If you spend just ten minutes doing interval training three times a week you’ll find yourself becoming noticeably fitter, healthier and slimmer. Canadian sports scientists have written about it in PLoS One. And it doesn’t stop there: during the very short training sessions, you only have to exert yourself to the max for 20 seconds, three times.
For a period of 12 weeks the researchers got nineteen healthy men with a sedentary lifestyle to train in a gym three times a week. Six men did not training and functioned as the control group. [CTL]
Ten men cycled for 45 minutes at an intensity of 70 percent of their maximal heart rate [MICT]. Nine men did an interval training [SIT] session that lasted only ten minutes. During this short period the men cycled as fast as they could three times for 20 seconds. Between the short explosive bursts the men cycled for two minutes at low intensity.
The men in the two training groups all lost a small amount of body fat. In both groups the fat percentage decreased by two percentage points.
The maximal oxygen uptake, the most important indicator of fitness, increased by almost twenty percent in both training groups.
PRE = before training started; MID = after 6 weeks of training; POST = after 12 weeks of training.
The figure below shows that the short interval training improved insulin sensitivity almost as much as the traditional longer training sessions did. The researchers regard this as “perhaps the most striking and novel finding from the present work”.
The researchers took a small piece of muscle fibre from their subjects’ vastus lateralis muscle and measured the activity of the mitochondria using citrate synthase. The enzyme citrate synthase is needed for the first step of the citric acid cycle, a complex reaction in which cells convert nutrients into energy.
The figures below show that the interval training and conventional training sessions boosted the activity of citrate synthase by the same amount.
“The major novel finding from the present study was that 12 weeks of sprint interval training in previously inactive men improved insulin sensitivity, cardiorespiratory fitness, and skeletal muscle mitochondrial content to the same extent as traditional moderate-intensity continuous training, despite a five-fold lower exercise volume and training time commitment”, the researchers wrote.
“This investigation represents the longest comparison of sprint interval training and moderate-intensity continuous training to date and demonstrates the efficacy of brief, intense exercise to improve indices of cardiometabolic health.”
“While sprint interval training is clearly a potent stimulus to elicit physiological adaptations, this type of exercise requires a very high level of motivation and is clearly not suited for everyone.”
Twelve Weeks of Sprint Interval Training Improves Indices of Cardiometabolic Health Similar to Traditional Endurance Training despite a Five-Fold Lower Exercise Volume and Time Commitment
We investigated whether sprint interval training (SIT) was a time-efficient exercise strategy to improve insulin sensitivity and other indices of cardiometabolic health to the same extent as traditional moderate-intensity continuous training (MICT). SIT involved 1 minute of intense exercise within a 10-minute time commitment, whereas MICT involved 50 minutes of continuous exercise per session.
Sedentary men (27±8y; BMI = 26±6kg/m2) performed three weekly sessions of SIT (n = 9) or MICT (n = 10) for 12 weeks or served as non-training controls (n = 6). SIT involved 3×20-second ‘all-out’ cycle sprints (~500W) interspersed with 2 minutes of cycling at 50W, whereas MICT involved 45 minutes of continuous cycling at ~70% maximal heart rate (~110W). Both protocols involved a 2-minute warm-up and 3-minute cool-down at 50W.
Peak oxygen uptake increased after training by 19% in both groups (SIT: 32±7 to 38±8; MICT: 34±6 to 40±8ml/kg/min; p<0.001 for both). Insulin sensitivity index (CSI), determined by intravenous glucose tolerance tests performed before and 72 hours after training, increased similarly after SIT (4.9±2.5 to 7.5±4.7, p = 0.002) and MICT (5.0±3.3 to 6.7±5.0 x 10?4 min-1 [?U/mL]-1, p = 0.013) (p<0.05). Skeletal muscle mitochondrial content also increased similarly after SIT and MICT, as primarily reflected by the maximal activity of citrate synthase (CS; P<0.001). The corresponding changes in the control group were small for VO2peak (p = 0.99), CSI (p = 0.63) and CS (p = 0.97).
Twelve weeks of brief intense interval exercise improved indices of cardiometabolic health to the same extent as traditional endurance training in sedentary men, despite a five-fold lower exercise volume and time commitment.