Archives of Physical Medicine and Rehabilitation journal homepage: www.archives-pmr.org Archives of Physical Medicine and Rehabilitation 2015;96:1627-33
ORIGINAL RESEARCH
Normative Values for Grip and Pinch Strength for 6- to 19-Year-Olds Victoria A. McQuiddy, MHS, BSOT,a Carol R. Scheerer, EdD, BSOT,b Ryan Lavalley, MOT, BLA,b Timothy McGrath, MOT, BLA,b Li Lin, MSc From the aDivision of Occupational and Physical Therapy, Cincinnati Children’s Hospital Medical Center; bDepartment of Occupational Therapy, Xavier University; and cCenter for Professional Excellence Research & Evidence-Based Practice, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH.
Abstract Objectives: To provide current normative data for grip and pinch strength in children and young adults aged 6 to 19 years as well as to examine the effect of age, sex, and hand dominance on grip and pinch strength. Design: Descriptive cross-sectional. Setting: Two grade schools, 2 high schools, and 1 university. Participants: Participants (NZ1508; 741 male students and 767 female students) aged 6 to 19 years. Interventions: Not applicable. Main Outcome Measures: Means and SDs were calculated for each strength measurement (grip, tip pinch, lateral pinch, palmar pinch) and stratified by age and sex. Analysis of covariance and 2-sample t tests were used to analyze the data. Results: The analyses demonstrated that age and sex had a significant effect on hand strength values, as evidenced by increasing hand strength with age as well as greater hand strength in males than in females. Hand dominance was not shown to have a significant effect on hand strength. The results of this study were statistically significantly different from previously published normative values, with most hand strength values being lower than those published 28 years ago. Conclusions: Having updated normative data are paramount for rehabilitation practitioners to compare the grip and pinch strength of their clients with the average values to objectively assess impairment and tracking progress. The statistical significance observed for most data collected in this study as compared with those previously published supports the need for continually updating normative data. Archives of Physical Medicine and Rehabilitation 2015;96:1627-33 ª 2015 by the American Congress of Rehabilitation Medicine
Grip and pinch strength is the most commonly evaluated function of the hand1 because hand strength measurements reflect overall hand function2 and grip strength is considered an indicator of general health.3 At present, no normative data published in the United States are available on grip and pinch strength collected from a single sample, incorporating school-age children and young adults, and stratified by age in 1-year increments; additionally, much of the data were not collected according to standard
Presented to Xavier University, April 19, 2013, Cincinnati, OH; Ohio Occupational Therapy Association, November 13, 2013, Columbus, OH; and American Occupational Therapy Association, April 4, 2014, Baltimore, MD. Supported by Cincinnati Children’s Hospital Medical Center and Xavier University. Disclosure: none.
procedures to ensure valid and reliable instruments. Establishing current and comprehensive normative data collected using rigorous procedures is imperative in allowing judicious decision making for assessment and intervention. Practice rooted in up-todate research is mandated by ethical standards to which rehabilitative health care providers are held.4,5 Therefore, the objective of this study was to provide current, comprehensive, reliable, and valid data that allow pediatric clinicians to compare their clients’ grip and pinch strength measurements with normative values. Many studies providing normative data for grip and pinch strength in children and young adults have been published nationally and internationally over the past 30 years. Specifically, normative data have been collected worldwide using hand-held instruments, most often for grip strength6-17 and less
0003-9993/15/$36 - see front matter ª 2015 by the American Congress of Rehabilitation Medicine http://dx.doi.org/10.1016/j.apmr.2015.03.018
1628 Table 1
V.A. McQuiddy et al Characteristics of data collection sites
Characteristic Race White Black Asian Hispanic/Latino Other/not reported Other demographic information Low socioeconomic status indicator* Persons with reported disabilitiesy
Elementary School 1
Elementary School 2
High School 1
High School 2
University
Ohio
United States
75.0 13.0 2.0 2.0 8.0
76.0 13.0 2.0 2.0 7.0
48.5 48.7 0.6 2.2 0.0
89.3 4.7 2.9 2.8 0.3
78.6 8.4 2.6 3.4 7.0
80.7 12.5 1.8 3.3 1.7
63.0 13.1 5.1 16.9 1.9
13.0
24.0
40.0
0.0
19.0
14.2
13.8
2.0
9.0
23.0
0.0
8.0
13.3
12.0
* Elementary and high school: percentage receiving free or reduced lunch; University: percentage receiving federal grants; State and country: percentage below poverty line. y Elementary and high school: number of individualized education plans; University: number registered for disability services.
often for pinch strength.6,7,11,13,17,18 Evidence of decreased grip strength has been noted internationally in the past 3 decades. For example, in 5 cities in Spain, data collected from 2001 to 2002 (nZ399) and from 2006 to 2007 (nZ392) revealed an average decrease by approximately 4.5kg in hand strength in adolescents of both sexes aged 12.5 to 17.5 years.19 In England, grip strength data collected from 10-year-old children attending 6 randomly selected schools decreased by 6.3% over a 10-year period from 1998 (nZ309) to 2008 (nZ315).20 Grip strength data collected from 2087 participants aged 6 to 19 years selected from 15 sites across Canada revealed that from 1981 to 2009 hand grip strength in a typical 12-year-old boy decreased by 5kg and in a typical girl by 3kg.21 The review by Silverman22 was the only study located that explored secular trends in hand strength in the United States and Canada. In Silverman’s review, studies conducted in the United States did not include a nationally representative sample; furthermore, instrumentation was varied. In addition, the individual studies conducted in the United States did not explore changes in hand strength over time. Because of these factors, it is difficult to draw conclusions from Silverman’s review about whether grip strength of children in the United States has changed between 1966 and 2011. No studies of secular changes in pinch strength were located. Because it is unknown if hand strength changes in the United States have occurred over time, the 4 normative studies6,7,9,18 of school-age children and young adults conducted and published solely in the United States in the past 3 decades were more closely reviewed. A study by Mathiowetz et al6 is widely cited and used clinically because it is the most recently published study in the United States that includes normative data for both grip and pinch strength (tip, lateral, palmer) in children and young adults. Mathiowetz collected data from 471 children and young adults aged 6 to 19 years. The only other normative study published in the past 3 decades for this age group containing data for both grip and pinch strength was published in 1984 and included a sample of 574 children aged 5 to 12 years.7 Other studies collected only grip strength data from 736 children and young adults aged 5 to 19 years9 or only pinch strength data from 414 children aged 5 to 12 years.18 Mathiowetz presented results
List of abbreviations: ANCOVA analysis of covariance ASHT American Society of Hand Therapists
stratified by age in 2-year increments, and the other 3 studies presented results stratified by age mostly in 1-year increments. The 4 domestic studies6,7,9,18 used various data collection procedures. Mathiowetz6 most closely adhered to American Society of Hand Therapists (ASHT) standards including those related to positioning, verbal cueing, and reporting the mean of 3 trials. Deviation from ASHT standards occurred when suspending the dynamometer from its gauge during testing rather than lightly supporting the dynamometer’s base. Mathiowetz’s study6 included calibration verification at the beginning, middle, and end of data collection. Butterfield et al9 also adhered to ASHT standards for positioning, verbal cueing, and reporting the mean of 3 trials. Their study reported using a calibrated instrument; however, it did not report the frequency of calibration verification.9 Surrey et al18 followed ASHT positioning standards and reported the results of 3 trials but did not report whether verbal instructions were given or if instrument support was provided while collecting data. Their study reported verification of instrument calibration before and midway through data collection, a frequency below ASHT standards. Ager et al7 used multiple procedures that deviated from ASHT standards by having participants rest their arm on a table, adjusting the dynamometer handle position based on hand size, reporting only 1 measurement for each hand strength, and failing to report information on the calibration of instruments. As such, and according to ASHT standards,23 Mathiowetz presented the most rigorously standardized normative hand strength study of children and young adults available today. Results on hand dominance, sex, and age were generally consistent across the 4 studies6,7,9,18 conducted in the United States. Three of the 4 studies6,7,9 reported that hand dominance was not a significant factor in determining hand strength; Surrey18 did not report trends in hand dominance. Mathiowetz6 and Ager7 reported sex as a significant factor affecting hand strength, whereas Butterfield9 noted sex as a significant factor only for children 12 years or older. Surrey combined sexes when reporting normative values, thus not reporting trends. Finally, all 4 studies recognized a positive correlation between age and hand strength; Butterfield noted that the strength of the correlation was dependent on both age and sex. As discussed previously, studies conducted in the United States providing normative values for grip and pinch strength have limitations. It is important to collect normative data using reliable and valid instruments, adhering to standard procedures, and www.archives-pmr.org
Normative values for hand strength
1629
Table 2 Characteristics of study participants: age, sex, and hand dominance Males
Females
Dominant Hand
Dominant Hand
Age (y)
No. of Participants Per Age
n
Right
Left
n
Right
Left
6 7 8 9 10 11 12 13 14 15 16 17 18 19 Total
108 99 110 111 109 111 100 110 113 102 107 105 108 101 1508
55 48 43 49 52 54 47 50 54 55 69 51 63 51 741
47 44 40 44 47 42 45 43 45 51 60 42 59 46 655
8 4 3 5 5 12 2 7 9 4 9 9 4 5 86
53 51 67 62 57 57 53 60 59 51 38 54 55 50 767
45 44 57 57 51 52 49 58 55 46 35 48 49 43 689
8 7 10 5 6 5 4 2 4 5 3 6 6 7 78
regularly verifying calibration of instruments. Therefore, the primary objective of this study was 2-fold: (1) to provide current normative data for grip and pinch strength in children and young adults aged 6 to 19 years by using rigorous data collection methods and (2) to determine the effects of age, sex, and hand dominance on grip and pinch strength. A secondary objective was to compare the data of the present study with the data previously published by Mathiowetz6 to determine whether normative values have changed during the ensuing time.
Methods Participants In the fall of 2012, study participants aged 6 to 19 years were selected by convenience from 5 schools (2 elementary schools, 2 high schools, 1 university) in the Cincinnati metropolitan area. Individuals from whom data were collected exhibited neither cognitive impairment (inability to understand and/or follow directions) nor physical impairment of the upper extremity (visible swelling or the presence of a splint or cast).
Procedures Thirteen researchers, consisting of 11 graduate occupational therapy students and 2 occupational therapists, established interrater reliability for data collection procedures. Before conducting the study, the researchers obtained approval from the institutional review boards of the participating researchers’ institutions, including a waiver of written consent. A member of the research team screened each potential participant to ensure absence of impairments that prevented participation and obtained each participant’s sex, age, and hand dominance. On completing the screening and obtaining verbal assent from each potential participant, data collection occurred following ASHT23 www.archives-pmr.org
standards, including having the dynamometers set at the second handle position. Each participant sat in a chair with his/her feet flat on the floor, shoulder adducted and neutrally rotated, elbow flexed at 90 , forearm in a neutral position, and wrist positioned between 0 and 30 extension and between 0 and 15 ulnar deviation. A researcher gave verbal instructions and demonstrated each testing position. Participants received verbal encouragement to exert maximal force during each trial. Researchers tested each participant using 3 consecutive trials for each hand to collect grip, tip pinch, lateral pinch, and palmar pinch strength data. To prevent dropping, researchers supported dynamometers lightly at the base and the pinch gauges at the distal end. If a participant did not maintain correct position during testing, researchers discarded the measurement and repeated the trial.
Instrumentation This study used 3 Jamara hydraulic hand dynamometers to measure grip strength. The Jamar hydraulic hand dynamometer has established validity and reliability for measuring grip strength24-26 and has been described as the criterion standard for measuring hand strength.27-29 The study used 3 B & L Engineeringb pinch gauges to measure pinch strength (tip, lateral, palmar). Studies have found that the B & L Engineering pinch gauge has high calibration accuracy.30,31
Calibration Because of concerns about instrument calibration,30,32 researchers routinely verified instrument calibration using known weights and a verification station constructed according to procedures outlined by Fess.32 This process verified each instrument’s calibration after approximately every 30 to 45 participants. Throughout the study, a total of 117 individual instrument calibration verification occurred in the 6 instruments. Each instrument was required to obtain a minimum of .9994 Pearson product-moment correlation coefficient and a difference in means of
ORIGINAL RESEARCH
Normative Values for Grip and Pinch Strength for 6- to 19-Year-Olds Victoria A. McQuiddy, MHS, BSOT,a Carol R. Scheerer, EdD, BSOT,b Ryan Lavalley, MOT, BLA,b Timothy McGrath, MOT, BLA,b Li Lin, MSc From the aDivision of Occupational and Physical Therapy, Cincinnati Children’s Hospital Medical Center; bDepartment of Occupational Therapy, Xavier University; and cCenter for Professional Excellence Research & Evidence-Based Practice, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH.
Abstract Objectives: To provide current normative data for grip and pinch strength in children and young adults aged 6 to 19 years as well as to examine the effect of age, sex, and hand dominance on grip and pinch strength. Design: Descriptive cross-sectional. Setting: Two grade schools, 2 high schools, and 1 university. Participants: Participants (NZ1508; 741 male students and 767 female students) aged 6 to 19 years. Interventions: Not applicable. Main Outcome Measures: Means and SDs were calculated for each strength measurement (grip, tip pinch, lateral pinch, palmar pinch) and stratified by age and sex. Analysis of covariance and 2-sample t tests were used to analyze the data. Results: The analyses demonstrated that age and sex had a significant effect on hand strength values, as evidenced by increasing hand strength with age as well as greater hand strength in males than in females. Hand dominance was not shown to have a significant effect on hand strength. The results of this study were statistically significantly different from previously published normative values, with most hand strength values being lower than those published 28 years ago. Conclusions: Having updated normative data are paramount for rehabilitation practitioners to compare the grip and pinch strength of their clients with the average values to objectively assess impairment and tracking progress. The statistical significance observed for most data collected in this study as compared with those previously published supports the need for continually updating normative data. Archives of Physical Medicine and Rehabilitation 2015;96:1627-33 ª 2015 by the American Congress of Rehabilitation Medicine
Grip and pinch strength is the most commonly evaluated function of the hand1 because hand strength measurements reflect overall hand function2 and grip strength is considered an indicator of general health.3 At present, no normative data published in the United States are available on grip and pinch strength collected from a single sample, incorporating school-age children and young adults, and stratified by age in 1-year increments; additionally, much of the data were not collected according to standard
Presented to Xavier University, April 19, 2013, Cincinnati, OH; Ohio Occupational Therapy Association, November 13, 2013, Columbus, OH; and American Occupational Therapy Association, April 4, 2014, Baltimore, MD. Supported by Cincinnati Children’s Hospital Medical Center and Xavier University. Disclosure: none.
procedures to ensure valid and reliable instruments. Establishing current and comprehensive normative data collected using rigorous procedures is imperative in allowing judicious decision making for assessment and intervention. Practice rooted in up-todate research is mandated by ethical standards to which rehabilitative health care providers are held.4,5 Therefore, the objective of this study was to provide current, comprehensive, reliable, and valid data that allow pediatric clinicians to compare their clients’ grip and pinch strength measurements with normative values. Many studies providing normative data for grip and pinch strength in children and young adults have been published nationally and internationally over the past 30 years. Specifically, normative data have been collected worldwide using hand-held instruments, most often for grip strength6-17 and less
0003-9993/15/$36 - see front matter ª 2015 by the American Congress of Rehabilitation Medicine http://dx.doi.org/10.1016/j.apmr.2015.03.018
1628 Table 1
V.A. McQuiddy et al Characteristics of data collection sites
Characteristic Race White Black Asian Hispanic/Latino Other/not reported Other demographic information Low socioeconomic status indicator* Persons with reported disabilitiesy
Elementary School 1
Elementary School 2
High School 1
High School 2
University
Ohio
United States
75.0 13.0 2.0 2.0 8.0
76.0 13.0 2.0 2.0 7.0
48.5 48.7 0.6 2.2 0.0
89.3 4.7 2.9 2.8 0.3
78.6 8.4 2.6 3.4 7.0
80.7 12.5 1.8 3.3 1.7
63.0 13.1 5.1 16.9 1.9
13.0
24.0
40.0
0.0
19.0
14.2
13.8
2.0
9.0
23.0
0.0
8.0
13.3
12.0
* Elementary and high school: percentage receiving free or reduced lunch; University: percentage receiving federal grants; State and country: percentage below poverty line. y Elementary and high school: number of individualized education plans; University: number registered for disability services.
often for pinch strength.6,7,11,13,17,18 Evidence of decreased grip strength has been noted internationally in the past 3 decades. For example, in 5 cities in Spain, data collected from 2001 to 2002 (nZ399) and from 2006 to 2007 (nZ392) revealed an average decrease by approximately 4.5kg in hand strength in adolescents of both sexes aged 12.5 to 17.5 years.19 In England, grip strength data collected from 10-year-old children attending 6 randomly selected schools decreased by 6.3% over a 10-year period from 1998 (nZ309) to 2008 (nZ315).20 Grip strength data collected from 2087 participants aged 6 to 19 years selected from 15 sites across Canada revealed that from 1981 to 2009 hand grip strength in a typical 12-year-old boy decreased by 5kg and in a typical girl by 3kg.21 The review by Silverman22 was the only study located that explored secular trends in hand strength in the United States and Canada. In Silverman’s review, studies conducted in the United States did not include a nationally representative sample; furthermore, instrumentation was varied. In addition, the individual studies conducted in the United States did not explore changes in hand strength over time. Because of these factors, it is difficult to draw conclusions from Silverman’s review about whether grip strength of children in the United States has changed between 1966 and 2011. No studies of secular changes in pinch strength were located. Because it is unknown if hand strength changes in the United States have occurred over time, the 4 normative studies6,7,9,18 of school-age children and young adults conducted and published solely in the United States in the past 3 decades were more closely reviewed. A study by Mathiowetz et al6 is widely cited and used clinically because it is the most recently published study in the United States that includes normative data for both grip and pinch strength (tip, lateral, palmer) in children and young adults. Mathiowetz collected data from 471 children and young adults aged 6 to 19 years. The only other normative study published in the past 3 decades for this age group containing data for both grip and pinch strength was published in 1984 and included a sample of 574 children aged 5 to 12 years.7 Other studies collected only grip strength data from 736 children and young adults aged 5 to 19 years9 or only pinch strength data from 414 children aged 5 to 12 years.18 Mathiowetz presented results
List of abbreviations: ANCOVA analysis of covariance ASHT American Society of Hand Therapists
stratified by age in 2-year increments, and the other 3 studies presented results stratified by age mostly in 1-year increments. The 4 domestic studies6,7,9,18 used various data collection procedures. Mathiowetz6 most closely adhered to American Society of Hand Therapists (ASHT) standards including those related to positioning, verbal cueing, and reporting the mean of 3 trials. Deviation from ASHT standards occurred when suspending the dynamometer from its gauge during testing rather than lightly supporting the dynamometer’s base. Mathiowetz’s study6 included calibration verification at the beginning, middle, and end of data collection. Butterfield et al9 also adhered to ASHT standards for positioning, verbal cueing, and reporting the mean of 3 trials. Their study reported using a calibrated instrument; however, it did not report the frequency of calibration verification.9 Surrey et al18 followed ASHT positioning standards and reported the results of 3 trials but did not report whether verbal instructions were given or if instrument support was provided while collecting data. Their study reported verification of instrument calibration before and midway through data collection, a frequency below ASHT standards. Ager et al7 used multiple procedures that deviated from ASHT standards by having participants rest their arm on a table, adjusting the dynamometer handle position based on hand size, reporting only 1 measurement for each hand strength, and failing to report information on the calibration of instruments. As such, and according to ASHT standards,23 Mathiowetz presented the most rigorously standardized normative hand strength study of children and young adults available today. Results on hand dominance, sex, and age were generally consistent across the 4 studies6,7,9,18 conducted in the United States. Three of the 4 studies6,7,9 reported that hand dominance was not a significant factor in determining hand strength; Surrey18 did not report trends in hand dominance. Mathiowetz6 and Ager7 reported sex as a significant factor affecting hand strength, whereas Butterfield9 noted sex as a significant factor only for children 12 years or older. Surrey combined sexes when reporting normative values, thus not reporting trends. Finally, all 4 studies recognized a positive correlation between age and hand strength; Butterfield noted that the strength of the correlation was dependent on both age and sex. As discussed previously, studies conducted in the United States providing normative values for grip and pinch strength have limitations. It is important to collect normative data using reliable and valid instruments, adhering to standard procedures, and www.archives-pmr.org
Normative values for hand strength
1629
Table 2 Characteristics of study participants: age, sex, and hand dominance Males
Females
Dominant Hand
Dominant Hand
Age (y)
No. of Participants Per Age
n
Right
Left
n
Right
Left
6 7 8 9 10 11 12 13 14 15 16 17 18 19 Total
108 99 110 111 109 111 100 110 113 102 107 105 108 101 1508
55 48 43 49 52 54 47 50 54 55 69 51 63 51 741
47 44 40 44 47 42 45 43 45 51 60 42 59 46 655
8 4 3 5 5 12 2 7 9 4 9 9 4 5 86
53 51 67 62 57 57 53 60 59 51 38 54 55 50 767
45 44 57 57 51 52 49 58 55 46 35 48 49 43 689
8 7 10 5 6 5 4 2 4 5 3 6 6 7 78
regularly verifying calibration of instruments. Therefore, the primary objective of this study was 2-fold: (1) to provide current normative data for grip and pinch strength in children and young adults aged 6 to 19 years by using rigorous data collection methods and (2) to determine the effects of age, sex, and hand dominance on grip and pinch strength. A secondary objective was to compare the data of the present study with the data previously published by Mathiowetz6 to determine whether normative values have changed during the ensuing time.
Methods Participants In the fall of 2012, study participants aged 6 to 19 years were selected by convenience from 5 schools (2 elementary schools, 2 high schools, 1 university) in the Cincinnati metropolitan area. Individuals from whom data were collected exhibited neither cognitive impairment (inability to understand and/or follow directions) nor physical impairment of the upper extremity (visible swelling or the presence of a splint or cast).
Procedures Thirteen researchers, consisting of 11 graduate occupational therapy students and 2 occupational therapists, established interrater reliability for data collection procedures. Before conducting the study, the researchers obtained approval from the institutional review boards of the participating researchers’ institutions, including a waiver of written consent. A member of the research team screened each potential participant to ensure absence of impairments that prevented participation and obtained each participant’s sex, age, and hand dominance. On completing the screening and obtaining verbal assent from each potential participant, data collection occurred following ASHT23 www.archives-pmr.org
standards, including having the dynamometers set at the second handle position. Each participant sat in a chair with his/her feet flat on the floor, shoulder adducted and neutrally rotated, elbow flexed at 90 , forearm in a neutral position, and wrist positioned between 0 and 30 extension and between 0 and 15 ulnar deviation. A researcher gave verbal instructions and demonstrated each testing position. Participants received verbal encouragement to exert maximal force during each trial. Researchers tested each participant using 3 consecutive trials for each hand to collect grip, tip pinch, lateral pinch, and palmar pinch strength data. To prevent dropping, researchers supported dynamometers lightly at the base and the pinch gauges at the distal end. If a participant did not maintain correct position during testing, researchers discarded the measurement and repeated the trial.
Instrumentation This study used 3 Jamara hydraulic hand dynamometers to measure grip strength. The Jamar hydraulic hand dynamometer has established validity and reliability for measuring grip strength24-26 and has been described as the criterion standard for measuring hand strength.27-29 The study used 3 B & L Engineeringb pinch gauges to measure pinch strength (tip, lateral, palmar). Studies have found that the B & L Engineering pinch gauge has high calibration accuracy.30,31
Calibration Because of concerns about instrument calibration,30,32 researchers routinely verified instrument calibration using known weights and a verification station constructed according to procedures outlined by Fess.32 This process verified each instrument’s calibration after approximately every 30 to 45 participants. Throughout the study, a total of 117 individual instrument calibration verification occurred in the 6 instruments. Each instrument was required to obtain a minimum of .9994 Pearson product-moment correlation coefficient and a difference in means of
