PMID 29785399

Research
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Timing of Exercise Affects Glycemic Control in Type 2 Diabetes Patients Treated with Metformin

Huang T, Lu C, Schumann M, Le S, Yang Y, Zhuang H, Lu Q, Liu J, Wiklund P, Cheng S

Question

Does the timing of a single HIIT session after breakfast and metformin administration affect acute glucose and insulin responses in adults with type 2 diabetes?

Summary

This randomized crossover study tested one cycling HIIT session at 30, 60, or 90 minutes after breakfast and metformin in adults with type 2 diabetes. All exercise timings lowered glucose immediately after exercise compared with metformin-only control. Exercise at 60 or 90 minutes after breakfast produced larger in-exercise glucose declines than exercise at 30 minutes, while 30- and 60-minute timing produced larger insulin decreases than metformin alone. The study is acute, not a training program.

Methodology

  • Adults aged 30-65 with type 2 diabetes diagnosed within 5 years and treated with metformin only.
  • 26 participants.
  • Cycle ergometer.
  • Work intervals: 1 min at 85% maximal watts.
  • Recovery: 3 min at 40% maximal watts.
  • Intensity: 85% maximal watts.
  • 27 min.
  • Single session at each timing with at least 48 h between exercise sessions.
  • Acute crossover trial.
  • Randomized crossover acute exercise trial with four laboratory conditions.
  • Blood glucose, Insulin, and Superoxide dismutase were tracked.

Outcomes

Immediate postexercise glucose

All three HIIT timing conditions reduced glucose more than metformin alone immediately after exercise.

EX30 -2.58 mmol/L, EX60 -2.13 mmol/L, EX90 -1.87 mmol/L versus Metf; all p<0.001.

Improved

Glucose during exercise

Glucose reductions during exercise were larger at 60 and 90 minutes postbreakfast than at 30 minutes.

EX60 and EX90 reductions were significantly larger than EX30, p<0.001.

Mixed

Insulin

Compared with metformin alone, insulin decreased more in EX30 and EX60.

Both p<0.001.

Improved

SOD activity

Postexercise SOD activity changes did not differ from metformin-only control.

No clear change

Insights

  • For type 2 diabetes users, HIIT timing relative to breakfast and medication may affect acute glucose changes.
  • This paper is useful for medical caveats and content, not generic workout prescription.
  • The protocol used only 6 minutes of hard work but 27 minutes total exercise because recoveries were long.

Limitations

  • Acute study only.
  • No exercise-only condition.
  • Only metformin-treated patients.
  • Only postbreakfast exercise was studied.
  • Insulin sensitivity and long-term glycemic control were not assessed.

Safety

  • The timing window was selected partly because prior evidence suggested minimal hypoglycemia risk.
  • No exercise-related adverse-event finding was highlighted.