Comparative effects of combined aerobic and resistance training versus high-intensity interval training on insulin resistance, glycaemic control, body composition and quality of life in type 2 diabetes: A 12-week randomised controlled trial

BACKGROUND: Exercise training is a cornerstone in managing type 2 diabetes mellitus (T2DM), yet direct comparisons between combined aerobic-resistance training (A + R) and high-intensity interval training (HIIT) across clinical and patient-reported outcomes remain limited.

OBJECTIVE: To compare the effects of A + R and HIIT on insulin resistance, glycaemic control, body composition, physical function, and quality of life in adults with T2DM, relative to standard care.

DESIGN AND PARTICIPANTS: A single-centre, randomised controlled trial involving 90 participants with T2DM (aged 30-65 years), allocated to A + R, HIIT, or control groups.

INTERVENTIONS: A + R consisted of moderate-intensity aerobic and resistance exercises, while HIIT comprised structured interval sessions. Both programs were delivered 3-5 times weekly for 12 weeks. The control group received usual care without structured exercise.

MEASUREMENTS: Primary outcomes included fasting insulin (FI), Glycosylated Hemoglobin (HbA1c), and insulin resistance (HOMA-IR). Secondary outcomes included fasting glucose (FG), 6-minute walk distance (6MWD), subcutaneous and visceral fat, muscle mass, and WHOQOL-BREF domains.

RESULTS: Compared with control, the HIIT group showed a greater reduction in fasting glucose (Mean Difference [MD] -29.1 mg/dL; 95% CI -41.2 to -17.0) and the A+R group also improved (MD -20.6 mg/dL; 95% CI -31.0 to -10.2). HbA1c was lower versus control in both HIIT (MD -3.35%; 95% CI -4.11 to -2.58) and A+R (MD -3.33%; 95% CI -4.03 to -2.62). Fasting insulin decreased relative to control in HIIT (MD -7.16 mIU/L; 95% CI -10.04 to -4.28) and A+R (MD -8.87 mIU/L; 95% CI -11.77 to -5.97). HOMA-IR improved versus control in A+R (MD -2.33; 95% CI -3.63 to -1.03) with a non-significant trend in HIIT (MD -1.17; 95% CI -2.47 to 0.13). Functional capacity (6-minute walk distance) increased versus control in HIIT (MD +178.9 m; 95% CI 130.5 to 227.4) and A+R (MD +233.6 m; 95% CI 191.8 to 275.5). Body composition favored both interventions: fat-free mass increased (HIIT MD +7.54 kg; 95% CI 4.71 to 10.36; A+R MD +5.96 kg; 95% CI 3.06 to 8.86) while subcutaneous fat (HIIT MD -7.16%; 95% CI -9.33 to -4.99; A+R MD -8.37%; 95% CI -10.65 to -6.09) and visceral fat (HIIT MD -4.70%; 95% CI -5.93 to -3.47; A+R MD -4.58%; 95% CI -5.86 to -3.31) were reduced. Quality of life improved across domains versus control in both groups (e.g., physical domain: HIIT MD +10.29; 95% CI 4.06 to 16.51; A+R MD +13.77; 95% CI 6.62 to 20.91). All results were derived from covariate-adjusted mixed models with multiple comparison corrections (Benjamini-Hochberg FDR, q = 0.05; Bonferroni-adjusted α = 0.002).

LIMITATIONS: Findings are limited to adherent participants, and generalizability is restricted to those without advanced complications. The 12-week duration precludes assessment of long-term sustainability.

CONCLUSION: Both HIIT and A+R significantly improved metabolic, functional, and psychosocial outcomes compared with control. HIIT yielded greater benefits for fasting glucose and muscle mass, while A+R conferred broader improvements in HbA1c, fat reduction, and quality of life. These findings support tailoring exercise prescriptions to therapeutic goals and highlight the complementary roles of HIIT and A+R in routine diabetes care.

CLINICAL TRIAL REGISTRATION: The trial is registered with the Clinical Trial Registry of India (reference no: CTRI/2022/04/041762).