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A 45 minute full HIIT workout should burn about ~1000 calories; not exactly trivial.

DenisM 12y ago
That's absurdly high. If you can sustain that level of activity, you likely don't have the weight problem in the first place. I'm a couch potato, I can burn about 300 cals per half-hour (according to the stationary bike machine or elliptical). In my better days, that was up to 350 cals per half-hour, I was quite fit but not athletic.
revelation 12y ago
This is of course trivially verifiable. To burn 1000 calories in 45 minutes if your body is an average 25% efficient requires around 385W of continous power output. The majority of women will struggle to output this for a mere minute while most men won't last 5. So no, your 45 minutes of HIIT isn't burning 1000 calories, and if calories are your goal, you would obviously not be doing HIIT in the first place (what's the point in getting nauseous when you can just produce these steady watts). (That said, I still heavily disagree with the grandparent; exercise is as much part of a diet as is calories in / out. If you can do 150W for a grand total of 5 hours every week, that totals 2500kcal or more than an extra days worth. For many people, time spent exercising is also time spent not sitting idly in front of a TV and eating.)
- a8da6b0c91d 12y ago
  Genuinely curious where you get the 25% efficient number. Is that an established figure for cyclists or something?
  - dietrichepp 12y ago
    It would be interesting to know the particulars, but in general you hook up a cyclist up to a dynamometer and a ventilator, and you measure both the amount of work done and the amount of CO2 produced. I say "cyclist" because they're the easiest ones to hook up to a dynamometer.
  - revelation 12y ago
    http://www.ncbi.nlm.nih.gov/pubmed/12471319 http://www.ncbi.nlm.nih.gov/pubmed/12471319 quotes gross mechanical efficiency at 24.5 +/- 0.7% for world class cyclists. More importantly, however, http://www.ncbi.nlm.nih.gov/pubmed/15241718 http://www.ncbi.nlm.nih.gov/pubmed/15241718 finds no differences in efficiency between world-class and recreational cyclists. In any case, the "cycling" bit is somewhat of a smoke-screen; it just so happens that it's most easily measured and objective data has long been available through power meters. There is no free-lunch, regardless of the particulars of any sport. (I should however probably clarify that the power numbers quoted above are mechanical power as measured during cycling, which is pretty much the only sport that even has ways of measuring power reliably)
    - deleted 12y ago
      [deleted]
tspiteri 12y ago
You'd need to be a pretty good athlete to burn 1000 calories in 45 minutes straight.
tomjen3 12y ago
You have to be in pretty fucking great shape to last 45 minutes of HIIT.
- smackfu 12y ago
  True, but it's pretty easy to do 600 calories of exercise in 45 mins. Which is still a hamburger or so (not the fries.)
  - tomjen3 12y ago
    But a lot easier (and faster) to skip the hamburger.
    - robotresearcher 12y ago
      > But a lot easier (and faster) to skip the hamburger. I wish I found it as easy as that.

That's absurdly high. If you can sustain that level of activity, you likely don't have the weight problem in the first place. I'm a couch potato, I can burn about 300 cals per half-hour (according to the stationary bike machine or elliptical). In my better days, that was up to 350 cals per half-hour, I was quite fit but not athletic.

revelation 12y ago

This is of course trivially verifiable. To burn 1000 calories in 45 minutes if your body is an average 25% efficient requires around 385W of continous power output. The majority of women will struggle to output this for a mere minute while most men won't last 5. So no, your 45 minutes of HIIT isn't burning 1000 calories, and if calories are your goal, you would obviously not be doing HIIT in the first place (what's the point in getting nauseous when you can just produce these steady watts). (That said, I still heavily disagree with the grandparent; exercise is as much part of a diet as is calories in / out. If you can do 150W for a grand total of 5 hours every week, that totals 2500kcal or more than an extra days worth. For many people, time spent exercising is also time spent not sitting idly in front of a TV and eating.)

a8da6b0c91d 12y ago
Genuinely curious where you get the 25% efficient number. Is that an established figure for cyclists or something?
- dietrichepp 12y ago
  It would be interesting to know the particulars, but in general you hook up a cyclist up to a dynamometer and a ventilator, and you measure both the amount of work done and the amount of CO2 produced. I say "cyclist" because they're the easiest ones to hook up to a dynamometer.
- revelation 12y ago
  http://www.ncbi.nlm.nih.gov/pubmed/12471319 http://www.ncbi.nlm.nih.gov/pubmed/12471319 quotes gross mechanical efficiency at 24.5 +/- 0.7% for world class cyclists. More importantly, however, http://www.ncbi.nlm.nih.gov/pubmed/15241718 http://www.ncbi.nlm.nih.gov/pubmed/15241718 finds no differences in efficiency between world-class and recreational cyclists. In any case, the "cycling" bit is somewhat of a smoke-screen; it just so happens that it's most easily measured and objective data has long been available through power meters. There is no free-lunch, regardless of the particulars of any sport. (I should however probably clarify that the power numbers quoted above are mechanical power as measured during cycling, which is pretty much the only sport that even has ways of measuring power reliably)
  - deleted 12y ago
    [deleted]

tspiteri 12y ago

You'd need to be a pretty good athlete to burn 1000 calories in 45 minutes straight.

tomjen3 12y ago

You have to be in pretty fucking great shape to last 45 minutes of HIIT.

smackfu 12y ago
True, but it's pretty easy to do 600 calories of exercise in 45 mins. Which is still a hamburger or so (not the fries.)
- tomjen3 12y ago
  But a lot easier (and faster) to skip the hamburger.
  - robotresearcher 12y ago
    > But a lot easier (and faster) to skip the hamburger. I wish I found it as easy as that.