The goal of this clinical trial is to assess the efficacy of combined aerobic and resistance training in enhancing physical reserve in older adults with physical frailty. Investigator contend that enhanced physical reserve will enable preservation of cognitive and physical function. The main questions aims to answer are: (1) Compared with usual care (i.e., CON), will 3-month aerobic and resistance training (ATRT) improve physical reserve in older adults with physical frailty? (2) Compared with CON, will ATRT lead to changes in the neural network organization? (3) Will improved physical reserve lead to better maintenance of cognitive and physical functioning in spite of presence of white matter hyperintensities (WMH)?