I've been looking through a few of the threads but I'm still somewhat fuzzy on the HIIT and LISS stuff so I've got a few questions.

I plan on keeping pretty fit so would it be ok to do HIIT (30s sprint, 90s recuperation) in the mornings (starting on about 6 minutes and increasing) with weights in the arvo on Monday, Wednesday and Friday, if I did LISS on Tuesday and Thursday afternoons with weights?

I'm 15, 5'6'' and I weigh about 54 kg's so my weights are unbelievably light but I've been trying to do more reps to increase lean body mass, but how many exactly should I be aiming to do? Sorry that these questions are stupid but I'm trying to get a grip on maximising my training during off season so I figure it's worth asking some silly ones :o

I'm a high jumper by the way =]

I've been looking through a few of the threads but I'm still somewhat fuzzy on the HIIT and LISS stuff so I've got a few questions.

I plan on keeping pretty fit so would it be ok to do HIIT (30s sprint, 90s recuperation) in the mornings (starting on about 6 minutes and increasing) with weights in the arvo on Monday, Wednesday and Friday, if I did LISS on Tuesday and Thursday afternoons with weights?

I'm 15 and 5'6'' so my weights are unbelievably light but I've been trying to do more reps to increase lean body mass, but how many exactly should I be aiming to do? Sorry that these questions are stupid but I'm trying to get a grip on maximising my training during off season so I figure it's worth asking some silly ones :o

First of all, off season? Are you active in sports? If so, what sport you are active in will determine how you should train off season.

More reps doesn't increase lean body mass much at all, at least if you passed the 15-20 rep range (even that may be high). What causes an increase in lean mass is heavier weights. And that's not enough either. On top of that you need to eat a whole lot of good nutritious food. If you really want to build muscle, you need to eat more energy than what you spend (your bodyweight should go up).

If you are focusing on building mass, your interval training and other cardio is perfectly fine, but you will need to spend even more time at the dinner table eating. I guess that's the basics.

Very important: At your age I don't think you should take too much notice of what is being done here (bulking/cutting/calorie counting etc.), but instead focus on building very good habits for the future and living a balanced life.

Eating a whole bunch definitely helps. Remember to try to get those meals in 6x a day, at least 5x. Your pretty young and I don't think you should go into that whole counting stuff too much. It's hard since you live at home and you eat whatever you parents make. But you can make some adjustments for your other meals and just eat a crapload. But I'm assuming you have a fast metabolism. Putting more specific stats might help other members give you more detailed advice.

Heck Chicanerous has abused Taco Bell for years and look at his progress.

Just from my experience, LISS helps me with my cardiovascular system. What I mean by that is I don't see a ton of fat fall off by doing LISS, but I do see a HUGE improvement in my overall stamina, beathing, etc. HIIT has helped me immensely with fat loss and raising metabolism. It may be different with you, you'll have to analyze which one you'll wanna concentrate on compared to your goals. I'm trying to build endurance and lose fat, so I split them up, but since I'm trying to lose fat, I concentrate on HIIT alot more. Good luck!

Sorry that these questions are stupid but I'm trying to get a grip on maximising my training during off season so I figure it's worth asking some silly ones :o

There are no stupid questions. We're glad to have you here.

What sport do you play? If you've got the summer to train, you will go back in the fall with quite a vengeance! I bet we can put something together for you.

I'm actually a high jumper. It's frustrating because I need to be able to deal with endurance as competitions can last for a few hours so you're out in the sun for ages but the actual take off and layout is sprinting so I thought a combo of HIIT and LISS would be beneficial. I just have to get motivated to wake up early and actually venture outside :p

Also, I know you should eat quite a few meals a day but I didn't realise people would be suggesting I eat lots & lots :D not complaining at all, only I can't help but fret at the idea of gaining weight, but it's muscle so thats ok?

I'm actually a high jumper. It's frustrating because I need to be able to deal with endurance as competitions can last for a few hours so you're out in the sun for ages but the actual take off and layout is sprinting so I thought a combo of HIIT and LISS would be beneficial. I just have to get motivated to wake up early and actually venture outside :p

Also, I know you should eat quite a few meals a day but I didn't realise people would be suggesting I eat lots & lots :D not complaining at all, only I can't help but fret at the idea of gaining weight, but it's muscle so thats ok?

I was actually a high jumper in high school too. If I knew how to train then like I know now, I would have been a lot better (my best jump was only 5'10).

I think the best thing you can do for yourself this summer is to start training squats. Do you have access to a gym and free weights? This will be the #1 factor to improving your vertical.

For conditioning, LISS and HIIT would also be fine. Short, explosive sprints will also help your jumping ability, especially when you explode off the blocks.