Any exercise you do (upwards of 1 or 2 secs if I remember correctly) will
utilise a mixture of fats and glucose. All that line is saying is that 75
seconds of maximal exercise (maximal in terms of - you can't sustain it past
75 seconds) gives an even split. You still won't be using much of anything
within 75 seconds. Repeated bursts (intervals) rapidly switch the balance
to more lipid utilisation since muscle glycogen takes time to replenish.

Also, since the body can convert glocose to fats and vice versa, what's
important is total calories burnt. How you burn those calories is up to
you. Steady state, intervals, whatever you're comfortable with and have
time for.

There is an argument that fat burning is not important, its cardiovascular
training. This is supported by body fat dropping out as a causal factor
when looking at things like heart disease, when you factor in activity
levels (sorry no references). However, I haven't seen a mechanism for this.
Possibly its something mundane like exercising the heart muscle. So in
terms of what the most effecient exercise is for staying healthy I think
theory is lacking at practice. I did see stats in one huge study that said
the largest gains were made going from sedantry to minimum activity (e.g.
walking briskly for 30mins a week). However, gains appeared to always be
made with increasing activity, just the amount gained reduced when
increasing from a higher level.


----- Original Message -----
From: "McFarlane, David"
Sent: Thursday, September 11, 2008 7:05 AM
Subject: [BIOMCH-L] Is Maximal Exercise for 75 seconds the Most Efficient
way of Burning off Fat?

Dear All,
Recently I came across an interesting research paper that suggests that
maximal exercise for 75 seconds is the most efficient away of burning
off fat. The paper concluded that; "The duration of maximal exercise at
which equal contributions are derived from the anaerobic and aerobic
energy systems appears to occur ... most probably around 75 seconds"
(Gastin P, 2001). It sounds almost too good to be true; did nobody
understand the implications? You'd think it would have been front-page
Professional athletes bulk themselves up on carbohydrates and though
they are motivated by sporting ambition, weight is not usually a crucial
issue as they have ample time to burn off their excess calories with
work-outs. The average person is mainly motivated by the desire to shed
excess fat.
Public Health bodies such as Heart Foundations recommend that people do
at least half an hour (or 20 minutes at the very least) of maximal (or
near maximal) physical activity on most (and preferably every) day of
the week for health benefits. As far as I can tell from sports training
literature typical athletes in training ("jocks") aspire to at least 30
minutes of near maximal anaerobic training (at 60 - 80% of maximal Heart
Rate or more) to "burn off the fat". However, most ordinary people in
the workforce tell me that they cannot devote this amount time to
exercise due to their long working hours and their endless
time-consuming commuting (thanks to the parlous state of our congested
roads and public transport). People who are not working tell me that
they find such as regimen too tiring and many find such a regimen so
daunting that they just give up before they even start.
This research data suggests that breaks for exercise (and short stints
of vigorous exercise) could make a real difference to combating obesity
and maintaining the fitness of the workforce as even 2 or 3 minute
work-outs should be helpful. Five-minute breaks are not unfeasible in
many workplaces and there is an interest in warm-ups in some workplaces
where the work is physically arduous.
Can anyone make any recommendations regarding the frequency and content
of short keep-fit work-breaks?


David McFarlane MAppSc (Ergonomics)
Ergonomist, WorkCover NSW

Gastin P, (2001), "Energy system interaction and relative contribution
during maximal exercise", Sports Med, 31(10), 725-41. Hyperlink;


Any recommendation concerning the use or representation of a particular
brand of product in this document or any mention of them whatsoever
(whether this appears in the text, illustrations, photographs or in any
other form) is not to be taken to imply that WorkCover NSW approves or
endorses the product or the brand

************************************************** ************************************************** ************************************

This message, including any attached files, is intended solely for the
addressee named and may contain confidential
information. If you are not the intended recipient, please delete it and
notify the sender. Any views expressed in this
message are those of the individual sender and are not necessarily the views
of WorkCover NSW. Please consider the environment
before printing this E-mail.

************************************************** ************************************************** ************************************