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Time-efficient high-intensity exercise improves glycaemic control similarly to moderate-intensity exercise in overweight humans
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Friday 23 October Papers / Journal of Science and Medicine in Sport 19S (2015) e57–e87
Award Finalist 165 Exercise and visceral fat loss: is waist circumference a useful predictor? N. Johnson 1,∗ , S. Keating 1 , K. Way 1 , A. Sainsbury 2 , M. Baker 3 , V. Chuter 4 , I. Caterson 2 , J. George 5 1
Faculty of Health Sciences, University of Sydney, NSW, Australia 2 Boden Institute, Sydney Medical School, University of Sydney, NSW, Australia 3 School of Exercise Science, Australian Catholic University, NSW, Australia 4 School of Health Sciences, University of Newcastle, Newcastle, Australia 5 Storr Liver Centre, Westmead Millennium Institute, NSW, Australia Introduction: It is now widely accepted that fat stored around the abdominal organs as visceral adipose tissue (VAT) is more strongly linked to cardiovascular and metabolic disease risk than body weight or total body fat. Studies using computed tomography or magnetic resonance imaging have shown that regular exercise can reduce subcutaneous adipose tissue (SAT) and VAT. However, the ability to measure these outcomes, and therefore the efficacy of an exercise intervention, is limited by the availability, invasiveness and cost of these techniques. Waist circumference is often used as a surrogate measure for abdominal fatness, but there is little data concerning the validity of waist circumference measurement for inferring VAT change with therapeutic interventions. We aimed to examine the efficacy of waist circumference change for predicting abdominal fat change in response to exercise programs delivered according to current recommendations. Methods: Forty-five previously inactive and overweight/obese (BMI >25 kg/m2 ) adults (29–59 y) were randomised to receive 8 weeks of aerobic exercise (n = 36, 30–60 min per session at 50–70% of VO2 peak, 3–4 days per week) or resistance exercise therapy (n = 9, 8–10 exercises per session, 8–12 reps, 2–3 sets per exercise at 80–85% of 1-repetition maximum, 3 days per week). VAT and SAT were measured before and after exercise training interventions via magnetic resonance imaging. Change in waist circumference was compared with change in VAT and SAT volumes using Pearson coefficients. Values are reported as means ± SE. Results: There was a significant reduction in waist circumference (1.9 ± 0.3 cm), SAT (440 ± 111 cm3 ) and VAT (259 ± 55 cm3 ) with exercise training. There was a weak correlation between change in waist circumference and SAT (r = 0.322, P = 0.031). However, there was no significant correlation between change in waist circumference and VAT (r = 0.190, P = 0.211). Discussion: These preliminary results suggest that exercise training is effective for reducing visceral adipose tissue in overweight/obese adults. However, change in waist circumference may be a poor predictor of this benefit. Valid, readily accessible options for measuring changes in visceral adiposity in practice are needed. http://dx.doi.org/10.1016/j.jsams.2015.12.179
166 Time-efficient high-intensity exercise improves glycaemic control similarly to moderate-intensity exercise in overweight humans L. Parker 1,∗ , C. Shaw 2 , L. Banting 1 , K. Hill 1 , A. McAinch 1 , I. Levinger 1 , N. Stepto 1 1
Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Australia 2 School of Exercise and Nutrition Sciences, Deakin University, Geelong, Australia Background: Obesity and physical inactivity are associated with impaired glycaemic control which can lead to insulin resistance and chronic lifestyle disease. While physical activity improves glycaemic control and reduces the risk of disease, 62% of Australians do not achieve the current physical activity guidelines with “lack of time” the most commonly cited barrier. We therefore compared the effect of “time-efficient” high-intensity interval exercise (HIIE) on glycaemic control to that of continuous moderate-intensity exercise (CMIE) in inactive, overweight/obese males and females. Methods: Twenty-seven inactive, overweight/obese participants were matched and randomised into HIIE (9 females, 5 males; mean age 30.3, range 23–38 years; BMI = 29.2 ± 5.2 kg m−2 ; M ± SD) or CMIE (8 females, 5 males; mean age 30.4, range 19–40; BMI = 30.0 ± 6.6). One hour after breakfast the HIIE group performed a single session of 8 × 1 min cycling bouts (100% Wmax) interspersed with 1 min recovery, whereas the CMIE group performed 38 ± 1 min of continuous cycling exercise (50% Wmax). Continuous glucose monitoring (CGM) was conducted 24 h before (non-exercise control day) and after exercise (exercise day). Standardised meals for breakfast, lunch and dinner were consumed throughout. Results: Baseline glucose concentrations on the exercise day (HIIE: 4.72 ± 0.34, CMIE: 5.05 ± 0.97 mmol/l) and non-exercise day (HIIE: 4.50 ± 0.38, CMIE: 4.99 ± 1.03) were not different between groups or intervention (p > 0.05). Compared to non-exercise control days CGM data showed similar reductions in average 2 h postprandial glucose levels after dinner with HIIE (−13 ± 20%; p < 0.05) and CMIE (−8 ± 12%; p = 0.05). HIIE and CMIE similarly decreased 24 h average glucose levels (−7 ± 8%, −4 ± 6%; p < 0.05), 24 h peak glucose concentrations (−10 ± 11%, −10 ± 13%; p < 0.05), and 24 h total glucose area under the curves (−7 ± 9%, −4 ± 6%; p < 0.05), respectively. The percentage of time spent above 7 mmol/l over the 24 h period was decreased with HIIE (−2 ± 2%; p < 0.05). HIIE significantly increased the time spent below 3.9 mmol/l over the 24 h period compared to CMIE (+16 ± 17% vs. +1 ± 13%; p < 0.05, respectively), coinciding with a significant decrease in time spent between 3.9 and 7.0 mmol/l compared to CMIE (−14 ± 18% vs. +1 ± 15%; p < 0.05, respectively). Discussion: HIIE and CMIE both improved glycaemic control in the 24 h period following exercise. The HIIE was however ⊕38% more time-efficient, consisted of ⊕23% less total work (Watts), and increased the time spent with lowered glucose levels over a 24 h period. HIIE therefore may be a convenient and physiologically beneficial exercise model to be included in exercise programs for overweight and inactive populations who are at risk of developing chronic lifestyle disease. http://dx.doi.org/10.1016/j.jsams.2015.12.180
Friday 23 October Papers / Journal of Science and Medicine in Sport 19S (2015) e57–e87
Award Finalist 165 Exercise and visceral fat loss: is waist circumference a useful predictor? N. Johnson 1,∗ , S. Keating 1 , K. Way 1 , A. Sainsbury 2 , M. Baker 3 , V. Chuter 4 , I. Caterson 2 , J. George 5 1
Faculty of Health Sciences, University of Sydney, NSW, Australia 2 Boden Institute, Sydney Medical School, University of Sydney, NSW, Australia 3 School of Exercise Science, Australian Catholic University, NSW, Australia 4 School of Health Sciences, University of Newcastle, Newcastle, Australia 5 Storr Liver Centre, Westmead Millennium Institute, NSW, Australia Introduction: It is now widely accepted that fat stored around the abdominal organs as visceral adipose tissue (VAT) is more strongly linked to cardiovascular and metabolic disease risk than body weight or total body fat. Studies using computed tomography or magnetic resonance imaging have shown that regular exercise can reduce subcutaneous adipose tissue (SAT) and VAT. However, the ability to measure these outcomes, and therefore the efficacy of an exercise intervention, is limited by the availability, invasiveness and cost of these techniques. Waist circumference is often used as a surrogate measure for abdominal fatness, but there is little data concerning the validity of waist circumference measurement for inferring VAT change with therapeutic interventions. We aimed to examine the efficacy of waist circumference change for predicting abdominal fat change in response to exercise programs delivered according to current recommendations. Methods: Forty-five previously inactive and overweight/obese (BMI >25 kg/m2 ) adults (29–59 y) were randomised to receive 8 weeks of aerobic exercise (n = 36, 30–60 min per session at 50–70% of VO2 peak, 3–4 days per week) or resistance exercise therapy (n = 9, 8–10 exercises per session, 8–12 reps, 2–3 sets per exercise at 80–85% of 1-repetition maximum, 3 days per week). VAT and SAT were measured before and after exercise training interventions via magnetic resonance imaging. Change in waist circumference was compared with change in VAT and SAT volumes using Pearson coefficients. Values are reported as means ± SE. Results: There was a significant reduction in waist circumference (1.9 ± 0.3 cm), SAT (440 ± 111 cm3 ) and VAT (259 ± 55 cm3 ) with exercise training. There was a weak correlation between change in waist circumference and SAT (r = 0.322, P = 0.031). However, there was no significant correlation between change in waist circumference and VAT (r = 0.190, P = 0.211). Discussion: These preliminary results suggest that exercise training is effective for reducing visceral adipose tissue in overweight/obese adults. However, change in waist circumference may be a poor predictor of this benefit. Valid, readily accessible options for measuring changes in visceral adiposity in practice are needed. http://dx.doi.org/10.1016/j.jsams.2015.12.179
166 Time-efficient high-intensity exercise improves glycaemic control similarly to moderate-intensity exercise in overweight humans L. Parker 1,∗ , C. Shaw 2 , L. Banting 1 , K. Hill 1 , A. McAinch 1 , I. Levinger 1 , N. Stepto 1 1
Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Australia 2 School of Exercise and Nutrition Sciences, Deakin University, Geelong, Australia Background: Obesity and physical inactivity are associated with impaired glycaemic control which can lead to insulin resistance and chronic lifestyle disease. While physical activity improves glycaemic control and reduces the risk of disease, 62% of Australians do not achieve the current physical activity guidelines with “lack of time” the most commonly cited barrier. We therefore compared the effect of “time-efficient” high-intensity interval exercise (HIIE) on glycaemic control to that of continuous moderate-intensity exercise (CMIE) in inactive, overweight/obese males and females. Methods: Twenty-seven inactive, overweight/obese participants were matched and randomised into HIIE (9 females, 5 males; mean age 30.3, range 23–38 years; BMI = 29.2 ± 5.2 kg m−2 ; M ± SD) or CMIE (8 females, 5 males; mean age 30.4, range 19–40; BMI = 30.0 ± 6.6). One hour after breakfast the HIIE group performed a single session of 8 × 1 min cycling bouts (100% Wmax) interspersed with 1 min recovery, whereas the CMIE group performed 38 ± 1 min of continuous cycling exercise (50% Wmax). Continuous glucose monitoring (CGM) was conducted 24 h before (non-exercise control day) and after exercise (exercise day). Standardised meals for breakfast, lunch and dinner were consumed throughout. Results: Baseline glucose concentrations on the exercise day (HIIE: 4.72 ± 0.34, CMIE: 5.05 ± 0.97 mmol/l) and non-exercise day (HIIE: 4.50 ± 0.38, CMIE: 4.99 ± 1.03) were not different between groups or intervention (p > 0.05). Compared to non-exercise control days CGM data showed similar reductions in average 2 h postprandial glucose levels after dinner with HIIE (−13 ± 20%; p < 0.05) and CMIE (−8 ± 12%; p = 0.05). HIIE and CMIE similarly decreased 24 h average glucose levels (−7 ± 8%, −4 ± 6%; p < 0.05), 24 h peak glucose concentrations (−10 ± 11%, −10 ± 13%; p < 0.05), and 24 h total glucose area under the curves (−7 ± 9%, −4 ± 6%; p < 0.05), respectively. The percentage of time spent above 7 mmol/l over the 24 h period was decreased with HIIE (−2 ± 2%; p < 0.05). HIIE significantly increased the time spent below 3.9 mmol/l over the 24 h period compared to CMIE (+16 ± 17% vs. +1 ± 13%; p < 0.05, respectively), coinciding with a significant decrease in time spent between 3.9 and 7.0 mmol/l compared to CMIE (−14 ± 18% vs. +1 ± 15%; p < 0.05, respectively). Discussion: HIIE and CMIE both improved glycaemic control in the 24 h period following exercise. The HIIE was however ⊕38% more time-efficient, consisted of ⊕23% less total work (Watts), and increased the time spent with lowered glucose levels over a 24 h period. HIIE therefore may be a convenient and physiologically beneficial exercise model to be included in exercise programs for overweight and inactive populations who are at risk of developing chronic lifestyle disease. http://dx.doi.org/10.1016/j.jsams.2015.12.180