The Joint Health Blueprint: Preventing Arthritis, Frozen Shoulder, and Bone Loss as You Age

**Dr. Gabrielle Lyon** (0:00)
Muscle will develop more quickly than the tendon adaptation. Why are tendons important? What are they? How do we think about them in a global sense?

**Gerard D'Onofrio** (0:08)
By the time your tendons and ligaments start to adapt to the athletic endeavor you're engaging in, you're almost looking at six to nine months.

**Dr. Gabrielle Lyon** (0:15)
When someone is thinking about osteoporosis prevention, what do we have to do?

**Dr. Jocelyn Wittstein** (0:20)
Many of them are on menopausal women with low bone density. The most effective programs seem to combine some impact and some strength training.

**Dr. Gabrielle Lyon** (0:29)
This book does something that I've never seen. It brings a history of muscle. Tell me about why. Why this book?

**Daniel James Lieberman** (0:36)
Most books about muscle tell you what to do, and this one's different because it's descriptive, it's not prescriptive.

**Gerard D'Onofrio** (0:44)
Well, you're not just progressive overloading your muscle, you're progressively overloading your tendon.

**Dr. Jocelyn Wittstein** (0:48)
People have to be, I think, more thoughtful about what they're eating. You could easily fill yourself with things that don't give you the nutrients you need.

**Dr. Gabrielle Lyon** (0:55)
I'm curious as to what your thoughts on what we're getting right versus what we're getting wrong.
There are a number of topics that I'd love to discuss on this podcast, which include and are not limited to the things that limit our ability to progress, like tendon issues, like back pain, hip pain, things that ultimately limit the quality of life. But let's start with one of the things that I think that we both see in clinical practice, are issues with tendons. And why are tendons important? What are they? How do we think about them in a global sense?

**Gerard D'Onofrio** (1:37)
Muscle is contractile tissue. Muscle is made of actin, amylase and filaments. You have this incredible cross-linking phenomenon that's mediated by our energy molecule ATP. And we contract muscle and ultimately to move bone, but muscle doesn't attach directly to bone. It attaches to bone through tendons. And collagen is our most abundant protein in the body, and no surprise, tendons, that tendonous attachment from muscle to bone is predominantly made of collagen. So tendons are, by definition, they are non-contractile tissue. They're almost like, if you think about a short bungee. So they exist in a relaxed state called the crimp state, and when the muscle contracts, it pulls on that tendon, takes the slack out, and then it winds up attaching to the bone to move the bone. And tendons have this incredible quality called viscoelasticity, which is a cool word, but it's-

**Dr. Gabrielle Lyon** (2:27)
Everyone is gonna be quizzed on this later.

**Gerard D'Onofrio** (2:28)
There you go, so viscoelasticity. It means that the mechanical behavior of that structure changes the degree of strain that you put on it. So at low strain rates, tendons dissipate energy. At high strain rates, they really put down the force. And so you can think about as you're walking, you might be putting some tension through your Achilles tendon by definition, but you're not putting as much tension through it as you are when you're running, and it's like a really tight spring. So the mechanical behavior of it does change.
The tendons are on sort of an organizational level. You know, muscles have the contractile elements, you have muscle fascicles, and fascicles, for those who are listening, are bundles of proteins. So you have the structures, you have a larger structure, and then you also have within that, these composition of these microstructures of fascicles. And fascicles are a fascinating thing because they are present in muscle, tendon, and nerve. And the reason for that is because we don't, we're not uniplanar individuals. We don't just function in one plane. We function in forward and backwards, left and right, and also we rotate. And so muscles and tendons, as they're trying to move a bone, they need to have specific elements stressed, not the entire system stress simultaneously, but the fascicles actually allow for tendons to be strained specifically. So you could think about like a pitcher. So a pitcher, the job of a rotator cuff, this is a cool point that I really like. The job of a rotator cuff is actually to stabilize the ball on the socket. We think about rotator cuff strengthening exercise. You'll see a lot of people with bands and cables and strengthening up the rotator cuff, and it does that. It does rotate the arm, hence its name. But the shoulder is an inherently very mobile joint. It's comprised of four different joints, actually. It starts over here. And at the sternoclavicular joint, you have your AC joint, and then you have your true glenohemeral joint, and you have the scapula shoulder blade that rests on the back of the rib cage. So, there's a lot of mobility in it, which is why, on average, unless you're a raquette, you can raise your arm higher in the air than you can your leg. Okay, so similar ball and socket joint with the hip, but more stability there. Job of the rotator cuff is to stabilize the head of the ball and socket joint. It's almost like thinking about a golf ball on a tee. So as you raise your arm into a pitching motion, all of your rotator cuff muscles are active, but different fascicles are actually more stressed during different phases of that. So that's one of the fascinating elements of this. It's a really cool mechanical adaptive thing that we've evolved to have. And we have it in all of those mobile structures of the musculoskeletal system. We have it in muscle, we have it in tendon, and we also have it in nerves to allow us to be more athletic in multiplanar motion. So it's very cool. In collagen itself, most of tendon dry weight is type 1 collagen. And then you have lesser components of type 3, type 11 You have other types as well. And when a tendon starts to become diseased or overloaded, that can change. It's actually part of the process of developing tendinopathy.