VO2 Max/ Zone 5:  
This workout will increase your VO2 max and reduce your chances dying.

Warm up/ Tissue prep/ Core
3 mins of gentle cardio pulse raiser, use the same modality you are going to use in the workout.

Core:
McGill Sit up 5-30 seconds x 4 hand/ leg combinations 
Side plank max duration e/s, scale to use your knee if needed 
Bird dogs x 10 
Have a stretch
Jump back on the cardio and build up to zone 3-4 for a couple of minutes. Building up here makes it easier to get to zone 5 quickly when you start your max intervals.

Main Effort, VO2 max builder
4 minutes of Zone 5 as hard as you can go, 4 minutes recovery.
The first round is the worst. Keep going! 

Top tips:
1. Find a friend to suffer with. Makes it much easier when you can see someone else suffering as much as you are.
2. Know your zone 5 HR range and have your HR visible as you are working. For me, using a watch with a chest strap means I can put the watch where I can see it otherwise I tend to ease off and let my HR drop into Z4.

Scaling: 
Small: 1-2 rounds. 
Medium 2-3 rounds. 
Large 4-5 rounds
XL 6 rounds
If you do fewer than 6 rounds, consider dropping intensity to Zone 2 for the remainder of this 48 minute workout.

Warning:
This is a high intensity workout that will cause considerable fatigue. You have to earn volume.
If you are new to this kind of training, push for the highest intensity you can manage, but limit the volume, this will limit the depth of your fatigue.
Start with the Small or medium scaling. A smart approach might be to start with one or two 4 minute reps this week and add a rep each week until you are doing all 6.

You need to put this workout into the context of everything else you're trying to train on the subsequent days of the week. If you jump in and do 6 reps without having built up to it, I don't doubt you could do it, but your recovery will likely spank you for a couple of days meaning you should be on zone 1 recovery workouts + yoga until you are fully recovered.

The typical newbie will ignore the need for full recovery and just smash straight into the next workout, and the next and the next, gradually degrading themselves until they hit a wall of fatigue at around week 3. Then they stop, get a cough or a cold and feel terrible.  Not smart. We've all done it, some of us many times (some of us are slow learners and refuse to believe we're not 21 any more). Modern devices like Garmins will tell you your recovery.

Be aware that fatigue does not work like a straight multiplier of intensity x duration. It is more like an exponential curve. If you double the volume at a high intensity, you get way more than double the fatigue.

Photo by Jon Tyson via Upsplash