Mass... does not equal Gas?

Part 1: It's not that simple...

Let’s create a scenario.

You’ve just finished up your last practice for the fall and you’re building out offseason plans for your pitching staff this winter. Out of all of your players, there’s one in particular that really makes you excited. As a freshman, this kid has a chance to be a really special player. He’s long and lanky at 6’4 and weighs just 160 pounds, but don’t let the scale fool you. This kid can throw. Despite having twigs for arms and legs, this kid can already run it up to 84-87. Just imagine what his velo would look like if he got a steady dose of deadlifts and protein shakes this offseason. You decide to give him a goal: If he shows up at 175 next spring, he’ll touch 90.

When he showed up next spring at 180 lbs., you couldn’t have been happier. His skinny arms and twig legs were now chiseled with muscle thanks to an aggressive bodybuilding-style workout program. All of his compound lifts had doubled, his physicality was night and day, and he was looking exactly how you hoped when you envisioned his 90 mph body. He wasn’t going to be sitting 84-87 anymore when he started throwing off a mound again. He was going to be touching 91-92 with ease.

That’s where it gets interesting.

In his first bullpen of the year, his fastball didn’t even touch 83. Figuring he’s just shaking off some rust, you don’t get worried and decide to see how things play out. This changes when he’s one month into practices, his fastball hasn’t touched 84, and his elbow throbs every time he picks up a ball. You can’t figure it out. This kid did everything you asked him, crushed the weight room, added 20 lbs., and now his velo has fallen off a cliff. You don’t just feel bad. You feel like someone has repeatedly punched you in the gut until you can’t breathe anymore. The guy who was supposed to be one of your top three arms might not be able to throw any meaningful innings at all this year. The best part?

You only have yourself to blame.

Remember when you thought he wasn’t big or strong enough at the end of the fall? Turns out, that young man was actually pretty strong in the first place. He just didn’t fit the mold of what most of us tend to think of as strong. The situation from above wasn’t made up. In fact, it happens a lot more than you would think. Young, eager athletes looking for more velocity often try to find solutions in the weight room and at the dinner table. This is because we currently have a catchy phrase going around in baseball: Mass = Gas. The translation is pretty simple. Players who weigh more are able to throw the ball harder.

The application, however, is not so simple.

Mass equals gas might sound catchy to say, but it’s not totally accurate. The young man from above – along with the many others who have made his same mistake – are great reminders that adding mass can hurt performance as much as it can help it. This article is going to attempt to explain why.

Where did Mass = Gas come from?

Before we get into the pitfalls of adding mass, let’s start with where the idea of mass = gas comes from. We don’t have to go any further than Isaac Newton’s second law of motion: Force equals mass times acceleration (F=M*A).

According to Newton’s findings, the amount of potential force a system can produce is dependent on its mass and how quickly it’s able to overcome inertia. This is pretty straight forward. If it’s heavier and it gets up to speed faster, it’s probably going to do a lot more damage. From a training perspective, this seems to transfer well. Justin Verlander, Madison Bumgarner, and Noah Syndergaard aren’t small dudes. They’re physical specimens with a big motor and a quick trigger. 

The average weight for an MLB player has steadily increased over the last several decades. In 1970, the average big leaguer weighed about 184 pounds. Today, that number is north of 200 lbs. As of 2017, the average MLB pitcher weighed in at about 215 pounds – a 25-pound increase from 1970. This past season, the average weight of starting pitchers with the top 10 hardest fastballs was 210.8 lbs. This list included:

  1. Luis Castillo (97.4 mph, 200 lbs.)
  2. Dinelson Lamet (97.0 mph, 228 lbs.)
  3. Gerrit Cole (96.7 mph, 225 lbs.)
  4. Brandon Woodruff (96.6 mph, 215 lbs.)
  5. German Marquez (95.9 mph, 225 lbs.)
  6. Yu Darvish (95.8 mph, 225 lbs.)


As you can see, the majority of the arms on this list exceed 200 lbs. This itself isn’t a bad thing. Additional mass can absolutely have a positive influence on performance. However, it’s not because F=M*A. Newton’s laws give us information about force production in linear systems. They fall short when applied to rotational systems. This is a problem if we’re trying to gauge force output in rotational athletes. 

If we want to explain why mass can positively influence pitching velocity, we have to think using a slightly different lens.  This is where torque comes into play.

I was fortunate to talk about this topic with Jimmy Buffi – current CEO of Reboot Motion and former analyst with the Los Angeles Dodgers. Torque is something Buffi brought up because it gives Newton’s laws more depth when it comes to force production in rotary athletes. By definition, torque measures the forces that cause an object to rotate about its axis. This is really important for baseball players. Force is plane specific. If we want to gauge how much force a pitcher is able to produce, we need to look at the planes of motion in which that force is being produced. Torque helps us do just that.

Below is the equation for torque:

  • Torque = Inertia*Angular Acceleration

I know it seems a little complicated at first glance, but it doesn’t have to be. The first part of the equation – inertia – can be calculated as follows:

  • Inertia = Mass*(Radius^2)
    • This is the most simplified equation for Inertia. Feel free to read more about this here.

This is pretty straight forward. Inertia simply looks at how heavy something is and how far the mass is being applied in relationship to the center axis of rotation (radius). We’ll dive into this one in just a second. First, let’s break down the second part of the equation: Angular Acceleration.

  • Angular Acceleration = Angular Velocity/Time

Don’t get too lost in physics on this one. Angular vector quantities simply give us information about how something is moving in a circular motion (i.e. rotation). Velocity over an elapsed period of time gives us information on acceleration. As a result, angular acceleration is going to give us information about how something is accelerating during a rotational movement.

So why the hell is any of this important when it comes to mass = gas?

Let’s go back to inertia. If you’re in the mass = gas crowd, you should pay close attention to this part. According to inertia, an increase in mass or an increase in the distance from the axis of rotation is going to result in greater torque. The more torque you can create, the more velocity you can produce. This is important. If the mass you’re adding helps you produce more torque, you’re going to be able to throw the ball harder. Newton’s laws kind of alluded to this, but using torque helps us clarify it. If we’re dealing with rotary athletes, we have to measure how force is being produced rotationally. Linear equations don’t cut it. 

Alright, easy enough. Baseball players with more mass should produce more force based on what we know about torque. Therefore, adding more mass should help you throw harder.

Come on, you didn’t think it was going to be that simple. Did you?


Read Part 2 >>