Common testing errors with hand dynamometer & how can it be reduced with the latest technology for upper extremity assessments

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Grip strength is a strong indicator of our overall health. Greater grip strength is linked with better cognitive functioning, higher life satisfaction, better subjective well-being and less depression, anxiety symptoms. Therefore, errors in measuring grip strength may cause serious problems. Therapists come across various testing errors while measuring the grip strength using a dynamometer. Error happens for multiple reasons, it can be reliability issues, instrumental error, grip strength measured following the wrong method, gravitational error, obstruction due to hand injury.

Now therapists get options for dynamometers such as, manual dynamometer and digital hand-held dynamometers. But they feel that digital dynamometers are more convenient than manual dynamometers.  Manual or conventional dynamometer is completely regulated by therapists, and there can be a high chance of manual/ testing error, and this can be easily avoided when hand strength is measured by digital dynamometer because it is automated.

It has been seen that the reliability of a digital dynamometer is greater than a manual dynamometer.

Before diving into the topic, let’s define Reliability.

Reliability refers to the ability of an instrument to measure a certain value consistently and predictably. Instruments with a high degree of reliability provide authentic value. They show consistency and similarity of values between multiple consecutive sessions. Reliability is expressed in terms of correlation coefficient and standard error of measurement.

Therefore, if you measure patients’ grip strength with a less reliable instrument, you may end up getting the wrong value. Wrong values of grip strength (testing errors) may impact the whole therapeutic intervention programs by misleading you. To avoid these testing errors, you must check the reliability of the dynamometer; whether it is manual or digital.

When experts check reliability of the dynamometer, they check total three types of reliability; such as inter-rater reliability, intra-rater reliability, and test retest reliability.

Inter-rater reliability: It shows the measurement variation between two or more raters who measure the grip strength of the same person.

Intra-rater reliability: shows the variation of measurement data by single rater across two or more trials.

Test-retest reliability: shows the variation of grip strength evaluated by a single hand dynamometer on the same person under the same conditions.

Experts have seen that the values of the above three reliability measures for a digital dynamometer are more correlated than a manual/ conventional dynamometer. So, you can choose a digital dynamometer over a conventional one.

Till now we’ve talked about instrumental reliability and associated testing errors. Now we are going to explain other errors while measuring the grip strength; such as Gravitational error, injury related errors.

What is Gravitational error?

It is a functional testing error. When our upper limb moves in the horizontal plane, there will be no gravitational error while measuring the grip strength. However, it appears when therapists measure grip strength of the upper limb during vertical movement because upper limbs not only work against the dynamometer, but also either aided or opposed by gravity. In most of the cases therapists don’t consider gravitational force during grip strength evaluation.

What are Injury related measurement errors?

Hand injury and other hand conditions may cause measurement issues. If patients’ hands have pain due to trauma or accident or loss the normal functionality of the index finger or thumb due to injury, therapists may find different measurements between healthy functional hand and injured hand.

Technology makes therapists’ grip strength measuring job easy & error-free

There are different technological interventions that help rehab care therapists to measure and evaluate grip strength flawlessly, and facilitates rehabilitation in intensity, repetition, engagement, adherence, compliances, and evaluation. Technologies such as robotics, gamification, virtual reality, body sensors, wearable devices, and tele-rehabilitation are widely used in the rehab care interventions to get more accurate results with real-time feedback.

Robots make the evaluation process easy by giving real-time feedback, and improve functionality of the hand by increasing intensity, and dose of the rehabilitative exercises. Robotic upper limb is gaining traction in the rehabilitative field because it is used by therapists to supplement the repetitive labor-intensive manual therapy.


On the other hand, video-games and virtual reality are specifically used to boost adherence to treatment.

Electronic devices such as body sensors, and wearable devices are used for upper-extremity distant motor assessments; rehabilitation with sensor-based devices is more interactive by integrated games and audio-visual feedback that allows patients to move their upper extremities including shoulder, elbows, and wrist in the proper way. Also, It evaluates the muscle strength, grip strength, and active range of motion of the upper limb.

Interactive wearable systems have also become popular in upper-body rehabilitation. They are mainly used for monitoring the upper extremity movements and delivering real-time feedback.

Tele-rehabilitation along with remote monitoring processes are used to track and monitor rehabilitative progress constantly on a real-time basis.

All of these technologies are not only meant to be developed to evaluate grip strength, instead they are used to boost the quality of overall upper extremity rehabilitative care. We can not say that all these technologies will completely help you to overcome testing errors coming from hand-held dynamometers, but their detailed insights of hand & finger movements, strength measurements, and real-time feedback gives you a vivid idea of patients upper extremity conditions including functionality and rehabilitative progression.

For example, Squegg is a blue-tooth enabled digital dynamometer, smarter than a conventional dynamometer. Digital technology makes this device more accurate with no chance of manual error. It works both as a dynamometer and a grip strengthener. It not only minimizes the error but also helps in patient-engagement. Its in-built app with exciting games encourages patients to continue high repetition exercises without getting bored.

This two in one product is highly beneficial for hand therapists  because it makes their job easy. It not only evaluates grip strength but also tracks subtle improvements. So, if you are a therapist then you must try this product, at least once.

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