Ramadan Diurnal Fasting and Aerobic Performance of Professional Long-Distance Runners in Pakistan: A Repeated-Measures Field Study

Abstract

This repeated-measures field study examined the effect of Ramadan diurnal (dawn-to-dusk) fasting on aerobic performance in professional long-distance runners training and competing in Pakistan. Twenty-four national-level male long-distance runners (age 24.6 ± 3.2 years) were assessed at three time points: one week before Ramadan (Pre-Ramadan), during the third week of Ramadan (Ramadan), and two weeks after Ramadan ended (Post-Ramadan). Outcome measures included maximal oxygen uptake (VO₂max), 10-km time-trial performance, running economy, body mass, and rating of perceived exertion (RPE) during a standardized submaximal run. Hydration status during Ramadan was estimated using urine specific gravity (USG). Results: VO₂max declined significantly during Ramadan relative to Pre-Ramadan (M = 2.68 mL·kg⁻¹·min⁻¹, p < .001, d = 1.89) and partially recovered Post-Ramadan. Ten-kilometer time-trial performance slowed by a mean of 1.60 minutes during Ramadan (p < .001, d = 1.90), and running economy worsened by 9.5 mL·kg⁻¹·km⁻¹ (p < .001). Hydration status during Ramadan was moderately associated with running economy impairment. Diurnal fasting during Ramadan was associated with a measurable, largely reversible decline in aerobic performance markers among elite Pakistani distance runners, most plausibly attributable to hypohydration, glycogen depletion, and altered training/sleep timing rather than fasting per se. Practical strategies for training periodization and nutrition timing during Ramadan are discussed.