I just started a whole new approach. I have switched to 4 meals a day. Changed from 2x a week total body lifting to 3x split routine. And changed from traditional cardio running to HIIT.

I did the first 4 x 30 second intervals. This was amazingly difficult. I was thinking 4 would be way easy. The first one got my attention and the fourth had me saying: "no way I could do 5". I have not done any "sprinting" (hey I was going as fast as I could - but slow-sprinting might be more accurate) in years. How fast will I adapt to this workout? I'm 46 years old. Is that too old for this kind of stuff?

First, congratulations on what you've been doing and for taking on the HIIT. Second, no, you are not too old. No way! I'm 59 and have a few medical issues that limit me to low impact HIIT on my NordicTrack elliptical (which I respectfully call "The Terminator.") I've gotten such wonderful results with the HIIT that I will be starting strength training in the next week or two, depending on how soon I can get with a trainer.

HIIT was really hard when I started and to tell you the truth, if you do it correctly by increasing time, it does not get any easier! The good news is, IT WORKS!

Try the HIT of 15 seconds on the 45s and and build up, finish what u can't get in HIT time with steady rate cardio that u can do. For sure only on none lifting days with the HIT of course.
I am going on 46 this year and I do them. You will get there no worries, but they are great. You know u busted some cells.

bu

Yup, I'm 44 and HIIT what I do most often for my cardio. It works - burns more calories than anything else, and makes me know I'm alive (every breath is appreciated)! Just once a week then a good hike on the weekend, the rest is weight training for 1 hour 4 days a week. My shape is changing almost daily...

Gotta chime in here, too. I started true HIIT (15sec/45-50sec intervals) 2 weeks ago, and man it kicks my butt. But in a good way, I do it on my stationary bike, and I found my weekend mountain biking gettng a little easier because of it.

I just got my mom doing it......she's 58, and she has a love/hate relationship with it, too.

Ok, I did the second day of 4x 30. It may have been a little easier. If the first day way say 10 on the difficult scale. The second was about 9.95! At least this time my jaw did not hurt. I guess I was so "stressed" when I was running I got tension in my jaw. How do you do 15 of these? I guess it is always just on the edge of what is possible.