Personal training is one of the fastest growing occupations and there are several reasons behind it. Firstly, a growing percentage of population are facing obesity problems and there is a strong need for prevention. Secondly, the population is retiring at a fast rate (10,000 per day or 3.6 million per year) but people live on average 20 years longer than a previous generation. People are not old at their 65 and most are physically active. Unfortunately, a big percentage of the retired population will have health related issues and will need professional care and assistance. This is a new fast growing market for various medical professionals and personal trainers.
The fitness industry seems not to be short of 20–30 year-old personal trainers that can easily relate to their peers of similar age. 
However, working with an older client could be more challenging, require more experience and knowledge. It does not come naturally for a younger person to understand needs, goals and fears of an older clientele. Personal trainers may become certified to work with special populations, including elderly, still they may find it challenging to relate to a client of a different generation. On the other hand it can be far less intimidating and more motivating for a senior to be guided by a fitness guru of a similar age.
This is a good reason for a healthy and fit individual who is in his/her 60s or even over to become a professional personal trainer. Moreover, some fitness establishments claim to have strong interest in hiring personal trainers for elderly and prefer senior personal trainers. The South Yuba Club in Nevada is one of them. So if you are retired and still in great health and feel passion for fitness you are in a good position to fill the niche. You will need to become certified to be hired by a gym or a fitness club and the best way to choose the certification is finding out which one is preferred by your potential employer.
Personal trainer certifications with emphasis on training elderly population:
NSCA certified Special Population Specialist (CSPS)
ISSA Senior Fitness Certification
SFA’s Senior Personal Trainer educational program
NASM Senior Fitness Specialization*
ACE Senior Fitness Specialty Certification*
Other Personal Trainer Certifications
* current certification or an equivalent professional credential required to enrol