Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Background: Abundant evidence supporting the ergogenic effect of caffeine during endurance exercise exists. Single sporting events, laboratory based studies and inappropriate research design questions the applicability of these studies to triathlon performance.
Objectives: The main aims of this study were to i) investigate the ergogenic effect of caffeine supplementation during a triathlon; ii) evaluate parameters that could in part explain why caffeine supplementation is ergogenic, iii) investigate possible factors influencing the ergogenicity of caffeine supplementation and iv) investigate possible confounding factors influencing triathlon performance.
Methods: A double-blind, randomized, crossover, controlled, clinical field trial was conducted. Performance data (time to complete (TTC), rating of perceived exertion (RPE) and mood state), parameters explaining the mechanism of action (endocrine-stress response, oxidative stress and plasma lactate), factors influencing ergogenicity (lifestyle, gender and genetics) and triathlon performance (general health, energy- and nutrient intake, body composition, training regime, side-effects of caffeine withdrawal- and supplementation and hydration status) was collected during two Olympic-distance triathlons (T1 and T2).
Results: Twenty six Caucasian triathletes (Nm=14, Nf=12) participated (age: 37.8±10.6 years, habitual caffeine intake: 412.7±504.8 mg/day, percentage body fat: 14.5±7.2 %, training/week: 12.8±4.5 hours). There was a 3.7% reduction in swim time (33.5±7.0 vs. 34.8±8.1 minutes) (p=0.05*) and a 1.3% reduction in the overall time to complete the triathlon (149.6±19.8 vs. 151.5±18.6 minutes) (p=0.02*) in the caffeine group. Caffeine did not statistically influence mood state (p=0.72) or RPE (p=0.87), however, a trend was observed for decreased RPE values in the caffeine group. Caffeine supplementation made no difference to markers of endocrine-stress, except for cortisol, which increased beyond the effect observed from exercise (p=0.00*). Oxidative stress was more pronounced in the caffeine group, as seen with elevated leukocyte (p=0.05*), lymphocyte (p=0.05*) and monocyte (p = 0.05*) counts. Caffeine facilitated greater blood lactate accumulation (p=0.04*). Lifestyle, menstrual cycle, menopause, oral contraceptive use and CYP1A2 gene polymorphisms did not statistically influence the effect of caffeine supplementation on triathlon performance. The mean energy- and nutrient intake two days before T1 and T2 was low for energy (36.5±17.6 and 38.9±18.2 kcal/kg BW), estimated energy availability (estEA) (27.9±28.0 and 28.8±25.6 kcal/kg fat free mass) and carbohydrate (CHO) intake (4.1±1.6 and 4.6±2.5 g/kg body weight (BW)) compared to recommendations. The pre-event meal was low in CHO (0.7±0.4 and 0.7±0.5 g/kg BW) and only 62% (N=16) ingested a carbohydrate-electrolyte solution during T1 (CHO: 1.6±2.3 g/kg BW) and T2 (CHO: 0.7±0.4 g/kg BW). Eighty-five percent (N=22) used supplements. Seventy-two percent of pre-menopausal (Nf pre-men=5) and 40% of post-menopausal (Nf post-men=2) females were osteopenic. Of the males, 18% (Nm<50 = 2) had low anterior-posterior spine BMD and 33% (Nm>50 = 1) were osteopenic. Caffeine withdrawal presented as headaches (46%, N=12) and flu-like symptoms (38%, N=10). Side effects of caffeine experienced included shakiness (42%, N=11), heart palpitations (38%, N=10) and gastrointestinal disturbances (38%, N=10). Plasma volume and hydration was not influenced (p=0.70).
Conclusion: Caffeine enhanced triathlon performance, but the effect was not as pronounced as seen in previous laboratory trials and did not affect RPE or mood state. Caffeine supplementation augments the endocrine-stress response by further increasing cortisol levels beyond that resulting from endurance exercise and it induces leukocytosis, neutrophillia and lymphocytosis, suggesting the primary ergogenic effect of caffeine may result due to stimulation of both the central and autonomic nervous systems. Lifestyle, gender and genetics did not significantly influence caffeine’s effect on triathlon performance in this cohort. The subjects had low energy, estEA and carbohydrate intake and a high prevalence of osteopenia. / AFRIKAANSE OPSOMMING: Agtergrond: Voldoende bewyse rakende die ergogeniese effek van kaffeïen gedurende uithouvermoë oefening bestaan. Enkel sportsoorte, laboratorium studies en ongeskikte navorsingsontwerpe bevraagteken die toepaslikheid van hierdie studies op driekamp prestasie. Doelwitte: Die hoofdoelwitte van die studie was om i) die verbetering van prestasie of ergogeniese effek van kaffeïen supplementasie tydens ‘n driekamp kompetisie waar te neem; ii) om verskeie parameters wat die ergogeniese effek van kaffeïen supplementasie deels te verduidelik te ondersoek, iii) om moontlike faktore wat die ergogeniese effek van kaffeïen supplementasie kan beïnvloed te ondersoek en iv) om moontlike faktore wat Olimpiese-afstand driekamp prestasie kan beïnvloed te ondersoek.
Metodes: ‘n Dubbel-blinde, lukrake, oorkruis, gekontroleerde, kliniese veldproef is uitgevoer.
Prestasie data (tyd om die driekampe te voltooi, waargenome inspanning en gemoedstoestand), parameters wat moontlik die aksie van kaffeïen kan verduidelik (endokrien-stress respons, oksidatiewe stress en plasma laktaat), faktore wat die ergogeniese effek van kaffeïen kan beïnvloed (lewensstyl, geslag en genetika) en faktore wat moontlik driekamp prestasie kan beïnvloed (algemene gesondheid, energie- en nutriëntinname twee dae voor en op die dag van die driekampe, liggaamsamestelling en beendigtheid, oefening twee dae voord die driekampe, newe-effekte van kaffeïen ontrekking- en supplementasie en hidrasie status) is ingesamel tydens twee Olimpiese afstand driekampe (T1 en T2).
Resultate: Ses-en-twintig Kaukasiese driekamp atlete (Nm=14, Nf=12) is ingesluit (ouderdom: 37.8±10.6, daaglikse kaffeïen inname: 412.7±504.8 mg/dag, % liggaamsvet: 14.5±7.2%, oefening/week: 12.8±4.5 uur). Daar was 'n 3.7% afname in swem tyd (33.5±7.0 teenoor 34.8±8.1) (p=0.05*) en 'n 1.3% afname in totale tyd om die driekampe te voltooi (149.6±19.8 teenoor 151.5±18.6) (p=0.02*) in die kaffeïen groep. Kaffeïen het nie ‘n statisties beduidende effek op die gemoedstoestand (p=0.72) of die waargenome inspanning (p=0.87) gehad nie, maar 'n tendens is waargeneem vir laer waargenome inspannings-waardes in die kaffeïen groep. Kaffeïen het geen verskil gemaak aan parameters van die stres respons nie, behalwe vir kortisol, wat verhoog het bo- en behalwe die effek van oefening (p=0.00*). Oksitdatiewe stres was meer uitgesproke in die kaffeïen groep, soos waargeneem deur verhoogde witbloedsel (p=0.05*), limfosiet (p=0.05*) en neutrofiel (p = 0.05*) tellings. Kaffeïen fasiliteer die verhoging in bloedlaktaat vlakke (p=0.04*). Lewensstyl, menstruele siklus, menopause, orale voorbehoedmiddel gebruik en CYP1A2 geen polimorfismes het geen beduidende effek op die vermoë van kaffeïen om driekamp prestasie te beïnvloed gehad nie. Die gemiddelde energie- en nutriëntinname twee dae voor T1 en T2 was laer as die aanbevelings vir energie (36.5±17.6 en 38.9±18.2 kcal/kg LG), geskatte energie beskikbaarheid (29.9±28.0 en 28.8±25.6 kcal/kg vetvrye massa) en koolhidraat (CHO) inname (4.1±1.6 en 4.6±2.5 g/kg LG). Die voor-driekamp ete was laag in CHO (0.7±0,4 en 0.7±0.5 g / kg LG) en slegs 62% (N=16) het ‘n koolhidraat-elektroliet oplossing tydens T1 (CHO: 1.6±2.3 g/kg LG) en T2 (CHO: 0.7±0.4 g/kg LG) ingeneem. Vyf-en-tagtig persent (N=22) gebruik dieetaanvullings. Twee-en-sewentig persent van die pre-menopausale (Nf pre-men=5) en 40% van die post-menopausale (Nf post-men=2) vroue het osteopenie volgens die totale liggaams been mineraal digtheid. Van die mans, het 18% (Nm<50 = 2) met lae beendigtheid van die anterior-posterior spina en 33% (Nm>50 = 1) met osteopenie gepresenteer. Waargenome ontrekkingsimptome van kaffeïen was hoofpyn (46%, N=12) en griepagtige simptome (38%, N=10) en newe-effekte was bewerigheid (42%, N=11), hartkloppings (38%, N=10) en spysverteringskanaal versteurings (38%, N=10). Plasma volume en hidrasie was nie beïnvloed nie (p=0.70).
Gevolgtrekking: Kaffeïen verbeter driekamp prestasie, maar die effek is nie so uitgesproke soos waargeneem tydens laboratorium studies nie en het nie ‘n beduidende effek op waargenome inspanning of gemoedstoestand getoon nie. Kaffeïen verhoog die stres respons deur die verdere verhoging van kortisol vlakke, bo- en behalwe vlakke waargeneem tydens uithouvermoë oefening en verhoog witbloedsel, limfosiet en neutrofiel tellings. Dit dui daarop dat die primêre ergogeniese effek van kaffeïen supplementasie moontlik as gevolg van stimulasie van beide die sentrale en autonome senuweestelsel voorkom. Lewensstyl, geslag en genetika het nie ‘n beduidende effek op die ergogeniese vermoë van kaffeïen getoon in hierdie studiepopulasie nie. Die deelnemers het ‘n lae energie, geskatte energie beskikbaarheid en koolhidraatinname gehad. Die studiegroep het ‘n hoë prevalensie van osteopenie.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/80060 |
| Date | 03 1900 |
| Creators | Potgieter, Sunita |
| Contributors | Smith, C., Wright, H. H., Warnich, L., Nel, D. G., Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Interdisciplinary Health Sciences. Human Nutrition. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 317 p. : ill. |
| Rights | Stellenbosch University |
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