Table 1.
Characteristics of reviewed high-intensity exercise studies on healthy people without diabetes, and effects on insulin sensitivity and blood glucose
| Study | Gender | Intervention group Age (years) BMI (Kg/m2) Weight (Kg) Mean ± SD | Number in intervention group | Intervention | Study duration | Number in comparison group | Effect on measure of blood glucose |
|---|---|---|---|---|---|---|---|
| Richards et al39 | 5 male 7 female (sedentary or recreationally active) |
Age: 29 ± 3 BMI: 26.2 ± 1.3 Weight: 76 ± 6 |
12 | SIT (4 to 7 × 30 sec maximal cycle ergometer efforts separated by 4 minutes of rest). | Six SIT sessions over 2 weeks. Eight minutes of high-intensity exercise/week. | Single SIT control: 9 Sedentary control: 10 |
Six SIT sessions increased insulin sensitivity significantly 3 days after the last session compared to baseline, and comparison groups. No effect on FBG. |
| Babraj et al44 | Male (sedentary or recreationally active) | Age: 21 ± 2 BMI: 23.7 ± 3.1 Weight: 82 ± 17 |
16 | SIT (4 to 6 × 30 seconds of maximal cycle ergometer efforts separated by 4 minutes of rest). Total time commitment of 17 to 26 minutes per session. | Six SIT sessions over 2 weeks. Average of 7.5 minutes of high-intensity exercise/week. | Compared to baseline | 2 to 3 days after the last session, insulin sensitivity improved 23% (P < 0.01), and plasma glucose area under the curve decreased (P < 0.01) compared to baseline. No effect on FBG. |
| Burgomaster et al45 | Male (active) | Age: 22 ± 1 Weight: 80 ± 4 |
8 | SIT (4 to 6 × 30 seconds maximal cycle ergometer efforts separated by 4 minutes of rest). | Three sessions per week for 6 weeks. An average of 7.5 minutes of high-intensity exercise per week. | Compared to baseline | Muscle GLUT4 increased 20% after 1 week of SIT and remained elevated 6 weeks postexercise. |
| Whyte et al46 | Male Sedentary |
Age: 32 ± 9 BMI: 31 ±4 Weight: 94 ± 13 |
10 | SIT (4 to 6 × 30 seconds of maximal cycle ergometer efforts separated by 4.5 minutes of rest). | Six sessions over 2 weeks. | Compared to baseline | No change in FBG and glucose area under the curve at 24 and 72 hours after exercise, but insulin sensitivity index higher at 24 hours (P = 0.027). |
| Nybo et al47 | Male Sedentary |
Age: 37 ± 3 Weight: 96 ± 3 |
8 | 5-minute warm-up, then 5 × 2-minute intervals of running with heart rate 95% of maximum at the end of the interval (total exercise time 40 minutes/week). | Two sessions per week for 12 weeks. Twenty minutes of high-intensity exercise/week. |
9, performed 1-hour continuous running at 65% VO2max (about 150 minutes/week) 11, no exercise | Similar lowering of FBG and blood glucose 2 hours after a 75 g glucose tolerance test, done 48 hours after the last exercise session. |
| Sandvei et al48 | 4 males 7 females Sedentary to moderately trained |
Age: 18 to 35 BMI: 23 ± 1 Weight: 70 ± 3.5 |
11 | 10-minute warm-up, then 5 to 10×30 seconds near maximal sprints with 3-minute rest periods. | Three sessions/week for 8 weeks. | 12 performed continuous running at 70% to 80% maximal heart rate for 90 to 180 minutes/week | High-intensity running, but not continuous running, improved insulin sensitivity 60 hours after last exercise session. FBG significantly improved in both groups. |
Abbreviations: BMI, body mass index; SD, standard deviation; SIT, sprint interval training; FBG, fasting blood glucose; GLUT4, glucose transporter protein 4; VO2max, maximal oxygen uptake.