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.