Author(s): DE POLI, R., TESO, M., ROGERS, B., ÇABUK, R., AL-MULLA, M., MUSA, N., MURIAS, J.M. , Institution: HAMAD BIN KHALIFA UNIVERSITY (HBKU), Country: QATAR, Abstract-ID: 1420

INTRODUCTION:
Performance fatigability is a multifactorial construct involving interacting neuromuscular, perceptual, and autonomic mechanisms that determine exercise tolerance (1, 2). Reductions in fractal correlation properties of heart rate variability measured by the short-term exponent of detrended fluctuation analysis (DFAα1) have been proposed as a promising marker of durability during exercise near maximal metabolic steady state (MMSS) (2). However, whether changes in DFAα1 are associated with the neuromuscular and perceptual components of fatigability at this intensity remains unclear. Therefore, this study investigated whether reductions in DFAα1 are associated with neuromuscular performance fatigability and perceptual responses when exercising near the MMSS.
METHODS:
Sixteen healthy participants (8 males, 8 females) completed two sessions: 1) A cycling step-ramp-step test to determine the ramp-corrected power output at the respiratory compensation point (estimation of MMSS); 2) a constant-load ride at 95% of MMSS until task failure (TF). During session 2, neuromuscular performance fatigability was assessed at baseline (BL), after 7.5 min of exercise, and at TF using maximal voluntary contractions combined with supramaximal peripheral electrical stimulation. Voluntary activation (VA%) was estimated using the twitch interpolated technique, and peripheral function was assessed via potentiated twitch force (Tw). Ratings of perceived exertion (RPE) and DFAα1 were assessed at the same time points. Repeated-measures ANOVA with Bonferroni post hoc assessed within-exercise changes. Pearson correlations assessed associations between absolute changes in DFAα1 and corresponding changes in neuromuscular and RPE from BL to 7.5 min and from BL to TF. Significance was set at p< 0.05.
RESULTS:
Time to TF was 44.6 ± 9.6 min. VA% decreased at 7.5 min and further at TF (Δ from BL: −3.1 ± 2.9% and −7.8 ± 3.3%, respectively; p≤ 0.03). Tw force declined progressively at 7.5 min and TF (Δ from BL: −39.5 ± 14.1% and −52.4 ± 15.7%, respectively; p< 0.01). RPE responses increased from BL to 7.5 min and further at TF (7 ± 1, 12 ± 2, and 16 ± 3 a.u., respectively; p< 0.01). DFAα1 decreased across the same time points (1.39 ± 0.16, 0.86 ± 0.24, and 0.60 ± 0.27, respectively; p< 0.01). No associations were found between changes in DFAα1 and neuromuscular or RPE responses from BL to 7.5 min. However, absolute reductions in DFAα1 from BL to TF were associated with increase in RPE over the same period (r= −0.68; p< 0.01), with no association with neuromuscular performance fatigability.
CONCLUSION:
Reductions in DFAα1 from BL to TF were associated with increases in RPE, whereas no associations were observed with neuromuscular fatigability responses. These findings suggest that reductions in DFAα1 are more closely related to the perceptual dimension of exercise fatigability than to neuromuscular impairment.

(1) Iannetta et al 2022, JAP, 133(2),323–34/ (2) Rogers et al 2025, EJAP, 125(6),1619–31