Effects of a 12-Week Aerobic Spin Intervention on Resting State Networks in Previously Sedentary Older Adults

Abstract

Objective: We have previously demonstrated that aerobic exercise improves upper extremity motor function concurrent with changes in motor cortical activity using task-based functional magnetic resonance imaging (fMRI). However, it is currently unknown how a 12-week aerobic exercise intervention affects resting-state functional connectivity (rsFC) in motor networks. Previous work has shown that over a 6-month or 1-year exercise intervention, older individuals show increased resting state connectivity of the default mode network and the sensorimotor network (Voss et al., 2010b; Flodin et al., 2017). However, the effects of shorter-term 12-week exercise interventions on functional connectivity have received less attention.Method: Thirty-seven sedentary right-handed older adults were randomized to either a 12-week aerobic, spin cycling exercise group or a 12-week balance-toning exercise group. Resting state functional magnetic resonance images were acquired in sessions PRE/POST interventions. We applied seed-based correlation analysis to left and right primary motor cortices (L-M1 and R-M1) and anterior default mode network (aDMN) to test changes in rsFC between groups after the intervention. In addition, we performed a regression analysis predicting connectivity changes PRE/POST intervention across all participants as a function of time spent in aerobic training zone regardless of group assignment.Results: Seeding from L-M1, we found that participants in the cycling group had a greater PRE/POST change in rsFC in aDMN as compared to the balance group. When accounting for time in aerobic HR zone, we found increased heart rate workload was positively associated with increased change of rsFC between motor networks and aDMN. Interestingly, L-M1 to aDMN connectivity changes were also related to motor behavior changes in both groups. Respective of M1 laterality, comparisons of all participants from PRE to POST showed a reduction in the extent of bilateral M1 connectivity after the interventions with increased connectivity in dominant M1.Conclusion: A 12-week physical activity intervention can change rsFC between primary motor regions and default mode network areas, which may be associated with improved motor performance. The decrease in connectivity between L-M1 and R-M1 post-intervention may represent a functional consolidation to the dominant M1.Topic Areas: Neuroimaging, Aging.

Exercise, Fitness and the Aging Brain: A Review of Functional Connectivity in Aging

“…Mean trial duration was 5.25 months (SD = 3.03), with the longest trial lasting 12 months and the shortest just six weeks. Intervention conditions primarily consisted of a combination of supervised and unsupervised walking sessions titrated so that participants reached 50-80% of their maximum heart rate, though several interventions also included other aerobic activities in their exercise protocols, such as cycling (McGregor et al, 2018;Prehn et al, 2017), dancing (Voss et al, 2019), and/or jogging (Flodin, Jonasson, Riklund, Nyberg, & Boraxbekk, 2017). One study employed a commercially available video game designed to enhance fitness that included a variety of both aerobic (dancing, running in place) and strength (e.g., yoga) exercises, with participants completing all exercise sessions independently in their own homes.…”

“…It is possible that non-aerobic exercise exerts unique effects on DMN connectivity compared to aerobic exercise. Indeed, there is evidence that improvements in aerobic fitness levels may mediate some proportion of the effects of exercise on DMN connectivity (Flodin et al, 2017;McGregor et al, 2018), indicating that aerobic exercise may contribute more robustly to functional network integrity compared to other nonaerobic forms of exercise. Further, one study found evidence to suggest that the magnitude and direction of the relationship between exercise and DMN connectivity is dependent on premorbid cognitive status (Chirles et al, 2017).…”

“…Although the specific networks found to be influenced by exercise varied across studies, all 9 interventions observed changes in functional network organization amongst individuals who engaged in exercise compared to those who did not. DMN coherence was most often shown to be modified by exercise (Chirles et al, 2017;Flodin et al, 2017;McGregor et al, 2018;Voss, Prakash, et al, 2010a), an intriguing finding given that this network also appears to be most sensitive to the deleterious effects of aging relative to other large scale networks (Buckner et al, 2008;Damoiseaux et al, 2008;Hafkemeijer et al, 2012;Jones et al, 2011;Petrella et al, 2011;Sheline et al, 2010;Sperling et al, 2009). Exercise-induced changes in functional network organization were also observed in the dorsal attention (Voss et al, 2019), salience (Voss et al, 2019), and frontal executive networks (Voss, Prakash, et al, 2010a), each of which support cognitive processes known to decline with age (e.g., decision making, attentional control, conflict monitoring, inhibitory control, emotion recognition and regulation (Menon, 2015;Vossel et al, 2014).…”

“…For example, depressed mood is associated with cognitive decline and dementia onset (Bassuk, Berkman, & Wypij, 1998;Geerlings et al, 2000), and has been shown to be responsive to the effects of exercise (Schuch et al, 2016). Moreover, depression is characterized by disruptions of the DMN (Hamilton, Farmer, Fogelman, & Gotlib, 2015), one of the primary networks implicated in age related cognitive decline that is also known to be sensitive to the effects of exercise (Chirles et al, 2017;Flodin et al, 2017;McGregor et al, 2018;Voss, Prakash, et al, 2010a) Given these associations, it is reasonable to hypothesize that exercise-induced changes in DMN coherence may yield improvements in mood independently of or in concert with improvements in cognitive functioning. Late-life depression is challenging to treat and accelerates decline in other aspects of functioning (Knöchel et al, 2015;Yuan et al, 2017), highlighting the need for additional research exploring the mechanisms by which exercise might impact mood outcomes in late life.…”

Modulation of Distinct Intrinsic Resting State Brain Networks by Acute Exercise Bouts of Differing Intensity

“…Most of the previous rs-fMRI literature was, however, not focused on investigating the transient effects of acute exercise bouts, but rather on long-term effects of repeated exercise training over several months [1][2][3][4]: Stronger rs-FC was reported between the right parahippocampal gyrus and motor, sensory, and mood regulating areas after 16 weeks of training [4]. On the other hand, 12 weeks of exercise induced increased FC between the default mode network (DMN) and primary motor areas [3], eventually indicating improved motor performance. Conversely, another study found no significant changes in intrinsic brain activity after a six months of aerobic exercise [2].…”