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The changes in acid-base balance during moderate-duration, high-intensity endurance exercise
Thesis (MSc)--Stellenbosch University, 2025.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867614092490964992 |
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| access_status_str | Open Access |
| author | Jacobs, Izelle |
| author2 | Terblanche, Elmarie |
| author_browse | Jacobs, Izelle Terblanche, Elmarie |
| author_facet | Terblanche, Elmarie Jacobs, Izelle |
| author_sort | Jacobs, Izelle |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2025. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/134639 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:46:32.674Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/134639 The changes in acid-base balance during moderate-duration, high-intensity endurance exercise Jacobs, Izelle Terblanche, Elmarie Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Sport Science. Acid-base imbalances Thesis (MSc)--Stellenbosch University, 2025. Jacobs, I. 2025. The changes in acid-base balance during moderate-duration, high-intensity endurance exercise. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/da7227f4-c4b5-4060-aa6f-3fe367ad8704 Exercise-induced fatigue (EIF) reduces performance, with metabolic acidosis recognized as a key contributing factor during short-duration, high-intensity exercise. Subsequently, extensive research has examined the efficacy of exogenous buffering agents, most notably sodium bicarbonate, to counteract hydrogen ion (H⁺) accumulation and the associated decline in pH during strenuous exercise (Ak11z et al., 2024; Freis et al., 2017; Krustrup et al., 2015). The acid-base response to exercise of moderate-duration but high-intensity, and the potential for sex-specific differences, are not well documented. Therefore, this study set out to examine changes in acid-base balance during a 10 km running time-trial (TT). Twenty-four healthy men and women took part (mean ± SD: age 22.88 ± 2.69 years, body mass 69.13 ± 13.85 kg, height 173.06 ± 11.04 cm, VO₂max 54.01 ± 4.99 mL·kg⁻¹·min⁻¹). Measurements of blood lactate concentration (B[La]), blood bicarbonate concentration ([HCO₃⁻]), blood pH, and base excess (BE) were collected at baseline (0 km) and again during the TT at 6, 8, and 10 km. The rating of perceived exertion (RPE) was recorded immediately after completion of the 10 km TT. Across time, significant changes were found in BE, [HCO₃⁻], B[La], and pH (p <0.001). BE displayed a significant sex effect (p =0.03), and initial analyses revealed significant time × sex interactions for all four variables (p ≤0.03). When aerobic capacity measures (VO₂max and Vpeak) were included as covariates, only pH revealed a significant main effect of sex (p <0.001, η²p =0.59) and a significant time × sex interaction (p <0.05). Performance-wise, men were significantly faster than women across all measures of the TT: total time (TTotal), time for the first 9.5 km (T0–9.5 km), and the final sprint (TEnd-sprint) (p <0.03). Significant correlations were identified between relative VO₂max, Vpeak, and absolute changes in acid-base variables over the 10 km TT (r >0.47, p <0.02). Similar perceptual responses were observed between men and women, with RPE values confirming that the 10 km TT was performed at a high intensity (17.65 ± 2.11). Reliability testing showed that TTotal was highly consistent, with excellent reliability (ICC =0.98; CV =1.2%; TEM =45 s). TEnd-sprint demonstrated good reliability, but greater variability (ICC =0.87; CV =4.5%). In summary, the 10 km TT provoked clear and significant disturbances in BE, [HCO₃⁻], pH, and B[La], confirming its nature as a high-intensity exercise challenge. No sex differences were apparent for BE, [HCO₃⁻], or B[La] after adjusting for aerobic capacity. The pH responses retained significant sex and time × sex effects, indicating a genuine sex-specific difference. Although men achieved significantly faster completion times, women reported similar cardiovascular and perceptual strain. The significant correlations between aerobic capacity (VO₂max, Vpeak) and acid-base disturbances emphasize the close connection between endurance fitness and metabolic stress. Furthermore, the excellent reproducibility of this TT supports its use as a reliable performance test for both athletes and researchers. These findings carry implications for training design, evaluation of nutritional strategies, and the development of ergogenic aids that are relevant across sexes. Masters 2025-12-19T13:31:45Z 2025-12-19T13:31:45Z 2025-12 Thesis https://scholar.sun.ac.za/handle/10019.1/134639 en Stellenbosch University 98 pages : ill. application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Acid-base imbalances Jacobs, Izelle The changes in acid-base balance during moderate-duration, high-intensity endurance exercise |
| title | The changes in acid-base balance during moderate-duration, high-intensity endurance exercise |
| title_full | The changes in acid-base balance during moderate-duration, high-intensity endurance exercise |
| title_fullStr | The changes in acid-base balance during moderate-duration, high-intensity endurance exercise |
| title_full_unstemmed | The changes in acid-base balance during moderate-duration, high-intensity endurance exercise |
| title_short | The changes in acid-base balance during moderate-duration, high-intensity endurance exercise |
| title_sort | changes in acid base balance during moderate duration high intensity endurance exercise |
| topic | Acid-base imbalances |
| url | https://scholar.sun.ac.za/handle/10019.1/134639 |
| work_keys_str_mv | AT jacobsizelle thechangesinacidbasebalanceduringmoderatedurationhighintensityenduranceexercise AT jacobsizelle changesinacidbasebalanceduringmoderatedurationhighintensityenduranceexercise |