Similar metabolic adaptations during exercise after low volume sprint interval and traditional endurance training in humans

TLDR

Low‑volume sprint interval training (SIT) can rapidly enhance muscle oxidative capacity to levels similar to traditional endurance training (ET), yet metabolic adaptations during exercise after these regimes have not been compared. The study tested whether SIT and ET produce comparable changes in skeletal muscle carbohydrate and lipid metabolism and metabolic control during exercise despite differing training volumes. Twenty‑three‑year‑old untrained participants performed a 1‑hour cycling test at 65 % VO₂peak before and after 6 weeks of either SIT (four to six 30‑s all‑out Wingate bouts, 4.5 min rest, 3 days/week) or ET (40–60 min continuous cycling at 65 % workload, 5 days/week), with SIT requiring ~1.5 h/week versus ~4.5 h/week and ~225 kJ versus 2250 kJ total weekly volume. Both training protocols similarly increased mitochondrial markers for carbohydrate and lipid oxidation and PGC‑1α, reduced glycogen and phosphocreatine use, lowered whole‑body carbohydrate oxidation, raised lipid oxidation, and produced equivalent metabolic adaptations, demonstrating SIT’s time‑efficiency.

Abstract

Low‐volume ‘sprint’ interval training (SIT) stimulates rapid improvements in muscle oxidative capacity that are comparable to levels reached following traditional endurance training (ET) but no study has examined metabolic adaptations during exercise after these different training strategies. We hypothesized that SIT and ET would induce similar adaptations in markers of skeletal muscle carbohydrate (CHO) and lipid metabolism and metabolic control during exercise despite large differences in training volume and time commitment. Active but untrained subjects (23 ± 1 years) performed a constant‐load cycling challenge (1 h at 65% of peak oxygen uptake before and after 6 weeks of either SIT or ET ( n = 5 men and 5 women per group). SIT consisted of four to six repeats of a 30 s ‘all out’ Wingate Test (mean power output ∼500 W) with 4.5 min recovery between repeats, 3 days per week. ET consisted of 40–60 min of continuous cycling at a workload that elicited ∼65% (mean power output ∼150 W) per day, 5 days per week. Weekly time commitment (∼1.5 versus ∼4.5 h) and total training volume (∼225 versus ∼2250 kJ week −1 ) were substantially lower in SIT versus ET. Despite these differences, both protocols induced similar increases ( P < 0.05) in mitochondrial markers for skeletal muscle CHO (pyruvate dehydrogenase E1α protein content) and lipid oxidation (3‐hydroxyacyl CoA dehydrogenase maximal activity) and protein content of peroxisome proliferator‐activated receptor‐γ coactivator‐1α. Glycogen and phosphocreatine utilization during exercise were reduced after training, and calculated rates of whole‐body CHO and lipid oxidation were decreased and increased, respectively, with no differences between groups (all main effects, P < 0.05). Given the markedly lower training volume in the SIT group, these data suggest that high‐intensity interval training is a time‐efficient strategy to increase skeletal muscle oxidative capacity and induce specific metabolic adaptations during exercise that are comparable to traditional ET.