What is "rate of force production?"

Rate of force production is important for many activities. If you lift a max deadlift, the bar speed is slow and so you can easily recruit your maximum force along the entire path. If you putt a shot, it moves more quickly and it takes training to generate force against the moving ball. For a baseball, even a pro pitcher can't generate similar forces on such a rapidly accelerating object, thus the kinetic energy is much less than that of a shot.

This still doesn't make sense to me. In a max deadlift, the bar doesn't move slow for the sake of allowing you to generate maximum force; instead, the lifter generates maximum force, and the bar moves slowly because it's heavy in relation to the amount of force produced. If you exerted maximum effort against a lighter weight, you would generate the same amount of force and move much faster.

The maximum amount of force one can generate depends on the speed that the object is moving. You can measure an athlete's force-velocity curve and train it.

If you lift a max deadlift and measure the force being applied, then you cut the weight in half and repeat, you can't generate the same max force. You don't simply have a max force that you you apply F=ma to and get acceleration for lighter masses. It's increasingly difficult to generate high forces the lighter the object. It accelerates while you try to apply force and you can't stay with it.

It must have something to do with leg speed velocity.

Your question seems like a physics question, here goes: Work (or energy) is force x distance, so you are doing the same work by day moving up a 50kg weight to a height of 1 meter quasi-statically or rapidly like Olympic weightlifters, but the power (=energy per unit time) is much more for the rapid lifter; same concept for sprinting vs. “distance running” 100m.

The physiological basis is a muscle is made of many fibers and how forceful a motion is depends on how many fibers are firing.

When a barbell is lifted, you can continue using more and more of a muscle until the weight moves and then finish the motion.

When throwing a shot, the faster you can go from 0 to 100% muscle use the farther the shot will go. When sprinting the faster you can go from 0 to 100% when your foot hits the ground the faster you will go.

A complication is muscles can produce more force when they are not contracting, which is another reason why you want to hit max force in a muscle as quickly as possible. Once what you are pushing or pulling on starts moving possible force you can apply will go down.

You're right, there is no unit for F/t which is a pretty good indication that it's not a useful measurement (unless the rate of the force applied is changing with time).

This is the average number of nikes a 9 year old factory worker in Bangladesh can produce per hour.

#slowfashion

@anabellopez.r

There is a resulting motion, so there is distance. Force times distance divided by time is power. Power is the answer.

interested to hear your explanation for this little nugget

I assume he means an isotonic contraction.

Two main reasons but might be others.

First is that there is a limit to how fast a muscle can contract. So taking it to the limit, if the muscle is already contracting as fast as it can you can't apply any force to anything moving at that speed or faster.

The other is the fiber shortens because one part of the fiber pulls a different part. When it is actively contracting I believe it can't form as many 'cross-bridges', where the pulling actually takes place.

Couple examples of how your body automatically tries to generate as much force as possible at the beginning of forward velocity is jumping or throwing.

The first motion when trying to jump as high as you can or throw a baseball as hard as you can is in the opposite direction; you drop your center of mass or draw the baseball back relatively quickly.

In the backward motion your body works to activate the entire muscle and form all the cross-bridges. Ideally this will be completed just before velocity shifts direction (just before so that some elastic energy from the back motion can be stored) and initial jumping or throwing force is maximized.

Bringing this back it running. This is probably why plyometrics increases running efficiency. Trains your muscles to get the timing right for maximum initial force off of the foot strike.