Evaluation of Hand-Grip Strength Measurement Using the Pablo Virtual Reality System in Young Adults

Introduction

Assessment of hand-grip strength is a simple, non-invasive, and widely available method of assessing the muscular strength of the upper limb [1]. Cylindrical, lateral, and 2-point grips are considered crucial for performing most manual activities in everyday life [2–5]. The cylindrical grip involves wrapping the fingers around a cylindrical object and is important for actions like holding a cup or bottle, or for using tools. The 2-point lateral hand grip is used for everyday activities that require great hand strength, also known as power grips [6]. The lateral grip is used, for example, when opening a door with a key, and uses the distal phalanx of the thumb and the lateral side of the index finger [7]. Many studies have shown that hand-grip strength can be used as a prognostic biomarker of global muscle strength in both healthy people and people with various chronic diseases [2–4]. The results of previous studies indicate that reduced hand-grip strength is associated with an increased risk of falls and fractures, higher mortality, and lower quality of life in older people [8]. According to research results, in young people, muscle strength may be associated with level of aerobic capacity [6,7] and also, in adolescents, with the likelihood of maintaining a high level of health in adulthood [9]. Although studies more often emphasize the usefulness of hand-grip strength as a biomarker in older populations, some authors also indicate that the reference values of this indicator can be used in assessing health status and planning health promotion activities among young adults [10].

The most widely used tool for hand-grip strength assessment is the Jamar dynamometer, invented in 1954. This tool is considered to be the gold standard for the assessment of grip strength, because among the currently available tools, it has been characterized by the highest reliability and repeatability of measurement, as confirmed by the results of many studies [8,11,12]. The Camry dynamometer is also characterized by high reliability and credibility of measurement, and is comparable to the Jamar dynamometer; this has been confirmed by, among others, the results of research carried out by Tai et al [13] as well as Huang et al [14]. There are more and more reports in the literature showing high reliability and validity in assessing hand and finger strength using a dynamometer and pinchometer. Such devices include, among others, the Biometrics E-LINK EP9 [15] and the Digitalized Pinch Dynamometer [16].

Along with the dynamic development of modern technologies used in rehabilitation, the availability of devices for comprehensive rehabilitation of the upper limb is also increasing, in terms of improving both the range of mobility and muscle strength. Pablo is one of these devices. It is a technology based on training in virtual reality (VR) [17]. It is a system that allows the user to perform upper limb exercises in conjunction with a computer. The system consists of a computer and a set of wireless sensors and handheld devices connected to this computer [18]. Pablo technology is based on the phenomenon of biofeedback, because during exercises, the patient receives visual feedback on the computer screen regarding the precision and quality of the movement being performed [19,20]. A large number of games to choose from allows for the implementation of various therapeutic goals, such as improving mobility, the strength of individual grips, or visual-motor control [21]. As shown in previous studies, the gaming system used in VR-based rehabilitation technologies, in addition to leading to functional results, also has the beneficial effect of increasing the patient’s motivation and attentiveness in therapy [22]. The results of previous studies have confirmed the usefulness of modern technologies based on the phenomenon of biofeedback in improving upper limb function in patients after strokes or cranio-cerebral injuries, as well as in elderly people without neurological deficits [23–26]. Some of the demonstrated beneficial effects of Pablo technology include improving upper limb function in patients after stroke and aiding post-operative rehabilitation in oncology patients [18,19].

In addition to the therapeutic module, the Pablo system enables the assessment of muscle strength through sensors equipped to measure both motion and force, connected to a computer via a USB interface. For this reason, the system can be used not only as a therapeutic tool, but also as a diagnostic one. Making systematic assessments in the therapeutic process allows the progress of the patient in improving muscle strength to be monitored on an ongoing basis [19]. Previous studies have compared the possibility of using the Pablo device for diagnostic purposes with standard goniometry and dynamometry [21].

According to the literature review, despite the increasingly widespread use of the Pablo device and the indicated therapeutic benefits, there are no reports on inter- and intra-rater reliability of assessment using this device in the fields of cylindrical hand-grip strength and finger-grip strength including lateral grip and 2-point lateral grips (II–III, III–IV, and IV–V). This observation was the motivation to undertake research that will provide the first reports in this regard. Therefore, this study aimed to evaluate the credibility and reliability of cylindrical, lateral, and 2-point lateral hand-grip strength measurement in 104 healthy young adults using the Pablo (Tyromotion) VR gaming device.

Material and Methods

ETHICS STATEMENT:

The study was approved by the Bioethics Committee of the University of Rzeszów (No. 2022/059). In accordance with the Declaration of Helsinki, all participants were informed about the purpose and procedure of the study and gave their informed consent to participate in the study.

STUDY DESIGN:

The study was conducted at the Donum Corde Rehabilitation and Medical Care Centre in south-eastern Poland from January to October 2023. The assessment of the strength of particular grips was carried out in a group of 104 physiotherapy students of the University of Rzeszów. The tests were conducted twice by 2 independent investigators, with an interval of 2 weeks between the first and second test.

PARTICIPANTS:

The study was conducted in a group of 104 subjects aged 20–26. The inclusion criteria were full manual dexterity of the upper limbs and informed consent to participate in the study. People with dysfunctions in the upper limbs resulting in limited strength and manual dexterity were excluded from the study (including those in the early period after fractures, dislocations, or sprains; and those with muscle atrophy, increased muscle tension, lesions in soft tissues due to burns, and functional limitations due neurological and rheumatoid conditions).

SAMPLE SIZE:

The minimum number of people needed to participate in the study was determined using the Raosoft sample selection calculator [27]. Parameters such as maximum error of 5%, confidence level of 95%, and fraction size of 50% were included in the sample size calculation. Based on the adopted parameters and data on population size, 104 subjects were included in the study.

PROCEDURES AND OUTCOME MEASURES:

Strength tests of particular grips (cylindrical, 2-point lateral, and between-fingers II–III, III–IV, and IV–V grips) of the right and left hands were performed using the Pablo Plus System (Tyromotion, Graz, Austria) [16,17]. The tests were conducted twice, with a 2-week gap between the tests, by 2 independent investigators who had no contact with each other during the data collection. To maintain the reliability of the measurements, a repeated test was carried out under the same conditions, in the same studied group and by the same investigators.

The Pablo Plus System is a multifunctional system used for diagnostics and interactive therapy of the upper limb with the use of biofeedback. It allows assessment of the strength of various hand grips, measurement of the range of motion in the shoulder, elbow, and wrist joints, as well as motor regeneration training of the upper limb conducted in VR. Software-compatible mobile devices, wireless sensors, and multiboard and multiball systems are used for diagnostics and therapy [20].

Before each test session, the device was calibrated according to the manufacturer’s recommendations. The tests were conducted in a sitting position, with the arm in the adductive position, a bend in the elbow joint to 90 degrees, and with the forearm stabilized in accordance with the guidelines of the American Society of Hand Therapists [28]. The Pablo Sensor Handle was used for the tests. The following grips were assessed: cylindrical (Figure 1), 2-point lateral grip (Figure 2A), and between-fingers grip: II–III (Figure 2B), III–IV (Figure 2C), and IV–V (Figure 2D). Each grip was assessed in the left and right hand, and the strength of each grip was measured for 3 seconds. Each test was conducted 3 times, using the mean of the 3 measurements for calculations, in accordance with the methodology proposed by Wieczorek et al [29].

STATISTICAL METHODS:

The tables present the results of the repeatability (consistency) analysis of measurements made by 2 investigators at the same time and the same investigator at 2 time points. In total, therefore, 4 comparisons of 2 data series were made for each parameter.

The mean value and standard deviation for each series of measurements were calculated, along with the mean and standard deviation of the differences between the compared series of measurements. The assessment of the significance of differences in the mean level of 2 series of measurements was made using the t-test for dependent samples, in which no significant values should be observed, but it should be remembered that this is not a key factor in assessing the consistency of measurements. The series were compared using Pearson’s linear correlation coefficient, as well as the interclass correlation coefficient (ICC), a key measure of the consistency of the 2 measurements. As an alternative measure of consistency, the Bland-Altman method was proposed.

The level of statistical significance was set at P<0.05.

Results

CHARACTERISTICS AND FLOW OF STUDY PARTICIPANTS:

The number of people recruited for the study was 176. After taking into account the inclusion criteria, 132 participants joined the study. Written consent was obtained from 117 participants. Of these, 110 subjects participated in test I but 6 of them did not appear for test II. The detailed flow of participants is shown in Figure 3.

The final studied group therefore consisted of 104 subjects, including 70 women (67.31%) and 34 men (32.69%). The mean age of the participants was 22.60 years, the youngest was 20.00 years old and the oldest was 26.00 In the studied group, the mean height of the participants was 1.70 m, and mean body weight was 65.90 kg. The mean body mass index (BMI) score in the studied group was 22.6 points (Table 1).

ASSESSMENT OF 2-POINT LATERAL BETWEEN-FINGERS GRIP STRENGTH (II–III):

The assessment of the strength of the 2-point lateral between-fingers II–III grip (Figure 2B) in the right and left hands showed high consistency of measurements. The ICC indicator was in the range of 0.991–0.998. The mean differences ranged from −0.04 kg (between test I and II for investigator I) to 0.03 kg (between investigators I and II in test II). Similar conclusions were made by observing the Bland-Altman plots – it was noted that the highest single outlier point was a difference of nearly 1.0 kg between investigators I and II in test I (Table 2).

ASSESSMENT OF 2-POINT LATERAL BETWEEN-FINGERS GRIP STRENGTH (III–IV):

Another parameter studied was the 2-point lateral between-fingers III–IV grip (Figure 2C). For the right hand, the mean measurements were slightly higher than those for the left hand. However, observing the consistency of the measurements, it was concluded that the values were very similar to each other. The only significant difference in mean values, 0.03 kg, was observed in the left hand between test I and II for investigator II, but the key measure of ICC consistency in this case was as high as 0.998. The Bland-Altman plot shows that only a few outliers of ±0.7 kg were recorded. Finally, it can be concluded that the recorded values for grip strength are highly consistent both between tests and between investigators (Table 3).

ASSESSMENT OF 2-POINT LATERAL BETWEEN-FINGERS GRIP STRENGTH (IV–V):

Another parameter studied was the 2-point lateral between-fingers IV–V grip (Figure 2D). The highest consistency of the recorded measurements was observed in the left hand between investigators I and II in test II and between test I and II for investigator I, which is evidenced by the lack of significant differences between the means, high correlation coefficient (0.96–0.98) and the level of ICC indicator of 0.98–0.99. The repeated tests of the 2-point grip strength proved to be consistent both between the tests and between the investigators (Table 4).

ASSESSMENT OF LATERAL GRIP STRENGTH:

Next, the consistency of measurements of the right and left hand lateral grip strength (Figure 2A) was analyzed. It was noted that the results differed the most between investigators I and II in the second test, but it should be noted that these differences were not significant. Individual values reached a maximum of 0.6–1.1 kg, but the vast majority were in the range of up to 0.5 kg. The above finding is supported by the ICC indicator of 0.992 (the least favorable for the assessment of lateral grip strength) (Table 5).

ASSESSMENT OF CYLINDRICAL GRIP HAND-GRIP STRENGTH:

Consistency of measurements of cylindrical grip strength (Figure 1) in the right and left hands between tests and between investigators was also analyzed. It was noted that the lowest consistency (although at a high level) was noted for the grip strength of the right hand between investigators I and II in test II. The difference in mean values was 0.3 kg, which turned out to be statistically insignificant. High consistency was confirmed by a high Pearson linear correlation coefficient (r=0.95) and ICC indicator (0.974). The remaining ICC coefficients of consistency for the assessment of flexion strength were within the range of 0.984–0.999 (Table 6).

Discussion

The aim of the study was to evaluate the reliability and credibility of cylindrical, lateral, and 2-point between-fingers grip strength measurements in 104 healthy young adults using the Pablo VR gaming device (Tyromotion). We found the Pablo Tyromotion system to be reliable in assessing hand grip and pinch grip, both in terms of inter-rater and intra-rater reliability.

Based on the high ICC scores in our study, the force sensation test for cylindrical grip, lateral finger grip, and 2-point lateral between-fingers grip (II–III, III–IV, and IV–V) showed good reliability.

The tested grips are important in the functioning of Activities of Daily Living (ADL) and Instrumental ADL; therefore their use as a tool of assessment in clinical practice is very important [30,31]. Based on world literature, no studies have been found on the reliability and credibility of the Pablo Tyromotion system in the assessment of particular grips. Our research results have shown that it is a device that can generate credible and repeatable data in clinical assessment. In addition, research is rarely carried out on the reliability and accuracy of many digitized dynamometers [16,32]. Fess emphasizes the importance of examining the reliability of each new assessment tool before it is used in clinical settings [33].

In the assessment of 2-point lateral between-fingers grips II–III and IV–V for the right and left hands, no differences were found, which was confirmed by the high correlation coefficient and the key measure of consistency of the 2 assessments (ie, ICC=0.991–0.998, ICC=0.98–0.99). Therefore, measurements both between investigators and between tests can be considered to be highly consistent. Similarly, the results of the study by Li et al, using an electronic digital force dynamometer in a population of young people, showed good reliability (ICC=0.752–0.903) [34]. Other researchers assessed the credibility of the measurements of particular grips, and the standard dynamometer obtained good credibility for 5 of the 7 test grips, but poor measurement credibility for the assessment of lateral grip [35].

The Jamar dynamometer is the most popular tool in assessing grip strength, and many studies have shown high reliability of this device [36,37]. However, the Jamar dynamometer requires frequent calibration to maintain reliability, and readings taken from an analogue scale can result in measurement error [16]. To this end, tests were carried out using the Pablo Tyromotion assessment system, and the results showed that it is characterized by high internal and external consistency in the assessment of hand-grip strength. ICC consistency coefficients for both flexion and extension strength assessment ranged from 0.984 to 0.999.

In addition, Shin et al believe that the main advantage of a digitalized dynamometer is increased accuracy, thanks to the digital display, ease of data processing, and precise measurement [16]. Amin et al compared 2 measuring devices: the Jamar® Hydraulic Hand Dynamometer and the Squegg™ Smart Dynamometer-Handgrip Trainer, concluding good concurrent validity and good-to-excellent test-retest reliability. In addition, the authors emphasized that the Squegg results were less accurate, depending on the width of the hand, and with lack of standardization of the grip [38]. It should be emphasized that the grip sensor in the Pablo Tyromotion system shows no age or anthropometric restrictions during testing and therapy; therefore, it is a good tool for assessing particular grips. Moreover, the clinical implications of this are supported by the results of Abdelmoniem et al. These authors report that the Pablo system is useful not only in the rehabilitation of women with breast cancer but also in the assessment of hand-grip strength and wrist range of motion [18]. By evaluating the use of VR in the Pablo system, Kuo et al, in their randomized study, confirm the improvement of functional efficiency of the upper limb among people after stroke. The authors also used the Pablo system to assess the range of motion and muscle strength of the upper limb [26].

Our study had a notable limitation that should be considered: only right-handed people participated in the study. However, a small number of the population in Poland show left-hand dominance; therefore, due to the homogeneity of the studied group, only right-handed people were included. Left-handed people may also be included in subsequent studies. Only young, healthy people without diseases of the upper limbs were included in this assessment of the credibility and reliability of the Pablo Tyromotion interactive device. Other age groups could also be considered in future studies to assess the reliability and credibility of the device in a broader sample group.

Conclusions

The relatively high correlation in the ICC values obtained in our study indicate good reliability; our results demonstrate that the Pablo Tyromotion interactive device has good intra- and inter-rater reliability. It can therefore be concluded that this interactive dynamometer is an appropriate instrument for measuring precision grips and grip strength. An additional advantage of Pablo Tyromotion is the ease of data processing and precise measurement. The Pablo Tyromotion device can therefore be recommended for daily clinical practice.