

15 minute workout

The first 8 minutes consist of:
16 rounds of 2 intervals of 15 seconds, no rest for the entire 8 minutes!

1st exercise: Mountain Climbers on medicine ball - hands on medicine ball (I used a 12 lbs).  You can do the mountain climber on the ground as an intermediate modification or standing up as a beginner modification.

2nd exercise: Lunge Jumps holding medicine ball (or weight, if you have that more accessible).  Modification: no weights or medicine ball.  Impact modification: step the lunge, don't jump.

The next 4 minutes consist of:
1st exercise: 10 plie squats with knee tucks to overhead medicine ball.
Description:  Stand in plie squat (feet turned out 45 degrees, knees over ankles).  Knee should line up with the middle toe.  
Have a medicine ball or weight and lift overhead.  Straighten your legs and lift your right knee and bring the medicine ball/weight down towards your lifted knee.  Sink back down into plie squat.  
Do 5 reps on right, then 5 reps on left.


2nd exercise;
5 left leg squat
5 right leg squat

Repeat these two exercises 4 times (takes about 4 minutes!)

Calf Raises:
Standing on a step, toes on edge (use a stair):
16 calf raises on both feet (I had 15 lb weights in each hand)
16 calf raises on left foot (I had one 15 lb weight in right hand)
16 calf raises on right foot (I switched the 15 lb weight to left hand)
Repeat individual foot raises adding a pause at the top of each rep.
Then do 16 calf raises on both feet again (I had 15 lb weights in each hand again).  

20 squats, 8 squat jumps – fast squats and fast squat jumps
20 side to side lunges – fast, 8 sumo jacks (jump feet out into wide stance and squat down, feet turned out 45 degrees knees follow midline of foot)
20 forward lunges

(in all sets above, one foot equals one rep)
Repeat 3 x

Beginners mod for above:
-remove the squat jumps in the first exercise set.
-remove the sumo jacks and replace with half jacks (step one foot out at a time to the side)

Standing on a stair edge, with or without weights.  Beginners, do not use weights.  Intermediate try 5 lbs in each hand.  Advanced, try 8-10 lbs in each hand.  Extreme-ists: try 15-20 lbs in each hand.

Calf Raises:
Both feet – 16 raises
Left foot, 16 raises
Right foot, 16 raises

Hamstrings: lie on floor, bend knees, lift glutes.  Raise left leg and extend, keeping knees and thighs parallel to each other.  Lift and lower glutes working the hamstrings of the right leg.
Do 12 lift and lower on right leg
Do 12 lift and lower on left leg
Do 12 with both feet on floor, lift and lower glutes
Repeat: 2nd round add a pause at the top of the raise after each raise.

Wall Squat: back against the wall, slide down until knees are at 90 degress.  Hold this position for 60-90 seconds.
Advanced modification: add bicep curls

Core:
Plank sequence:
30 seconds in freestyle plank (your choice!)
Rest for 10 seconds
Repeat 4 times, feel free to change the plank style each time
Side Plank left – 30 seconds, rest for 10 seconds – do 3 times.  Then do on right side.

Lie on back, legs straightened.  Palms under glutes.  Lift legs 6 inches off floor.  Hold for 15 seconds.  Rest for 10 seconds.  Repeat 4 times.