Add some sprints....

This one looked interesting.

Adding a few sprints to your basic steady state cardio added fun, did not feel harder and increaed energy expenditure...

Adding sprints to continuous exercise at the intensity that maximises fat oxidation: Implications for acute energy balance and enjoyment.

The objective was to examine the effect of adding sprints to continuous exercise at the intensity that maximises fat oxidation (Fat(max)) on energy expenditure, substrate oxidation, enjoyment and post-exercise energy intake in boys. Nine overweight and nine normal weight boys (8-12 years) attended the laboratory on three mornings. First, body anthropometrics, peak aerobic capacity and Fat(max) were assessed. On the remaining two sessions, resting metabolic rate was determined before participants completed 30 min of either continuous cycling at Fat(max) (MOD) or sprint interval exercise consisting of continuous cycling at Fat(max) interspersed with four-second maximal sprints every two minutes (SI). Energy expenditure and substrate oxidation were measured during exercise and for 30 min post-exercise, while participants completed a modified Physical Activity Enjoyment Scale (PACES). This was followed by a buffet-like breakfast to measure post-exercise energy intake. Fat oxidation rate was similar between groups and protocols (P>0.05). Both groups expended more energy with SI compared to MOD, resulting from increased carbohydrate oxidation (P<0.05), which was not compensated by increased energy intake. Participants indicated that they preferred SI more than MOD, although there was no significant difference in PACES score between the protocols (P>0.05). In summary, the addition of short sprints to continuous exercise at Fat(max) increased energy expenditure without compromising fat oxidation or stimulating increased post-exercise energy intake. The boys preferred SI and did not perceive it to be any harder than MOD, indicating that sprint interval exercise should be considered in exercise prescription for this population.

BBC discovers intervals

how long is it since that Tabata study?  The BBC finally discover intervals



I commented on this over at the Body By Science site

Just watched the BBC Horizon programme and the key bit was about what they called HIT but was really HIIT - interval training on an exercise bike. This benefitted the subject who improved his insulin sensitivity but - due they said to his genetics - did not improve his VO2 Max. They explained how this intense exercise had an impact on his glucose metabolism, emptying his muscles of glycogen so that they were able to absorb more glucose form the blood.

This was good in that we are inching along towards an understanding of the benefits of intense exercise, but disappointing in that we never seem to go the whole way from interval training to intense resistance training. If you really want to empty your glycogen stores and have some intense exercise, then go for BBS style HIT!

The other thing was that I found it disconcerting that the scientist who was extolling HIIT was not lean but on the way to obesity…..

I go over all of this science in by book Hillfit by the way.

Martin Gibala has been researching this too for a while and at least he looks lean

The Complete Guide to Interval Training





More Health and Fitness

Another week....another study on intervals

Well, another week and another study on the benefits of interval training.  This time it is Gibala's team again (they have done other work on intervals in the past e.g. this)  from  McMaster University in Ontario. The news story is here

Each session involved pedaling on a stationary bike for 10 repetitions of 60 seconds apiece at about 90 percent of maximal heart rate, interspersed with 60 seconds of rest, capped by a short warm-up and cool-down. Each entire exercise session lasted 25 minutes of which only 10 minutes was spent performing vigorous intensity exercise

The muscle biopsies revealed higher amounts of mitochondrial proteins, suggesting that the high-intensity, low-volume training increased the numbers of muscle cell power generators, a marker of improved metabolic health. Although the training regimen didn't decrease body mass in any of the participants, it did increase the maximal workload that each was able to achieve on the stationary bike and decreased heart rate during exercise, markers of improved fitness.

Again this is both exciting and frustrating.  Yes, short bursts of intense exercise have big impacts on mitochondrial biogenesis, insulin sensitivity and VO2 Max.....so for me I am excited that adding some sprints to my day can have a big benefit.  But as Alex Hutchison has pointed out recently in relation to a similar study how many people are likely to be motivated enough to find time even for this minimal exercise?

The abstract is here and the whole study is available here.

Low-volume high-intensity interval training reduces hyperglycemia and increases muscle mitochondrial capacity in patients with type 2 diabetes

Low-volume high-intensity interval training (HIT) is emerging as a time-efficient exercise strategy for improving health and fitness. This form of exercise has not been tested in type 2 diabetes and thus we examined the effects of low-volume HIT on glucose regulation and skeletal muscle metabolic capacity in patients with type 2 diabetes. Eight patients with type 2 diabetes (63±8 yr, BMI 32±6 kg/m2, HbA1C 6.9±0.7%) volunteered to participate in this study. Participants performed six sessions of HIT (10 x 60 s cycling bouts eliciting ~90% maximal heart rate, interspersed with 60 s rest) over 2 wk. Before training and from ~48-72 h after the last training bout, glucose regulation was assessed using 24-h continuous glucose monitoring under standardized dietary conditions. Markers of skeletal muscle metabolic capacity were measured in biopsy samples (vastus lateralis) before and after (72 h) training. Average 24-h blood glucose concentration was reduced after training (7.6±1.0 vs 6.6±0.7 mmol/L) as were the sum of the 3-h postprandial areas under the glucose curve for breakfast, lunch and dinner (both p<0.05). Training increased muscle mitochondrial capacity as evidenced by higher citrate synthase maximal activity (~20%) and protein content of Complex II 70 kDa subunit (~37%), Complex III Core 2 protein (~51%), and Complex IV subunit IV (~68%, all p<0.05). Mitofusin 2 (~71%) and GLUT4 (~369%) protein content were also higher after training (both p<0.05). Our findings indicate that low-volume HIT can rapidly improve glucose control and induce adaptations in skeletal muscle that are linked to improved metabolic health in patients with type 2 diabetes.