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Thursday, 26 March 2009

The evidence for intervals trumping aerobic cardio

Here's some evidence as to why interval training must be a regular, tough, sweat-fest of a session on your training timetable!

This really is just some of the piles of research I have next to me!

Let's look at some answers to sceptics, aerobics fans and those who 'don't have time'...

But I want to improve my stamina for running / cycling etc

Gibala et al (2006) compared low volume sprint training with high volume endurance (typical of running fanatics).

Both groups performed 6 sessions over 14 days.

The HIIT group performed 4-6 x 30 second intervals @ 250% of VO2 max (very hard!) with 4 min rest inbetween.

The endurance group performed 90-120 min cycling at 65% of VO2 max (moderate).

The HIIT group did 2.5 hours of training over 2 weeks whilst the endurance group did 10.5h.

The results?

Muscle oxidative capacity improvements was similar in both groups so muscle endurance capabilities will have improved at about the same rate, but the HIIT group spent 8 hours less doing it over 2 weeks!

Aerobic exercise burns fat so it's better for fat burning

5 well trained distance runners were tested at each of the following:

2 hours @ 24% of VO2 max (low intensity)
10 minutes @ 81% of VO2 max (relatively high intensity but continuous)
2 minutes on 2 minutes off @ 89% of VO2 max (high intensity intervals)

(Brockman et al, 1993)

After one hour of finishing the sessions, oxygen consumption was significantly higher following the intermittent exercise.

After just 40 minutes, oxygen consumption had returned to base level in the walking test. This means no more fat burning until you do mroe exercise.

This means metabolic rate was much higher - more calorie / fat burning whilst at rest!

I've heard you burn more calories at the time of aerobic exercise.

This MAY be true but check this study out!

A 20 week endurance program was compared with a 15 week High Intensity Interval Training program. (Tremblay et al, 1994)

Over those weeks, the endurance group burned 120mJ of energy during exercise whereas the HIIT group burned 57.9mJ.

Surely endurance wins then?

Not when you consider that the HIIT group showed more pronounced reduction in body fat!

So they trained for 5 weeks less but lost more fat - SHORTER TIME TO RESULTS!

When they adjusted the results to compare fat loss in proportion to the cost of energy of the exercise sessions, the HIIT group lost 9 TIMES as much fat.

It should be pretty clear now why I force home the point that how many calories you burn in a session is largely irrelevant - ignore calorie counters on cross-trainers etc!

Yeah lots of science but does it work for real people?

Testimonial shots from normal people following


Anonymous said...

Great post Jon! Just found your blog...recommended by a 'web friend' at SmoketheBlowfish blog. Awesome HIIT videos of you crankin' it out!

Looking forward to reading your earlier posts...thanks!


SmoketheBlowfish said...

Jon, I hope you don't mind (now that Fred spilled the beans). I posted a couple of your video clips showing what real effort during an Interval really is. The one showing you wearing the weighted vest earned you the Nutbag Award. This award is highly coveted by a number of my friends.

As for "evidence for intervals trumping aerobic cardio"...the proof is there. Personally, I dropped 30lbs in about a year doing moderate cardio, diet modification, and haphazard lifting (no plan). The fat loss didn't kick in until I started using HIIT....dropped BF% from 23% down to 15%.

Now that I've seen your version of Intensity (almost threw up the first time I cranked the incline to 9 degrees on the treadmill), my goal of sub 10% Bodyfat seems well within reach.