Abstract
AbstractCompetitive cycling is both physiologically and psychologically demanding with competitive time trial (TT) events lasting between 10 to 60 min of high intensity exercise. Investigations into the enhancement of exercise performance has been of great interest to sports physiologists, especially with respect to the use of nutritional ergogenic aids. One such ergogenic aid, which has seen much research is sodium bicarbonate (SB) which acts as a buffering agent. It has been shown to aid in the resistance against fatigue caused by increasing hydrogen ion (H+) concentration that decreases muscle pH, which contribute to the fatigue process. However, one of the main disadvantages of using SB as an ergogenic aid, is the possibility of gastrointestinal (GI) upset/distress. Therefore, the use of enteric-coated SB capsules may enhance buffering capacity and improve performance while reducing the risk of GI side-effects. It is also not clear how a meal taken prior to supplementation will affect the GI upset and sports performance.
The aim of this overall thesis was to determine the effects of a 0.3 g∙kg-1 BM dose of SB ingested prior to the start of a 16.1 km cycling time trial in cyclists, of different levels and with or without pre ingestion of food.
Study 1
Purpose: The use of sodium bicarbonate (SB) as a pre-exercise ergogenic aid has been extensively studied in short duration high-intensity exercise. Very few studies have considered the effects of SB ingestion prior to sustained high-intensity exercise (>10 mins) (eg >80-95% heart rate maximum (HRmax). The aim of the present study was to determine the effects of a 0.3 g∙kg-1 body mass (BM) dose of SB ingested prior to the start of a 16.1 km cycling time trial in cyclists. Methods: Ten trained male cyclists (age 31.1 ± 9 y, height 1.84 ± 0.05 m, Body Mass (BM) 82.8 ± 8.5 kg and VO2peak 60.4 ± 3.1 ml∙kg-1∙min-1) completed this study. Participants ingested 0.3 g∙kg-1 in gelatine (SB-G) and enteric capsules (SB-E) one week apart to determine individualised time-to-peak alkalosis for each ingestion form. Using a randomised crossover design, participants then performed simulated 16.1 km time trials following ingestion of either SB-G, SB-E or a placebo. Results: There were significant differences in performance between the SB and placebo ingestion strategies (f = 5.50, p = 0.014, pη2 = 0.38). Performance time was significantly improved by SB ingestion (mean improvement: 34.4 ± 42.6 s, p = 0.031 and 40.4 ± 45.5 s, p = 0.020 for SB-G (2.5%) and SB-E (2.1%) respectively) compared to the placebo. Gastrointestinal symptoms were considerably higher in the SB-G condition compared to SB-E (MD = 30.7, t = 14.98, p < 0.001, g = 7.09).
. Conclusion: This study demonstrates that increased buffering capacity following acute pre-exercise SB ingestion, can improve endurance cycling time trial performances, the use of SB could be considered for use in 16.1 km cycling time trials, but further work is required to establish the effects of both SB-G and SB-E following a pre-exercise meal.
Study 2
Purpose: Very few studies have considered the effects of SB-E supplementation after ingestion of a pre-exercise meal (2 g∙kg-1 BM carbohydrate) prior to sustained high-intensity exercise (>10 mins). The present study aimed to determine the effects of a 0.3 g∙kg-1 BM (BM) dose of SB-E ingested before the start of a 16.1 km cycling time trial in elite cyclists in a fed state and fasted state. Methods: Based on previous studies we recruited eight well trained male cyclists (age 32.1 ± 7 y, height 1.83 ± 0.07 m, BM 82.1 ± 9.6 kg and VO2peak 61.2 ± 2.2 ml ± kg-1∙min-1) completed this study. Participants ingested 2 g∙kg-1 of carbohydrate followed by enteric capsules (SB-E) and (PLA) one week apart with and without a pre-exercise meal to determine individualised time-to-peak alkalosis for each ingestion form. Using a randomised crossover design, participants then performed simulated 16.1 km time trials following ingestion of either SB-EF (FED), SB-E (FASTED) or PLA (PLACEBO) separated by at least 7 days. Results: There was a significant effect of SB supplementation on exercise performance (p< 0.001, 0.7). Ingestion of SB-E and SB-EF significantly improved TT performance; exercise performance was significantly faster in the fed (p=0.013, mean difference 29.9 seconds, 95% CI [6.9-52.8]) and fasted (p=0.029, mean difference 22.9 seconds, 95% CI [2.3-43.3]) state compared with the placebo. Gastrointestinal symptoms were lower following SB-EF (0 ± 0 AU) compared to SB-E fasted (4 ± 3 AU) state. Conclusion: This study demonstrates that increased buffering capacity following a pre-exercise meal, can improve endurance cycling TT performances. Feeding also seemed to decrease the GI issues when compared to previous studies. The use of SB-E in a fed state, rather than simply alone, could be considered for use in 16.1 km cycling time trials, but further work is required to establish these effects following a pre-exercise meal.
Study 3
Purpose: Study 3, similar to study 2, aimed to determine the effects of a 0.3 g∙kg-1 BM (BM) dose, (similar to previous work in the field) of SB-E ingested before the start of a 16.1 km cycling time trial in club cyclists in a fed state and fasted state. Methods: As in previous research, eight recreationally trained cyclists (age 37.1 ± 12 y, height 1.76 ± 0.09 m, BM 83.8 ± 8.5 kg and VO2peak 51.3 ± 3.2 ml∙kg-1∙min-1) completed this study. Participants ingested 2 g∙kg-1 BM carbohydrate followed by enteric capsules (SB-E) and (PLA) one week apart with and without a pre-exercise meal to determine individualised time-to-peak alkalosis for each ingestion form. Using a randomised crossover design, participants then performed laboratory-based 16.1 km TTs following ingestion of either SB-EF (FED), SB-E (FASTED) or PLA (PLACEBO). Results: There was no significant effect of SB supplementation on exercise performance (P=0.320). Ingestion of SB-E and SB-EF showed no significant improvement on exercise performance, although the mean completion time was similar between conditions (CON, 1475±43 sec; PLA, 1468±39 sec, FED, 1457±38 sec; FASTED, 1469±42 sec). Gastrointestinal symptoms were lower following SB-EF (0 ± 0 AU) compared to SB-E fasted (4 ± 3 AU) state. Conclusion: The research findings suggest that ingestion of SB in enteric-coated capsules after a pre-exercise meal can notably reduce gastrointestinal distress and manipulate blood pH, HCO3, and lactate levels. While there was no significant improvement in exercise performance overall, there are some indications that the group taking SB performed better than those taking a placebo. These results are important for future studies, highlighting the need for further exploration into how SB affects performance across various exercise types and intensities.
| Date of Award | 7 Oct 2024 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | LARS MCNAUGHTON (Director of Studies) |
Keywords
- Effects of Sodium Bicarbonate Supplementation