Sunday, November 11, 2007

Research update - Interval Training

The post on Kettlebell Science promoted a little bit of debate in the comments, which is always encouraging. One of the themes in that post was that the exercise protocol that is chosen is important in terms of the results that you are trying to achieve. This of course is the basic principle of specificity - you'll get a result specific to what you are training. A(n) high intensity interval (HIIT) type protocol, for example, will stress the metabolic / energy pathways that lead to an improved Vo2 max.

On this subject, there were a couple of new pieces of research published last week on interval training:

Similar metabolic adaptations during exercise after low volume sprint interval and traditional endurance training in humans.


Low-volume "sprint" interval training (SIT) stimulates rapid improvements in muscle oxidative capacity that are comparable to traditional endurance training (ET) but no study has examined metabolic adaptations during exercise after these diverse training strategies. We hypothesized that SIT and ET would induce similar adaptations in markers of skeletal muscle carbohydrate (CHO) and lipid metabolism and metabolic control during exercise despite large differences in training volume and time commitment. Active but untrained subjects (23+/-1 y) performed a constant-load cycling challenge (1 h at 65% of VO2peak) before and after 6 wk of either SIT or ET (n=5 men and 5 women per group). SIT consisted of 4-6 repeats of a 30 s "all out" Wingate Test with 4.5 min recovery per d, 3 dwk-1. ET consisted of 40-60 min of continuous cycling at ~65% VO2peak per d, 5 dwk-1. Weekly time commitment (~1.5 vs ~4.5 h) and total training volume (~600 vs ~3000 kJwk-1) was substantially lower in SIT vs ET. Despite these differences, both protocols induced similar increases (P<0.05) in mitochondrial markers for skeletal muscle CHO (pyruvate dehydrogenase E1alpha protein content) and lipid oxidation (3-hydroxyacyl CoA dehydrogenase maximal activity) and protein content of peroxisome-proliferator-activated receptor-gamma coactivator-1alpha. Glycogen and phosphocreatine utilization during exercise were reduced after training, and calculated rates of whole-body CHO and lipid oxidation were decreased and increased respectively, with no differences between groups (all main effects, P<0.05). Given the markedly lower training volume in the SIT group, these data suggest that high-intensity interval training is a time-efficient strategy to increase skeletal muscle oxidative capacity and induce specific metabolic adaptations during exercise that are comparable to traditional ET.

So, from a perspective of time efficiency do intervals. You get the same benefits for a fraction of the time investment!

IGF-I and IGFBP-3 during Continuous and Interval Exercise.

The purpose of this research was to compare changes in circulating levels of total IGF-I and IGFBP-3 during continuous, moderate-intensity exercise (CE) and high-intensity interval exercise (IE) of equal duration. Ten healthy males completed 2 exercise sessions and a resting control session (R) in random order. The CE was 20 minutes of cycling at 60 - 65 % of V.O (2max). During IE, subjects cycled at 80 - 85 % of V.O (2max) for 1 minute followed by 40 seconds of active recovery, with the cycle repeated for a total of 20 minutes. In each session blood samples were drawn at - 10, 0, 5, 10, 20 and 30 minutes. Both IGF-I and IGFBP-3 increased during exercise (p < 0.05) and repeated measures ANOVA revealed a significant effect for session (IE, CE > R, p < 0.05). Area under the curve (AUC) analyses showed no difference in IGF-I between sessions, however, the IGFBP-3 AUC was significantly greater during IE than R (p < 0.05). These results suggest interval and continuous exercise will result in similar changes in circulating IGF-I and IGFBP-3. This could be beneficial to individuals who can exercise longer and at a higher intensity in intervals than would be possible using a continuous protocol.



Not sure if this adds to the discussion or not...

8 comments:

Greg said...

Man trying to force interval training on a treadmill just looks awkward. Was I the only one thinking get off the damn treadmill?

Chris said...

No, not the only one.

I've got a bit of a prejudice against treadmills - can't understand how people pay money to go and run indoors, when you can do it for free outside.

(OK I do sometimes use the treadmill for intervals if I'm honest)

Mark Reifkind said...

chris,

am I reading it wrong or did they use 4.5 rest intervals with the 30 sec of work?that seems odd. great stuff though dude, thanks

Chris said...

Rif - yeah, that is how I am reading the first study. That is one of the interesting things about all this science. There is a fair bit of research being doen at the moment on interevals, but the scientists all seem to be usign different protocols from 8 seconds on 12 secs off to this 30s on 4.5 min off. So just saying "do intervals" is not telling people enough! What sort of intervals?

Anonymous said...

The only thing this research shows is that intervals are superior to lousy training. Duh! So far, you haven't shown any research at all that suggests intervals are superior or more time efficient than training continuously at moderate to hard intensities.

Chris said...

Mr anon

you seem to have made up oyur mind on this one already?

Check out

http://conditioningresearch.blogspot.com/2007/07/sprint-intervals-time-efficient-too.html it points to a study that claims interalsa re more time efficient.

or

http://conditioningresearch.blogspot.com/search/label/intervals

or

http://hillfit.blogspot.com/2007/09/science.html

Anonymous said...

You should really read the research that you post. It always involves some pathetically easy percentage of max heart rate. There hasn't been a single study comparing intervals to a good bout of equal duration say at 85%.

The EPOC studies pointing to fat-burning nearly always conveniently stop after an hour. But the reality is that EPOC lasts longer when the intensity is high AND the duration is longer. A short HIT workout only gives a short fat burn. A longer, harder workout gives more EPOC.

You're on a bandwagon with HIT but the research is a lot weaker than you characterize it.

Anonymous said...

You should really read the research that you post. It always involves some pathetically easy percentage of max heart rate. There hasn't been a single study comparing intervals to a good bout of equal duration say at 85%.

The EPOC studies pointing to fat-burning nearly always conveniently stop after an hour. But the reality is that EPOC lasts longer when the intensity is high AND the duration is longer. A short HIT workout only gives a short fat burn. A longer, harder workout gives more EPOC.

You're on a bandwagon with HIT but the research is a lot weaker than you characterize it.