Like any impact movement, when the stabiliser Muscles aren't engaged or are weak or fatigued, the joint can be compromised.
Good point. So much so, that I put on a pair of socks and tried it on a wood floor just now, sliding through the movement. I only did a few reps to see if it was feasible, and it is not how I did it this morning. When I do intervals again next week, I’ll try it both ways and see how the intervals compare.
I can see what your trying to do: 1. Be time efficient, H.I.T and H.I.I.T. 2. Program Cardio that doesn't fatigue Muscles before H.I.T. Have you tried Sprinting on the spot for 1 minute? Use some soft flooring of course.
What I have been doing up until now, and will continue to do, is a bit of quasi-HIIT right before my HIT workout. Quasi, because if I went all out, then it would compromise the resistance work. But it gets the blood flowing, since I work out first thing in the morning. So the quasi-HIIT consists 120 air squats at max speed, which take me about 80 seconds to do, immediately followed by 2 ab exercises for 40 reps each. I then take less than a minute rest and do my leg set. I prefer to do the air squats over any other movement as the pre-HIT work for 2 reasons. First, it works the legs, which are the biggest muscles in the body. And, second, I only do one set for upper legs, so it serves as a weak "pre-exhaust" and warmup for the leg set. I wouldn't do a true HIIT workout on a resistance workout day, because I think it would compromise the HIT. And it would be overkill if I really went all out on both. At least for me. Yes, I thought about running in place, and even tried it for about 10 seconds just to get a general feel for it, but it didn't appeal to me. Plus, I like when there is more contraction of the working muscles. However, several years ago, while working out in the gym, which I was then doing in the late afternoons, I would do my cardio right after the resistance work. I had read about burst training online (essentially HIIT), and tried it on the treadmill. If I recall correctly, I angled the treadmill at 15 degrees, but I don't remember the speed I set it at. And then I did 3 bursts of 40 seconds each. I don't recall exactly how long I rested between the intervals. But I do remember that it was annihilating! One time, the person on the treadmill behind me said he was worried I was having a cardiac event while I was resting between intervals. I was breathing that hard. I would probably do such sprints if I already had a treadmill at home. To your point no. 1, yes, I do prefer the efficiency of both HIT and HIIT. I never, ever liked doing steady state medium intensity duration cardio. It was always the broccoli on the ice cream for me. For years. And it was mind numbingly dull, even when my breathing became labored. I really like the challenge of going to my very limit, and getting there fairly quickly (i.e., a set rather than an "event"). That can never get boring.
Read the book. HIIT can improve VO2 max to a greater degree. It can accelerate the increase in mitochondrial content more rapidly than medium intensity steady state cardio. Athletes have used intervals to break through plateaus and improve performance. So how many reps do you do? What is "many repetitions" for you? And just to clarify, the idea of intervals is more a matter of duration under intensity rather than reps. As to form, my own opinion is that not all exercises are well-suited for HIIT because of the need for speed. That's why the best HIIT movements are very basic, in my view. For resistance work, I also like to keep it fairly basic, focusing on deliberate and correct form. If your form goes bad, you're not doing it right. I know, because I had done that for years when I was younger, and I paid the price. Going hard doesn't mean your form has to suffer; you just have to go to failure in good form and not resort to body English.
It depends on the exercise. For example, Upright rows using just the bar as resistance which is attached to the back of a Soloflex machine -- maybe about 200 per set until I feel I can't do anymore and holding the last rep a few seconds for isometric contraction. Inverted rows with bodyweight as resistance -- maybe about 200 per set until I feel I can't do anymore and holding the last rep a few seconds for isometric contraction. Abdominal wheel moving to the right or left, but not straight -- 23 minutes which is around 500 reps. This is not to failure, but it's not too far away. I don't try to do the movements fast, so it's not the same as in the video, but they are still not easy to do at the end.
If you’re trying to build strength, then I think 200 reps are far too many. I’d stick to the 3-20 reps range if I were you. Too many repetitions can shift the focus away from stimulating fast-twitch muscle fibers towards slow-twitch fibers. Doing fewer than 20 allows for the slow-twitch fibers to sequentially fatigue and thereby activate the important and larger fast-twitch motor units. It is the fast-twitch fibers that are the first to go in the case of age-related sarcopenia. They are the ones you want to build up and preserve.
My goal is to stay fit without getting hurt, and using lower resistance with higher reps seems to work for me. Besides resistance, I also do aerobic exercise (81 minutes of high-cadence, low resistance pedaling on an exercise bicycle) and walking. I know it's against conventional wisdom, but I generally do the same exercises every day (unless sick or hurt). This might be relevant. https://www.humanlocomotion.com/five-simple-exercises-to-prevent-age-related-muscle-loss
Interesting. The 60-rep study appears to be something of an outlier, and one I've never even heard of. The same link cites studies that show favorable results using lower reps as well. And by lower, I mean 15 reps or so, which is really not low in the scheme of things. I guess we'll each stick with what feels right for us. If you like it and will keep doing it, and you're getting the results you want, then that's what you should do.
Do 5x1 minute sets of power snatch or jerks (with shallow catch) and tell me there is anything harder in life.