GripAble: An accurate, sensitive and robust digital device for measuring grip strength.

INTRODUCTION: Grip strength is a reliable biomarker of overall health and physiological well-being. It is widely used in clinical practice as an outcome measure. This paper demonstrates the measurement characteristics of GripAble, a wireless mobile handgrip device that measures grip force both isometrically and elastically-resisted for assessment and training of hand function. METHODS: A series of bench tests were performed to evaluate GripAble's grip force measurement accuracy and sensitivity. Measurement robustness was evaluated through repeated drop tests interwoven with error verification test phases. RESULTS: GripAble's absolute measurement error at the central position was under 0.81 and 1.67 kg (95th percentiles; N = 47) when measuring elastically and isometrically, respectively, providing similar or better accuracy than the industry-standard Jamar device. Sensitivity was measured as 0.062 ± 0.015 kg (mean ± std; 95th percentiles: [0.036, 0.089] kg; N = 47), independent of the applied force. There was no significant performance degradation following impact from 30 drops from a height >1.5 m. CONCLUSION: GripAble is an accurate and reliable grip strength dynamometer. It is highly sensitive and robust, which in combination with other novel features (e.g. portability, telerehabilitation and digital data tracking) enable broad applicability in a range of clinical caseloads and environments.

Proof-of-Concept of a Sensor-Based Evaluation Method for Better Sensitivity of Upper-Extremity Motor Function Assessment.

In rehabilitation, the Fugl-Meyer assessment (FMA) is a typical clinical instrument to assess upper-extremity motor function of stroke patients, but it cannot measure fine changes of motor function (both in recovery and deterioration) due to its limited sensitivity. This paper introduces a sensor-based automated FMA system that addresses this limitation with a continuous rating algorithm. The system consists of a depth sensor (Kinect V2) and an algorithm to rate the continuous FM scale based on fuzzy inference. Using a binary logic based classification method developed from a linguistic scoring guideline of FMA, we designed fuzzy input/output variables, fuzzy rules, membership functions, and a defuzzification method for several representative FMA tests. A pilot trial with nine stroke patients was performed to test the feasibility of the proposed approach. The continuous FM scale from the proposed algorithm exhibited a high correlation with the clinician rated scores and the results showed the possibility of more sensitive upper-extremity motor function assessment.

Sensory integration of apparent motion speed and vibration magnitude.

Tactile apparent motion can display directional information in an intuitive way. It can for example be used to give directions to visually impaired individuals, or for waypoint navigation while cycling on busy streets, when vision or audition should not be loaded further. However, although humans can detect very short tactile patterns, discriminating between similar motion speeds has been shown to be difficult. Here we develop and investigate a method where the speed of tactile apparent motion around the user's wrist is coupled with vibration magnitude. This redundant coupling is used to produce tactile patterns from slow&weak to fast&strong. We compared the just noticeable difference (JND) of the coupled and the individual variables. The results show that the perception of the coupled variable can be characterised by JND smaller than JNDs of the individual variables. This allowed us to create short tactile pattens (tactons) for display of direction and speed, which can be distinguished significantly better than tactons based on motion alone. Additionally, most subjects were also able to identify the coupled-variable tactons better than the magnitude-based tactons.

Horseback riding therapy for a deafblind individual enabled by a haptic interface.

We present a haptic interface to help deafblind people to practice horseback riding as a recreational and therapeutic activity. Horseback riding is a form of therapy which can improve self-esteem and sensation of independence. It has been shown to benefit people with various medical conditions-including autism. However, in the case of deafblind riders, an interpreter must stand by at all times to communicate with the rider by touch. We developed a simple interface that enables deafblind people to enjoy horseback riding while the instructor is remotely providing cues, which improves their independence. Experiments demonstrated that an autistic deafblind individual exhibits similar responses to navigational cues as an unimpaired rider. Motivation is an important factor in therapy, and is frequently determinant of its outcome; therefore, the user attitude toward the therapy methods is key. The answers to questionnaires filled by the rider, family, and the instructor show that our technique gives the rider a greater sense of independence and more joy compared to standard riding where the instructor is walking along with the horse.