How Interval Training Works – Lactic Acid, Oxygen Debt, and Recovery

September 10, 2009

I talk about different forms of interval training and circuit training on this blog on a regular basis. I tend to shy away from discussing things like lactic acid and oxygen debt, because these are “zone out” terms.

Many people tend to skim when blogs begin to read like Biology text-books. I want to explain how intervals work and go into more details, without making this a mind-numbing technical article.

interval training for fat loss

[A skull engulfed in flames smashing a guitar? I have no idea how this fits in with the article …maybe the burn from lactic acid?]

Why Do We Push, Then Rest A Little, Then Push Hard Again?

Since intense exercise burns a lot of calories, why don’t we just push hard the whole time instead of mixing in periods of active rest?

I mean…if you have 15 minutes to do some form of training aimed at fat loss, why not spend the whole time running hard on a treadmill or exercise bike? It will make sense when I explain lactic acid, oxygen debt, and their roles in fat loss.

Increase Oxygen Debt For Maximum After-Burn Effects

When you do a sprint or an intense circuit, your body can’t supply oxygen at a rate fast enough to fuel the muscle. Another energy system (anarobic) has to kick in to “assist” with providing energy to the muscle.

After the intense effort is completed, your body has to basically repay that “borrowed energy”…it owes oxygen to get those muscles back to their normal state.

The more energy your body borrowed during an intense effort the more oxygen it owes…this is called Oxygen Debt.

A Large “Oxygen Debt” is Key in Boosting the Metabolism

So after an intense effort like a sprint, you continue to breath hard and your heartbeat is raised…this is your body’s way of repaying the oxygen debt. Does that makes sense?

Your metabolism is operating at a higher rate (breathing and heart rate)…to repay the oxygen it borrowed. I’m simplifying this a bit, but this is the basic principle.

The larger the oxygen debt created by your workout the longer it will take to repay it…with the benefit of more calories burned for a longer period of time after you are done exercising.

The Best Way to Create a Large Oxygen Debt

To create an oxygen debt, the effort has to be intense enough to switch over to “borrowed energy” -or- anaerobic mode.

Sprinting or proper resistance training is the way to accomplish this. The reason things like intervals, kettlebell circuits, and other forms of resistance intervals work so well is that you are performing the next intense effort before “catching your breath”.

The combo of intense efforts while already breathing hard, is the best way to insure maximum oxygen debt. This is one of the reasons why interval training is ideal for boosting the metabolism.

The New Way of Looking at Lactic Acid

Lactic acid is the result of intense effort and coaches used to tell athletes to avoid training in a way that produced too much lactic acid. Professor Thomas D. Fahey of California State University thinks differently…

“The body converts glucose, a substance removed from the blood only sluggishly, to lactate, a substance removed and used rapidly…Using lactic acid as a carbohydrate middleman helps you [metabolize] carbohydrates from your diet, without increasing insulin or stimulating fat synthesis.”

So…lactic acids helps your body burn more carbohydrates and ultimately more calories…assisting your weight loss efforts.

The Best Way to Increase Lactic Acid

Again…An intense effort that can’t be sustained for long is what it takes to increase lactic acid. It makes sense you would want to do a few of these intense efforts.

So, you would do an intense effort, rest a bit, then do another intense effort…sound familiar? This is an exact description of interval training.

Doing the Intense Part of the Interval With Little Rest

We already talked about why pushing hard before catching your breath all the way was a way to increase oxygen debt, it is also a way to increase lactic acid. After an intense effort you accumulate a bit of lactic acid in the muscle and then your body begins to remove it.

You want to perform another intense effort before the body is recovered to assist the body in accumulating more lactic acid in your muscles. With enough intervals you will have a buildup of lactic acid…and because of this, your body will be able to burn more calories than normal after your workout is finished.

Proper Intervals Increase Lactic Acid and Oxygen Debt

So the reason why a trainer like Craig Ballantyne recommends short rest after his Crazy 8 Body Weight Circuit is to insure that you increase both lactic acid and oxygen debt.

This is the same reason that you don’t rest 5 minutes in between intense efforts when doing HIIT.

A proper interval training routine should be just enough rest to be able to push hard for the next intense effort…and you should be breathing pretty damn hard when the whole series of intervals is finished!

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{ 50 comments… read them below or add one }

Helder September 10, 2009 at 5:42 pm

Perfectly explained in a simple way, nothing to add, excellent post to help anyone understand how things function without boring people 🙂

Adam September 10, 2009 at 5:49 pm

Great Post Rusty!! I love interval training, its so good. Since dropping cardio and starting intervals i’ve gone from staying around 12% bf down to 8%. Also Ive just finished at the gym bout an hour as as a one off I thought i’d test myself and I did 5 different Tabata interval one after another. I did 4 mins of burpees, 4 mins on the rower, 4 mins on the bike, 4 mins on the cross trainer and 4 mins on the treadmill. It was amazing and I feel great!! Might do this more often.


Avery September 10, 2009 at 5:51 pm

Interesting post – Ironically, I’ve been hearing a lot of buzz about proper breathing techniques before, during and after strength training routines. I’m not well versed in the details but it has something to do with “in the nose out the mouth” (yes, I know…Karate Kid) along with timing and pace of breathing during the routine. Do you have any input or advise on breathing techniques that can help maximize recovery?

Adam September 10, 2009 at 5:51 pm

also was the hardest workout Ive done in years, I was nearly sick by the end of it haha reminds me of when we used to do hill sprints for rugby lol

Donkey Lips September 10, 2009 at 6:43 pm

Great article Rusty. I enjoy doing sprints on soccer or football fields. I have an exact routine I do and increase it every so often. I do all sorts of other interval training but I am convinced that nothing gets a person more ripped than tough all out running sprints. Rows, BWC, Jump Rope, Bike, Treadmill are all good too and good for mixing it up but sprinting on a track or football field is best in my opinoin. Of course as I’ve learned from your blog diet is the most important part. I love that my workouts are shorter, less often, more convenient (done at home or outside instead of the gym) and more fun because of all the variation than they were before I started reading your blog. Plus the results have been mind blowing. Thanks so much as always for everything you’ve done. No go to Oaxaca in Ballard already and get some of the best Mexican food you’ll ever eat.

Josh September 10, 2009 at 7:31 pm

I had been thinking I would go into “hibernation mode” and do a couple of times a week 5×5 routine as I had made some awesome progress over the summer using intervals and such. Well I dusted off my 53lb KB and worked this routine today.. I am going to scrap the 5×5 for now! Wow! I thought I had worked intervals to death and was in great condition. The stomping that this workout gave me bought me right back to reality! It is a whole different level of conditioning. I also really love the one stop get your strength, cardio, flexibility, and mental toughness all in one workout!

Michael - The Fat Loss Authority September 10, 2009 at 8:21 pm

Good points Rusty.

I’ve been experimenting with 30 second rest periods in my resistance training with higher rep ranges (12-15). The oxygen debt created is a wicked feeling. Honestly, I can’t imagine working out like a bodybuilder any more (2 minutes between sets), just doesn’t make sense to me anymore.


Dan September 10, 2009 at 9:24 pm

Interesting read Rusty. It is nice to know the science behind the effectiveness of intervals.

No updates on your tropical vacation? I remember you saying something about Costa Rica. With the cold weather approaching over here I’m about ready to start looking at Caribbean spots.

BetterBody September 10, 2009 at 9:27 pm

This is an amazing post. I love it when this “nerdy” stuff is explained in easy-to-understand terms. It helps when teaching people because you can explain it from a different perspective.

Tim D September 10, 2009 at 9:36 pm

I just purchased the Kettlebell workouts that you recommended, but I need an idea on how to incorporate them into my current routine without over-training? Here is my current workout routine:

Mon- Off
Tues-Chest, Back, Abs, HIIT and Steady state cardio
Wed- Off
Thurs-Body weight Circuits and Steady state Cardio
Fri-Shoulders, Arms, HIIT
Sat-Body weight Circuits
Sun-Chest, Back, Abs, HIIT and Steady state Cardio

How do I work in those Kettlebell Workouts?

Thank you so much for everything that you do you’ve changed my life!

Norbi September 11, 2009 at 2:26 am


cool article, even cooler picture! How you find these things…. 🙂 Anyway, thanks for the explanation, it makes perfect sense, especially for those who already know that HIIT does work VERY well, this gives a little bit of more background info on it.

baz September 11, 2009 at 2:52 am

Rusty i always knew this about interval training. The reasoning behind it that is. What i want to know is how much rest is enough in between hard sprints? And how long should the hard sprints last? For example is a minute of sprinting followed by a minute of walking then a minute of sprinting etc etc a good way to do it or would you recommend something else? Also how long should the entire workout last? I start off with a 5 minute warm up then do intervals for 15 minutes and i’m absolutely stuffed after those 20 minutes. 20 minutes is intense but it doesnt seem like its long enough to get to single digit bf.
What do you think?

Thats my cardio that is. I’m happy with my weights sessions at the moment they’re going well.

Thanks a lot

ricky September 11, 2009 at 7:10 am

hey have you heard of rippetoe 3×5 …wht do u think about that workout combined with hiit !!!

i am thinking to start that as it says to do compound excersices for overall development !!

sorry for going off the topic…

gus September 11, 2009 at 7:48 am

great post.

i love doing intervals after my workouts, it gives me a great feel the rest of the day after im done and this is definitely the type of exercise that gives you the most benefits as u explained.

tuscanystone September 11, 2009 at 9:27 am

I love reading your blog. It’s one of my fave’s 🙂 Very informative and easy to read. I know that sounds dim but some blogs just go on and on and on….whereas you make your points simply and coherently 🙂 Thanks for taking the time Rusty xx

I’m just off to do a tabata 😉

Tusc 😀

Oh, love the pic too 🙂

Rafi Bar-Lev September 11, 2009 at 9:31 am


Really cool article. Even though you didn’t quote studies like usual everything here seems pretty logical. The “oxygen debt” thing explains why we continue to breathe hard after a hard workout!


Rodney September 11, 2009 at 12:47 pm

Great post, Rusty. I have a related question I have been wondering about. If I remember correctly, the majority of growth hormone release occurs after a single interval. While this isn’t true for oxygen debt/lactic acid, would running a single sprint at the end of my daily walks (after warming up to avoid injury) or even 4-5 times weekly be beneficial? Getting 70% of the GH of a longer workout 4-5 times would equal 3 times the GH release of a single workout. Maybe a mix of one full workout to address today’s topic, with 3-4 single sprints throughout the week for a little extra GH. Am I missing something here or is there some merit to this idea?


Jason G September 11, 2009 at 2:14 pm

I am convinced that the next step is to embrace some of the theories that make HIIT great and start using them in weight lifting like Michael hinted towards. I have been experimenting with one set to failure with only enough rest to make it to the next exercise. I have also been doing weight lifting with only two sets where I take a ten second break in between each set. In this way I go through a full body workout of about twenty exercises including body weight exercises in about an hour. I alternate between low rep and high rep from workout to workout. Obviously super sets, circuit training, and multiple sets are other great ways to incorporate more intensity and less rest in to your routine. I truly believe that the true secret to an efficient workout for those of us who do not want to live in the gym is to minimize rest in between sets.

The benefit of this type of training is that it increases your metabolism and hgh response more than traditional weight lifting and results in better cardiovascular conditioning. I will never go back to the “two minutes of rest between sets” way of working out again. It seems a little ridiculous choosing to measure our strength after long periods of rest when we can just as easily measure how conditioned are body is with only small periods of rest(even with strength training). The performance of the first set is the most important measurement anyway when using progressive overload techniques so going out of your way with excessive rest for later sets is counterproductive.

FitJerk - Flawless Fitness September 11, 2009 at 5:35 pm

You’ve got the nack for making things simple, so bravo to that.

For those curious, you can also improve your general tolerance to the lactic acid burn if you decide to progressively push yourself further each workout. Your body will be able to handle it in high loads and overtime the burning feeling is something you’ll be able to live with.

Reason for this? Some research has shown that the mitochondria in the cells can use lactic acid as a fuel source itself.

Burn baby burn!

drew from Grays Harbor September 11, 2009 at 5:51 pm

Great post. Interval training is now my key fat loss technique. I usually jog 2 miles, then run hard sprints for about a mile until i hit this stadium structure at the nearest highschool where i push out some stair climb sprints until i am completely in oxygen debt. totally dead tired and flushed.then i rest for a few minutes and finish off with 5-7 miles of jogging. This routine allows me to stay slim since I LOVE to drink beer. it also helps sweat out the bad stuff i should probably stay away from.
Overall, since starting the HIIT, I can lose weight any time, any amount so i dont feel so guilty now if i want a burger and a beer or 6. I owe alot to you Rusty, you are a great motivator.

tim September 11, 2009 at 7:29 pm

in ese what should the calorie range be for the regular days of eating when your trying to lose weight

Hulbs September 12, 2009 at 4:04 am

nice simple explanation of some complex science Rusty.

I think I’ll have to get myself one of those kettlebells soon

Baz September 12, 2009 at 6:56 am

Just on your sports analogy also, the majority of the guys on here won’t have ever heard it but we have an awesome sport called Australian football (AFL) over here. It’s a long 120 minute fast paced and very physical game without the use of that protection the Americans wear, and these guys are ripped. Aside from the larger forwards who don’t do too much running the average players are very fit and do look it as well. The fast nature of the game allows for hard running with short rests similar to interval training.

Nate - Fit-Life Online September 12, 2009 at 6:04 pm

All I could think about while reading this article was Tabatas. Definitely one of the best ways to get get all of these benefits in a short amount of time.

ken adler September 13, 2009 at 1:36 am

There is an article in the NYTimes magazine section about how weight loss and healthy behaviors can be attributed to your friends and community.

I have been losing weight lately and getting healthier and I attrtibute that partially by hanging out on this site and surrounding myself with people’s positive and determined comments.

I’m 175cm and I was 85kg and now down to 80kg and making progress. Thanks


Curt September 13, 2009 at 1:06 pm

Hi Rusty,

Good article. One thing I have to question is whether the lactic acids glucose burning power is going to really help with weight loss. I don’t think it amounts to whole lot of calories burned. Probably better to eat in a way that causes your body to use stored fat for fuel instead.

Interval training can be helpful for fat loss though. Seems to be mainly do to the increased oxygen consumption post-exercise that matters most. There are studies that show this help people burn calories from stored body fat for several hours post-workout. Some experts also believe the increase in growth hormone caused by increased lactic acid levels helps with fat loss too.


Tom Parker - Free Fitness Tips September 13, 2009 at 2:27 pm

Interesting post Rusty. I never knew lactic acid had these benefits. Definitely a different theory to what we were told at school which was that the build up of lactic acid was the reason your muscles ache after exercise. Your theory makes a lot more sense.

I think one of the main ways you can see how effective HIIT is as you quote in the article – “you should be breathing pretty damn hard”. As a general rule I think you can base a workout’s effectiveness on this principle. The best workouts are always the ones where you are breathing hard, your heart is beating rapidly and the sweat is pouring out.


P.S. Love the pic…even if you can’t figure out how it relates to the article 🙂

sangita September 14, 2009 at 3:49 am

Hello Rusty. Superbly explained. I did a flow chart of all the points in the article which made it even clearer (rather easy to remember). The rest between the intervals should be just enough to go on to or make it to the next interval, not to bring your breathing to normal – I needed to know that.

Caliph September 14, 2009 at 10:51 am

Great article Rusty! I really like doing the sprint intervals in the field around my old high school as it is an easy and quick way to get in a good workout and stimulate fat loss. After reading your blog and Mark’s Daily Apple – as well as an article about compensatory eating from working out too hard on cardio – I can only shake my head at all the people in my neighborhood who go jogging/running for 30mins to an hour at a time on a regular basis. What’s the point unless you like to wear out your joints and overeat on bread and pasta afterwards? At best, they all look skinny-fat to me.

tim September 14, 2009 at 3:22 pm

I know your against leg work which I am now too. But do you do anything for your calves or do you just let them be as well

Drew September 14, 2009 at 5:48 pm

Good article. I am glad I came across your website; finally a website to call out the mainstream crap. I am a personal trainer and have been incorporating the same theory on eating and training with my clients over the past year and am amazed at the results I have seen. Its a hard theory to hammer into peoples heads, but when you start seeing dramatic results it speaks for itself.

Bill September 15, 2009 at 7:31 am

Hey Rusty,

Really enjoying the progress from your Vacation Body Blueprint,
and was wondering if it’s a good idea to super-set the exercises you talk about? Would this add to the hormonal effect, or should I just stick to doing it as mentioned?

Really Rockin’ with your tips while enjoying your post too …especially those pics man!!!

Enjoy a Good One!

admin September 15, 2009 at 6:26 pm

I just have a few minutes to run through these comments…I will see how many questions I can hit!


I am not too knowledgeable of advanced breathing techniques…other than to slowly breath out when you are exerting the tough part of the lift.

Donkey Lips,

I do need to hit Oaxaca in Ballard. I have been procrastinating for too long. Glad you have been getting great results.


I am going to master kettlebells this year. I also plan on doing more body weight training. I still love lifting weights, but just want to become more well-rounded.


I really love lifting weights and resting in between sets…but I know intervals are so much more time efficient. Plus you can’t create a balanced look from weights alone. I am still doing some lifting, but increasing the amount of intervals.


I am still planning on going to Costa Rica with my girlfriend…just had to delay it a bit.


Here is what I would recommend. Do your body weight circuits on Tuesday after your workout and skip the steady state cardio. Same thing on Sunday. Do kettlebells on Thursday and Saturday. Substitute HIIT for body weight circuits when your muscles feel sore.


I pay and buy licenses for the photos on my site most of the time. I just like photos that you don’t see everywhere else.


What you are doing now…5 minute warmup and 15 minutes of HIIT…is plenty. As far as sprinting vs rest goes…make sure and vary it. It is obviously tougher to do a longer sprint and less rest period, but then you can’t push as hard on the sprint. I like 30 seconds of tough and a minute rest…or 30 and 30.


I am not familiar with the Rippetoe 3X5.


I try to make a blog post just long enough so people won’t skim it, but not too short either. I want you guys to get the info and then move on and implement it.


That sounds like a great idea to me. In theory it should work well. Give it a try and tell me how it goes.

Jason G,

What you described very well, was exactly what Craig Ballantyne’s main course “Turbulence Training” is all about. He gets amazing results for himself and clients with this approach.


I should have discussed tolerance to lactic acid burn…good point! Oh well. A topic for another day.


Thanks for the compliment. It seems you have created the perfect workout for your circumstances. I love it when people customize incredibly effective workouts based on solid principles. Plus…life without beer or burgers? Unthinkable!


That is a tough one because it depends upon so many factors.


I am a newbie to kettlebell lifting as well. I love the idea of working so many different muscles while boosting the metabolism and HGH.


Those Australian Rules Football guys are in amazing shape…I have watched it on ESPN a few times. Crazy sport…and fun to watch. In the NFL in the US…a lot of the football players have a ton of fat with muscle. A few positions have elite agile athletes…but not many. Some pretty big tough guys however even though they wear pads.


The internet can help a lot in that respect. Especially sites with lots of comments and interaction.


I agree 100% with the idea that diet is where it all starts. If the diet is wrong than the rest of this stuff really doesn’t matter much when it comes to fat loss.


I spend 1-2 hours per week searching for sharp articles. Some are certainly better than others…I paid for this one, but had to get it.


Some people rest way too long between intervals. It is much less effective when done in that manner. You almost have to use a clock for some of this stuff. When I do Craig Ballantyne’s body weight training intervals, I am only allowed to rest 60 seconds in between the entire giant set, before hitting the next one. When you are in oxygen debt, 60 seconds feels like 10 seconds…you almost have to force yourself to push hard again.


I feel bad for people who jog miles and miles every day without getting great results. My hope is that I can reach a lot of people. Mark Sisson is such a great educator about this, because he used to be a big time distance runner. He was on the cover of Runner’s World at one point. So when he says long distance running isn’t a good idea, it comes from a place of decades of experience.


I’m okay with leg work when it is done in interval fashion. I am more against heavy squats and deadlifts. Things like body weight circuits, kettlebell circuits, and HIIT work your legs in a way that keeps them strong and athletic without adding excess bulk. I like the way Mark Sisson describes how he works calves in the Primal Blueprint…he walks on his toes on a treadmill on an incline while wearing socks.


If they get results they will be hooked and you will have more clients than you know what to do with!


I like to do 2-3 workouts per week that are basic strength training and then add either HIIT after lifting or body weight circuits. There are times when I have done nothing but circuit with great results, so really it is up to you. My plan this year is to master kettlebells while mixing in body weight circuits. I really enjoy lifting weights, so I will never quit that entirely…but the best bang for your buck are the various types of “resistance intervals”. So my final answer…there is a lot of flexibility here.


Nick @ MMA Explosion September 15, 2009 at 8:16 pm

Thanks for the info. This is a very different way of looking at lactic acid than what everyone has been taught traditionally.

Stephanie September 17, 2009 at 5:56 am

I’m desperate, Rusty. I’m female, 5’4” and 134 lbs , 14 pounds from my goal weight, but my weight fluctuates from day to day, sometimes as much as 5 pounds. I haven’t been binging, and I use to lose maybe 5 pounds a week with just 15 minutes of HIIT with a skipping rope a day.

Now I’m at the gym 4-5 times a week, doing HIIT on elliptical machine for 15-20 minutes, then hitting the treadmill for another 20-30. I’m on a low carb, low cal diet, and don’t eat at least 5 hours before I exercise. I take weekends off from my diet, and I eat normally when I hit plateaus. My stamina has improved, and I do notice I’m a little leaner, but I’ve been doing this for almost three months( going to the gym) and the change has been so small I am at my wit’s end. Please Help!

Nate - Breakout Workout September 21, 2009 at 12:36 am

I’m a big fan (always have been) of interval training. Maybe its just how I’m wired, but I’ve always disliked endurance cardio type sports etc. So when the concept of EPOC or “afterburn” was introduced to me back in 2000, it made sense to me as to why I was so lean in high school but NEVER ran. I was a martial artist and gymnast and thats all we did was high intensity, short burst, strength related exercises…continuously. Good post Rusty, hope more people start to see this as completely viable and in some cases BETTER than endurance activities…especially if you don’t like them!

Neil September 25, 2009 at 7:55 am

Glad I found this site, great articles and info! Also prefer HIIT over regular cardio, and I started doing bodyweight circuits as part of a fat loss program last year and attribute that as being a major factor in digging out that last 10lbs and FINALLY popping my lower abs.

Question though, think I know the answer but want a 2nd opinion… About to embark on a muscle gain phase but normally put a bit too much fat on and a couple inches on the old waist as I tend to do VERY little cardio. This time though having worked hard for the abs, I’m determined to limit the fat gain, so was gonna throw in 2 x 20min or so HIIT cardio sessions per week. HOWEVER, I just found the TT Crazy 8 bodyweight circuit on this site and was wondering if that would be a good one to add or whether that would maybe have a detrimental impact on the muscle gain? Appreciate any thoughts on this. Thanks.

Angela September 27, 2009 at 10:16 pm

Thanks for the insight! I’ve been following your blog for some time and appreciate your real world approach to quality fitness. 🙂

And I like the photos…well not so much the ladies (since I’m a lady) but I can appreciate what you’re going for…not too muscular but slphysique and all.

Marc October 3, 2009 at 1:51 pm

I’ve been running in a very hilly area for years and always enjoyed “attacking” every hill on my routes. By the time I topped out on a hill I’d be heavily in oxygen debt and would back off on the downhill. When I reached the next hill I’d repeat the routine all over again. From what I’m reading here, it looks like I was unknowingly doing interval training. Cool.

anthony October 13, 2009 at 10:10 am

G’day Rusty,

I’m a big fan of interval training and have used it for years. I find it a great way to burn off the fat. I also like Don Lemmon’s approach to weight training and have used it for years.

Michael Mills October 19, 2009 at 5:26 pm

Great Post Rusty!

I am a firm believer in High Intensity Interval Training. I employ various techniques and training modes to keep my clients progressing. I have my clients use an HR monitor to determine how they are adapting to each round of activity. A good sign that people are training at the right intensity is that their HR will drop below 130 within 60-120 seconds of rest. If the HR cannot drop below 130 in 2 minutes, the intensity and/or duration is too great.


Regarding your specific problem… I highly suggest that you stop starving yourself prior to each workout. Exercising on an empty stomach has received much controversy lately, however, research indicates that exercising intensely on an empty stomach stimulates more cortisol – which inhibits fat burning potential.

If you want to lose weight – and preferably fat mass vs. muscle mass – then having a pre-workout meal plan is critical. Eat a high protein, moderate carbohydrate/fat meal (30-40 grams protein, 20-30 grams carbohydrate, and 10-15 grams fat) within 1.5 hours of your workout. Do the same for post-workout too.

Kprice December 30, 2009 at 5:21 pm

Rusty, I just had a quick question and I probably should have read this post first. I have bad knees that are on the verge of falling apart. I really like HIIT, because its short and I really feel like I pushed myself to the limit. Can you suggest any HIIT workouts that are not hard on the knees?

Christina February 25, 2010 at 10:31 pm

Is this kind of workout safe for those w/ lower back problems? It seems as if it might not be. In that case, how could one w/ arthritis get a good enough work out to lose weight? I’m 46, 132 lbs, but am 10 lbs over my comfortable weight. I’ve been trying to get it off for months now, but nothing is budging. I know that hormones play a big role on this extra weight. What to do? Anyone?

Tracey March 14, 2010 at 12:57 am

I am late to post here, BUT I HAVE TO SHARE MY HIIT EXPERIENCE!!!!

This evening I tried HIIT on the eliptical for the very first time and it was fantastic!!!! I had been doing it on the treadmill only, but needed a break from the hurting shins.

Eliptical :
1 min normal fast
1 min running fast

Do this for 15 -20 minutes with 20 minutes of steady state cardio (normal fast) afterwards.

I hope that makes sense. All I know is for the running part I had to hunch down a bit and hold on. By the time I was 10 minutes into it I was dripping with sweat. I have lost 5 pound in the past 9 days by cutting my calories to 1300 per day and doing HIIT with SSC everyday.

I was worried I wouldn’t get enough of a workout on the eliptical – boy was I wrong!!!!

Robin H May 21, 2010 at 4:43 am

hi rusty!
i just discovered your blog a few days ago. wonderful resource here, thank you!
about lactic acid, i just started HIIT a week ago and have felt good but also extremely fatigued during the rest of the day. i’m finding it a little hard to be productive lately and feel the need to sleep too much. i think this is supposed to be a symptom of lactic acid buildup, isn’t it? what would you do to counter this effect?

xbox ring of death fix January 22, 2011 at 10:07 pm

Wow this blog provide a very good content about exercise and burning fat and i am thanking the blog owner because of this. The information of this blog should be paid and i am surprise it is free.I hope this blog will continue to succeed.

Simon Wheeler August 22, 2011 at 11:27 pm

The keywords that stick in my mind. Is intense, intense and intense. Oh I am exhausted reading this well articulated fitness piece!

David January 9, 2012 at 1:20 am

Hi Rusty, great post, I cover this topic more in detail for MMA fighters and the benefits it has to build a well overall conditioned body, at my article in:


I have also post there the famous Spartacus Workout popularized by the TV show, check that out!

Niko - noeXcusefitness February 3, 2012 at 9:31 pm

Hey Rusty, nice post. Through the use of interval training I have managed to drop my body fat to 9%, whilst still maintaining muscle. Check out my take on AFTERBURN EFFECT EXERCISES and how they incinerate fat:


Mabel September 30, 2012 at 2:47 pm

It’s awesome to go to see this web page and reading the views of all mates regarding this article, while I am also keen of getting know-how.

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