Post-Exercise Acid-Base Profiles and Functional Recovery Following a 10 km Time Trial in Recreational and Trained Runners

Abstract

Thesis (MSc)--Stellenbosch University, 2025.Mandell, K. J. 2025. Post-Exercise Acid-Base Profiles and Functional Recovery Following a 10 km Time Trial in Recreational and Trained Runners. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/0b7b5898-9642-4bd1-a4e0-a48f0444b4d8This M.Sc. thesis, conducted at Stellenbosch University under the supervision of Prof. Elmarie Terblanche, investigated sex differences in acid–base profiles and functional recovery following a 10 km time trial (TT) in recreational and trained runners. Endurance exercise research has predominantly focussed on elite athletes or short-duration high-intensity protocols, often incorporating supplementation, which leaves significant gaps in understanding unsupplemented and passive recovery dynamics in non-elite populations. This study addressed these voids by profiling 24-hour recovery in non-elite men and women, incorporating individual factors such as VO₂max to provide practical insights for training optimisation and injury prevention among recreational and trained athletes. The primary aim was to quantify TT-induced metabolic acidosis and subsequent 24-hour acid–base recovery, including markers like pH, bicarbonate ([HCO₃⁻]), base excess ([BE]), and lactate ([La-]). Secondary aims examined sex differences in these recovery patterns and explored inter-relationships across metabolic, neuromuscular (countermovement jump [CMJ] height and power), and subjective (muscle soreness [MS] via visual analogue scale [VAS] and perceived recovery status [PRS]) domains. Hypotheses proposed that the TT would induce significant acidosis normalising within 24 hours, with women exhibiting faster acid-base and neuromuscular recovery due to physiological advantages like enhanced lipid oxidation and oestrogen-mediated buffering. A repeated-measures cross-sectional design was employed with 24 recreational and trained runners (12 men: age 24.2 ± 3.0 years, VO₂max 56.3 ± 4.6 mL·kg⁻¹·min⁻¹; 12 women: age 22.2 ± 2.0 years, VO₂max 51.8 ± 4.4 mL·kg⁻¹·min⁻¹). Participants completed a maximal incremental treadmill test to determine VO₂max and ventilatory thresholds, followed by one 5 km familiarisation run and then two 10 km TTs (one week apart; faster analysed). Capillary blood samples and assessments at 0, 10, 30, 60 minutes, and 24 hours post-TT. Mixed-model ANOVA analysed sex × time interactions, with Pearson correlations and Hedges’ g effect sizes (p < 0.05). Results confirmed marked metabolic acidosis (pH drop to 7.15–7.20) and peak lactate 13.1 ± 4.4 mmol·L⁻¹, with acid–base markers normalising by 24 hours, supporting the primary hypothesis. Men exhibited greater initial disruptions (e.g., 28% higher lactate, 0.1 unit lower pH; p < 0.05) due to faster TT times (48 vs. 53 minutes; p = 0.03), but women cleared quicker in early phases (0–30 minutes). Neuromuscular recovery (CMJ) declined 15–20% post-TT, returning to normative ranges by 24 hours, while subjective markers (MS ~3–4 VAS, PRS ~4–6) remained impaired. Correlations linked acid–base status to Countermovement jump (CMJ) height and power (r = 0.50–0.70) but weakly to Muscle soreness (MS) and Perceived recovery status (PRS), partially supporting secondary hypotheses. Sex differences highlighted intensity-driven acidosis in men and oxidative advantages in women. The findings advocate multidimensional monitoring for recreational and trained athletes, with sex-tailored strategies: buffering supplements for men, lipid nutrition for women. This advances exercise physiology by emphasising non-elite contexts. Limitations include small sample (n=24), controlled lab conditions, unmatched intensities confounding sex effects, 24-hour follow-up missing prolonged fatigue, and no hormonal/muscle damage profiling. Future research should extend timelines (48–72 hours), incorporate hormone assessments, and use field settings for broader applicability.Master