Significance of Research Question/Purpose: Subjective cognitive decline (SCD) is regarded as the first clinical manifestation in the AD-dementia continuum and currently has a prevalence of 11.2% in adults over the age of 45, with incidence increasing with greater age. Furthermore, population-based studies suggest that between 50% and 80% of older individuals (aged 70 years and older) who perform normally on cognitive tests, report some form of perceived decline in cognitive functioning when asked. The SCD state is unique as this population is more likely than their healthy peers to present with AD biomarkers such as neurodegeneration and amyloid burden, and therefore represents probable preclinical AD relative to other causes of SCD. Likewise, growing evidence suggests that a significant proportion of those adults are subsequently found to develop MCI, or AD, following the classic SCD-MCI-AD trajectory, with SCD increasing MCI risk 1.5-3 fold. Preventing Alzheimer's disease (AD) is arguably the most important approach to address the dementia epidemic worldwide because 99.6% of drug trials failed and no drugs can yet prevent, cure, or even slow AD. A treatment that delays the onset of AD by five years could save $89 billion in 2030.This highlights an urgent and pressing need to develop behavioral interventions to prevent AD and slow its progression. This study will use a randomized, 2-parallel group, trial design that is guided by the Consolidated Standards of Reporting Trials (CONSORT)and the SPIRIT checklist. We will randomize 104 community-dwelling older adults to one of two arms for 3 months: home-based (asynchronous telerehabilitation) Exergame (HbExergame) or home-based (asynchronous telerehabilitation) aerobic exercise (HbAEx). Randomization will allocate subjects on a 1:1 allocation ratio within each age stratum (65-74 and \>75), and will use permuted blocks of 8 and 4. We do not expect equal numbers of subjects in each age stratum, but want to balance the groups for each age. Investigators will be blinded to group assignment. All participants will be blinded to study aims and reminded as needed not to discuss their experiences with outcome assessors. Outcome assessors (also blinded to group allocations) will measure: 1) feasibility (attendance, adherence to exercise dose, systems usability scale), 2) preliminary cognition: fluid cognition \[primary outcome\], attention, episodic memory, and processing speed \[secondary outcomes\] using the NIH Toolbox cognition battery and aerobic fitness \[VO2peak and 6-minute walk distance\], and 3) blood neurotrophic biomarkers.