Abstract
Background: The aim of this article was to explore retrospectively the Takei dynamometer as a valid and reliable outcome measure tool for hand and wrist pathology in the Great Britain amateur boxing squad between 2010 and 2014. Methods: Longitudinal retrospective injury surveillance of the Great Britain boxing squad was performed from 2010 to 2014. The location, region affected, description, and duration of each injury were recorded by the team doctor and team physiotherapists. For each significant injury, we recorded hand grip scores using the Takei handheld dynamometer and compared the scores with baseline measures. Results: At the hand, fractures and dislocations were highly detected with an average difference of 40.2% (P < .05) when comparing postinjury to baseline measures. At the wrist, carpometacarpal and carpal joint injuries were highly detected with an average difference of 32.6% (P < .05). Other injuries provided varied results. In the absence of pathology, up to 15% difference between left and right scores can be considered normal with a predominance observed below 10%. A difference of 20% can be indicative of a form of pathology, although pathologies can also be present with lower difference or no apparent changes. A difference of >20% should be highly considered for significant pathology. Conclusions: The Takei dynamometer is a valid and reliable outcome measure tool for hand and wrist pathologies in boxing. Our study highlights the importance of appropriate clinical tools to guide injury management in this sport.
Keywords: boxing, hand, wrist, injuries, sport, handheld dynamometer, outcome measures
Introduction
Hand-wrist strength and function are essential components of daily living in both a sporting and nonsporting population. From throwing a dart to turning a door handle, the importance of hand-wrist function remains somewhat understated. The hand-wrist represents the most sophisticated tool in the human being, demanding a large amount from the nervous system in relation to its size.2 The correlation of hand-wrist strength in the presence of disease and pathology is a wide and ever expanding area of research, with close links to malnutrition and arthritis.15
When evaluating hand-wrist strength and function, an understanding of the different grips is important especially in relation to the specific demands of various sports and activities. The 3 main prehensile patterns described are power grip, pinch grip, and key grip.9 Closing a hand with the thumb in opposition to all other fingers together generates a power grip.13 Pinch grip is generated by pressing the thumb pulp against the pulp of the index, middle, ring, and little fingers’ distal phalanges.16 Finally, key grip is achieved by pressing the thumb pulp against the lateral aspect of the proximal interphalangeal joint of the index finger.
Power grip measures a maximum voluntary force of the hand-wrist using a dynamometer.19 Two of the most commonly discussed dynamometers within the current literature are the Jamar and the Takei. The Jamar dynamometer is comprised of an adjustable anatomical rigid handle, hydraulic system, and analog display.1 It has been found to be an accurate and reliable objective tool, being described by some authors as a gold standard for documenting manual grip strength.21 Conversely, when assessing the sensitivity of this dynamometer in detecting submaximal grip effort on a healthy sample size, it was found that using current protocols allowed for patients to make deliberate weak efforts resulting in a false loss of grip strength.3 This indicates that when using and interpreting data, it is important to be fully aware of the targeted patients to reduce false-positive results from lack of intent. Similar to the Jamar, the Takei has also been found to be a valid and reliable tool to measure power grip.4 It uses an adjustable rectified and complacent handle shape, electromechanical system and a digital or analog display.
The literature surrounding these dynamometers indicates that they are both valid tools in measuring power grip,4,21 but the results cannot be directly compared. The best possible protocol to follow for all dynamometers remains inconsistent, but based on the results to date, it appears that certain criterion can be confidently chosen: 3 repetitions per hand, allowing the patient to perform without strict instructions, minimum of 2-s hold per repetition, and straight arm or bent arm. What has been highlighted by the current literature is that irrespective of the type of protocol chosen, using either the Jamar or Takei dynamometer, it is important to consistently maintain those criteria as any change will not allow a comparison with previous data (Table 1).
Table 1.
Review of Protocols Used for Handheld Dynamometers.
| Authors | Protocol used |
|---|---|
| Watanabe et al20 | Interval measurements with a 1-min rest period after each set (2 reps per set) |
| Amaral et al1 | Three maximal isometric efforts held for 6 s with 2-min rest between reps |
| Ashford et al3 | Three reps per hand starting with the right, then left |
| Luna-Heredia et al15 | Three measurements made consecutively starting with right hand with 5-s rest between reps |
| Cadogan et al5 | Three maximal isometric contractions help for 6 to 7 s with 30-s rest between trials |
| Goodson et al9 | Best of three attempts recorded |
| Nayak16 | One maximal effort recorded per hand with 1-min rest between measurements |
| Fenter et al7 | Two test reps held for 2- to 4-s duration following 2 practice attempts; 2-min rest between trials |
The objective of a boxer is to succeed in delivering a clean and correct punch to the opponent without getting punched in return.10 Strength in a boxer’s upper and lower limbs is essential for victory and is seen as one of the keys to success.6 The position of the hand in a glove is maintained in a closed fist. The boxers tend to have a relatively loose fist, and like in most other combat sports, a fist is made before prior impact onto the opponent. This could be linked to energy losses from soft tissue motion possibly being reduced by up to 50% by tensing muscles at contact.18 The ability to make a power grip becomes therefore essential in this terminal aspect of a punch phase, as an inability to do so due to pathology can result in decreased punch force and potentially cause further damage to the hand-wrist. In the Great Britain boxing squads, injuries to the hand-wrist account for 23.2% to 33.7% of all significant injuries resulting in the highest amount of time loss.8 It is therefore important to have robust objective measures to understand when potentially significant injuries are occurring.
Over a period of 5 years (2010-2014), hand-wrist function was assessed using the Takei dynamometer by measuring 2 components: (1) the peak strength produced by each boxer during a biannual screening process, producing a comparative baseline in a healthy state for the different weight categories and sexes, and (2) potential pathology assessed for individuals who had described symptoms in the area due to either a known or unknown mechanism of trauma. The aim of this article was to identify the Takei dynamometer as a valid and reliable outcome measure tool for hand pathology in a sport like boxing.
Methods
Data were collected retrospectively from the Great Britain Boxing Physiotherapy Injury records. The participants included all boxers at any time between January 1, 2010, and December 31, 2014. A total of 129 male and 31 female boxers (aged 23.7 ± 3.9 years) were included in the study. The boxers were in each Olympic weight category from 49 (light flyweight) to 91 kg (super heavy weight). Injuries were then grouped into 2 categories: hand and wrist. Hand injuries were classed from the tip of the distal phalanx to the base of the metacarpals. Wrist injuries were classed including carpometacarpal (CMC) joints, carpal bone and joints, distal radioulnar joint (DRUJ), and radiocarpal and ulnocarpal joints. For both categories, all significant soft tissue and bone injuries were included.
The Takei T.K.K.5401 GRIP-D handgrip dynamometer (Takei Scientific Instruments Co., Ltd, Tokyo, Japan) was used for all data collection. This was performed with the participants in standing, arm by their side with full elbow extension. All measurements were performed alternatively 3 times with no rest. For each measurement, the participant was asked to squeeze the dynamometer for 3 s. The peak value of strength was recorded. The current literature provides inconclusive evidence into the effects that posture, position of the upper extremity, and overall elbow position have on grip strength.11,17,18 Measuring grip strength is however very reproducible between days if a standard procedure is followed.17 This protocol was maintained by every practitioner. Fifty-four injuries in total were collected, with 27 classed equally for both the hand and wrist.
The percentage difference between the boxers’ left and right scores at baseline was compared against the percentage difference between the boxers’ left and right scores after injury. The difference between baseline and postinjury scores was assessed using a paired t test. Reliability of each measure was examined using the intraclass correlation coefficient (ICC). The following benchmarks for ICC were used: “Poor” (0.00-0.20), “Fair” (0.21-0.40), “Moderate” (0.41-0.60), “Substantial” (0.61-0.80), and “Almost Perfect” (0.81-1.00) agreement.12
Results
An almost perfect correlation for the Takei hand grip dynamometer was found for all scores when used for both sexes, across all the Olympic weights, and for both sides (Table 2). There was no significant difference between left and right grip scores. When assessed for individual weight categories, the grip scores at baseline got progressively stronger as the weight of the boxer increased (Table 3).
Table 2.
Reliability of the Takei HG Dynamometer for Sex and Dominance.
| Measurement |
ICC | 95 CI (%) | n | |||
|---|---|---|---|---|---|---|
| 1st | 2nd | 3rd | ||||
| HG (total): men | ||||||
| Left | 49.2 ± 10.3 | 48.1 ± 10.1 | 47.6 ± 10.3 | 0.939 | 0.939-0.955 | 129 |
| Right | 49.1 ± 10.6 | 48.4 ± 10.7 | 48.0 ± 11.0 | 0.948 | 0.932-0.962 | 129 |
| HG (total): women | ||||||
| Left | 36.4 ± 6.1 | 35.2 ± 6.1 | 34.5 ± 5.9 | 0.898 | 0.824-0.946 | 31 |
| Right | 36.0 ± 6.2 | 35.2 ± 6.4 | 34.0 ± 6.2 | 0.910 | 0.845-0.952 | 31 |
Note. ICC = intraclass correlation coefficient; CI = confidence interval; HG = hand grip.
Table 3.
Hand Grip Averages at Baseline for Olympic Boxers per Weight Category.
| Weight, kg | Left | Right | |
|---|---|---|---|
| Men, n | |||
| 11 | 49 | 37.2 ± 5.6 | 38.2 ± 5.6 |
| 13 | 52 | 37.4 ± 3.3 | 38.3 ± 3.5 |
| 15 | 56 | 42.9 ± 6.3 | 41.2 ± 8.3 |
| 11 | 60 | 43.2 ± 4.3 | 41.2 ± 4.4 |
| 11 | 64 | 45.4 ± 5.5 | 45.0 ± 3.6 |
| 17 | 69 | 48.2 ± 4.8 | 48.9 ± 5.6 |
| 16 | 75 | 52.8 ± 4.5 | 54.4 ± 4.4 |
| 13 | 81 | 54.3 ± 7.9 | 53.4 ± 7.9 |
| 11 | 91 | 59.4 ± 7.7 | 60.8 ± 7.8 |
| 11 | 91+ | 63.4 ± 10.1 | 64.2 ± 10.9 |
| Women, n | |||
| 13 | 51 | 35.6 ± 4.5 | 33.6 ± 5.7 |
| 12 | 60 | 35.0 ± 7.0 | 35.4 ± 6.2 |
| 6 | 75 | 38.3 ± 4.7 | 41.4 ± 1.4 |
Hand
The baseline measure had an average percentage difference of 6.3% when compared with postinjury measure with an average of 23.7% (Table 4). The difference between both measures was statistically significant (P < .05 by 2-tailed t test). Fractures and dislocation (n = 4) showed an average difference of 46% (24.2%-78.1%) when compared with baseline measures with an average of 6.2% (9.1%). Injuries to the metacarpophalangeal (MCP) joints showed a wide range. A difference of 6.9% was recorded at baseline with an even lower difference of 3.1% recorded after an injury of the fifth MCP. Contrastingly another fifth MCP joint injury indicated a difference of 40.2% after injury when compared with an 8.3% difference at baseline.
Table 4.
Hand Injuries: Percentage Comparison of Baseline and Postinjury Data.
| No. | Wt | BL | BR | DIFF (%) | PIL | PIR | DIFF (%) | Injury | |
|---|---|---|---|---|---|---|---|---|---|
| 1 | 52 | 40.4 | 41.5 | 2.7 | 35.1 | 41.5 | 15.4 | Left | 4th and 5th MCP joint sprain |
| 2 | 75 | 54.9 | 53.6 | 2.4 | 50.4 | 54.5 | 7.5 | Left | 2nd MCP joint sprain |
| 3 | 75 | 53.7 | 57.7 | 6.9 | 46.6 | 35.3 | 24.2 | Right | Undisplaced crush fracture base of 5th MC bone |
| 4 | 69 | 45.7 | 48 | 4.8 | 45.4 | 29.6 | 34.8 | Right | 2nd MCP joint sprain with RCL sprain |
| 5 | 75 | 51.3 | 54.4 | 5.7 | 28.1 | 59.7 | 52.9 | Left | 2nd MCP sprain |
| 6 | 91 | 66.5 | 55.1 | 17.1 | 62.3 | 50.1 | 19.6 | Right | 3rd MCP sprain |
| 7 | 69 | 54.6 | 54.3 | 0.5 | 45.3 | 21.6 | 52.3 | Right | Fractured base 5th MC bone |
| 8 | 91+ | 54.2 | 58.2 | 6.9 | 55.6 | 53.9 | 3.1 | Right | 5th extensor hood bruising/edema |
| 9 | 91 | 67.3 | 67.7 | 0.6 | 61.3 | 57.2 | 6.7 | Right | Extensor hood tear |
| 10 | 81 | 66.3 | 67.3 | 1.5 | 54.5 | 53.0 | 2.8 | Right | Extensor hood injury |
| 11 | 60 | 45.3 | 44.2 | 2.4 | 41.4 | 31.1 | 24.9 | Right | 3rd MCP joint sprain |
| 12 | 60 | 45.3 | 44.2 | 2.4 | 40.4 | 41.4 | 2.4 | Right | 2nd MCP extensor tenosynovitis |
| 13 | 91+ | 74.5 | 78.2 | 4.7 | 74.6 | 69.6 | 6.7 | Right | 3rd MCP joint sprain |
| 14 | 69 | 43.2 | 39.6 | 8.3 | 41.0 | 28.9 | 29.5 | Right | 1st MCP joint dislocation |
| 15 | 69 | 43.2 | 39.6 | 8.3 | 41.5 | 24.8 | 40.2 | Right | 5th MCP joint sprain |
| 16 | 81 | 39.7 | 40.5 | 2.0 | 56.4 | 49.4 | 12.4 | Right | 3rd joint MCP sprain/capsule synovitis |
| 17 | 91 | 34.2 | 39.6 | 13.6 | 46.0 | 55.0 | 16.4 | Left | 5th MCP joint sprain with soft tissue bruising |
| 18 | 81 | 63.7 | 70.1 | 9.1 | 66.7 | 14.6 | 78.1 | Right | Fractured base 3rd MC bone |
| 19 | 60 | 47.6 | 40.6 | 14.7 | 50.3 | 41.6 | 17.3 | Left | 2nd MCP extensor tenosynovitis |
| 20 | 56 | 35.6 | 39.2 | 9.2 | 28.4 | 36.9 | 23.0 | Left | 3rd MCP joint sprain |
| 21 | 56 | 35.6 | 39.2 | 9.2 | 29.3 | 37.6 | 22.1 | Left | 3rd MCP joint sprain |
| 22 | 56 | 39.4 | 40.7 | 3.2 | 44.5 | 33.1 | 25.6 | Right | 2nd-4th MCP joint sprain and soft tissue bruising |
| 23 | 56 | 39.4 | 40.7 | 3.2 | 18.0 | 25.0 | 28.0 | Left | Ruptured UCL 1st IP joint |
| 24 | 64 | 42 | 47.5 | 11.6 | 45.4 | 44.0 | 3.1 | Right | 3rd MCP joint sprain |
| 25 | 69 | 48 | 48.9 | 1.8 | 52.2 | 51.6 | 1.1 | Right | 2nd MCP joint sprain |
| 26 | 56 | 53.3 | 55.5 | 4.0 | 29.6 | 48.9 | 39.5 | Left | 3rd MCP joint sprain |
| 27 | 60 | 44.2 | 47.7 | 7.3 | 40.9 | 33.5 | 18.1 | Right | 3rd-5th MCP joint sprains |
Note. Shaded area = injured side; Wt = weight (kg); BL = baseline left (kg); BR = baseline right (kg); DIFF = percentage difference between left and right; PIL = post injury left (kg); PIR = post injury right (kg); MCP = metacarpophalangeal; MC = metacarpal; RCL = radial collateral ligament; UCL = ulnar collateral ligament; IP = interphalangeal.
Wrist
The baseline measures had an average of 5.7% when compared with postinjury measures which had an average of 34.5% (Table 5). The difference between both measures was statistically significant (P < .05 by 2-tailed t test). Most injuries recorded in this area occurred at the CMC joint and carpal bones (n = 22) with a percentage difference of 38.1% (7.7%-81.2%) when compared with baseline measure difference of 5.5% (1.0%-14.7%). This indicated a high percentage difference for injuries occurring in this region. Other injuries (n = 5) were recorded in the region between the radius-ulna and proximal carpal bones. A difference of 12% (2%-24%) after injury was recorded when compared with 6.3% (0.8%-15.8%) at baseline.
Table 5.
Wrist Injuries: Percentage Comparison of Baseline and Postinjury Data.
| No. | Wt | BL | BR | DIFF (%) | PIL | PIR | DIFF (%) | Injury | |
|---|---|---|---|---|---|---|---|---|---|
| 1 | 75 | 54.9 | 53.6 | 2.4 | 58.4 | 53.9 | 8 | Right | 5th CMC joint sprain (mild) |
| 2 | 75 | 54.9 | 53.6 | 2.4 | 58.5 | 37.4 | 36 | Right | Fractured hamate and 5th CMC joint subluxation |
| 3 | 52 | 35.1 | 35.4 | 0.8 | 35.5 | 33.6 | 5 | Right | Mild wrist jarring |
| 4 | 51 | 29.3 | 26.3 | 10.2 | 29.6 | 27.0 | 9 | Right | 2nd CMC joint sprain |
| 5 | 75 | 59.7 | 55.6 | 6.9 | 52.9 | 47.4 | 10 | Left | Wrist jarring with radiocarpal ligament sprain |
| 6 | 75 | 59.7 | 55.6 | 6.9 | 56.9 | 44.7 | 21 | Right | 5th CMC joint sprain with hamate bruising |
| 7 | 75 | 59.7 | 55.6 | 6.9 | 53.7 | 35.8 | 33 | Right | 5th CMC joint sprain with hamate bruising |
| 8 | 75 | 59.7 | 55.6 | 6.9 | 56.7 | 8.4 | 85 | Right | 3rd and 4th CMC joint sprain (grade 2) |
| 9 | 75 | 59.7 | 55.6 | 6.9 | 48.1 | 16.6 | 65 | Right | 3rd and 4th CMC joint sprain (grade 2) |
| 10 | 91 | 54.2 | 58.2 | 6.9 | 42.7 | 57.2 | 25 | Left | 2nd CMC joint sprain (mild) |
| 11 | 56 | 44.2 | 37.2 | 15.8 | 29.8 | 39.3 | 24 | Left | ECU tendinitis |
| 12 | 60 | 45.3 | 44.2 | 2.4 | 41.1 | 12.7 | 69 | Right | 3rd CMC joint sprain/avulsion fracture base 3rd MC |
| 13 | 60 | 45.3 | 44.2 | 2.4 | 33.9 | 42.5 | 20 | Left | 2nd and 3rd CMC joint sprain |
| 14 | 60 | 45.3 | 44.2 | 2.4 | 43.8 | 37.3 | 15 | Right | Distal carpal jarring (capitate/trapezoid) |
| 15 | 64 | 43.8 | 44.9 | 2.4 | 19.9 | 42.1 | 53 | Left | 2nd and 3rd CMC joint sprain |
| 16 | 64 | 43.8 | 44.9 | 2.4 | 22.0 | 46.5 | 53 | Left | 2nd and 3rd CMC joint sprain/instability |
| 17 | 60 | 47.6 | 40.6 | 14.7 | 44.3 | 14.0 | 68 | Right | 2nd and 3rd CMC joint sprain |
| 18 | 60 | 47.6 | 40.6 | 14.7 | 49.4 | 36.6 | 26 | Right | Midcarpal instability/2nd and 3rd CMC sprains |
| 19 | 81 | 55.4 | 54.3 | 2.0 | 52.0 | 53.2 | 2 | Left | Ulnar-lunate impaction |
| 20 | 64 | 50.7 | 50.2 | 1.0 | 50.5 | 29.4 | 42 | Right | 2nd and 3rd CMC joint sprains |
| 21 | 64 | 42 | 47.5 | 11.6 | 40.7 | 31.5 | 23 | Right | 2nd CMC joint sprain |
| 22 | 60 | 41.4 | 42 | 1.4 | 45.3 | 32.9 | 27 | Right | 3rd CMC joint sprain |
| 23 | 60 | 41.4 | 42 | 1.4 | 42.3 | 32.4 | 23 | Right | 3rd CMC joint sprain |
| 24 | 69 | 48 | 48.9 | 1.8 | 49.3 | 38.3 | 22 | Right | Multiple injuries throughout carpal joints |
| 25 | 69 | 48 | 48.9 | 1.8 | 46.3 | 38.3 | 17 | Right | DRUJ joint stiffness |
| 26 | 56 | 53.3 | 55.5 | 4.0 | 24.0 | 47.6 | 50 | Left | 2nd CMC joint sprain |
| 27 | 56 | 53.3 | 55.5 | 4.0 | 46.1 | 23.8 | 48 | Right | 2nd and 3rd CMC joint sprains |
Note. Shaded area = injured side; Wt = weight (kg); BL = baseline left (kg); BR = baseline right (kg); DIFF = percentage difference between left and right; PIL = post injury left (kg); PIR = post injury right (kg); CMC = carpometacarpal; MC = metacarpal; ECU = extensor carpi ulnaris; DRUJ = distal radioulnar joint.
Discussion
The aim of this article was to identify the Takei dynamometer as a valid and reliable outcome measure tool for hand pathology in a sport like boxing. At the hand, fractures and dislocations were highly detected with an average difference of 40.2% (P < .05) when comparing postinjury measures with baseline measures. As these injuries occur in both training and competition, early detection is important to prevent further damage to the area. Soft tissue injuries at the MCP joint showed a variation of results, indicating this tool as not valid in accurately detecting these pathologies. From the injury reports, it was however observed that when a significant percentage difference was recorded in these areas, the handheld dynamometer was used as an effective clinical objective measure. This provided safe guidance of injury progression till resolution of symptoms.
At the wrist, CMC and carpal joint injuries were highly detected with an average difference of 32.6% (P < .05) when comparing postinjury measures with baseline measures. Injuries in these regions have been reported as having the greatest impact on training availability.14 It is therefore important to have an objective clinical tool that assists in diagnosing an injury to these areas, and guide management. Injuries at the DRUJ indicated a smaller but still significant percentage average difference of 12% when compared with 6.3% at baseline. When compared with CMC and carpal injuries, DRUJ injuries impact less on training availability.14 DRUJ injuries still require appropriate interventions and monitoring to prevent subsequent regression of the pathology.
The Takei handheld dynamometer was found to be highly reliable using the protocol described in this study. This protocol was maintained by each practitioner for every boxer tested. There has been research into the effects that posture, position of the upper extremity, and overall elbow position have on grip strength. One study found that there was no statistical difference between grip strength when measured at 0°, 30°, 60°, and 90° of elbow flexion.17 Similarly, another study found that grip strength was unaffected by position when tested in seated, supine, and standing positions.18 Another study observed some differences on grip strength values by altering differences between elbow, shoulder, and forearm positions.11 Measuring grip strength is very reproducible between days if a standard procedure is followed.17 Based on the current literature and lack of conclusive evidence regarding the best testing position, the hand grip dynamometer can be a highly reliable tool if it is used with a procedure and testing position that can be easily reproducible. Great Britain boxing used the position of 0° shoulder flexion, shoulder adducted, elbow extended, and forearm in a neutral position.
The information from this current study indicates that grip strength, which is an important aspect of hand function, is affected by pathology in boxing. Baseline data are therefore important to compare data between sides after injury. Comparing unaffected and affected sides at the time of injury using the handheld dynamometer provided a very useful clinical criterion for further management. From the data collected, a recommendation that up to about 15% difference between left and right hand/wrist can be considered normal, with the majority of reading expected to fall below 10%. A difference of 20% is indicative of a form of pathology, although pathologies can also be present with lower difference or no apparent changes. That is why a comparison with baseline, especially in the sporting environment, can provide more accurate information. A difference of >20% with a suspicion of fracture/dislocation/ligamentous rupture should be considered for investigation. Although this study was performed in boxing, the hand grip dynamometer should be considered as a useful objective marker for injury assessment and progression in other sports.
Conclusion
In this cohort of elite amateur boxers, the Takei handheld dynamometer was found valid and reliable in detecting significant injuries occurring at the hand and wrist anatomical regions. Fractures and dislocations at the hand, followed by soft tissue injuries at the CMC and carpal bones, are more highly detected than any other injury incurred in boxing. MCP joint injuries vary between individuals with the handheld dynamometer providing additional useful information to symptoms described. Further research into other sports is required to fully understand the role of grip strength and pathologies.
Footnotes
Ethical Approval: This study was approved by our institutional review board.
Statement of Human and Animal Rights: All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2008.
Statement of Informed Consent: As the data are anonymized, no informed consent was obtained.
Declaration of Conflicting Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding: The author(s) received no financial support for the research, authorship, and/or publication of this article.
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