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
Stellenbosch University https://scholar.sun.ac.za
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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.
