Most studies evaluating the efficacy of exercise tend to overlook inter-individual variability( Reference King, Hopkins and Caudwell 1 ). The aim of the present study was to investigate the effect of 12 weeks of high intensity interval training on metabolic control, beta-cell secretion and insulin resistance among ten individuals with newly diagnosed type 2 diabetes. Baseline measures included body composition, glycosylated haemoglobin (HbA1c), lipid profile and tests performed were meal tolerance test (MTT) and frequently sampled intravenous glucose tolerance test (FSIVGTT). Measures of fasting (M0) and postprandial (M1) beta-cell responsiveness, and acute insulin response to glucose (AIRg) were determined and HOMA-IR calculated as a measure of insulin resistance. Interval training was scheduled 3 times·week−1 and used individualized exercise intensities determined using the heart rate reserve (HRR) method. Following an introductory phase during weeks 1 and 2, training progressed to 20–40 min periods of interval training consisting of low-intensity periods of 1–2 min at 40–50% HRR and high-intensity periods of 1, 2 or 3 min at 80–90% HRR (weeks 3–12). All baseline measurements and tests were repeated post intervention.
Average [range] compliance was observed as 63.0[38.9–80.5]% at an intensity of 77.3[65.8–86.5]% HRR. Group analysis indicated there were significant changes following intervention in BMI (30.0 vs. 28.7 kg.m−2; p=0.006), waist circumference (101.4 vs. 97.2 cm; p=0.021), HbA1c (6.4 vs. 6.0%; p=0.007), total cholesterol (5.3 vs. 4.6 mmol.L−1; p=0.046), low-density lipoprotein (LDL) cholesterol (3.2 vs. 2.6 mmol.L−1; p=0.028), M0 (11.5×10−9 vs. 7.0×10−9 pmol.kg−1.min−1; p=0.009), AIRg (20.4 vs. 27.2; p=0.05) and HOMA-IR (3.0 vs. 2.1; p=0.049). However, the Table below illustrates that within the group there were also considerable variations in response to interval training both among individuals and among the measured parameters.
Values presented are percentage (%) change in relation to baseline.
Although in some instances inter-individual variation may be explained by compliance( Reference Manninen, Elo and Frick 2 ) it is plausible that response to exercise stimuli can vary from one individual to another( Reference Bouchard and Rankinnen 3 ). Individuals and measured parameters may be described as showing ‘high’ or ‘low’ sensitivity to exercise stimuli( Reference Booth and Laye 4 ). Exercise programmes modelled on personalised interventions which provide greater consideration of variation in response among individuals and parameters of interest should be promoted and further researched.
