In fact, the way most people are encouraged to train is to build up to some decent mileage (at least 20 miles per week) and then mix in speed work, which varies from simply faster runs, to Fartlek (speed play), to intervals.
Knowing this, it becomes obvious why runners fall in love with speed work: they might do a "traditional" training plan and run slow, high volume for 3 months, and see minimal but steady gains. Then they do 3 weeks of sprints and make huge gains! Awesome! But those gains were a reflection of the base work. Think of it like sharpening an old, abused, rusty knife: you don't go right for the fine grit. First, you grind it down, then successively apply finer grits. The knife won't cut a tomato without the fine grits, but if you skipped straight to them, you'd be at it forever.
The other reason one should be wary of HIIT is the increased risk of injury. Especially in running, if you go from couch to sprinting, you're highly likely to be injured. It is important to run slow and often, so that your tendons, ligaments, and joints (not just your muscles and heart!) are ready for the strenuous demands of running.
Similar concepts are often spoken of in weightlifting, where you are encouraged to start with just the bar and work up.
Other than that, yes, HIIT is an effective cardio protocol, and much research has shown that intensity matters when it comes to cardio.
What's discounted here is the full picture of fitness and training: cardio alone isn't sufficient, especially as you leave your 20s and 30s and suffer age-related muscle loss (sarcopenia).
The pretty cool thing about effective training programs is that significant gains, and certainly maintenance of a pretty high level of performance, can be attained on fairly minimal training. Three times a week, 10-20 minutes of cardio, and 30-40 minutes of lifting (less if you stick to big compound lifts) can do a huge amount for general fitness. Some abilities take longer to train -- especially skill sports. But the body is amazingly adaptive to constructive stress.
For 2 months I've been doing 50 minutes of cardio M-F at 6AM before breakfast, before work. So far I've lost about 12 lbs, but most importantly my energy level and focus throughout the working day is vastly improved.
I would like to incorporate strength/weight training into my routine. What would be the best way to go about this? Do I have to stop doing the cardio? Can I do both (as I would prefer to)? Can you point me to some good routines to get started? I posted on /r/fitness but didn't really get any valuable responses.
Another good basic primer: http://www.liamrosen.com/fitness
If you're looking for a good solid strength program, buy Mark Rippetoe's Starting Strength and do the program.
A slightly more varied, and less hardcore program is in Schuler & Cosgrove's The New Rules of Lifting. I find the texts complementary. SS has the better (IMO) beginner's program, TNROL has more complete information on overall fitness and diet.
SS is also going to benefit more from access to a proper gym with power cages, chin bars, and bumper plates (ideally). TNROL can be done largely at home with fairly a bit of equipment.
Once you pick a program and start doing it, re-read the FAQs and basics, then post any specific questions you've got to a decent forum (/r/fitness is pretty good).
No need to give up cardio completely, just swap it for a few strength training days.
I highly recommended it for people with lack of space or exercise equipment
Even though I attended a humble Scottish state school, a lot of the time our PE sessions seemed like something from an episode of Ripping Yarns.
Min 1: 1 burpee... yep, then stand around for 54 seconds.
Min 2: 2 burpees.
Min 14: 14 burpees, you probably only have 8 seconds of rest.
Min 17: 17 burpees, no time to rest, keep going!
Min 18: 18 burpees, but you never rested after the previous 17 so you just keep going!
And so on and so on. You can do it with pushups, squats, etc. It is a great and super-painful way to break a plateau.
Used to do something similar in weightlifting if we got stuck too long at a certain max of some kind. You start at the lightest weight possible and do 10 reps and move up 5 or 10 lbs each set with no rest between them.
You lift each set to failure (easier on a machine so you aren't dropping weight on your chest or head) and as soon as you fail (no more than 10 reps) you or your partner adds the weight for the next set.
When you can't even do a single rep then you stop and start taking weight off and coming back down to 0 again (or wherever you stared, e.g. just the 45lbs bench bar or something).
You'll want to throw up, but it breaks your muscle down so completely it'll scoot past those barriers.
So I think no problem, head down to his lab, and the first sign that something is going to be rough is that his friends are there (other students/guinea pigs) joking about how likely they are to throw up this time. Apparently it's fairly common to throw up after doing the trial properly, but it just doesn't seem plausible. After all, you are only cycling for a couple minutes. Even for a lazy bastard like me, that seemed doable.
I sit there with growing concern as the guy before me finishes his run and staggers over to one of the tables and crawls upon it. He lays there alternately going bright red and white and trembling like a fish too long out of water. He doesn't speak, and doesn't respond when spoken to.
My turn comes and my brother, laughing, takes me over to the stationary cycle where he tells me it has been set to an incline calibrated against my weight/height to cause maximum stress during the all out segments.
I start peddling slowly until he shouts NOW in my ear and then I grab the handle bars and peddle for all I'm worth, elbows and knees flying everywhere. Meanwhile my brother is shouting at me like a drill sergeant and through a combination of naivety and adrenaline I make it through my first 30 second sprint without too much difficulty. At this point my legs are burning quite a bit and I'm bright red with exertion, but otherwise ok. I coast for another 60 seconds and then the yelling starts again. RIDE YOU BASTARD, RIDE!!! I give it my best, but it's a bit harder this time, my legs haven't recuperated from the previous sprint and I am even more ungainly if possible. Twice more we go through the cycle and by the last time my legs don't even seem to be responding to my brain, they feel hard liked they have been pumped full of oh I don't know, blood and acid, and have barely any power to them. My final sprint is so uncoordinated that my brother has to lean on the cycle to stop it from flopping over. Lance Armstrong's testicle was undoubtedly spinning in its grave. A group of my brothers friends cheer me on, however the guy who went before me is still absent.
Finally, I make the end of the sprint, and stagger off the bike. My legs don't work, I feel like one of those floppy inflatable plastic guys they attach to a fan and use to promote used car lots, alternately staggering around stiff and floppy legged. I don't feel too bad yet, and some sort of manic euphoria has hold of me. You see, I tell my brother, some of us are just built out of tougher stuff. He laughs in my face and tells me to go sit down in a corner. I start to repeat my claims of being fine, but suddenly I feel like the earth has dropped away and I am in free fall. He looks at me again and his smile fades and a look of concern comes into his eyes. Seriously, go sit down. Apparently, I have turned an unholy shade of green. I stagger over to a corner, now feeling like I have reached terminal velocity and sort of flump to the floor. Apparently my body is so full of lactic acid or what have you, that it is overwhelmed, and starts wondering if perhaps a good upchuck would help. At this point my vision narrows to about the size of a penny, filled with dancing patterns and lights. I don't throw up but I assume it's only because my body just can't get it together to do that. I am vaguely aware of people standing over me, concerned, calling my name, but responding to them seems like an Everest of a task so I lay there in my flump, thinking to myself: You see? I was right, exercise is a terrible terrible thing. Even 2 minutes is too much. Never ever again. I begin to vibrate softly as every muscle in my body twitches.
My brother leans down and puts his hand on my head and says: "You'll be ok. If you need to throw up, please use the bucket in the corner. Sometimes people just throw up on themselves and it makes a mess. And hey, at least now you know what it's like so it won't be so bad when you come back next week".
I suppose he must have spotted the sort of mad murderous gleam that popped into my eye, because I doubt my mangled bleat of "whaaabastardfuhnextweekafuhcrazy" through nerveless lips was all that intelligible. He laughed and said, "yeah, I have to get two sample points, a week apart! So you have to come back, didn't I mention that?"
I did go back in the end, but I sure as shit didn't pedal all out. So I'm not sure if the body got better aerobics or insulin whatevers, but the brain, the brain learned its lesson.
I'm not sure if this is a vasovagal response or not (http://en.wikipedia.org/wiki/Vasovagal_response) but I have this response also. In fact, mentioning it to my doc won me a full cardio work-up from a cardiologist. I get the response from intense weight-lifting and anaerobic cardio exercise (like what you describe) if I suddenly stop.
If, however, I keep doing very light exercise, I don't "nearly" pass out (I've never fully passed out from it, only gotten to the dim-vision gray-out/dizziness described here, so I think I was close to passing out but not exactly sure).
Did your brother have any opinion on how that compared to a longer period of less intense exercise? /what were their findings
By the time I was done I was similar to yourself. I dont' even remember the last part of the test, just that I somehow did it and ended up in a chair with folks around me having that look that makes you wonder if someone should be dialling 911. They hook you up to a machine after the test to check your blood pressure and what not (I guess to avoid having people pass out afterwards?). I had to wait there for a 1/2 hour because the damn thing kept thinking that I had no pulse, which didn't help everyone's expressions (I was so out of it I thought it was funny)
Thankfully I passed with two seconds remaining, but the ole brain reinforced the idea that maybe doing police work just wasn't in the cards for me
It's also interesting to read about the genetic test for aerobic fitness progress. I wonder will the future allow better tailoring of health care where genetic evidence helps people get far more precise nutritional and exercise profiles? For example, if you are a non-responder you might be hurt by too much exercise, which is non-productive and which makes you hungry.
Do they have a 'HIIT mode' on exercise equipment yet? Attempting to do the intervals on stationary bikes or treadmills while mashing the down button after a sprint is difficult.