Kinetics of submaximal DFA α1 prior and post maximal efforts in trained and highly trained male and female cyclists

Purpose To investigate the kinetics of a non-linear heart rate (HR) variability parameter (DFA α1) during submaximal cycling in male and female trained and highly trained cyclists in a non-fatigued state and after repeated maximal cycling bouts. Methods N = 47 participants (17 female) completed a cycling protocol consisting of two blocks (Block1, Block2), each including two standardised submaximal cycling bouts performed prior (PRE) and post a maximal incremental test (POST), having four time points (Block1: PRE1-POST1; Block2: PRE2-POST2). DFA α1, oxygen consumption ( V̇O_2 ), HR, respiratory frequency (RF) and rating of perceived exertion (RPE) were assessed during the submaximal bouts, and V̇O_2 peak and maximal power output (Wmax) during the maximal tests. A linear mixed effects model was used to analyse data. Results Block2 showed significantly lower V̇O_2 peak (β = − 2.51 mL·kg⁻¹·min⁻¹) and Wmax (β = − 24.3 W) values. DFA α1 decreased significantly from PRE1 (1.32 ± 0.19) to POST1 (1.12 ± 0.34) and remained suppressed at Block2 (1.14 ± 0.31, 1.09 ± 0.35). V̇O_2 (+ 2.37 mL·kg⁻ 1 ·min⁻ 1 ), HR (+ 15 bpm), RF (+ 8 breaths/min) and RPE (+ 2) increased significantly in Block1 and stayed elevated in Block2. Following POST2, HR decreased (–4 bpm) and RF increased (+ 1 breaths/min) significantly. Training status significantly influenced absolute levels of DFA α1, HR, and V̇O_2 , but did not influence RPE or RF. Sex did not significantly alter kinetics of DFA α1, HR, V̇O₂, RPE and RF. Conclusion DFA α1 during submaximal exercise reflects both acute fatigue and non-recovered state in a repeated maximal test setting and may provide complementary information on autonomic and systemic demands when interpreted alongside V̇O_2 , HR, RF and RPE.