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This analysis of secondary outcomes investigated the applicability of supramaximal high-intensity interval training (HIT) with individually prescribed external intensity performed on stationary bicycles. Sixty-eight participants with a median (min; max) age of 69 (66; 79), at the time not engaged in regular exercise were randomized to 25 twice-weekly sessions of supramaximal HIT (20-min session with 10 × 6-s intervals) or moderate-intensity training (MIT, 40-min session with 3 × 8-min intervals). The primary aim was outcomes on applicability regarding; adherence to prescribed external interval intensity, participant reported positive and negative events, ratings of perceived exertion (RPE 6–20), and affective state (Feeling Scale, FS -5–5). A secondary aim was to investigate change in exercise-related self-efficacy (Exercise Self-Efficacy Scale) and motivation (Behavioural Regulations in Exercise Questionnaire-2). Total adherence to the prescribed external interval intensity was [median (min; max)] 89 % (56; 100 %) in supramaximal HIT, and 100 % (95; 100 %) in MIT. The supramaximal HIT group reported 60 % of the positive (112 of 186) and 36 % of the negative (52 of 146) events. At the end of the training period, the median (min; max) session RPE was 15 (12; 17) for supramaximal HIT and 14 (9; 15) for MIT. As for FS, the median last within-session rating was 3 (−1; 5) for supramaximal HIT and 3 (1; 5) for MIT. Exercise-related motivation increased (mean difference in Relative Autonomy Index score = 1.54, 95 % CI [0.69; 2.40]), while self-efficacy did not change (mean difference = 0.55, 95 % CI [-0.75; 1.82]), regardless of group. This study provide support for supramaximal HIT in supervised group settings for older adults.

OBJECTIVE: This study investigated the effectiveness of supramaximal high-intensity interval training (supramaximal HIT) on muscle capacities and physical function compared to moderate-intensity training (MIT) for older adults.

METHODS: Sixty-eight older adults (66-79 years, 56% women), not engaged in regular exercise, were randomised to 3 months of twice-weekly supramaximal HIT (20 minutes including 10 × 6-second intervals) or MIT (40 minutes including 3 × 8-minute intervals). Both groups performed the training on stationary bicycles in a group setting. Target intensity was watt-controlled, with standardised cadence and individualised resistance. Outcomes analysed with linear-mixed models included leg power (Nottingham Power Rig), hand grip strength (Jamar dynamometer), static and dynamic balance (One leg stance, 30-second step test), chair stand (30-second chair stand), and anaerobic cycling performance (modified Borg Cycle Strength Test).

RESULTS: Baseline values were (supramaximal HIT/MIT, mean ± SD) leg power 198 ± 60/189 ± 53 W, hand grip strength 4.2 ± 1.0/4.3 ± 1.1 N/kg, static balance 64 ± 41/62 ± 41 s, dynamic balance 39 ± 7/38 ± 5 steps, chair stands 22 ± 6/22 ± 6 and anaerobic cycling performance 224 ± 60/217 ± 55 W. At 3-month follow-up, a between-group difference in favour of supramaximal HIT [95% CI] was observed in anaerobic cycling performance of 19[3;35] W. Within-group mean changes for supramaximal HIT/MIT were for leg power 8.4[0.9;15.8]/6.0[-1.3;13.3] W, hand grip strength 0.14[0.00;0.27]/0.13[-0.01;0.26] N/kg, static balance 11[3;20]/10[1;18] s, dynamic balance 1.6[0.3;2.8]/2.3[1.1;3.6] steps, 2.1[1.1;3.1]/1.4[0.4;2.3] chair stands and anaerobic cycling performance 31.3[19.6;43.0]/12.0[0.4;23.5] W.

CONCLUSION: Supramaximal HIT showed superior effect on anaerobic cycling performance when compared to MIT. Additionally, the results indicate that supramaximal HIT is comparably beneficial as MIT in terms of effects on muscle capacity and physical function for older adults.

Background: Regular physical exercise can counteract age-relatedphysiological and cognitive decline, reduce the risk of disease, andimprove quality of life. Even so, a considerable proportion of older adultsare insufficiently physically active. Supramaximal high-intensity intervaltraining (HIT) is a potential time-efficient, effective, and appealingalternative to longer duration moderate-intensity training (MIT).Research also indicates promising effects from supramaximal HIT forolder adults, but the interpretation of these results is limited to a fewsmall studies, highlighting a need for larger, high-quality randomizedcontrolled trials (RCT) for this population. The aims of this thesis wereto investigate motivational aspects of physical exercise, and controlledsupramaximal HIT in particular; and to examine the applicability andeffects of controlled supramaximal HIT in comparison to aerobic MIT,among older adults not engaged in regular physical exercise.

Methods: This thesis comprises four research papers, totaling 117participants (64-79 years old, 56% women). Paper I used cross-sectionaldata from 49 participants to investigate a neurobiological link betweendopamine and exercise-related motivation. Papers II-IV used data fromthe Umeå HIT Study, an RCT with 68 participants, to examineapplicability and effects from 3 months of twice-weekly controlledsupramaximal HIT (10×6-sec intervals, 20 minutes in total) compared toMIT (3×8-min intervals, 40 minutes in total). Both groups exercised onstationary bicycles in a group setting. All participants in the Umeå HITstudy received medical clearance before the training started. Paper IIdescribed the applicability of controlled supramaximal HIT and its effecton exercise-related motivation. Paper III examined the effects onphysiological and cognitive functions, such as cardiorespiratory fitnessand global cognitive function. Paper IV used data from 42 participantson structural and functional magnetic resonance imaging (MRI) toinvestigate the effects of the exercise on the hippocampus and episodicmemory.

Results: Paper I indicated a positive association between self-reportedexercise motivation and dopamine D2-receptor availability in the frontalparts of the brain. Paper II showed that non-exercising, but otherwiserelatively healthy older adults were able to exercise at supramaximaltraining intensities without compromising their physical and mentalwell-being during the training, or their exercise motivation. Theparticipation was high, and no serious adverse events occurred. Notably,the participants performing supramaximal HIT reported more positiveivand fewer negative exercise-related events compared to the participantsperforming MIT. The results from Paper III showed that three months ofcontrolled supramaximal HIT resulted in similar but also additionaleffects compared to MIT, despite the total training time being halved.Both groups improved fitness and cardiovascular function, and in favorof supramaximal HIT there was an improvement in muscular function.Neither group showed an effect on global cognitive function, but apotential improvement in working memory was observed in favor ofsupramaximal HIT. While the effects on episodic memory were mixed,Paper IV observed associations between change in cardiorespiratoryfitness and change in hippocampus function for the CA4/DG subfieldduring pattern completion, which in turn was associated with episodicmemory improvements in pattern completion.

Conclusion: Overall, this thesis supports controlled supramaximal HIT as an effective and appealing training method for older adults, which canmake meaningful contributions to their independence in daily lifeactivities. Although the connection between motivation, dopamine, andaging requires further research, an interesting observation in this thesiswas that, contrary to previous concerns, controlled supramaximal HIThad no negative impact on the participants' motivation. Controlledsupramaximal HIT can be a meaningful addition to the exerciseprograms commonly available for older adults, as providing moretailored and individualized training may contribute to promotingphysical exercise for health and well-being. The cognitive effects ofsupramaximal HIT were mixed, and future studies should aim for longerinterventions and more pronounced physiological changes. Further,research should evaluate controlled supramaximal HIT in a broaderpopulation, including individuals with chronic conditions and diseases,and explore how this form of exercise can be effectively implemented ineveryday settings.

BACKGROUND: This study examined the effects of regulated and controlled supramaximal high-intensity interval training (HIT) adapted for older adults, compared to moderate-intensity training (MIT), on cardiorespiratory fitness; cognitive, cardiovascular, and muscular function; and quality of life.

METHODS: Sixty-eight nonexercising older adults (66-79 years, 44% males) were randomized to 3 months of twice-weekly HIT (20-minute session including 10 × 6-second intervals) or MIT (40-minute session including 3 × 8-minute intervals) on stationary bicycles in an ordinary gym setting. Individualized target intensity was watt controlled with a standardized pedaling cadence and individual adjustment of the resistance load. Primary outcomes were cardiorespiratory fitness (V̇o2peak) and global cognitive function (unit-weighted composite).

RESULTS: V̇o2peak increased significantly (mean 1.38 mL/kg/min, 95% CI [0.77, 1.98]), with no between-group difference (mean difference 0.05 [-1.17, 1.25]). Global cognition did not improve (0.02 [-0.05, 0.09]), nor differed between groups (0.11 [-0.03, 0.24]). Significant between-group differences in change were observed for working memory (0.32 [0.01, 0.64]), and maximal isometric knee extensor muscle strength (0.07 N·m/kg [0.003, 0.137]), both in favor of HIT. Irrespective of the group, there was a negative change in episodic memory (-0.15 [-0.28, -0.02]), a positive change in visuospatial ability (0.26 [0.08, 0.44]), and a decrease in systolic (-2.09 mmHg [-3.54, -0.64]) and diastolic (-1.27 mmHg [-2.31, -0.25]) blood pressure.

CONCLUSIONS: In nonexercising older adults, 3 months of watt-controlled supramaximal HIT improved cardiorespiratory fitness and cardiovascular function to a similar extent as MIT, despite half the training time. In favor of HIT, there was an improvement in muscular function and a potential domain-specific effect on working memory.

CLINICAL TRIAL REGISTRATION: NCT03765385.

Background: Autonomous motivation to exercise occurs when the activity is voluntary and with a perceived inherent satisfaction from the activity itself. It has been suggested that autonomous motivation is related to striatal dopamine D2/3-receptor (D2/3R) availability within the brain. In this study, we hypothesized that D2/3R availability in three striatal regions (nucleus accumbens, caudate nucleus, and putamen) would be positively associated with self-reported autonomous motivation to exercise. We also examined this relationship with additional exploratory analyses across a set of a priori extrastriatal regions of interest (ROI).

Methods: Our sample comprised 49 older adults (28 females) between 64 and 78 years of age. The D2/3R availability was quantified from positron emission tomography using the non-displaceable binding potential of [11C]-raclopride ligand. The exercise-related autonomous motivation was assessed with the Swedish version of the Behavioral Regulations in Exercise Questionnaire-2.

Results: No significant associations were observed between self-reported autonomous motivation to exercise and D2/3R availability within the striatum (nucleus accumbens, caudate nucleus, and putamen) using semi-partial correlations controlling for ROI volume on D2/3R availability. For exploratory analyses, positive associations were observed for the superior (r = 0.289, p = 0.023) and middle frontal gyrus (r = 0.330, p = 0.011), but not for the inferior frontal gyrus, orbitofrontal cortex, anterior cingulate cortex, or anterior insular cortex.

Conclusion: This study could not confirm the suggested link between striatal D2/3R availability and subjective autonomous motivation to exercise among older adults. The exploratory findings, however, propose that frontal brain regions may be involved in the intrinsic regulation of exercise-related behaviors, though this has to be confirmed by future studies using a more suitable ligand and objective measures of physical activity levels.