The relation of exercise training mode, brain oxygenation and cognition in healthy older adults

Coetsee, Carla (2015-12)

Thesis (PhD)--Stellenbosch University, 2015

Thesis

ENGLISH ABSTRACT: Background: Physical exercise has been shown to prevent cognitive decline and dementia in later life and is generally proposed as a non-pharmacological treatment to reverse or delay the age-related deteriorations in physical and cognitive health. However, it is unknown how different types of exercise will compare with regards to gains in older individuals’ physical and cognitive function and, in particular, the role of high-intensity interval training, has not been extended to the cognitive function literature. Aims: The purpose of this thesis was to determine the effects of three different exercise training modalities (resistance training, high-intensity interval training and moderate continuous training) on physical and cognitive function, as well as cerebral oxygenation. Methods: Sixty seven inactive individuals (55 to 75 years) volunteered for this intervention study. Participants were allocated to a resistance training (RT) group (n=22), high-intensity interval training (HIIT) group (n=13), moderate continuous training (MCT) group (n=13) and a control (CON) group (n=19). Each training group performed three supervised exercise sessions per week over a period of 16 weeks. Cognitive function was assessed every four weeks with a computerized Stroop task, while physical function was assessed with the Timed-Up-and-Go (TUG) and submaximal Bruce treadmill tests. Changes in cerebral oxygenation during the Stroop task were measured at baseline and after the 16-week intervention period. Furthermore, muscle strength was assessed in the CON and RT groups with 10RM leg and bench press tests. The RT and CON groups repeated their baseline measurements after a subsequent 16-week detraining (DET) period. Results: Upper and lower body strength generally improved significantly after every four weeks of RT (with an increase after 16 weeks of 7.3 ± 4.9 kg and 86.6 ± 44.4 kg, respectively; P < 0.001), while TUG performance (-0.2 ± 0.4 s; P < 0.05) and submaximal endurance capacity (0.7 ± 0.9 min; P < 0.001) only improved after 16 weeks. Although muscle strength decreased after detraining, it remained at a level higher than baseline (P < 0.05). Submaximal endurance capacity improved after DET (P < 0.001), while TUG performance returned to baseline. The HIIT group showed a greater improvement in TUG performance (-0.3 ± 0.4 s; ES = 0.36) and walking endurance (1.4 ± 1.3 min; ES = 0.91) compared to RT and MCT. Within each group only RT showed statistically significant improvements, with HIIT and MCT presenting the same trend, beyond the 4-week intervention period, on the measures of executive cognitive function (ES > 0.70). The brain oxygenation results revealed higher relative O2Hb values in CON during the simple and complex Stroop tasks at the post-test compared to the pre-test values (P < 0.05), as well as compared to all three exercise training groups (P < 0.05). Conclusion: Increases in muscular and physical function in older individuals were not induced in a concurrent manner over the course of a RT programme. Furthermore, older adults retained a significant amount of muscle strength and submaximal endurance capacity after a period of DET, while functional mobility was completely reversed. HIIT proved to be most beneficial for the enhancement of older individuals’ aerobic fitness. Exercise training proved more beneficial for the enhancement of executive cognitive function compared to no training. It was also demonstrated that exercise training, independent of the mode, results in more efficient cerebral oxygenation during cortical activation, whereas HIIT and MCT proved to be superior to RT for task-efficient cerebral oxygenation and improved oxygen utilization during cortical activation in older individuals.

AFRIKAANSE OPSOMMING: Agtergrond: Fisieke inoefening word voorgestel as ‘n nie-farmakologiese behandeling om die ouderdomsverwante agteruitgang in fisieke en kognitiewe gesondheid teen te werk of te vertraag. Nietemin is dit onbekend hoe verskillende oefeningsmodaliteite met mekaar vergelyk in terme van die voordelige effek op ouer individue se fisieke en kognitiewe funksie. Die invloed van hoë-intensiteit interval inoefening op hierdie uitkomstes is nog nie ondersoek nie. Doel: Die doel van hierdie studie was om die effek van verskillende oefeningsmodaliteite (weerstands inoefening, hoë-intensiteit interval inoefening, en matige kontinue inoefening) op fisieke funksie, kognitiewe funksie en serebrale oksigenasie in ‘n ouer populasie te ondersoek. Metodes: Sewe-en-sestig onaktiewe individue (55 tot 75 jaar) het ingestem om aan die intervensie studie deel te neem. Deelnemers is aan die weerstands inoefening (RT) groep (n=22), hoë-intensiteit interval inoefening (HIIT) groep (n=13), matige kontinue inoefening (MCT) groep (n=13) en kontrole (CON) groep (n=19) toegeken. Drie oefensessies per week is onder toesig uitgevoer. Kognitiewe funksie is elke vier weke geevalueer deur middel van ‘n gerekenariseerde Stroop taak, terwyl fisieke funksie deur ‘n “Timed-Up-and-Go” (TUG) en submaksimale Bruce trapmeul toets geassesseer is. Veranderinge in serebrale oksigenasie gedurende die Stroop taak is tydens basislyn en na afloop van die intervensie periode gemeet. Die CON en RT groepe se spierkrag is deur middel van ‘n 10RM been- en armopstoot toets geëvalueer. Die RT en CON groepe het weer die basislyntoetse na ‘n addisionele 16 weke van onaktiwiteit (DET) uitgevoer. Resultate: Bo- en onderlyfkrag het oor die algemeen beduidend verbeter na elke vier weke in RT (met ‘n algehele toename van 7.3 ± 4.9 kg en 86.6 ± 44.4 kg, onderskeidelik; P < 0.001), terwyl TUG prestasie (-0.2 ± 0.4 s; P < 0.05) en submaksimale uithouvermoë kapasiteit (0.7 ± 0.9 min; P < 0.001) slegs na 16 weke verbeter het. Alhoewel ‘n afname in spierkrag plaasgevind het gedurende die periode van onaktiwiteit (DET), was dit steeds hoër as by die basislynmetings (P < 0.05). Submaksimale uithouvermoë kapasiteit het verbeter na DET (P < 0.001), terwyl TUG terugekeer het na basislyn. Die HIIT groep het ‘n groter toename in TUG prestasie (-0.3 ± 0.4 s; ES = 0.36) en stap uithouvermoë (1.4 ± 1.3 min; ES = 0.91) na die 16- week oefenprogram getoon. Geen beduidende veranderinge is in die MCT en CON groepe gevind nie (P > 0.05). Slegs RT het ‘n statisties beduidende verbetering in uitvoerende kognitiewe funksie vanaf die 4-16 week intervensie periode getoon, met HIIT en MCT wat ‘n soortgelyke tendens gevolg het (ES > 0.70). Die breinoksigenasie resultate na die intervensie het ‘n beduidende toename in CON se relatiewe oksihemoglobien (O2Hb) tydens die eenvoudige en ingewikkelde Stroop take getoon (P < 0.05). Hierdie verhoogde vlakke van O2Hb was ook beduidend hoër in vergelyking met die drie oefengroepe se post-toets waardes gedurende albei Stroop takies (P < 0.05). Gevolgtrekking: Die toename in spierkrag en fisieke funksie in ouer volwassenes het nie ‘n soortgelyke patroon gevolg oor die verloop van die 16 weke nie. Na DET is ‘n beduidende hoeveelheid spierkrag en submaksimale uithouvermoë kapasiteit behou, terwyl die funksionele mobiliteit teruggekeer het na basislyn. Daar is ook bevind dat HIIT meer voordelig is vir die verbetering van aërobiese fiksheid. Die resultate wys dat inoefening (teenoor onaktiwiteit) tot verhoogde uitvoerende kognitiewe funksie lei. Die huidige studie toon ook dat fisieke oefening meer effektiewe serebrale oksigenasie tydens kortikale aktivering induseer. HIIT en MCT was meer effektief as RT vir taak-effektiewe serebrale oksigenasie en verbeterde suurstofverbruik tydens kortikale aktivering in ouer individue.

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