Strain rate
Also called: loading rate
What it means
Strain rate is how quickly a force is applied to bone, not just how much force there is — and faster loading tends to stimulate bone cells more than slow loading of the same size.
Understanding that speed of loading matters, not just weight, helps explain why certain types of movement are considered more stimulating to bone than others.
Strain rate just means how fast a force is applied to your bone, not just how big the force is. A load applied quickly creates a stronger fluid flow around bone cells than the same amount of force applied slowly. That difference in speed turns out to matter a great deal to how bone cells respond.
Think of it this way: a slow, steady 600-pound squeeze gives your bone cells less stimulation than a rapid 600-pound compression, even though the force is identical. This is part of why impact-type movements like jumping or sprinting tend to be more osteogenic (bone-stimulating) than slower, steady activities like walking or swimming, even when the overall load is similar.
This idea builds on Wolff's Law, the old idea that bone adapts to the forces placed on it. Later work, including Frost's mechanostat concept, refined this by showing that both the amount of force and how quickly it's applied shape the cellular response. So strain rate is one of the key variables, alongside magnitude, that influences how bone reacts to loading.
How sure is this?
Graded Strong Clinical Evidence: Supported by multiple well-designed clinical studies in humans. Read each study with its grade in mind. One study is a piece of the picture, not the whole of it.
Where the Academy teaches it
This page is the short version. The lessons teach it in full, with the context around it and a quiz to lock it in.
Questions people ask about this
Yes, there's real science behind the idea that bone responds to mechanical force — it's not just a theory in the casual sense. It started over 130 years ago with a German surgeon's observations, and has since been refined by modern researchers who've worked out the cellular and biological mechanisms behind it.
Read the full answer →When you push on bone, it actually bends very slightly — far too little to see, but enough at the microscopic level to squeeze fluid through tiny channels inside the bone. That fluid movement is what your bone cells sense, and it's the very first step in a chain of signals that tells your bone "you're using me."
Read the full answer →Related words
The mechanostat is Frost's theory that bone acts like a thermostat, removing, maintaining, or building bone…
Mechanotransduction is how bone cells sense physical force and turn it into chemical signals that tell bone to adapt.
Wolff's Law says your bones adapt to the loads you put on them, getting stronger with use and losing density when…
Osteogenic loading means applying brief, high, muscle-generated force to your skeleton in a way that's strong enough…
Microstrain (µε) is a tiny measure of how much bone bends under force — one millionth of its original length.
Education only, not medical advice. Decisions about tests, medications and treatment belong with your own doctor. OsteoStrong does not diagnose, treat or cure any disease.
