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 (HbA_1c), 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 (AIR_g) 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), HbA_1c (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), AIR_g (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.