Date of Award

2014

Degree Type

Thesis

Degree Name

Master of Science

School

School of Exercise and Health Sciences

Faculty

Faculty of Health, Engineering and Science

First Advisor

Professor Robert U Newton

Second Advisor

Dr. Chris Abbiss

Third Advisor

Dr. Michael Baker

Fourth Advisor

Dr. Greig Watson

Abstract

Aerobic interval training, a form of high intensity interval training, is commonly prescribed to both the general and clinical populations. However, the acute physiological effects from a single bout of aerobic interval session are not fully understood. In training studies, these acute physiological effects may confound actual training adaptations when they occur following the final training session [1]. Furthermore, while recreationally active men perceived aerobic interval training to be more enjoyable than continuous moderate-intensity exercise [2], the preference of overweight and obese individuals has not been extensively researched. Since overweight and obese individuals tend to have lower exercise tolerance, it is possible that their perceived enjoyment may differ to recreationally active participants. Thus, the aim of this study was to examine the physiological effects and perceived enjoyment of an acute bout of aerobic interval (AI) and a continuous moderate-intensity (CME) in an overweight and obese population. In a randomised and counterbalanced order, eight overweight/obese (waist: 103 ± 10 cm) participants performed bouts of CME (40 min at 50% of peak power output (PPO)) and AI cycling (13 x 1 min at 85% of PPO: 13 x 2 min at 30% of PPO). CME and AI were matched for duration and total work performed. Salivary cortisol was measured before, 10 and 30 min post exercise and analysed using standard enzyme-linked immunosorbent assay kits. Blood pressure (BP), blood metabolites (glucose and lipid), insulin and resting metabolism were measured at baseline, post 24, 48 and 72 h exercise trials in a fasted and rested state. Peripheral BP was measured in duplicate using a manual sphygmomanometer and central BP and its associated hemodynamic parameters were derived from the radial pulse wave using a sphygmocardiogram (SphygmoCor). Resting metabolic profile was determined from gas exchange (TrueOne® gas analyser) measured in a supine and rested state over 40 min. Anthropometric (waist and hip circumferences and body composition) measurements were taken at baseline and at post 72 h after the last exercise trial. Participants completed the Physical Activity Enjoyment Scale (PACES) at the end of each trial. Salivary cortisol expressed as a percentage of baseline level increased in both trials and was significantly (mean ± SD) 189 ± 35% (p < 0.05) higher at 30 min post exercise. Resting brachial diastolic BP was lower in the AI trial compared with CME trial (82 ± 5 vs. 84 ± 5 mmHg respectively, p < 0.05). Resting brachial diastolic BP was lower than baseline (86 ± 12 mmHg) at 24 h (83 ± 5 mmHg, p < 0.05) and at 72 h (82 ± 5 mmHg, p < 0.05) post exercise, however, there was no significant interaction between exercise trials and time points (p = 0.07). Resting brachial mean arterial pressure was lower than baseline (102 ± 14 mmHg) at 24 h (99 ± 6 mmHg, p < 0.05), 48 h (98 ± 6 mmHg, p < 0.05) and 72 h (98 ± 6 mmHg, p < 0.05) post exercise. Resting brachial mean arterial pressure was also lower in the AI trial compared with CME trial (98 ± 6 vs. 100 ± 5 mmHg respectively, p < 0.05), however, there was no significant interaction between exercise trials and time points (p = 0.07). Derived resting aortic diastolic BP was lower in the AI trial, compared with the CME trial (83 ± 5 vs. 85 ± 5 mmHg respectively, p < 0.05). Compared with baseline (87 ± 4 mmHg), derived resting aortic diastolic BP was lower at 24 h (83 ± 5 mmHg, p < 0.05) and 72 h (82 ± 5 mmHg, p < 0.05) post exercise. No significant interaction effects were observed for derived resting central diastolic BP (p = 0.10). Derived resting mean aortic pressure was lower in the AI trial, compared with the CME trial (98 ± 6 mmHg vs. 100 ± 5 mmHg, respectively, p < 0.05). Compared with baseline (102 ± 5 mmHg), derived resting mean aortic pressure was lower at 24 h (99 ± 6 mmHg, p < 0.05), 48 h (98 ± 6 mmHg, p < 0.05) and 72 h (98 ± 6 mmHg, p < 0.05) post exercise. There was a trend towards interaction effects for resting derived mean aortic BP, however significance was not reached (p = 0.063). Resting carbohydrate oxidation rate was higher than baseline (0.10 ± 0.06 g/min) at 72 h post exercise (0.16 ± 0.02 g/min), with no significant difference observed between trials. PACES scores were significantly higher for the AI than the CME trial (109 ± 13 vs. 96 ± 10). The main finding from this study is that a single AI and CME session can elicit acute physiological effects that last up to 72 h, with no significant difference observed between conditions. Significant decrements in diastolic and mean arterial pressures were observed up to 72 h and resting carbohydrate oxidation rate was significantly higher 72 h following exercise. Therefore, training studies should look at scheduling post study measurement sessions more than 72 h after the last exercise session bout to avoid confounding acute physiological effects with training adaptations. Finally, the study has also demonstrated that overweight/obese males enjoy the AI session more than the CME session.

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