The answer is Yes.
A study, by Western State Colorado University, has found older adults were able to adapt to personalised cardio-respiratory and functional/resistance training and improve health-related fitness to the same extent as younger people.
However the exception, in the physical fitness findings, between the older adult and younger people, is that older people have more difficulty increasing their lower-body strength compared to the younger group. Dr. Dalleck, the researcher from Western State Colorado University, explains that this may be due to the fact that the older group may have lost some type 2 muscle fibres simply as a result of aging, meaning that health coaches and exercise professionals may want to temper expectations when it comes to absolute strength gains seen in older adults.
What this research proves is that clients are never too old to see meaningful gains as a result of a well-designed exercise program.