Episode #5: Force-Velocity Profiles (Principles of Movement Series)

Welcome back to the show, and to episode #5 of More To Movement.

If you’ve lifted weights before, you know the equation for success: lift the weight up, then back down, and repeat.  Do it until you’re tired and can’t do them anymore, and voila! You have muscular development.

Of course, there is some truth in that, but like most things in life, overlooking the simple or foundational things can delay results.  Muscle contraction is no exception.

Have you ever given thought to how you are lifting?  I don’t mean reps and load or how it feels, but the contractions, or better yet, the phases of contractions, themselves?  Have you ever thought, “why am I performing these reps this way?”

Tissue response to a stimulus and, most of the time, the only stimulus we focus on is when we lift the weight and how fatiguing it feels.

But if we understand the phases of contraction and what we are training, we can manipulate the stimulus to optimize our development and achieve our goals much more efficiently. 

I don’t like to waste reps.  It comes down to my motto: move with purpose and move as optimally as possible.

To begin, let’s make sure we understand the phases of muscle contraction.

Now, I’m not going to dive into how the actual tissue contracts.  I’ve written a post covering more of the science on that topic, so if you’re interested in that, check it out at moretomovement.com/why-movement-matters. Now, if you all want me to do a podcast episode diving more in-depth into the science of muscle contraction, let me know by reaching out or leaving a comment, and I’ll be happy to oblige.  It’ll give me an excuse to really nerd out!

What I’m going to focus on today are the types and phases of contractions, specifically isotonic and isometric contractions.

Phases of Muscle Contraction

Isotonic refers to a contraction where movement is occurring.  This is what you think about when you lift weights- an up and a down movement. Those “up” and “down” phases are called concentric and eccentric phases. 

If you can, take your right hand and place it on your upper left arm.  Then, bring your left hand up towards your shoulder.  You’ll feel the muscle (the biceps brachii) under your right hand “ball up.”  This is the concentric phase.

Microscopic myofilaments in the muscle attach to each other, and pull the tissue in, causing the muscle to shorten. Using the gym lingo, that is what is occurring anytime you “flex” a muscle or make it “big.”  

Now, keep your right hand on your upper left arm, but bring your left hand back down to a resting position.  You felt that “balled” up muscle shrink.  It didn’t’ shrink; it just lengthened.  This is the eccentric phase.  Those myofilaments I mentioned before slowly release and the tissue begins to return to the rested, lengthened state.

More on these in a minute.

The other type of contraction is an isometric contraction, meaning muscles stay at a fixed length.  This can be for a brief period, like holding a grocery bag while you walk from the car to the house, or for an extended, focused period, like a plank exercise.

All of these contractions work together to stabilize, create, or prevent movement, but each has unique characteristics that, if applied and trained specifically, can yield precise outcomes.

Contrary to popular belief, eccentric contractions generate the highest amount of force and require less metabolic energy than the other types.  Keep in mind that although tissue is lengthening during the eccentric phase, it is not merely releasing.  It is resisting and slowing the lengthening action, which puts enormous tension on the tissue.  Further, a protein called titin fights like crazy to avoid being lengthened, thus increasing the force potential. 

Training the eccentric phase has many benefits.  A focus on the eccentric phase can increase tensile force, leading to greater strength gains.  It can improve the tissue’s ability to store elastic energy, leading to greater force or ballistic production.  And due to the high amounts of force and subsequent overall muscle fatigue, it can enhance hypertrophic, or muscle size, outcomes.

One thing to consider- due to the high amounts of tension, eccentric-focused training typically leads to higher levels of delayed onset muscle soreness (DOMS), which can prevent you from training due the longer time needed for recovery and supercompensation.

Next on the “force list” is isometric contractions.  The force generated during these contractions aren’t as high as the eccentric but are typically greater than concentric contractions.  What’s unique about isometric contractions is that the force can be used to activate or target specific muscles by utilizing the contraction at specific joint positions.

This can be extremely helpful at targeting underactive muscles that may not be doing their part during movement.  I use isometric contractions to target muscles that are underdeveloped or are not engaging properly to improve or correct movement.  For example, I may have a client squat to a particular angle and hold it to get targeted muscles at that specific angle to start firing. Isometric contractions are also great to use for improving the stability of joints. 

Though concentric may have the lowest force production in comparison, these contractions have the greatest velocity production, as well as the highest muscle activation. 

These require much more metabolic energy but can enhance motor unit recruitment and rate coding, or firing rate of action potentials instigating muscle contraction.  This can result in optimal muscular development and maximal rate of force development. When you think of moving something, such as a dumbbell, concentric contractions are in action.

I’ve mentioned force and velocity quite a bit.  To truly implement effective training strategies, we need to understand how these phases affect the force-velocity relationship.

Force-Velocity Profiles

Force and velocity have an interesting relationship.  Though they influence each other, they have a tough time sharing the spotlight.  On one side, force is vital, because it allows for maximal muscle recruitment expressed as strength. On the other hand, sometimes we need to move very quickly.

In terms of exercise, think of a maximally loaded squat, meaning it’s the most weight you can do.  When you perform that squat, is it quick?  Not at all.  As we say, you grind it out, and you move very slowly because you are recruiting every muscle fiber you have to stand up with the weight. 

Now, shift your thoughts to jumping.  To leave the ground, what must happen?  You can move as slow as you want, but you cannot leave the ground without a high-velocity contraction.   The rate of contraction is the most important.  

This is the interesting duality: maximal force and maximal velocity cannot coexist. 

Think of a continuum, with force on one end, and velocity on the other.  This continuum represents a muscle’s ability to produce tension at differing shorting velocities.  As velocity increases, we will see a decrease in muscle tension.  And of course, as force increases, we will see a reduction in contraction rate. However, not all is lost. 

Though maximal force and velocity cannot coincide, optimal levels can.  The two intersect as a point, which means you can have an optimal level of force and an optimal level of velocity at the same time, and this point changes for different movements.  And that is influenced by the emphasis we place on how and what we train.

Most movements have a degree of both traits.  So, putting it all together, it means that many exercises or movements can be modified to develop these characteristics.  No more time wasted just lifting weights, but actually training with a purpose.  

So what are the takeaways so we can implement these strategies?  How can we actually use this?

1. Review how you have been training.  What is the primary purpose? 

Are you training to be stronger, or are you working to lose weight?  Do you want to build muscle, or improve your endurance?  Maybe you want to move faster, quicker, or more explosively?  Whatever the goal, evaluate your approach, and see if how you are training matches your goals.

2. Next, see how implementing both force and velocity characteristics could benefit or enhance your development. 

We know movement is a combination of force and velocity, so find areas that a change in focus could merit better results.

Here are a couple of examples.

If your goal is muscular development, then add eccentric-focused phases to your training.  This causes an increase in tension, which can lead to muscular fatigue and contribute to an increase in muscle size.

If your goal is weight loss, think about adding velocity profiles with fast concentric action.  This requires more metabolic demand, which can lead to higher caloric expenditure and muscle fatigue, which is very beneficial if you’re trying to lose weight.

Or, this can be done within exercises themselves.  You can perform a squat exercise with a heavy load to develop force, but you could also perform a squat quickly with a lighter weight to build contraction speed.  Further, you could perform a squat with a moderate load at a set tempo to improve both force and velocity.

These are a few examples, but you get the picture.  The possibilities are endless if you understand what you are trying to achieve.

So to summarize today, remember these points:

• Force and velocity have an inverse relationship, but developing optimal levels of each characteristic can greatly influence movement, leading to better overall development.
• Phases of contractions contribute significantly to overall movement outcomes, and understanding how concentric, eccentric, and isometric contractions uniquely contribute to movement and muscular development can help you achieve your goals quicker and more efficiently.  You just have to be creative and have the know-how to make those modifications.

Thanks so much for listening to this episode and spending some time with me.

If you have questions or comments about training these phases or profiles, feel free to reach out to me by visiting my website MoreToMovement.com, and drop me a line.

We’ve been tackling this Principles of Movement Series pretty hard, and for good reason- we really need a sturdy foundation if we want to build a stellar house. However, I want to change it up for an episode and do a show on the FAQs that I receive from my students because I think many of their questions would really help you guys, but additionally, it puts this stuff I’ve been talking about into the real-world setting.  I think it’ll be a fun show!  I hope to see you then.

Thanks again and remember-where ever you are: keep moving.