I started HIIT a couple of years ago and kept going for about 1.5 years. In that time I saw very minor improvement, I was injured frequently, the training was very uncomfortable and it wore away at my will to improve
I eventually decided to try going to the gym more frequently but with a much lower intensity. I ran slower and without an incline but I would run without stopping, I also used lower weights and much higher reps and stopped when it started to hurt
Anyway I've had a gradual improvement since then and gotten much better. I was just talking with my sister about it and she said it's nonsense, HIIT is the best for everyone, things like natural levels of endurance of high twitch muscle fibres are irrelevant and if I switch back to HIIT I'll get huge improvements in a matter of weeks. She said I should've pushed through the pain and tearing muscles only makes them stronger and then got mad and refused to talk
My sister has always been a lot more athletic than me and on the one hand I'm wondering if I really am just naturally weaker and I need this lower level of training to progress, or if my sister is better because she pushes herself through the pain and I'm just too weak willed. I'm reluctant to give up this low intensity high frequency training I have been doing since it's given me such amazing results, and I know the HIIT didn't work for me and was very uncomfortable and made me dread exercising, and I don't have the pain tolerance to keep going with torn muscles and it worries me that I'll only get gradually worse, especially since pushing through the pain using painkillers only seemed to make my injuries even worse and didn't make me stronger
I don't want to sound like I'm just making excuses. And maybe I was doing HIIT wrong and all the gym instructors were incorrect in what they showed me. I just know that this kind of mild training has gotten me results and the HIIT didn't, whether I was doing it correctly or not.
What should I do? Should I give HIIT another try and maybe visit another gym to see if they can show me a better way to do it? Is there any scientific explanation to explain why one person might fail to get results with HIIT but get good results with low intensity and high reps, distance, time, number of gym sessions etc? Is pushing through the pain really so much better than training til you ache a bit but no farther?