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Research Bites

Bracko, Michael R. Ed.D., FACSM

doi: 10.1249/FIT.0b013e31823d02f6

More good news about High-Intensity Interval Training for Kids; The Exercise Gene?; How to improve exercise adherence: More important than why.

Michael R. Bracko, Ed.D., FACSM, is an exercise physiologist and director of the Institute for Hockey Research and Dr. Bracko’s Fitness in Calgary, Canada. He is an associate editor and regular contributor for ACSM’s Health & Fitness Journal® and works in three areas: 1) the health and fitness industry, by contributing to fitness magazines, media consulting, and presenting at health and fitness meetings such as the ACSM’s Health & Fitness Summit & Exposition; 2) sports physiology, where he conducts research on the performance characteristics of female ice hockey players, teaches high performance skating, and serves as the physiologist and strength and conditioning coach for the U.S.A. Men’s Deaf Olympic Hockey Team; and 3) occupational physiologist in the areas of back injury prevention, ergonomics, work-station stretching, and pre-work warm-up.

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There is a lot of new and exciting research on high-intensity interval training (HIIT), and this study is no exception. This study investigated the effects of brief, intense exercise compared with traditional endurance exercise on risk factors for cardiovascular disease in youth.

Forty-seven boys and 10 girls (16.4 ± 0.7 years) were divided into three groups: moderate-intensity, high-intensity, or a no-exercise control group. The moderate-intensity group (12 boys and 4 girls) and the high-intensity group (15 boys and 2 girls) performed three weekly exercise sessions for 7 weeks. Each session completed by participants in the high-intensity group consisted of four to six repeats of maximal sprint running within a 20-m area with 20 to 30 second recovery, whereas participants in the moderate-intensity group performed 20 minutes of continuous running within a 20-m area at 70% maximal oxygen uptake (V˙O2max).

Total exercise time during the study was 420 minutes for the moderate-intensity group and 63 minutes for the high-intensity group. Training volume was 85% lower for the high-intensity group. Total estimated energy expenditure was 907.2 kcal (high-intensity group) and 441.0 kcal (moderate-intensity group).

The results indicated that after 7 weeks there were significant improvements in systolic blood pressure, aerobic fitness, and body mass index in the high-intensity group. In the moderate-intensity group, systolic blood pressure was not improved, but there were significant improvements in aerobic fitness, percentage body fat, and body mass index. The authors suggest that HIIT is a time-efficient way of improving the cardiovascular risk factor profile in adolescents (2).

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In this groundbreaking study, the researchers investigated participants in the Health, Risk Factors, Exercise Training, and Genetics (HERITAGE) Family Study to see if there is an exercise gene that makes it easier to exercise and obtain results.

The researchers analyzed 324,611 single-nucleotide polymorphisms (SNPs) (also known as DNA sequence variations) to identify SNPs associated with improvements in V˙O2max in 473 sedentary adults, all whites, from 99 families of the HERITAGE Family Study. Although there were three separate studies, in each study, the exercise protocols for the subjects varied so that they exercised at various percentages of their V˙O2max. Each subject’s V˙O2max was measured before and after each exercise protocol study.

The results showed that some subjects improved their V˙O2max, and some had no improvements in V˙O2max. The researchers then looked at each subject’s SNPs to investigate if there was an association with improved V˙O2max. They found that there were 21 SNPs that accounted for 49% of the variance in V˙O2max trainability. Moreover, subjects who carried nine or less of the favorable SNPs improved their V˙O2max by 221 mL/min, whereas the subjects who carried 19 of the favorable SNPs gained V˙O2max, on average, by 604 mL/min.

The authors suggest that these gene predictors of the response of V˙O2max to regular exercise provide new targets for the study of the biology of fitness and its adaptation to regular exercise (1).

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In this study, the investigators conducted a meta-analysis (combines the results of several studies) and summarized the effects of interventions designed to increase physical activity among healthy adults. The investigation included 358 studies that were eligible for inclusion, comprising 99,011 subjects.

The analyses suggested that the characteristics of the most effective interventions were behavioral interventions instead of cognitive interventions. In other words, face-to-face individual targeted programs that focused on how to improve physical activity were more effective than programs that focused on why it is important to improve physical activity.

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The authors suggest that the focus of improving motivation needs to change from increasing a person’s knowledge about the benefits of exercise to talking about strategies aimed at making actual changes in behavior to increase physical activity (3).

Disclosure: The author declares no conflict of interest and does not have any financial disclosures.

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1. Bouchard C, Sarzynski MA, Rice TK, et al. Genomic predictors of the maximal O2 uptake response to standardized exercise training programs. J Appl Physiol. 2011:110(5):1160–70.
2. Buchan DS, Ollis S, Young JD, et al. The effects of time and intensity of exercise on novel and established markers of CVD in adolescent youth. Am J Hum Biol. 2011:23(4):517–26.
3. Conn VS, Hafdahl AR, Mehr DR. Interventions to increase physical activity among healthy adults: meta-analysis of outcomes. Am J Public Health. 2011:101(4):751–8.
© 2012 American College of Sports Medicine.