Fitness in 6 minutes of effort *a week* or Less? What does that mean? (Part I)

If in a training session, we can hurl ourselves into short blasts of all out effort (without hurling), we may just be able to get ourselves fit in 6 (to 9) mins of effort a week. Fit, to the same level and kind of strength capacity if we were doing 2-3 hours traditional endurance work/week. While this sounds cool, what does 6 mins of fitness give us, especially, relative to any body comp and strength desires? This is part one of a two part article. Part I (what you're reading now): research review. Part II: plain language take aways form the research.

Background:
Last year when talking about the difference between cradio and vo2max training and the benefits thereof, especially for enhancing mitochondrial density, the stuff that makes fat burn in the cells, i mentioned this pretty new research out of (happiness and joy) Canada:

Here's the abstract

Low-volume 'sprint' interval training (SIT) stimulates rapid improvements in muscle oxidative capacity that are comparable to levels reached following traditional endurance training (ET) but no study has examined metabolic adaptations during exercise after these different 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 years) performed a constant-load cycling challenge (1 h at 65% of peak oxygen uptake before and after 6 weeks of either SIT or ET (n= 5 men and 5 women per group). SIT consisted of four to six repeats of a 30 s 'all out' Wingate Test (mean power output ∼500 W) with 4.5 min recovery between repeats, 3 days per week. ET consisted of 40–60 min of continuous cycling at a workload that elicited ∼65% (mean power output ∼150 W) per day, 5 days per week. Weekly time commitment (∼1.5 versus∼4.5 h) and total training volume (∼225 versus∼2250 kJ week⁻¹) were substantially lower in SIT versus ET. Despite these differences, both protocols induced similar increases

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

Volume 586, Issue 1, 2008.

Pages: 151–160
Kirsten A. Burgomaster, Krista R. Howarth, Stuart M. Phillips, Mark Rakobowchuk, Maureen J. MacDonald, Sean L. McGee, Martin J. Gibala
Published Online: Jan 2 2008 12:00AM
DOI: 10.1113/jphysiol.2007.142109
quick note on terms: vo2peak is highest VO2 elicited in test to exhaustion; the more familiar vo2max which is the plateau hit for V02 when adding progressive load. So you can readily hit vo2max before exhaustion.

On the face of it, the big take away from the study, as the authors say themselves in the Discussion part of the article: the effect on carbs in the muscle and fat metabolism were comparable to the endurance training protocols, and here's the kicker

despite a much lower training volume and time commitment. By design, weekly training volume was ∼90% lower in the SIT group (∼225 versus∼2250 kJ week⁻¹ for ET) and necessitated a training time commitment that was only ∼one-third of that of the ET group (∼1.5 versus 4.5 h [over 6 weeks -mc]).

90% lower! in terms of time and effort. So, low volume (few repeats) of maximal effort with good recovery has the same effect as high volume mid intenstity.

Now some folks may say ya ya, we know intervals are more efficient at burning calories than lower intensity steady state: more effort you burn more. Duh. But calories burned is not the big exciting part of this story. It's the mitochondria and the carbohydrates that are kinda amazing.

Getting Endurance Effects from Resistance Like Training?
One of the big reasons people blend HIIT with steady state lower intensity (65%) cardio training is both for (1) elasticity of heart muscle health that say resistance training alone doesn't give (pick up Kenneth Jay's Viking Warrior Conditioning for more on this) and/or (2) creating cells that are better fat burners. Aerobic workouts both privilege fat as the fuel of choice AND they enhance the qualities of cells (mitochondria) that get fat oxidized (burned) for fuel.

Folks in the house who use kettlebells may be getting all smug here by saying that doing lots of swings with a mid sized bell does the endurance work, while all their presses, pulls and snatches takes care of the power/resistance stuff. Yes, it's a magic ball!

The thing is, again, the powerful finding of this work, is that it shows that that all important, highly sought-after mitochondria proliferation is occurring in super intense work in a way comparable to that 65% endurance work. That's not what we're doing in a ten minute swing set with a kb. And that's just not what would be predicted in the normal model of our metabolism. And here's why i love good science: the authors admit as much by saying they don't know why they are getting these results, citing that traditional and current understanding of strength/endurance

While the present study demonstrates the potency of SIT [sprint interval training -mc] to elicit changes in muscle oxidative capacity and selected metabolic adjustments during exercise that resemble ET [endurance training -mc], the underlying mechanisms are unclear. From a cell signalling perspective, exercise is typically classified as either 'strength' or 'endurance', with short-duration, high-intensity work usually associated with increased skeletal muscle mass, and prolonged, low- to moderate-intensity work associated with increased mitochondrial mass and oxidative enzyme activity (Baar, 2006).

In other words (i love good science, did i say that?) given what we've understood about how our bodies work, these results shouldn't happen (and this is the second time the authors have repeated these results - in fact that they're getting similar effects in this 6 week trial as they did in their 2 week trial is provocative in itself).

In other words the 02 deficit may be SO HIGH after this effort your body may up-regulate O2 consumption afterwards, which impacts the aerobic system. So it might be the rest intervals during and post the effort where the aerobic ET-like adaptation is occurring.

What does that mean? Time to update the model - and consider all the variables that may play a role, from the brevity of the interval (longer may be counter-productive) to an understanding of the recovery period processes. The authors speculate that part of the answer is that the intensity of effort turns on a particular gene expression PGC-1α due to a whole bunch of upregulated muscular related fuel events that we'll skip here but that are triggered by this kind of intensity burst.

Indeed, in a study by Gibala that came out just this past June, 2009, the author came back to some of these questions. And that transcripter seems to be a winner. The abstract reads, in part,

A key controller of oxidative enzyme expression in skeletal muscle is peroxisome proliferator-activated receptor gamma coactivator 1alpha (PGC-1alpha), a transcriptional coactivator that serves to coordinate mitochondrial biogenesis...Signaling through AMP-activated protein kinase and p38 mitogen-activated protein kinase to PGC-1alpha may therefore explain, in part, the metabolic remodeling induced by HIT, including mitochondrial biogenesis and an increased capacity for glucose and fatty acid oxidation.

The conclusion comes away saying that this KIND (and potentially duration) of interval has magical properties that blend endurance benefits for mitochondria building while being what looks like resistance training:

High-intensity interval exercise represents a unique and understudied model for examining the molecular regulation of skeletal muscle remodeling. Like strength or resistance training, interval exercise is characterized by brief intermit- tent bouts of relatively intense muscle contraction. However, interval exercise training induces phenotypic changes that resemble those elicited after traditional endurance training. Preliminary evidence suggests that signaling through AMPK and p38 MAPK to PGC-1a may explain, in part, the meta- bolic adaptations induced by HIT, including mitochondrial biogenesis and an increased capacity for glucose and fatty acid oxidation.

In other words, turning on PGC-1a is a big deal to generating this remodeling. And we know from the other studies - or at least strongly suspect - that it's hitting high intensity for these short blasts that does the turning on.

Carbohydrate AND Phosphocreatine Sparing? What's new?
But let's come back to the other big finding of this study - less sensational, but good to confirm:

The usual model is that, going anaerobic - which an all out sprint effort does - means that we burn fuel from the phosphagen system in the initial blast and then we hit carbs. Phosphagen gives us a small burn of 10-30secs. After that, carbs kick in for about another three minutes of burn. Important to note is that we mean these are the primary fuel systems - oxygen (and so some fat burning) is always working too or we'd croak.

Part of the reason folks do vo2max training is to be carbohydrate sparing - we want to make the body able to use oxygen for greater levels of work, so that it turns to carbs at only higher and higher demands for fuel. Why would we want to do this? Two reasons: we have way more fat available for fuel than we do carbs, and fat gives way more energy bang for the buck than do carbs. In other words we can go longer on a gram of fat than we can a gram of carbs.

If you're doing weight loss work, naturally getting fat burning optimized is a good thing. This effect is again why folks traditionally do lower intensity cardio: it privileges fat burning for fuel.

Likewise in the strength training space, the reason we supplement with creatine is to help keep the phosphagen system topped up - so we can get a few more reps in at that higher phosphogen level fuel system going.

Now here's a protocol that says it's both beneficial for phosphocreatine and carbohydrate sparing. THat's not surprising for interval training to claim. That's part of the reason, as said, we do that with resistance work to develop power, and with vo2max work for higher endurance. The kicker here is the achievement of same with very low volume.

Here's how they tested it: they tested their SIT and ET groups prior to the study commencing with a 65% of pre-training v02peak effort of cycling for an hour. They did the same thing after 6 weeks. The researchers found again comparable changes in fuel usage in both groups so there were both carb and phosocreatine benefits from super low volume training.

The results may not be cost free, but the cost may be minimal or negligible. The amount of ATP at rest in the SIT group was lower; it didn't change in the ET group. This means that amount of available material to be used for muscle contraction was lower in the SIT group. The researchers aren't sure why this was the case: it takes awhile to reamp ATP and it may just be from residual effects of the last excercise bout before the samples were taken, or it may be an effect of the chronic excercise protocol. Not sure. Dunno. Watch that space.

So finally we can dump aerobics/cardio training?

If we get all the tasty goodness of aerobic trad endurance training from these brief moments of vomitus activity, can we skip cardio entirely? Answer: we don't know (did i say i love science yet?)

It is also important to stress that the relatively limited array of metabolic measurements performed in the present study may not be representative of other physiological adaptations normally associated with ET. For example, SIT may differ from ET with respect to changes induced in the cardiovascular and respiratory systems, metabolic control in other organs (e.g. liver or adipose tissue) and protection from various factors associated with chronic inactivity (e.g. insulin resistance or lipid dysregulation).

Indeed, with respect to the all important insulin, and the goal of building insulin sensitivity, in another June 09 publication, Hawley and Gibala look at insulin intensity and exercise intensity and ask "how low can you go?" The authors wanted to get as close as current research findings, when synthesized, might suggest, how *intense* does exercise need to be to have a beneficial effect on insulin sensitivity. Conclusions so far?

It remains to be determined whether high-intensity, low-volume interval training protocols can confer all of the health-related benefits associated with less intense, more prolonged traditional endurance training programmes. [Based on the review of literature to date, however -mc] it seems prudent to recommend that, for patients with insulin resistance or type 2 diabetes, the minimal dose of physical activity needed to maintain or improve health is equivalent to ~4,000 kJ/week of low- to moderate-intensity exercise. However, for patients who only show modest improvements in clinical and metabolic outcomes at this level of activity-induced energy expenditure, an increase in the intensity of exercise may be considered because of the potential additional benefits in both metabolic control and cardiorespiratory fitness.

In other words going all out with sprint intervals is not for everyone or all conditions.

Is Even Less Even More?
Likewise, the current study measured 30s intervals for 6 mins of work. In a recent interview, Gibala said an upcoming study for fall 2009 will look at how low those intervals can go for benefit. Could a single two or three minute bout be as effective as those six minutes? Dunno!

A few Points on Gear.
I sense the kettlebeller within immediately wanting to give this protocol a go with kb snatching or some such. An important note, then.
The study was carried out on a stationary bike. That's the typical device for a wingate test. It's safe. Swimming is another safe place (no pounding for all those repeats) where one can get one's heart and system up to that intensity - though swimming is harder to gate. Easier on a bike.

The wingate test is a precisely set load on the individual: from .075kg/kg of athlete to 1.3kg/kg of athlete. It would be interesting to think about how to translate this kind of resistance to a *safe* kettlebell routine.

Of course the disadvantage of thinking about such a rep set might be that one's form goes to hell, and that's totally wrong, engraining poor rep quality is rather problematic neurologically not always to be going for a perfect rep.

A few questions about fitness and body comp
Most of us workout because we want to be strong and look half decent half dressed. What this study did not measure is what these results mean for the technical body comp (bf%, say) and the visual body comp (dress size, look in the mirror, buff-ness).

For instance, in a study from 2007, it seemed that for folks to maintain their desired body look and feel, they needed to workout for 5 hours a week, mixing up cardio, intervals and strength work.

Now while this study protocol hasn't been put forward as a training program that's sorta where the NYT interview, cited above, was coming from, and it's certaininly an interest of the folks doing the studies.

But the question might be, given body comp and strength goals, what would this 6 mins a week fitness regine get those of us who are, well, already fit enough to contemplate it?

Part II: What does this all really mean for our actual real workouts? 6 plain language take aways, next.

Burgomaster, K., Howarth, K., Phillips, S., Rakobowchuk, M., MacDonald, M., McGee, S., & Gibala, M. (2007). Similar metabolic adaptations during exercise after low volume sprint interval and traditional endurance training in humans The Journal of Physiology, 586 (1), 151-160 DOI: 10.1113/jphysiol.2007.142109