Response to Letter Regarding Article, “Aerobic Interval Training Versus Continuous Moderate Exercise as a Treatment for the Metabolic Syndrome: A Pilot Study”
Poelkens et al shared their concerns about our findings of larger improved insulin sensitivity with aerobic interval training than with continuous moderate exercise in patients with metabolic syndrome.1 On the basis of a study of overweight individuals2 (in which only 50% of the subjects completed the study) and a study3 including 69 patients with metabolic syndrome (not 171 as stated by Poelkens et al), they expected continuous moderate exercise to be equally effective as aerobic interval training on insulin sensitivity, as the training volume was the same in the 2 groups. They attributed our results to limitations of the homeostasis model assessment in assessing insulin sensitivity.
The homeostasis model assessment does have limitations, but we are confident that our conclusion remains well supported. This stems from the correlation of the homeostasis model assessment with signaling and metabolic markers measured in our study.1 There is little conclusive evidence for more favorable effects with aerobic interval training than with continuous moderate exercise in the literature, although there are some studies that suggest that high-intensity training provides more benefits to insulin action compared than does moderate/low-intensity exercise.4,5 However, these studies do not exclusively involve patients with metabolic syndrome. Moreover, it is difficult to compare the different studies, as our definition of moderate-intensity exercise (≈70% of maximum heart rate) corresponds to their definition of high-intensity exercise (65% to 80% of peak blood oxygen level).4,5 As discussed in our original article,1 larger multicenter studies with similar protocol should be performed to clarify this important issue.
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Houmard JA, Tanner CJ, Slentz CA, Duscha BD, McCartney JS, Kraus WE. Effect of the volume and intensity of exercise training on insulin sensitivity. J Appl Physiol. 2004; 96: 101–106.
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DiPietro L, Dziura J, Yeckel CW, Neufer PD. Exercise and improved insulin sensitivity in older women: evidence of the enduring benefits of higher intensity training. J Appl Physiol. 2006; 100: 142–149.
Evans EM, Racette SB, Peterson LR, Villareal DT, Greiwe JS, Holloszy JO. Aerobic power and insulin action improve in response to endurance exercise training in healthy 77–87 yr olds. J Appl Physiol. 2005; 98: 40–45.