Perceived Exertion Is Associated with Cardiovascular Strain but Not Glycemic Response to Gym-Based Exercise in Adults with Type 1 Diabetes: An Exploratory Randomized Crossover Trial

Adults with type 1 diabetes mellitus (T1DM) face elevated cardiovascular risk, and regular exercise is a key non-pharmacological mitigation strategy. However, safe prescription requires cardiovascular and glycemic monitoring, often unfeasible in real-world gyms. Low-cost psychophysiological tools (ratings of perceived exertion—RPE and enjoyment) may offer practical alternatives. This exploratory randomized crossover trial examined whether post-session RPE and enjoyment are associated with acute heart rate (HR) and capillary blood glucose (BG) responses to gym-based aerobic and resistance training. Twelve adults with T1DM (29.8 ± 7.8 years; HbA1c 7.7 ± 1.6%; LDL-c 119.5 ± 24.4 mg/dL) completed three ~30 min sessions: aerobic interval training (AE) and two resistance protocols (STA, STB). HR and BG were measured pre-, immediately post-, and 20 min post-exercise; RPE and enjoyment, post-session. Multiple linear regression, controlling for exercise session type, examined associations of RPE and enjoyment with resting HR, BG, and percentage of heart rate reserve (%HR). RPE was higher after STA and STB than AE (p < 0.001; η2p = 0.529), while enjoyment and %HR were similar across sessions. Neither variable was associated with resting HR or BG (all adjusted R2 < 0; all p > 0.05). Controlling for exercise session type, RPE was a significant positive predictor of %HR (β = 0.44, p = 0.044), whereas enjoyment was not (β = −0.06, p = 0.719); however, the overall %HR model did not reach statistical significance (adjusted R2 =0.119; F(4,31) = 2.183; p = 0.094). These exploratory findings suggest that RPE, but not enjoyment, may serve as a low-cost adjunct intensity marker to inform exercise prescription in adults with T1DM at elevated cardiovascular risk; however, replication in larger samples is needed before clinical recommendations can be drawn. Direct BG monitoring remains essential for safety.