In 1984 medical researchers at Harvard and Stanford universities concluded that sedentary life-styles lead to heart and lung diseases that shorten lives, strongly recommending middle-aged people to undertake some form of regular exercise.

True

Explanation:

This statement is true. Medical researchers at Harvard and Stanford universities found that leading a sedentary lifestyle (sedentary meaning minimal exercise with little movement) leads to a higher risk of health complications (which can be more prevalent in older age).

This finding strongly recommends that middle-aged people should undertake some form of regular exercise so as to not fall into the category of "sedentary".