A Comparison of the Effects of the Timing of Resistance Exercise on Glucose Levels Within the Target Range in People With Type 1 Diabetes (TREX Study): A Randomized Crossover Trial

AIM: The purpose of this paper is to examine the acute and nocturnal glycaemic response to morning fasted, fed or afternoon fed resistance exercise in people with type 1 diabetes. METHODS: In a crossover RCT, people with type 1 diabetes performed three acute bouts of resistance exercise in (1) morning (8 AM-10:30 AM) in a fed state, (2) morning (8 AM-10:30 AM) in a fasted state and (3) afternoon (3-8 PM) in a fed state, with interstitial glucose levels measured 6-h post-exercise and in the nocturnal period (11 PM-6 AM). RESULTS: In all participants (n = 66), mean glucose levels were lower in the 6-h period after afternoon fed versus morning fasted resistance exercise (9.46 ± 2.56 vs. 8.65 ± 2.04 mmol/L, P = 0.04), with no other differences noted. In multiple daily injections (MDI), users (n = 47), but not insulin pump users (n = 19), in the 6-h period post-exercise mean glucose levels were higher (9.63 ± 2.58 vs. 8.44 ± 1.93 mmol/L, P = 0.007), time-in-range (3.9-10.0 mmol/L) lower (50.9 ± 29.5% vs. 67.0 ± 27.6%, P = 0.007) and time above range (> 10.0 mmol/L) higher (44.4 ± 32.1% vs. 26.3 ± 25.3%, P = 0.003) in morning fasted versus afternoon fed state; no other differences were noted. CONCLUSION: Resistance exercise timing and feeding status (fed vs. fasted) independently influence post-exercise glycaemic responses in people with type 1 diabetes. Performing resistance exercise in the afternoon under fed conditions was associated with a more favourable glucose profile, particularly among MDI users. These findings indicate that consideration of both time of day and feeding status is important when optimising resistance exercise prescription in this population. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT05884814 (Registered on 10 May 2023).