For the sciency people, here are the science notes mentioned in the video:

As mentioned, your vagus nerve innervates your organs and viscera and plays a big role in the functioning of your immune system. The vagus nerve connects to the insular lobe of the brain where a lot of this information is processed. A portion of nerve endings in your musculature and fascia communicate to the insula and other parts of the brain via C-Fibers and this vagus nerve pathway.

0:00 - Intro

Hey, everybody! I'm Shane from MATRIX. And if you've been tuning into these tips, you'll know that yesterday we were doing some upper body strengthening exercises that not only create great neuromuscular control and upper body strength, but they also help strengthen your immune function. Today, we're continuing in that vein; working with the lower body and the arms. In yesterday's post, I did add a whole bunch of sciency stuff to tell you how these types of exercises do actually influence your immune system. And I'm going to put that same information in the post again today. So if you're somebody that's interested in those technical things, it's available for you there.

0:41 – Muscle Squeeze Basics 

Otherwise, there's not a whole lot else to say. Just know that the exercises that we're doing are very safe as long as you don't have any current injuries. We're going to be squeezing muscles. When you first squeeze them, think about staying at a level 3-5 out of 10. As you get better and better at practicing this, your goal is to work to get up to that level of a 10 out of 10. Another note is that I'm going to give some specific movements with these exercises, but they're not that important. As long as you can create the sensation in the part of the body where we're looking to create it. And when you're first working with these exercises, you're probably going to feel sensation in a lot of other body parts as you're learning to stabilize and trying to figure out how to squeeze more specifically. That's totally normal and okay. Just remember that part of your goal as you continue to train with these is to be able to isolate and isolate more into the muscle. The last thing you need to know moving into the exercises is -- I do recommend when possible -- feeling your own muscles so that you can feel the contraction that's happening and making sure that is what you think is happening is actually what's going on the muscle. Because you might find some soft spots where, if you weren't touching, you wouldn't know. But as soon as you feel that, you can start to figure out how to make them get strong again. So, without further ado, let's move into today's workout.

2:07 - Quads 

The first muscles that we're going to work are going to be our thigh muscles -- our quads. There are four muscles in this group. They all cross the knee joint. And because they cross the knee, they cause knee extension. So, that's the movement that we're going to be doing. One of those four muscles does cross the hip. So, I'll be giving you an added little piece that you can add in to get some more activation through that one. The sequence that we go through -- if you remember from yesterday -- is we always start with a stretch. We move into the squeeze. And we finished with a stretch again. I'm going to be showing you one full repetition on each leg. But if you're doing these workouts at home, think about doing 3 to 5 repetitions for maybe 3 to 5 seconds each. For your quad, the stretch is this kind of basic runner stretch that we've done before. If you need to hold on to something, that's fine. If you can't catch your ankle, just drawing the leg backward, will do the trick. Once you've come into the stretch position, you're going to extend the leg forward. And now you're going to try and extend it as much as you can. So you can really feel the muscles of the legs getting tight. This is one of those opportunities to actually poke around. Notice for any soft spots. I can feel one here that's not contracting that well. So I try to squeeze it a little bit more. And then after I've held the squeeze, I come back into the stretch position. Holding or not holding. It's really that simple. As we move to the other side, again, come into your stretch. As you come into the squeeze, we're extending the leg forward. Trying to get the muscles to fire up. Feeling around. Noticing where it's not quite as good as you want. Can you figure out how to make it tighter? And then release and stretch. As I mentioned -- for the quad -- most of it is about the knee extension. The last little piece that you can add in if you want for that extra muscle is after you do the stretch. And you do the squeeze here. You can also work on picking the leg up. And you're going to feel that fire up more, higher in towards your hip. Still a place where you can palpate and try to figure out the squeeze. Remember, that's an added little piece if you want to throw it in.

4:29 - Hamstrings 

Exercise number two is for the opposite part of the musculature of the thigh, and that's your hamstring. These are ones to be careful of -- just like the lat was yesterday. These are muscles that cramp up on people very easily. So start your squeezes very light in the beginning, slowly ramping up as you go. Because this is the opposing muscle to the quads. It's the exact same thing, but we're going in the opposite direction. The stretch position is bringing the leg out in front of you. Pulling the hip back so you get some nice length. Get some sensation through the back of the thigh. That's the stretch. Those of you who are more flexible, maybe you're picking the leg all the way up forward. Once you've come into that stretch position, the first thing you're going to do is start to pull your heel towards your butt. That's going to squeeze the lower part of the hamstring. You're going to feel closer to the knee. From there, you're trying to pull the thigh backward and you'll feel that squeeze. I got a little cramp myself. Move right up closer into the butt as you get the whole muscle to engage. And once you felt the squeeze, come back out into the stretch. If the muscle cramps up on you while you're doing it -- do what I did -- and just come out of it. Working the other side, same system. Start with your stretch. From your stretch, bend the knee. You should start to feel some work down in the bottom portion of the hamstring. And as you keep the heel tight to the butt and pull it back, that's when you'll really start to feel the squeeze through the whole muscle. Feel around. I can get a little tighter there. And then release and stretch it out. A common mistake when you're trying to add those different pieces together is pulling the heel to the butt and then, as you pull the thigh back, people let the heel drift away. That's going to release the tension on the lower part. And you're not going to get that full range of motion squeeze that you're looking for. Just be aware of that.

6:33 - Glutes

Exercise number three -- the glutes -- your big butt muscle. All right? So for this one, the stretch position is drawing the knee up and across the body. You're probably not going to feel a big stretch just doing it this way. It takes a lot more leverage to get it for most people. But just as long as you're coming into this position, you'll know you're lengthening the muscles of the glute. From here, the most important thing that we do is pull the thigh backward. You should really feel your glute fire up as you start to do that. Careful on this one that you're not pulling the heel to the butt or you'll engage the hamstring. Keep the knee pretty straight. With the thigh pulling straight back, you'll feel the butt engage. To get a little bit extra, rotate your knee to the outside. And push a little on the diagonal like an ice skater. You should feel that squeeze even more. And then you'll come back up and across into the stretch. Switching sides. Again, just going through this process. Find your stretch first. Bring the leg forward and across the body. Then, pulling the thigh backward. You don't have to worry about the knee bend. Rotate the knee a little towards the outside. And try to push a little bit more back on the diagonal to get the last little bit. Feel the full squeeze. And then come back up and across into the stretch.

8:04 - Calf

There's one more main muscle group in the legs, and that's the calf muscles. The muscles on the lower part of the leg that attaches with the Achilles tendon. They're very simple. It's only the ankle joint that moves with them for the most part. Your stretch position is going to be with the toes up and the knee straight. Most of the time, when we're really trying to get a stretch here, for a runner, we have the toes up on something so we can create steeper angles. Again, you don't really have to do that here. We're just trying to find end range of motion. Then from here, all we're doing is pointing the toes down and giving the knee just a little little bend. You should be able to feel the muscle squeeze up through the back of the leg here. Again, you can palpate around. Notice where it's not quite as tight. Squeeze it. And then stretch it back out. Switching over to the other side. Again, starting with toes pulled up. Knee straight. This will give you a pretty good stretch for the back of the leg there. And then little bend in the knee. Try to point the toes down. Feel the muscles work. You can see on me this isn't really firing at all. So, I'm going to try and roll the toes in a little. Ah, there it goes! And release. Stretch it out. Awesome.

9:34 – Transition to the Arms

So, those are the four main movers in the lower body -- quads, hamstrings, glutes, and calves. To wrap up today's workout -- and between yesterday and today's session giving you a pretty full body workout -- we're just going to do the arms now. The biceps and the triceps. They actually might be a little bit more complicated than you think.

9:56 - Biceps

For the biceps, what we're going to want to do is roll the palm in. Pull the arm back. And that should give you a nice stretch through the biceps itself. The full range of motion, now, is not just bending at the elbow -- like most people do -- but that is going to get the majority of it. You should also be turning the palm outward. To add to that squeeze, the last little piece is actually starting to bring the arm up and forward. You're thinking about bringing your elbow in as close to the front of your shoulder as you can. Feeling around. Finding the squeeze. Noticing where it's a little soft, there. And then release and come back into the stretch. We're going to try the other side again. Pulling back. Palm away. Rotating the palm out. Bending the elbow is going to give you a lot. And then -- to get into more of the upper portions of it -- adding that lifting of the elbow. Feeling around. Getting the squeeze. And release back into the stretch.

11:05 - Triceps

The triceps are the exact opposite of the biceps. The movements are the same but in the reverse order. When you put your emphasis on squeezing is when the arm is getting straightened. Your basic triceps stretch is elbow up overhead. You can use the other hand to help, but you don't have to. Just think about driving your elbow up towards the ceiling. Then from here, start to bring the arm down. Extending the elbow is going to get you some engagement through the triceps. Pulling the arm back is what is really going to finish it off. If you can reach, feel around. But otherwise, just notice where it's not engaging. Try to squeeze it. And then come back through. Find your stretch. Last one, other side. Elbow to ceiling. Drive up. Feel the stretch. Then as you come down, extending the arm. Squeezing. Drawing back to get a little bit extra. There are three different parts of the triceps. See if you're getting each and every one of them. Even more there. And then release. Stretch. Ah! And shake it all out.

12:19 - Summary 

You should be feeling pretty warm at this point. I'm actually sweating a tiny little bit. I can feel the work that I just brought it into my muscles. And again, we only did one rep on each and every muscle group instead of doing the 3 that 5 that I recommend for an actual workout. So you can imagine how much more intense that gets if you do it 3 to 5 more times.

12:38 - Farewell 

If you have any questions, please join me on the Q&A this afternoon. We'll be covering both yesterday's workout and today's. I would love to have you there to help clarify any of these things for you. Otherwise, tune back in tomorrow. We will move on to some other great tips to help your immune system and your relaxation. See then!