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Effects of accumulating short bouts of exercise on glucose tolerance and insulin action
Author
Yap, Margaret Mei Chan
Supervisor
Burns, Stephen Francis
Abstract
Background: Expert guidelines recommend that physical activity can be accumulated in bouts with a minimum duration of 10 min, to achieve the 30 min per day necessary for good health. Whilst the concept of accumulating exercise is attractive and may be more convenient and achievable than longer bouts of exercise, the evidence for its efficacy on health outcomes is limited.
Objective: The aims of the present study were: 1) To evaluate if glucose tolerance and insulin action could be improved following 30 min bouts of continuous or accumulated exercise compared with no exercise and; 2) To compare differences between 30 min of accumulated and continuous exercise on glucose tolerance and insulin action.
Design: Twenty healthy participants (10 male), aged 23.3 (3.2) years, BMI 21.1 (1.8) kg/m2 , and maximal oxygen uptake (∨02 max) 39.5 (7.9) ml/kg/min [mean (SD)] volunteered for this study. Each participant undertook an oral glucose tolerance test (OGTT) in a random order the morning after: (1) a no exercise resting control trial, (2) a continuous 30 min walk at 70% max and (3) accumulating three bouts of 10 min walking at 70% ∨02 max, with 20 min rest intervals. In the mornings, blood samples were taken fasted and in response to a standardised 2 hour, 75 g OGTT and analysed for glucose, insulin and C-peptide. Fasting insulin sensitivity was calculated using the homeostasis model assessment 2 (HOMA2) and whole body insulin sensitivity from fasting and OGTT measures using the Matsuda index. Fasted and summary data was compared among trials using one- way ANOVA. Differences in glucose, insulin and C-peptide among trials and over time were compared using two-way ANOVA. Post-hoc Bonferroni t- tests were used where appropriate.
Results: Fasting glucose and insulin did not differ among trials. The HOMA2 index significantly differed among trials in males with an improvement found after continuous exercise compared with control (Contd 238.5; Ctrl 167.0; p=0.04). In females HOMA2 index differed significantly among trials with an improvement after accumulated exercise (Acc 186.0; Ctrl 138.5; p=0.02), compared with control. There was no difference among trials in glucose, insulin or C-peptide after the OGTT. Whole body insulin sensitivity showed an improvement of continuous exercise over rest in males (Contd 8.51; Ctrl 6.34; p=0.06) and a trend for improvement of accumulated exercise over rest in females (Acc 7.88; Ctrl 6.26; p=0.07). There was no sex difference for fasting insulin sensitivity but whole body insulin sensitivity differed between males and females (p=0.04) in the continuous exercise trials (Matsuda index males 8.51; Matsuda index females 6.37).
Conclusion: The major findings from the present study are: 1) accumulating 30 min of vigorous exercise improved, or showed a trend to improve, fasting and postprandial insulin sensitivity in females and 2) in males fasting and postprandial insulin sensitivity improved only after 30 min of vigorous continuous exercise. These data may suggest improvements in insulin sensitivity can be achieved by completing exercise of a duration in line with current recommendations but the ideal pattern of exercise may differ between females and males.
Objective: The aims of the present study were: 1) To evaluate if glucose tolerance and insulin action could be improved following 30 min bouts of continuous or accumulated exercise compared with no exercise and; 2) To compare differences between 30 min of accumulated and continuous exercise on glucose tolerance and insulin action.
Design: Twenty healthy participants (10 male), aged 23.3 (3.2) years, BMI 21.1 (1.8) kg/m2 , and maximal oxygen uptake (∨02 max) 39.5 (7.9) ml/kg/min [mean (SD)] volunteered for this study. Each participant undertook an oral glucose tolerance test (OGTT) in a random order the morning after: (1) a no exercise resting control trial, (2) a continuous 30 min walk at 70% max and (3) accumulating three bouts of 10 min walking at 70% ∨02 max, with 20 min rest intervals. In the mornings, blood samples were taken fasted and in response to a standardised 2 hour, 75 g OGTT and analysed for glucose, insulin and C-peptide. Fasting insulin sensitivity was calculated using the homeostasis model assessment 2 (HOMA2) and whole body insulin sensitivity from fasting and OGTT measures using the Matsuda index. Fasted and summary data was compared among trials using one- way ANOVA. Differences in glucose, insulin and C-peptide among trials and over time were compared using two-way ANOVA. Post-hoc Bonferroni t- tests were used where appropriate.
Results: Fasting glucose and insulin did not differ among trials. The HOMA2 index significantly differed among trials in males with an improvement found after continuous exercise compared with control (Contd 238.5; Ctrl 167.0; p=0.04). In females HOMA2 index differed significantly among trials with an improvement after accumulated exercise (Acc 186.0; Ctrl 138.5; p=0.02), compared with control. There was no difference among trials in glucose, insulin or C-peptide after the OGTT. Whole body insulin sensitivity showed an improvement of continuous exercise over rest in males (Contd 8.51; Ctrl 6.34; p=0.06) and a trend for improvement of accumulated exercise over rest in females (Acc 7.88; Ctrl 6.26; p=0.07). There was no sex difference for fasting insulin sensitivity but whole body insulin sensitivity differed between males and females (p=0.04) in the continuous exercise trials (Matsuda index males 8.51; Matsuda index females 6.37).
Conclusion: The major findings from the present study are: 1) accumulating 30 min of vigorous exercise improved, or showed a trend to improve, fasting and postprandial insulin sensitivity in females and 2) in males fasting and postprandial insulin sensitivity improved only after 30 min of vigorous continuous exercise. These data may suggest improvements in insulin sensitivity can be achieved by completing exercise of a duration in line with current recommendations but the ideal pattern of exercise may differ between females and males.
Date Issued
2013
Call Number
QP301 Yap
Date Submitted
2013