. 2021 Oct 11;3(4):183–193. doi: 10.1016/j.smhs.2021.09.004

Table 3.

Influence of a single bout of exercise or repeated bouts of exercise on glycemic variability.

Author (publication date)	Study design	Primary findings	Conclusion	Strengths and limitations
Non-diabetic
Figueira FR et al. (2019)⁵²	Randomized crossover trial design; n = 15 2 experimental sessions; aerobic cycle ergometry; eccentric resistance exercise	Glucose variance and glucose %CV and SD were lower post-exercise compared to pre-exercise.	Acute aerobic and eccentric exercise promotes comparable reductions in glycemic variability.	Strengths: Controlled laboratory setting Limitations: Small sample size; exercise was of moderate to high intensity over an extended period
Little JP et al. (2014)⁵⁰	Randomized counterbalance trial design; n = 10 Two 3-day experimental exercise testing periods; continuous moderate-intensity (CMI) exercise; high-intensity interval exercise (HIIE)	Absolute PPG spike following standardized meals were significantly lower following HIIT exercise compared to no-exercise.	A single session of HIIE exercise improved overall postprandial glycemia in overweight or obese adults.	Strengths: Controlled laboratory setting. Limitations: Small sample size; inclusion of adults with impaired fating glucose
Parker L et al. (2017)⁵¹	Randomized clinical trial; n = 27 4-day experimental design; low volume high-intensity interval exercise (LV-HIIE); continuous moderate-intensity exercise (CMIE)	LV-HIIE resulted in lower mean glucose and peak glucose concentration, area under the curve, and time spent hyperglycemic compared to pre-exercise control.	LV-HIIE improves glycemic control similarly to CMIE in overweight and obese adults.	Strengths: Controlled laboratory setting Limitations: Small sample size; participants were not blinded to real-time CGM readings
*Type 1 diabetes*
van Dijk JW et al. (2016)⁵⁴	Observational during Nijegen Four Day Marches; n = 10 40–50 km walked per day over 4 days	CONGA-1 and CONGA-2 measures of glycemic variability were greater during walking event compared to habitual physical activity.	Prolonged continuous walking compared to habitual physical activity increased glycemic variability in type 1 diabetics.	Strengths: Examined a prolonged exposure to increase in physical activity Limitations: Small sample size; non-standard exercise modality
Manohar C et al. (2012)⁵³	Center-based clinical trial; n = 24 Increase daily energy expenditure 3-fold from measured basal metabolic rate over 3 monitored days	No change in %CV was noted in type 1 diabetic adults following meals with physical activity. Post-meal glycemic excursions were observed to be lower type 1 diabetics following meals with physical activity.	Performing low-intensity physical activity after meals, such as taking a short walk, potentially benefit type 1 diabetics by lowering postprandial glucose excursions.	Strengths: Age- and sex-matched healthy controls and type 1 diabetics; controlled laboratory setting Limitations: Small sample size; type 1 diabetics received insulin boluses prior to their meals
*Type 2 diabetes*
Farabi SS et al. (2015)⁵⁸	Center-based randomized clinical cross-over trial; n = 37 Two 3-day experimental trials both in morning; sedentary for 30 min; 30-min exercise session	Daytime CONGA-1 significantly decreased following exercise compared to sedentary trial.	A single bout of early morning moderate-intensity exercise reduced daytime glycemic variability in type 2 diabetic and/or impaired glucose tolerant obese adults.	Strengths: Controlled laboratory setting Limitations: Inclusion of adults with impaired glucose tolerance in the same group
van Dijk JW et al. (2013)⁵⁷	Randomized crossover trial; total n = 60; non-insulin treated n = 37; insulin treated = 23 Two 3-day intervention periods separated by a week; sedentary protocol; 45–60 min of continuous cycling	24-h mean glucose concertation, time spent hyperglycemic, and CONGA-1, CONGA-2, and CONGA-4 measures of glycemic variability were all lower following a single bout of exercise.	A single bout of moderate-intensity exercise reduces hyperglycemia and glycemic variability throughout the subsequent day following exercise.	Strengths: Use of CGM; inclusion of insulin and non-insulin treated type 2 diabetics Limitations: Only inclusion of males
Praet SF et al. (2006)⁵⁵	Intervention-based clinical trial; n = 11 Resistance exercise and aerobic exercise	Time spent hyperglycemic was significantly lower during the subsequent 24 h following exercise.	A single bout of exercise reduces the prevalence of hyperglycemia in insulin-treated, type 2 diabetic male adults.	Strengths: Implementation of resistance and aerobic exercise Limitations: Small sample size; large inter-subject variability
Figueria FR et al. (2013)⁵⁶	Randomized crossover design performed 7 days apart; n = 14 Aerobic exercise; aerobic plus resistance exercise	Changes in glycemic variability were noted in the aerobic plus resistance training group only.	Conventional analyses of glycemic variability may lack sensitivity to account for minor oscillations in glucose concentrations observed using non-conventional analyses.	Strengths: Implementation of resistance and aerobic exercise; use of conventional and non-conventional methods Limitations: Small sample size; no resistance exercise only group
Haxhi J et al. (2016)⁶⁰	Randomized crossover trial performed 7 days apart; n = 9 Control; 40-min split exercise (20-min pre-lunch, 20-min post-lunch); 40-min continuous exercise immediately post-lunch	Split exercise resulted in less time spent in hyperglycemia after lunch compared to continuous exercise. Continuous exercise reduced hyperglycemic time after breakfast consumed the morning after the exercise session.	Splitting an exercise session into 2 bouts, pre- and post-lunch, affects the glycemic response to lunch, while a single-continuous isoenergetic session exerts its effect later in the 24-h period.	Strengths: Implementation of a randomized crossover design; Evaluation of multiple measures of free-living glycemia. Limitations: Small sample size.
Myette-Cȏté É et al. (2016)⁵⁹	Randomized crossover design; n = 10 Morning-evening doses of metformin (no exercise); morning-evening doses of metformin with exercise; evening dose of metformin with exercise; morning dose of metformin with exercise	Morning-evening doses of metformin with exercise increased the average 2-h postprandial incremental AUC following standardize meals but did not affect daily mean or fasting glucose concentration.	The addition of a bout of exercise to metformin led to an increase in postprandial glucose levels without affecting mean glucose concentrations.	Strengths: Implementation of a randomized crossover design; Evaluation of metformin dosing with addition of exercise. Limitations: Small sample size; No exercise only group.
Terada T et al. (2016)⁶¹	Randomized, controlled, crossover design; n = 10 Fasted state high-intensity interval exercise (HIIEfast); post-breakfast HIIE (HIIEfed); fasted state moderate-intensity continuous exercise (MICEfast); post-breakfast MICE (MICEfed); no exercise control	Compared to the control condition, HIIEfast lowered 24-h mean glucose, fasting, overall postprandial glycemic increment, glycemic variability, and time spent in hyperglycemia.	HIIE is effective in lowering nocturnal/fasting glycemia. Exercise performed in the fasted state reduces postprandial glycemic increments.	Strengths: Implementation of a randomized crossover design; Evaluation of multiple modalities of exercise and comparing fasted versus fed state. Continual monitoring past the exercise or control condition. Limitations: Small sample size.
Dempsey PC et al. (2016)⁶²	Randomized cross-over trial; n = 24 8-h conditions on 3 separate days with 6–14 day washout period Uninterrupted sitting (control; SIT); sitting plus 3-min bouts of light-intensity walking (LW) every 30 min; sitting plus 3-min bouts of simple resistance activities (SRA) every 30 min	Compared with SIT, both activity-break conditions (LW and SRA) significantly attenuated incremental AUCs for glucose concentrations.	Interrupting prolonged sitting with brief bouts of LW or SRA attenuates acute postprandial glucose concentration responses in adults with type 2 diabetes mellitus.	Strengths: Implementation of a randomized crossover design; Evaluation of multiple modalities of exercise that are easily incorporated into everyday life. Limitations: Small sample size; no continuous exercise implementation to compare to breaks in sedentary time with exercise.
Dempsey PC et al. (2017)⁶³	Randomized cross-over trial; n = 24 8-h conditions on 3 separate days with 6–14 day washout period Uninterrupted sitting (control; SIT); sitting plus 3-min bouts of light-intensity walking (LW) every 30 min; sitting plus 3-min bouts of simple resistance activities (SRA) every 30 min	Compared with SIT, both LW and SRA reduced 22-h glucose and nocturnal mean glucose concentrations.	Interrupting prolonged sitting time with either LW or SRA reduced 22-h hyperglycaemia.	Strengths: Implementation of a randomized crossover design; Evaluation of multiple modalities of exercise that are easily incorporated into everyday life. Limitations: Small sample size; no continuous exercise implementation to compare to breaks in sedentary time with exercise.
Metcalfe RS et al. (2018)⁶⁴	Randomized, four-trial crossover study; n = 11 No exercise (Con); 30 min of continuous exercise (MICT); 10 × 1 min ∼90% HR_max of high-intensity interval training (HIIT); 2 × 20 s maximal exertion sprinting reduced-exertion HIIT (REHIIT)	Compared to CON, mean 24-h glucose concentration was lower following REHIIT, but not HIIT. Observed a lower glycaemic response to dinner AUC following both REHIIT and MICT but not HIIT.	REHIIT may offer a genuinely time-efficient exercise option for improving 24-h glycaemia in men with type 2 diabetes and warrants further study.	Strengths: Implementation of a randomized crossover design; Evaluation of multiple modalities of exercise. Limitations: Small sample size.

Table 3 presents studies that provided information regarding the influence of a single bout of exercise or following repeated bouts of exercise on glycemic control and glycemic variability in non-diabetic, as well as type 1 and type 2 diabetic adults. The table includes: 1) author information; 2) study design; 3) findings related to the alterations in glycemic control and glycemic variability; 4) conclusions derived from the findings on changes in glycemic control and glycemic variability; 5) strength and limitations of each study.

SD = standard deviation; %CV = percentage coefficient of variation; CMI = continuous moderate-intensity exercise; HIIE = high-intensity interval exercise; LV-HIIE = low volume high-intensity interval exercise; CMIE = continuous moderate-intensity exercise; CGM = continuous glucose monitor; CONGA-1 = continuous overlapping net glycemic action over 1-h; CONGA-2 = continuous overlapping net glycemic action over 2-h; CONGA-4 = continuous overlapping net glycemic action over 4-h; HIIEfast = fasted state high-intensity interval exercise; HIIEfed = post-breakfast high-intensity interval exercise; MICEfast = fasted state moderate-intensity continuous exercise; MICEfed = post-breakfast moderate-intensity continuous exercise; SIT = uninterrupted sitting; LW = light-intensity walking; SRA = simple resistance activities; REHIIT = reduced-exercise high-intensity interval training; AUC = area under the curve.