Welcome back to the Barbell Medicine Podcast. I'm Dr. Jordan Fagenbaum, today on Episode

254. We're going to talk about a topic that's very hot right now in the training world,

lengthened partials. Lengthened partials are exercises performed in a range of motion

where the muscles are elongated, but are not completed through a full range of motion.

Recent evidence has suggested that they may be as good, if not better, than full range

of motion exercises for stimulating muscle growth. So, let's take a look at this topic

and see if we can find some answers. First off, what is muscle hypertrophy?

Muscle hypertrophy is defined in most studies as the increase in the total mass of a muscle,

whereas a decrease in total mass of a muscle is referred to as atrophy. Now, each muscle

is made up of thousands to hundreds of thousands or even more muscle fibers, and in general,

it is thought that the number of skeletal muscle fibers in humans is more or less fixed

by the first year of life. While there's active debate around the idea that humans can

increase the number of muscle fibers that they have, this is termed hyperplasia, the

research suggests that the overwhelming majority of increased muscle mass is due to an increase

in muscle fiber size, not necessarily making new muscle fibers. An increase in muscle fiber

size occurs when muscle protein synthesis exceeds muscle protein breakdown for sustained

periods of time. While this may sound like muscle damage is needed for muscle growth,

hypertrophy seems to lag until muscle protein breakdown is minimized and muscle protein

synthesis predominates. In other words, hypertrophy lags until the individual adapts to the

training, and this typically takes place in the first four to five weeks of training.

If the training dose is too high, that actually may not happen at all. In any case, muscle

fibers change in size in response to the demands placed upon them by the way of altering

...