Grip Strength as a Digital Biomarker

Grip strength is the maximal force a person can generate squeezing a handheld dynamometer, reported in kilograms or newtons. It is the simplest measurement in this library and among the best evidenced: it takes seconds, requires no calibration of the person, and predicts all cause and cardiovascular mortality across populations and countries.

Its clinical role is as the strength component of sarcopenia and frailty. Consensus definitions of sarcopenia place reduced muscle strength first, and grip strength is the accepted way to measure it because it correlates with strength elsewhere in the body and is far easier to obtain than a leg press.

Digitally instrumented dynamometers add continuous force capture rather than a single peak reading, which allows the shape of the contraction to be described: how fast force develops, how well it is sustained, and how quickly it fatigues across repetitions.

The measurement uses a hand dynamometer, held in a standardised posture, with the person instructed to squeeze maximally for a few seconds. Standard practice takes the best of several attempts, alternating hands, with rest between.

Protocol is where the difficulty lies. Posture, elbow angle, handle position, encouragement given and number of attempts all change the result, and reviews of grip strength measurement in clinical and epidemiological studies have documented how much this variation limits comparison between cohorts and argued for standardisation.

Instrumented devices record the full force trace rather than a peak, which yields rate of force development and fatigue indices. Those additional measures are more sensitive to neuromuscular change than the peak alone, and they are also less standardised, so they are currently research measures rather than clinical ones.

The dominant uses are sarcopenia and frailty assessment, prognostic stratification before surgery and during cancer treatment, and nutritional assessment where muscle function is the outcome of interest. In large prospective cohorts grip strength has predicted mortality and cardiovascular events after adjustment for conventional risk factors.

In trials it serves as a functional endpoint in resistance training, nutrition and pharmacological studies targeting muscle, where it is often the primary strength measure.

It is reported alongside the pinch gauge test, which measures the same construct in the fingers, and alongside sarcopenia and frailty screening instruments including SARC-F, the FRAIL scale and the Edmonton Frail Scale, which capture the wider syndrome that reduced strength sits inside.

Grip strength is effort dependent, so it measures willingness as well as capacity. Pain, arthritis, recent hand injury and low motivation all reduce it without any change in systemic muscle function, and in cognitive impairment the instruction itself may not be followed.

Cut points for defining low strength differ between consensus definitions and between populations, so whether a given value counts as impaired depends on which framework is applied.

Unlike almost everything else in this library, it is not passively collected. Someone has to hand over a device and give an instruction, which limits frequency and rules out the continuous monitoring that makes other measures attractive. It is included because the prognostic evidence is strong enough to justify the effort, not because it fits the wearable model.

• Bohannon RW. Grip strength: an indispensable biomarker for older adults. Clin Interv Aging. 2019. pubmed.ncbi.nlm.nih.gov
• Leong DP, et al. Prognostic value of grip strength: findings from the Prospective Urban Rural Epidemiology (PURE) study. Lancet. 2015. pubmed.ncbi.nlm.nih.gov
• Roberts HC, et al. A review of the measurement of grip strength in clinical and epidemiological studies: towards a standardised approach. Age Ageing. 2011. pubmed.ncbi.nlm.nih.gov
• Kirk B, et al. The conceptual definition of sarcopenia: Delphi consensus from the Global Leadership Initiative in Sarcopenia. Age Ageing. 2024. pubmed.ncbi.nlm.nih.gov