Sarah L. Dunn

Factors that may impede the weight loss response to exercise-based interventions.

The results of exercise programmes designed to reduce body fat are disappointing. However, the reporting of weight loss as mean values disguises those individuals who do lose significant amounts of fat. Why some participants produce significant exercise‐induced fat loss whereas others lose little or increase fat stores is likely to be an outcome of a range of behavioural (e.g. sleep deprivation, caloric intake), inherited (e.g. muscle fibre type, gender) and physiological (e.g. hyperinsulinaemia, hypothyroidism) factors. The following review highlights possible factors involved in weight loss and discusses how individual differences may determine the extent of weight loss after an exercise intervention. Finally, implications for the treatment and prevention of obesity are discussed.

The relationship between cardiac autonomic function and maximal oxygen uptake response to high-intensity intermittent-exercise training

Abstract Major individual differences in the maximal oxygen uptake response to aerobic training have been documented. Vagal influence on the heart has been shown to contribute to changes in aerobic fitness. Whether vagal influence on the heart also predicts maximal oxygen uptake response to interval-sprinting training, however, is undetermined. Thus, the relationship between baseline vagal activity and the maximal oxygen uptake response to interval-sprinting training was examined. Exercisers (n = 16) exercised three times a week for 12 weeks, whereas controls did no exercise (n = 16). Interval-sprinting consisted of 20 min of intermittent sprinting on a cycle ergometer (8 s sprint, 12 s recovery). Maximal oxygen uptake was assessed using open-circuit spirometry. Vagal influence was assessed through frequency analysis of heart rate variability. Participants were aged 22 ± 4.5 years and had a body mass of 72.7 ± 18.9 kg, a body mass index of 26.9 ± 3.9 kg · m−2, and a maximal oxygen uptake of 28 ± 7.4 ml · kg−1 · min−1. Overall increase in maximal oxygen uptake after the training programme, despite being anaerobic in nature, was 19 ± 1.2%. Change in maximal oxygen uptake was correlated with initial baseline heart rate variability high-frequency power in normalised units (r = 0.58; P < 0.05). Thus, cardiac vagal modulation of heart rate was associated with the aerobic training response after 12 weeks of high-intensity intermittent-exercise. The mechanisms underlying the relationship between the aerobic training response and resting heart rate variability need to be established before practical implications can be identified.

The effect of a lifestyle intervention on metabolic health in young women

With the increasing obesity rates in Western countries, an effective lifestyle intervention for fat reduction and metabolic benefits is needed. High-intensity intermittent exercise (HIIE), Mediterranean eating habits (Mediet), and fish oil (ω-3) consumption positively impact metabolic health and adiposity, although the combined effect has yet to be determined. A 12-week lifestyle intervention on adiposity, insulin resistance, and interleukin-6 (IL-6) levels of young overweight women was administered. Thirty women with a body mass index of 26.6±0.5 kg/m2, blood pressure of 114/66±1.9/1.5 mmHg, and age of 22±0.8 years were randomly assigned to either an intervention group receiving Mediet advice, daily ω-3 supplementation, and HIIE 3 days/week for 12 weeks or a control group. The group receiving Mediet advice, daily ω-3 supplementation, and HIIE experienced a significant reduction in total body fat mass (P<0.001), abdominal adiposity (P<0.05), waist circumference (P<0.001), systolic blood pressure (P<0.05), fasting plasma insulin (P<0.05), IL-6 (P<0.001), and triglycerides (P<0.05). The greatest decreases in fasting plasma insulin (P<0.05) and IL-6 (P<0.001) occurred by week 6 of the intervention. Significant improvements in eating habits (P<0.05) and aerobic fitness (P<0.001) were also found following the intervention. A multifaceted 12-week lifestyle program comprising a Mediet, ω-3 supplementation, and HIIE induced significant improvements in fat loss, aerobic fitness, and insulin and IL-6 levels, positively influencing metabolic health.

Regional adiposity distribution and insulin resistance in young Chinese and European Australian women

Abstract Objective: Lower than normal leg fat mass and excessive trunk fat mass are predictive of insulin resistance (IR) in obese women of European descent. Whether this regional adiposity relationship applies to moderately overweight women of Chinese descent is undetermined. Thus, the relationship between leg and trunk fat mass and IR of young (22.3 ± 0.3 years) sedentary Australian women of either Chinese (CW; n = 22) or European (EW; n = 36) descent was examined. Material and methods: Subjects underwent a maximal oxygen uptake test, blood draw, and dual energy x-ray absorptiometry to measure body composition. Fasting insulin levels and C-reactive protein (CRP) were assessed by ELISA and IR was calculated by HOMA-IR. Blood lipids and glucose were quantified by an automated enzymatic method (Cholestech LDX, USA). Results: Total, arm, trunk, and leg fat was significantly greater (p < 0.05) for the EW group, whereas IR was significantly higher for CW. Fasting lipids and glucose were within normal levels for both groups, whereas CRP levels were significantly higher in EW. For EW trunk fat mass was the only variable significantly correlated with IR (r = 0.40, p < 0.05). In contrast, for CW leg fat mass was significantly correlated with IR (r = − 0.49, p < 0.05). Conclusions: Greater trunk fat mass was associated with higher IR of Australian women of European descent, whereas smaller leg fat mass was associated with higher IR of women of Chinese descent.

An Introduction to Statistical Analysis in Research: With Applications in the Biological and Life Sciences

An Introduction to Statistical Analysis in Research: With Applications in the Biological and Life Sciences develops a conceptual foundation in statistical analysis while providing readers with opportunities to practice these skills via research-based data sets in biology, kinesiology, and physical anthropology. Readers are provided with a detailed introduction and orientation to statistical analysis as well as practical examples to ensure a thorough understanding of the concepts and methodology. In addition, the book addresses not just the statistical concepts researchers should be familiar with, but also demonstrates their relevance to real-world research questions and how to perform them using easily available software packages including R, SPSS®, Excel®, and Numbers®. Specific emphasis is on the practical application of statistics in the biological and life sciences, while enhancing reader skills in identifying the research questions and testable hypotheses, determining the appropriate experimental methodology and statistical analyses, processing data, and reporting the research outcomes.