I had a client once tell me that she started working out with weights to keep from getting "loose on the bone." I had never heard that expression before, so I had to ask her want it meant. She explained that as people got older, she could always tell the one's who lifted weights as a part of their fitness program from those who did not. She said that the people who worked-out with weights always looked more fit and firm compared to those who primarily did cardiovascular exercise as part of their fitness programs. Thus, the term "loose on the bone" is an expression for that soft and jiggly look that people get as they age.
As a personal trainer with over 17 years of experience in the fitness industry, and being in my fifties, I can attest to the truth of getting "loose on the bone" if your fitness program consists mainly of cardiovascular exercise. While cardiovascular exercise should be a part of any fitness program, strength training also known as weight lifting should be the foundation of your exercise program as you approach your 40s and beyond.
You start to naturally lose muscle mass starting around age 40. Strength training can minimize, and even stop this from occurring. This is important because, muscle is the active component of your body that burns most of the calories that you consume. Muscle, also keeps you looking fit and firm. Each pound of muscle burns about 6 calories daily even at rest and more when you are active.
You naturally lose one to one and one-half pounds of muscle each year starting in your 40s, and this muscle loss is replaced by fat if you don't adjust your diet and your activity level accordingly. Cardiovascular exercise is great for burning fat, but it can't stop you form losing muscle, and too much cardiovascular exercise causes you to lose muscle even faster.
Therefore, as you approach your 40s, you should start to incorporate more weight lifting into your fitness routine. If you do it regularly, I promise you will never "get loose on the bone."