Reliability of two devices for shoulder strength assessment: Wii Fit Balance Board and hand-held dynamometer

Abstract

Background

The aim of this study was to compare the reliability and agreement between two devices – Wii Fit Balance Board (WBB) versus Hand-Held Dynamometer (HHD) to measure isometric strength during the athletic shoulder (ASH) test in healthy amateur rugby players.

Methods

Fifteen males (23.73 ± 2.8 years) completed two testing sessions. Maximal isometric contractions using the dominant arm (D) and non-dominant arm (ND) against a WBB and HHD were assessed at three angles of abduction (180°, ‘I’; 135°, ‘Y’ and 90°, ‘T’), in a prone lying position.

Results

The results indicate a very large correlation between the HHD and the WBB. WBB provides acceptable reliability at I-Test D (CV = 9.97%, ICC = 0.88) and HHD in the I-Test D (CV = 8.90%, ICC = 0.94), I-Test ND (CV = 8.60%, ICC = 0.95) in peak strength values. The HHD is most reliable in D ASH I-Y-T (CV = 10.94%) and WBB (CV = 11.05%). In the ND ASH I-Y-T test, the HHD is the most reliable (CV = 12.5%) compared to the WBB (CV = 14.43%).

Conclusions

These results suggest that WBB is a reliable device to assess strength in the ASH test with a very large correlation with the HHD. WBB and HHD are two affordable devices to assess isometric shoulder strength.

Introduction

The assessment of muscle strength output is an important clinical consideration for athletes and patients who may or may not have musculoskeletal disorders. ¹ Muscle strength has an important and beneficial relationship with physical/sports performance. ² Serial muscle strength assessments may allow quantification of treatment efficacy. The implementation of measurement instruments is increasingly necessary for clinical practice and scientific research. ³ To guarantee the quality of the measurement, the devices must undergo a validation and reliability process. ² Reliability refers to the reproducibility of values of a test, assay, or other measurements in repeated trials on the same individuals. ⁴ Better reliability implies better precision of single measurements to ensure interpretation and analysis.^4,5

Multiple isokinetic and isometric testing protocols have been described to examine shoulder strength.^6,7 The gold standard in strength measurement is the use of isokinetic devices, however, these procedures are relatively expensive and do not permit the evaluation of shoulder strength in similar positions to the mechanisms of injury.^8,9 In elite sports, isometric strength tests are used to assess muscle strength and muscle asymmetries between both limbs and monitor losses in muscle strength that may contribute to impaired athletic performance and increased muscle injury.^10–12 They can also be used regularly without influencing the athlete's training or performance. ¹³ The research group that devised the athletic shoulder (ASH) test has reported it to be reliable in assessing isometric shoulder strength in three different positions in rugby players. They also support its use as a reliable tool to quantify the ability to produce and transfer force across the shoulder girdle. ¹⁴ This test may form a part of a series of assessments involving strength, mobility and neuromuscular control to ensure a comprehensive view of all relevant components in maintaining shoulder stability. ¹⁴ It is important to note that the ASH test is the first test that measures upper limb isometric strength using a force platform. ¹⁴

The hand-held dynamometer (HHD) is a portable option with validity and reliability comparable to isokinetic dynamometry when assessing isometric muscle strength in several joint movements. ¹⁵ HHD has demonstrated higher sensitivity and intra- and inter-examiner reliability than manual muscle testing in identifying strength deficits of the rotator cuff. ⁶ Importantly, the equipment anchoring method improves validity and reliability. ¹⁶ Despite their usefulness and lower cost compared to an isokinetic dynamometer, they remain relatively expensive.^9,15 A valid possible alternative to the HHD is the aneroid sphygmomanometer, a well-known and low-cost tool commonly acquired to assess blood pressure. Studies have shown moderate reliability of the sphygmomanometer in various strength tests and across a range of different populations.^9,15 Recently, Morrison et al. ⁹ showed high concurrent validity (0.76–0.81) between the sphygmomanometer and the force platform in the ASH.

A new method for measuring muscle strength and balance is using a Nintendo Wii Balance Board (WBB) and customized software.^17–20 Its low cost (< US$50) and portability make it an alternative to current methods of measuring strength in research. This device has software that can record the isometric strength performed. The software has been shown to have high reproducibility and validity in assessing lower limb isometric strength.^17,21 A recent study has shown that the Wii is a validated instrument for measuring isometric handgrip strength in older adult patients. ²² In addition to this, Eika et al. ²¹ found that the WBB is a valid item to measure grip and lower limb muscle strength in asymptomatic persons of any age. Hence, the WBB has the potential to provide an accurate assessment of several physiological measures similar to a force platform.

In this context, the aim of this study was to compare the reliability and agreement between two devices, WBB versus HHD, in measuring isometric strength during the ASH test in healthy amateur rugby players. Because of the similarity of both devices, HHD and WBB, we hypothesized that the WBB would have high reliability in the three evaluated positions of the ASH test.

Material and methods

This study was designed to explore the reliability between the WBB and the HHD during the ASH test. Participants completed two testing sessions separated by one week by two assessors. Each session lasted 60 min. Anthropometric measurements (height, weight, body mass index (BMI), shoulder dominance, IPAQ questionnaire (Spanish version)) ²³ and The American Shoulder and Elbow Surgeons (ASES) scale (Argentine version) ²⁴ to classify participants as asymptomatic were collected during the first session.

Participants

Fifteen male healthy amateur rugby players (mean ± standard deviation [SD]: age = 23.73 ± 2.8 years, height = 177.73 ± 6.9 cm, weight = 87.26 ± 15.14 kg, BMI = 27.51 ± 3.31 kg m⁻², shoulder dominance 80% right, ASES 100 points) volunteered to participate in this study. All the participants included in this study were recruited through non-probabilistic sampling; they were excluded if they had a previous injury to the upper limbs, surgical history of the cervical spine and recent trauma. Participants were informed about the experimental procedures and their possible risks and benefits before starting the study. Written informed consent was obtained before the beginning of the study. The study protocol was approved by the bioethics research committee of the Instituto Universitario Italiano de Rosario (number 54/19). The procedure was by the latest version of the Declaration of Helsinki.

Instrument

The maximum voluntary isometric contraction was assessed through an HHD (Lafayette Instrument Company, USA, Model 01165) and the WBB (Nintendo, Kyoto, Japan). For this study, we had to create a set-up to stabilize the HHD on the floor to avoid the need for the operator to provide manual assistance. In light of this, the HHD was scanned into a 3D printer with the 3D model and then being used to stabilize the testing HHD device (Figure 1). A 3D printable file for this attachment can be found in Supplemental Material. The WBB is a small force plate, instrumented with four uni-axial stain gauge transducers positioned in each corner, typically seen in professional force platforms. Using Bluetooth human interface devices (HIDs), wireless and data were streamed to a computer (Dell Inspiron 14, Windows 10). Measurements to record the peak force were performed with the free software of Dr Ross Clark's low-cost functional study alternatives research group, the WBB Sway Program. ²⁵

Figure 1.

3D scanned model of the Hand-Held Dynamometer (HHD).

Procedures

The main experimental session was preceded by a standardized 10 min warm-up of joint mobility exercises, stretching and three sets of five repetitions of push-ups. Participants were randomized according to the order of the tests (i.e. WBB before HHD or vice versa) to minimize order effects. Neither the participant nor the researchers were blinded to the aims of the research. To become familiar with the test procedures, three submaximal contractions were performed to become familiar with the tests. The characteristics of the protocol are described below. The participants were evaluated in a university laboratory. All the participants included in the study were summoned to a single session. The evaluations were carried out on two occasions, with a difference of 1 week, by two physiotherapists (PT). PT 1 was in charge of the WBB assessments and PT 2 was in charge of the HHD assessment.

The tests were performed according to the description of the original test. ¹⁴ All tests were performed with the subject prone on the floor with their neck position standardized using a 4 cm foam block on which the forehead was rested. The hand was placed on platform WBB and HDD. The shoulder was in full abduction for the I test position, with the heel of the hand placed in the centre of the WBB and HHD. The Y test position required the arm to be abducted to 135° and the T-test position to 90° (Figure 2). The elbow was fully extended for all three tests. Participants were required to maintain their scapula in a natural position relative to the elevated arm.

Figure 2.

Athletic shoulder test positions. (a) I-test in HHD; (b) I-test in WBB; (c) Y-test in HHD; (d) Y-test in WBB; (e) T-test in HHD; (f) T-test in WBB.

WBB: Wii Balance Board; HHD: Hand-Held Dynamometer

Failure to comply with the instructions resulted in the trial being discarded before another was repeated after a 1-min rest period. The tests were always performed in the order of T, Y and I. In all cases, we started with the dominant shoulder and continued with the non-dominant shoulder. For each movement, participants will be asked to press as hard as possible against the evaluation device. The tests will consist of three tests of maximal voluntary isometric contraction for 3 s each, with 1-min rest between tests and 15-min intervals between each test device.

Statistical analyses

Descriptive data are presented as mean ± SD. The normal distribution of the data was confirmed using the Shapiro-Wilk test (p > 0.05). Paired sample t-test and standardized mean differences (Cohen's effect size [ES]) were used to compare the magnitude of the load between both testing sessions. The criteria to interpret the magnitude of the ES were as follows: null (<0.20), small (0.2–0.59), moderate (0.60–1.19), large (1.20–2.00) and very large (> 2.00). ²⁶ Reliability was assessed for each test by the coefficient of variation (CV) and the intra-class correlation coefficient (ICC model 3.1) and standard error of measurement (SEM). The following criteria were used to determine acceptably (CV ≤ 10%, ICC ≥ 0.80) and high (CV ≤ 5%, ICC ≥ 0.90) reliability. ²⁷ The mean CV value of the three tests was calculated to compare the reliability between the two devices examined in this study. Systematic bias was examined through Bland–Altman plots. Finally, Pearson's product–moment correlation coefficient (Pearson's r) was used to quantify the correlation between WBB and HHD in both testing sessions. The criteria to interpret the magnitude of the r were null (0.00–0.09), small (0.10–0.29), moderate (0.30–0.49), large (0.50–0.69), very large (0.70–0.89), nearly perfect (0.90–0.99) and perfect (1.00). ²⁶ All reliability assessments were performed using a customized spreadsheet, ²⁸ while other statistical analyses were performed using the JASP software (version 0.14.1). For all statistical calculations, a 95% confidence interval was used in the analysis. Statistical significance was accepted at p < 0.05.

Results

Peak strength values only reached an acceptable reliability at I-Test D in WBB (CV = 9.97%, ICC = 0.88) and I-Test D (CV = 8.90%, ICC = 0.94), I-Test ND (CV = 8.60%, ICC = 0.95) in the HHD (Table 1).

Table 1.

WBB and HHD reliability for the determination of isometric strength.

Test	Session 1 (kg) (mean ± SD)	Session 2 (kg) (mean ± SD)	p-value	ES (95% CI)	SEM (95% CI)	CV (95% CI)	ICC (95% CI)
WBB
I-Test D	12.5 ± 3.6	13.4 ± 3.6	0.105	0.23 (−0.46, 0.96)	1.29 (0.94, 2.04)	9.97 (7.30, 15.72)	0.88 (0.67, 0.96)
Y-Test D	9.2 ± 3.2	10.0 ± 2.8	0.029	0.29 (−0.45, 0.98)	0.98 (0.72, 1.54)	10.19 (7.46, 16.06)	0.91 (0.75, 0.97)
T-Test D	8.4 ± 3.1	8.8 ± 3.1	0.398	0.11 (−0.58, 0.84)	1.12 (0.82, 1.76)	13.00 (9.52, 20.50)	0.89 (0.70, 0.96)
I-Test ND	11.6 ± 3.5	11.8 ± 3.9	0.751	0.05 (−0.66, 0.77)	1.56 (1.14, 2.46)	13.30 (9.74, 20.97)	0.85 (0.60, 0.95)
Y-Test ND	9.0 ± 3.6	8.9 ± 3.0	0.771	0.05 (−0.55, 0.45)	1.45 (1.06, 2.28)	16.16 (11.83, 25.48)	0.83 (0.57, 0.94)
T-Test ND	8.4 ± 2.1	8.6 ± 2.6	0.618	0.09 (−0.36, 0.65)	1.18 (0.86, 1.85)	13.83 (10.13, 21.82)	0.78 (0.45, 0.92)
HHD
I-Test D	11.8 ± 3.9	10.6 ± 3.6	0.006	0.31 (−1.41, 0.35)	1.00 (0.73, 1.57)	8.90 (6.52, 14.03)	0.94 (0.83, 0.98)
Y-Test D	9.1 ± 2.7	9.2 ± 3.3	0.847	0.02 (−0.41, 0.59)	1.00 (0.73, 1.58)	10.94 (8.01, 17.25)	0.90 (0.74, 0.97)
T-Test D	8.1 ± 2.0	7.8 ± 2.5	0.459	0.13 (−0.75, 0.25)	1.03 (0.76, 1.63)	12.98 (9.51, 20.48)	0.82 (0.54, 0.93)
I-Test ND	11.1 ± 4.0	9.8 ± 3.6	0.002	0.32 (−1.56, 0.48)	0.90 (0.66, 1.42)	8.60 (6.30, 13.56)	0.95 (0.87, 0.98)
Y-Test ND	8.9 ± 2.7	8.3 ± 2.6	0.275	0.22 (−0.81, 0.20)	1.39 (1.02, 2.19)	16.11 (11.80, 25.41)	0.75 (0.41, 0.91)
T-Test ND	8.4 ± 1.9	7.9 ± 1.9	0.243	0.25 (−0.84, 0.17)	1.06 (0.77, 1.67)	12.99 (9.51, 20.49)	0.72 (0.34, 0.90)

SD: standard deviation; ES: Cohen's d effect size ([higher mean – lower mean]/SD both); SEM: standard error of measurement; CV: coefficient of variation; ICC: intra-class correlation coefficient; 95% CI: 95% confidence interval. WBB: Wii Balance Board; HHD: Hand-Held Dynamometer; Bold numbers indicate the inacceptable reliability (CV > 10%, ICC < 0.80).

Based on comparing the mean CVs of the three tests, the HHD is most reliable in ASH I-Y-T dominant test (CV = 10.94%), WBB (CV = 11.05%). In the ND ASH I-Y-T test, the HHD is the most reliable (CV = 12.5%) compared to the WBB (CV = 14.43%). Bland–Altman plots revealed low systematic bias in ASH Y-Test (−0.473 kg) and ASH T-Test (−0.648 kg) in the D and ASH Y-Test (−0.344 kg) and ASH T-Test (−0.348 kg) in ND (Figure 3).

Figure 3.

Bland–Altman plots for the measurement of peak strength between the HHD and the WBB. Each plot depicts the averaged difference and 95% limits of agreement (dashed lines), along with the regression line (solid line). (a) ASH I-test dominant arm; (b) ASH I-test non dominant arm; (c) ASH Y-test dominant arm; (d) ASH Y-test non dominant arm; (e) ASH T-test dominant arm; (f) ASH T-test non dominant arm.

WBB: Wii Balance Board; HHD: Hand-Held Dynamometer; ASH: athletic shoulder.

A very large association between the HHD and the WBB was observed (r range = 0.759–0.804; p < 0.0001) with the only exception of the test ASH-T test (r = 0.623; p = 0.0002) in the ND (Figure 4).

Figure 4.

Relationship of peak strength values between the HHD and the WBB. (a) ASH I-test dominant arm; (b) ASH I-test non dominant arm; (c) ASH Y-test dominant arm; (d) ASH Y-test non dominant arm; (e) ASH T-test dominant arm; (f) ASH T-test non dominant arm.

WBB: Wii Balance Board; HHD: Hand-Held Dynamometer; ASH: athletic shoulder.

Discussion

The present study was designed to compare the reliability of two devices, WBB versus HHD, in measuring isometric strength during the ASH test in healthy amateur rugby players. The main finding demonstrated that WBB is a reliable gadget to assess strength in the ASH test. Based on comparing the reliability between HHD and WBB, the findings showed that HHD is more reliable in ASH I-Y-T dominant test than WBB. In the same way, the HHD proved to be more reliable in the three test positions on the non-dominant side than WBB. Based on the results, peak strength values only reached an acceptable reliability at I-Test D in WBB and I-Test D and I-Test ND in the HHD. However, the very large correlation values suggest that WBB can be used as a low-cost alternative for quantifying shoulder strength.

Most shoulder injuries in rugby players occur in the latter stages of the matches (third and fourth quarters) due to repeated exposure to tackling and fatigue.^14,28 In this way, assessing shoulder force may possibly indirectly monitor accumulative or residual fatigue. ¹⁴ The criteria used to determine when an athlete is ready to return to sport should reflect the demands of that particular sport. The ASH test has shown discriminative validity to aid clinicians in determining readiness to return to sport after injury, between affected and unaffected shoulders. ¹⁴ This test closely represents the most common shoulder injury positions in a rugby match.^14,29 Therefore, the ASH test may have value in tackling sports and other sports, which expose the shoulder to longer lever stress. ²⁹ In the same way, Fanning et al. found moderate to excellent reliability in three dynamic close-chain tests that represent similar movements to that performed in collision sports. In contrast, they find no association between external and internal peak torque and these tests. ³⁰

This is the first study to explore the reliability of WBB in the ASH test for the measurement of muscle strength. In 2018, Blomkvist et al. found that WBB is a reliable instrument for measuring handgrip force steadiness and could become a relevant measure in the clinical setting. ²³ Similarly, Jorgensen et al. ³⁰ established that WBB showed high relative reproducibility and a good concurrent validity for measuring isometric lower limb strength in older adults. Those studies report similar findings to our study. On the other hand, Eshoj et al. ³¹ were determinate highly reproducible and poor concurrent validity compared to a force platform during shoulder sensorimotor control in prone lying.

Despite there are few studies that evaluate the reliability of the ASH test, our correlation coefficient values are comparable with that reported in the research of Morrison et al. ⁹ (r = 0.76–0.81). They validated the sphygmomanometer with the force platforms in rugby players to assess force in the I-Y-T positions. On the other hand, Blomkvist et al. ²⁰ found a correlation between WBB and isokinetic dynamometer higher (ICC = 0.919–0.950) than the results of our study. This difference may be explained because of the higher number of subjects evaluated in their study and the use of a gold standard method to assess force.

In our results, the ASH-T position in the non-dominant arm was the only position that had a large association (r = 0.623; p = 0.0002) between WBB and HHD. This could be due to this position being the last of a battery of six evaluations that the participants had to do, which entails greater fatigue in the shoulder muscles, being able to decrease the force applied in the WBB and HHD. Moreover, we found the same results as that seen in the study of Ashworth, where the muscles at these positions have less force than the I and Y positions. ¹⁴ The last finding might be taken with caution because of the lack of randomization of the test position.

Our testing procedure has some limitations. First, we had to create an HHD set-up to adapt and stabilize the gadget on the floor during the maximal press, avoiding the operator's participation. Secondly, during testing, an examiner was required to tell the athletes when to apply force and recover, record the results and at the same time check trunk compensation. Finally, we used different assessors for the WBB and HHD. The differences in the amount of verbal encouragement given to the subjects to gain maximal force could be an impact on the measure.

The study also has strengths. The WBB platform is a low-cost, novel and portable tool to assess force with very high reliability. Moreover, it doesn’t take much training to learn to use it. Future research should investigate the validity of the WBB with the gold standard of strength assessment in a randomization test position.

Conclusion

To summarize, the WBB is a reliable device to assess strength in the ASH test with a very large association with the HHD. Given these results, the WBB may be a valuable tool in clinical settings.