The Effect of Exercise Timing on Glycemic Control: A Randomized Clinical Trial

• Published in: Medicine and science in sports and exercise Vol. 52; no. 2; pp. 323 - 334
• Main Authors: TEO, SHAUN Y. M., KANALEY, JILL A., GUELFI, KYM J., MARSTON, KIERAN J., FAIRCHILD, TIMOTHY J.
• Format: Journal Article
• Language: English
• Published: United States Lippincott Williams & Wilkins 01-02-2020; American College of Sports Medicine
• Subjects: Area Under Curve; Blood Glucose - metabolism; Circadian Rhythm; Diabetes Mellitus, Type 2 - blood; Diabetes Mellitus, Type 2 - complications; Diabetes Mellitus, Type 2 - physiopathology; Diabetes Mellitus, Type 2 - therapy; Exercise Therapy - methods; Fasting; Female; Glycated Hemoglobin A - metabolism; Humans; Insulin - blood; Insulin Resistance; Male; Middle Aged; Obesity - complications; Obesity - physiopathology; Obesity - therapy; Postprandial Period; Skin Temperature; Time Factors; Wrist
• ISSN: 0195-9131; 1530-0315
• DOI: 10.1249/MSS.0000000000002139

Despite the acknowledgment of exercise as a cornerstone in the management of type 2 diabetes (T2D), the importance of exercise timing has only recently been considered.
PURPOSEThis study sought to determine the effect of diurnal exercise timing on glycemic control in individuals enrolled in a 12-wk supervised multimodal exercise training program. A secondary aim was to determine the effect of diurnal exercise timing on the circadian rhythm of wrist skin temperature.
METHODSForty sedentary, overweight adults (mean ± SD, age = 51 ± 13 yr; body mass index = 30.9 ± 4.2 kg·m; women, n = 23) with and without (n = 20) T2D diagnosis were randomly allocated to either a morning (amEX) or an evening (pmEX) exercise training group. The supervised 12-wk (3 d·wk) program, comprised 30 min of moderate-intensity walking and 4 resistance-based exercises (3 sets, 12–18 repetitions each). Glycemic outcomes (glycated hemoglobin, fasting glucose, postprandial glucose) and wrist skin temperature were assessed at baseline and postintervention.
RESULTSExercise training improved (main effect of time, all P < 0.01) all glycemic outcomes; however, this was independent of allocation to either the amEX (Hedge’s g, 0.23–0.90) or the pmEX (Hedge’s g, 0.16–0.90) group. Accordingly, the adopted exercise training program did not alter the circadian rhythm of skin temperature. When only T2D individuals were compared, amEX demonstrated greater effects (all Hedge’s g) on glycated hemoglobin (amEX, 0.57; pmEX, 0.32), fasting glucose (amEX, 0.91; pmEX, 0.53), and postprandial glucose (amEX, 1.12; pmEX, 0.71) but was not statistically different.
CONCLUSIONSTwelve weeks of multimodal exercise training improved glycemic control and postprandial glycemic responses in overweight non-T2D and T2D individuals. However, no distinct glycemic benefits or alterations in circadian rhythm were associated with morning versus evening exercise, when performed three times per week in this cohort.