Strength training is good for balance, immune function, cardiovascular health, bone health, and more, and it’s never too late to start building muscle. Sedentary adults over the age of 50 lose an average of .4 pounds of muscle mass a year, which adds up over time. For seniors, establishing a new strength-training program should be done under the care of an experienced trainer who understands the issues people face as they age, including loss of balance, and can make modifications during weight lifting sessions. In general, seniors should train about three days per week and add more weight when it’s no longer hard to lift the weight they’ve been using.