HIIT is a variant of a high intensity interval training. Thanks to swarms of "fitness experts" you can come across really bad ideas both on the Internet and at the gym. I have chosen the worst possible solutions which can be found on the Web. Interval training can include running, swimming or weight lifting and mixed exercises (e.g. crossfit).
Idea no. 1: inverse proportions.
Probably due to errors occurring when translating texts from other languages sometimes interval workouts have opposite proportions.
Here's an example:
"An example of HIIT based on running might look like the following:
- 5-minute dynamic warm-up (bending, skipping, jumping, arms swinging, torso twists, jumping jacks, hips circles, etc.)
- 30 seconds of sprint at almost maximum capacity
- 15 seconds of moderate trotting
Repeat steps 2 and 3 five times
- 5 minutes of cooling down and stretching."
What is the problem?
30 seconds of sprint is a very hard work. Sprint means running at the speed of 25-30 kph. This means that even a lousy runner within 30 seconds will do 170 m, and a good one: 200-250 m. Compare it to Usain Bolt who runs 200 m in 19,19 seconds. And after this maximum effort the author recommends only 15 seconds of moderate trotting? How will the next sprint look like? Like struggling up the hill with a 20-kilo backpack. This way HIIT loses its whole meaning.
Even in theoretical perfect conditions a five-time 30-second sprint means covering from 800 to 1200 metres. And that's a lot.
The idea of HIIT is to maintain similar parameters in subsequent approaches. A sudden break of the speed means only that you have started too quickly with a too intensive training. Preparation for intervals means months of regular running. In the end, if you perform true sprints even in the version: 15 seconds of sprint, 15 seconds of slowdown, you will do particularly heavy labour. 30 seconds of sprint and 15 seconds of rest will be reserved for the few best trained high-performance professionals, elite runners. If you are able to perform such a training you are either a fantastically prepared sportsmen or the intensity of your workout is minimal, and your "sprint" is mere running at 16 kph. Well, that's all right, but some do a half-marathon or a full marathon at the speed of your "sprint". The intensity of this work is light years from real sprint.
Idea no. 2: "how about doing a heavy running intervals after a strength training?"
What is the problem?
A high-intensity training can be very rarely combined with a strength training. What is particularly painful immediately after your interval workout is squats, front and back ones, lunges, deadlift, Bulgarian split squats, leg press etc. In some cases, 24-48 h after a legs training it is difficult to simply walk or trot, and you are thinking of a high intensity training? If you do a light weight training of the upper body (small weight, long breaks, machines etc.) you should be able to combine it with intervals.
What can you do?
Immediately after the strength training do a low intensity exercises, for example cardio. But... this is not recommended because it disrupts muscle growth processes (a different signal path) and increases the risk of inflammation and micro-injuries development.
Perform short intervals (5 to 10 minutes) stationary using for example a barbell, dumbbells, kettlebells, a sandbag, TRX or your own body weight. You can do mini-circuits using parallel bars and a horizontal bar. A great alternative at the end of your workout is burpees (squat, kick feet back, push up, return to squat, stand and end with jump) for 20-30 seconds and 20-30 seconds of jumping jacks or running in a place (alternately for 3-5 minutes)
Do an interval training in the morning and a strength training in the evening.
Do a strength training on a different day than running.