Low-volume high-intensity interval training reduces hyperglycemia and increases muscle mitochondrial capacity in patients with type 2 diabetes

TLDR

Low‑volume high‑intensity interval training is a time‑efficient exercise strategy that improves health and fitness. The study examined the effects of low‑volume HIT on glucose regulation and skeletal muscle metabolic capacity in patients with type 2 diabetes. Eight type‑2 diabetic patients (average age 63 yr, BMI 32 kg/m², HbA1c 6.9 %) completed six 10‑bout, 60‑second cycling HIT sessions over two weeks, with glucose regulation monitored by 24‑h continuous glucose monitoring and muscle metabolic capacity assessed via pre‑ and post‑training vastus lateralis biopsies. Low‑volume HIT reduced average 24‑h blood glucose from 7.6 to 6.6 mmol/l, lowered postprandial glucose excursions, and increased mitochondrial enzyme activity and protein content (citrate synthase ≈ 20 %, Complex II ≈ 37 %, Complex III ≈ 51 %, Complex IV ≈ 68 %, Mitofusin‑2 ≈ 71 %, GLUT4 ≈ 369 %), demonstrating rapid improvements in glucose control and skeletal muscle metabolic capacity in type‑2 diabetic patients.

Abstract

Low-volume high-intensity interval training (HIT) is emerging as a time-efficient exercise strategy for improving health and fitness. This form of exercise has not been tested in type 2 diabetes and thus we examined the effects of low-volume HIT on glucose regulation and skeletal muscle metabolic capacity in patients with type 2 diabetes. Eight patients with type 2 diabetes (63 ± 8 yr, body mass index 32 ± 6 kg/m(2), Hb(A1C) 6.9 ± 0.7%) volunteered to participate in this study. Participants performed six sessions of HIT (10 × 60-s cycling bouts eliciting ∼90% maximal heart rate, interspersed with 60 s rest) over 2 wk. Before training and from ∼48 to 72 h after the last training bout, glucose regulation was assessed using 24-h continuous glucose monitoring under standardized dietary conditions. Markers of skeletal muscle metabolic capacity were measured in biopsy samples (vastus lateralis) before and after (72 h) training. Average 24-h blood glucose concentration was reduced after training (7.6 ± 1.0 vs. 6.6 ± 0.7 mmol/l) as was the sum of the 3-h postprandial areas under the glucose curve for breakfast, lunch, and dinner (both P < 0.05). Training increased muscle mitochondrial capacity as evidenced by higher citrate synthase maximal activity (∼20%) and protein content of Complex II 70 kDa subunit (∼37%), Complex III Core 2 protein (∼51%), and Complex IV subunit IV (∼68%, all P < 0.05). Mitofusin 2 (∼71%) and GLUT4 (∼369%) protein content were also higher after training (both P < 0.05). Our findings indicate that low-volume HIT can rapidly improve glucose control and induce adaptations in skeletal muscle that are linked to improved metabolic health in patients with type 2 diabetes.