Grip strength appears in an unusual number of health studies, which has led to it being treated as significant in itself. Its actual role is as a convenient stand-in for something broader.
It is trivially easy to measure
A handheld dynamometer gives a numerical reading in seconds, requires no special facility and can be used with people who cannot easily perform other strength tests.
The protocol standardises well across sites, so results collected in different countries and decades remain broadly comparable.
Large population studies therefore include it as a matter of course, and the sheer volume of data is part of why it appears in so many findings.
It reflects general muscular condition
Strength across the body correlates substantially, since muscle mass, neural drive and overall condition are shared inputs into every strength measure.
Grip is not special in this respect, and leg strength would serve similarly if it were as easy to measure at scale.
Which is why grip readings behave as an index of overall muscular status rather than as a statement about the hands themselves.
Muscular condition sits downstream of many things
Nutrition, physical activity, chronic inflammation, hormonal status and the presence of undiagnosed illness all leave traces on muscle.
A low reading therefore functions as a general signal that something is affecting the body's ability to maintain tissue, without indicating what.
That is precisely the property that makes it useful in population research and considerably less useful as an individual diagnostic.
Correlation is being over-read
Reported associations between grip strength and a range of outcomes are frequently presented as though improving grip would improve those outcomes.
The more defensible reading is that both the grip reading and the outcome reflect an underlying state, and training the hands specifically would not move that state.
Improving overall strength and activity plausibly does, but that is a different intervention from the one the headline implies.
Where the measure earns its keep
In clinical settings, grip strength forms part of the assessment for frailty and for loss of muscle mass in older adults, alongside walking speed and other measures.
Its value there is in tracking change over time in an individual, which is a much narrower claim than predicting outcomes from a single reading.
Used that way it is a sensible, inexpensive screening tool, and used as a personal target it mostly produces stronger hands attached to an unchanged body.