norms forhand gripstrength · archives of disease in childhood, 1984, 59, 453-459...

Archives of Disease in Childhood, 1984, 59, 453-459

Norms for hand grip strengthD G NEWMAN, J PEARN, A BARNES, C M YOUNG, M KEHOE, AND J NEWMAN

Department of Child Health, University of Queensland, Australia

SUMMARY Norms for hand grip strength of healthy children are presented. Sex and age specificcentiles for age 5 to 18 years have been determined using a portable strain gauge dynamometerwith an accuracy of 0O5 N. The test group comprised 1417 healthy, urban school children from amiddle class suburb of Brisbane. Mean maximum grip strength (of four tests, two with each hand)and mean peak grip strength (best of four tests) were recorded. Mean values of peak grip strengthwere 10 to 15% higher than the average maximum grip in all age groups. At all ages girls had a

reduced grip strength compared with boys and although boys manifested a continual,approximately linear increase in grip strength through all age groups, girls manifested anapproximately linear increase up to 13 years after which mean hand grip usually remainedconstant. By the age of 18 years boys had a mean grip strength some 60% higher than girls.Correlations with height and weight are also presented. 'Handedness' influenced grip strengthand was most noticeable in children aged over 10 years. The clinical use of hand grip strengthcentiles for the early indication of neurological and muscular disorders and for following thenatural history of neuromuscular disease is discussed.

Hand grip strength is important as an index ofgeneral health and as a screening test for theintegrity of both the upper motor neurons andfunction of the motor unit. Testing against agecorrected norms for hand grip strength would form ahelpful clinical test in the differential diagnosis ofneuromuscular disease and in monitoring the natu-ral history of acute and chronic diseases affecting thelower motor neuron.

Grip strength has come to be regarded as the mostreliable clinical measure of human strength. It iswidely used in adults as an indication of strength infitness testing,23 and as such is seen as the singleitem most reasonably representative of total bodystrength. 6 Occupational therapists have investi-gated grip strength measures as an index of strengthand dexterity in university students7 and have usedthe test in the assessment of clinical progress aftertreatment.8 9 It has also been used for more than 30years to assess hand function and general weaknessin adult patients with rheumatoid arthritis."'1To be useful as a bedside and clinical tool in the

management of childhood diseases, age centiles forhand grip strength are required. Tests currently usedin surveillance of muscular activity in children withprogressive neuromuscular disease (such as thetimed stair climb) are complicated by a multiplicityof factors such as cardiopulmonary reserve and the

inability to separate isometric from isotonic func-tion. A simple, practical, and objective measure ofisometric muscle contraction would prove useful inthe progressive monitoring of muscular strength ofthese children.

Studies of grip strength (all from the United-States) have used a variety of dynamometers-pneum,atic and hydrolic manometers, springloaded resistances, and cable tensiometers. 11-15Most studies have sampled adults only and nonehave included children under 10 years of age.Almost all the dynamometers in clinical use haverelatively narrow ranges and test essentially isotoniccontraction. Cable tensiometers, despite their manyadvantages, are cumbersome and not really port-able. The recent development of a portabledynamometer, robust yet sensitive, which measuresisometric muscle contraction only and has linearload response curves at a wide range of loads hasenabled hand grip strength to be measured accu-rately in children' and we report a study to establishhand grip strength norms for Caucasian children.

Subjects and methods

Subjects. The subjects comprised all childrenattending the Indooroopilly State School, a primaryschool in a middle class suburb of Brisbane (major

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454 Newman, Pearn, Barnes, Young, Kehoe, and Newman

Table 1 Number of children by age group and sex

Age (yrs) Boys Girls

5 9 46 39 447 41 308 46 459 38 4510 57 5811 70 5212 71 5813 100 8214 85 7815 79 7016 55 5817 31 4218+ 18 12

urban metropolis of 1 000 000 people) and all pupilsat the Indooroopilly State High School in the samearea. There were 739 boys and 678 girls. Age andsex distributions are shown in Table 1. The subjectswere all Caucasian and over 90% were of AngloSaxon origin.

Dynamometer. The dynamometer, which has beendescribed previously and is shown in Figs. 1 and 2,'operates on the strain gauge principle. It consists ofa semi rigid steel U shaped handpiece to which astrain gauge is cemented. When the arms of thehandpiece are squeezed (actual physical movementis very small indeed and does not exceed 8 mm)changes in electrical resistance are proportional tothe force applied. These changes in resistance aremeasured by incorporating the gauge as one arm ofa balanced Wheatstone bridge. There is a peak holdreading system whereby rapidly fluctuating forcesmay be frozen at peak by the meter. The handpiece

Fig. 1 The portable, strain gauge dynamometer.

T s1&s2

G

...&....S.2..lip~~~~

H Handles: Extensions of steel barcovered with moulded blackpolythene.

T Protective White PVC 48 mm internaltube sleeve: diameter plumber's pipe.

Affixed to lower bar B2 byscrews P.

G Air gap between two arms of hand-piece.

B1 and B2 Bar arms The U-shaped handpieceswere cut from a single plate ofmilk steel bar, 12 mm thick.

P Screws-pins Attachment of lower hand-piece B2 to protective sleeve.

S1 and S2 Strain-gauge Affixed at right angles toupper arm B1 by Philipsgauge cement (PR 9244/04).

L Insulated electricalleads Connected to Bridge.

Fig. 2 The hand piece ofthe strain gauge dynamometer.

is a U shaped rigid steel bar in a protective hollowPVC pipe and two sizes were constructed for use inthis study-a smaller one for 6 and 7 year olds andthe larger one for all other children. Two gauges(120 ohm, EA06, 2-065, GF Micromeasurements)are cemented to the handpiece to provide automaticcompensation for environmental, temperature in-duced changes in resistance. The PVC pipe mount-ing provides a standard handhold for the contra-lateral hand/body position during testing.'3 16 Withthe subject seated this ensures a standardisedposture for the test which is important. The electri-cal bridge is a standard commercial model, StrainIndicator type 1200S with peak hold attachment(Strainstall, UK). The U shaped handpiece is easilymanufactured from a rod of iron or steel accordingto the details shown in Fig. 2. Unlike the common,commercially available clinical dynamometers (forexample the isotonic, Smedley's type ring gripinstrument), this more accurate instrument recordsisometric force which is more appropriate for testingchildren. Calibration was performed by hangingstandard weights from each of the handpieces, using3 kg increments. The functional range of theinstrument-0*5 to 1500 N-encompasses the rangeof human hand grip strength from that of a tinyneonate up to the force deliverable by an Olympicweightlifter.



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Norms for hand grip strength 455

Procedure. Each school class was given verbalinstructions and a demonstration before being testedand further instructions were provided at the time ofthe test. To encourage the children to make theirbest effort in a spirit of competition, each waspresent for the testing of at least one prior subjectand was also urged to give a maximum effort. Forthe test each subject was seated facing the re-searcher with the equipment mounted on a tablebeside them so that the gauge was visible to bothand the handpiece, attached to its length of cord,could be passed easily between them. The resear-cher demonstrated the hand grip squeeze and thesubject was then allowed one practice squeeze. Eachhand was then tested alternately, 10 seconds apart,and the test repeated, giving two readings for eachhand. It has been shown that in children more thantwo squeezes in a series produces a dramatic fatigueeffect and for this reason we believe that the usualthree squeeze series (with the mean calculated fromthese) is erroneous. This is especially so in youngerchildren in our experience. All four readings wererecorded, as well as handedness, height, weight, andage.

Results

Repeatability of hand grip measurements. Data on1417 subjects were analysed. Data for boys and girlswere analysed separately. Because of volitionalmode inherent in all strength testing studies, specialinterpretive care is needed with results. It is knownfrom earlier studies that (a) fatigue occurs quicklyand is universal after five or 6 sequential tests, (b)the variation in maximum grip strength at differenttest sessions is less than that between sequentialtests in the one sequence, and (c) that maximum andaverage strengths (in the sequence of tests) aredifferent and should be recorded as separate indicesof strength.Hand grip measurements were first analysed to

compare the degree of variability between repeatmeasurements on the same subjects with the rangeof values found between subjects in the same agegroup. This was done by estimating the between andwithin subject components of variance and express-ing the figures as a ratio (Table 2). Large values forthis ratio imply that measurements are repeatable byindividuals and is a desirable feature of this type ofresearch variable.

In boys aged 7 to 15 years this ratio took a valuebetween 2 5 and 4 5. Older and younger boys hadsmaller ratios implying that individuals are lessconsistent outside this age range. Girls showed thesame pattern of greater consistency in the age

Table 2 Ratio of between subject variance componentand within subject variance component

Age (yrs) Boys Girls

5 0-43 1-726 1 51 1-077 3-07 2-178 339 2319 293 3 1510 398 32311 2-64 1-7312 2-51 2-9213 4-51 2-1014 3-06 2-6415 3-49 1-6016 1-73 1-9517 3-08 1-2918+ 1-23 1-02

groups 7 to 15 years than in older and youngergroups. Over all ages there was slightly less con-sistency among girls than boys.Some of the within subject variability was due to

differences between right and left grip recordings.When this source of variability was removed fromthe within subject variance component the ratio washigher. With the possible exception of five year oldchildren and those of late teenage the analysesindicated an acceptable degree of consistency in thehand grip measurements standardised in the formatdescribed above. With hand grip strength based onfour repeat measurements per subject we found thateven for children outside the 7 to 15 year age groupthe data were satisfactory.

Age effects on average hand grip recordings. Twosummary statistics based on the four hand griprecordings were calculated; the average and themaximum of the four recordings. Sample variancesfor maximum values were usually larger than thecorresponding figures based on the averages. Themean value of the maximum hand grips werebetween 10% and 15% higher than the mean valuefor individual averages for all age groups.Age related increases in strength are shown in

Fig. 3. Boys showed a continual, approximatelylinear increase in strength throughout all agegroups. Girls showed an approximately linear in-crease up to the age of 13 years after which the meanhand grip remained relatively constant. At all agesgirls had lower average values than boys and afterpuberty this difference increased, until by the age of18 years boys had a mean hand grip 60% higher thangirls. Because of (a) the similarity between theaverages and peak grip strength and (b) the slightlygreater variability associated with peak gripstrengths, mean values only have been used in theconstruction of sex specific centiles.



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400.(Acric

Boys~Mean of

,.rnOXImum4,00- Man of

XP av.Oeraverages

5300 8 11114 15 16 17 18~~~~~~~~~~~~~~Meanof

in boys and girlsaccording tonage

V i b averages100.0__

5 lb79 10 1 12 t3 1 5 16 17 8Age Iyrs)

Fig. 3 Means ofaverage and maximum hand grip strengthin boys and girls according to age.

Variability between subjects' average hand griprecordings. The standard deviations for each of thepeer group distributions increased as the means ofthe distributions became larger. Variability ex-pressed as coefficients of variations (Table 3) wasfairly constant for all age groups and both sexes,being between 8% and 15%. For both boys and girlsthe most variable age groups were the younger ones(up to 8 years of age) and those with the lowestcoefficients of variations were the 9 to 13 year agegroups.An indication of the range of hand grip recordings

found in this study is given in Figs. 4 and 5, whichshow the median and five, 25, 75, and 95 centilerecordings for each year of age, by sex. The five and95 centile points may be interpreted as normalranges in the sense that 90% of a similar populationof children would be expected to have hand griprecordings within these limits.

Table 3 Coefficients of variation of the average of the fourhand grip recordings by age group and sex

Age (yrs) Boys Girls(%) (%)

5 15-9 12 26 14-2 14-67 12-9 12 78 11-3 15-59 9-8 9-810 7-7 10-711 8-8 10-412 8-9 9-113 8-5 10-614 10-2 11*015 11*4 11*516 13-6 10-817 10-7 11*618+ 11-5 11-5

Girls

*0 300-

a~~~~~~~~~~~~~da*a_s _ -- v /it~~~~~~-D-:o > _ , ~~~~~~~~~~~~~~5thD

Z¢ 200- . . .a

6 7 8 9 10 11 12 13 14 15 16 17 18

Age (yrs)

Fig. 4 Median and 5, 25, 75, and 95 centile recordings ofhand grip strength for each year ofage in girls.

_95th, 75th

Boysz' __

g ,' > ~~~~~~~~~25th

'/% , ~~~~5th

,,, 400.

a.CC

a

do 300-

a

.-

C4

ca . 200.c

_M@-

0

p oo-

6 7 8 9 10 11 12 3 14 15 16 17 18+Age (yrs)

Fig. 5 Median and 5, 25, 75, and 95 centile recordings ofhand grip strength for each year ofage in boys.

Influence of height and weight on hand grip. Subjectheight and weight were as strongly associated withhand grip strength as age (Figs. 6 and 7). Thisoccurred largely because of correlations betweenage, height and weight. Even within the age groupclasses, however, weight and height showed correla-tions with hand grip. For instance the correlationbetween hand grip and weight within age groupclasses was greater than 0-5 for some and was rarelyless than 0-3.These results suggest that at least some of the

subject to subject variation may be explained ifeither the subjects' heights or weights, or both aretaken into account in addition to the subjects' ages.Regression analyses were done to investigate this. Itwas found that linear weight and height terms werehighly statistically significant for both boys and girls.The best of these regression models was one inwhich both linear height and linear weight termswere used. Table 4 summarises the findings in thesemodels. The implications of height and weight



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- Girls

100 110 120 130 140 150 160 170 180Height (cm)

Fig. 6 Mean recordings ofhand grip strength related toheight in boys and girls.

Weight class (kg)

Fig. 7 Mean recordings ofhand grip strength related toweight in boys and girls.

effects are best illustrated by example. The coeffi-cients for the girls in Table 4 suggest that for each kgthat a subject was above or below her age group'smean weight, her hand grip rose or fell on average0-99 of one unit, and for each cm above or below theaverage height, the hand grip rose or fell by 1-13units.Although these height and weight corrections

were highly significant, they do not account for agreat deal of the subject/subject variation which isunaccounted for by age class (Table 4). It is,therefore, debatable whether the slight improve-ment in accuracy compensates for the necessity ofhaving to make the height and weight corrections.


Table 4 Weight and height regression coefficient andtheir standard errors (SE) for average hand griprecordings after first removing year of age effects.(Regression coefficients may be used to calculate correctionsfor expected hand grip recordings when a subject's weightand height are known in addition to age)

Coefficient for Coefficient for % of varianceweight (SE) (kg) height (SE) (cm) unaccounted for

by age butaccounted for byheight and weight(%)

Boys 1-92 (0-26) 1-50 (0-29) 24-7Girls 0-99 (0-17) 1-13 (0-21) 15-5

For a girl weighing x kg greater than the mean weight for her age and Y cmtaller than the corresponding mean height. the correction to be made to theexpected hand grip in Fig. 2 is 0-99x + 1-13y.

Various attempts were made to find other heightand weight based corrections which would improvefurther the accuracy of expected hand grip predic-tions. It was thought that separate linear height andweight corrections for each age group might achievethis but, surprisingly, this was not the case. In fact,the estimated corrections for height and weight foreach group were remarkably similar for all but thevery young and very old age groups. In these agegroups there was some suggestion that height andweight had slightly smaller influences than at in-termediate ages. Overall, there was no evidence thatdifferent corrections for each age group would bebeneficial.We thought that the underlying height and weight

influence on hand grip might be more complex thanhad been implied by simple linear corrections, andin particular that hand grip readings were probablyrelated to subject strength. Various non-linearcombinations of height and weight were calculatedas possible crude measures of strength. For instance,it was conjectured that the ratio of height and weightmight be related to strength by an over-turningcurve. That is, short heavy children at one extrememay be weaker on average than their normallyproportioned peers and this might also apply tothose at the other extreme-the tall, thin subjects.A quadratic correction for the height:weight ratiowhich allows for such an overturning relation wasinvestigated but proved no more advantageous thanthe more simple correction based on linear weightand height adjustments.

Influence of handedness on the right and left handgrips. The difference between the av rage of thetwo right and two left hand grips was c Llcilated foreach subject. These values are shown in Table 5 andthe extent to which they differ significantly from

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Table 5 Mean difjference between the average of the tworight and two left hand grip records. Evidence for adifference between hands is indicated by the probabilitythat the difference is not different from zero. (Number ofsubjects in parentheses)

Age Right handed subjects Left handed subjects(yrs)

Boys Girls Boys Girls

5 3-45 (9) 10-36 (4) - (0) -(()6 4.60 (31)' 1 57 (38) 1-30 (8) -7-77 (6)7 -3 01 (36) 5*01 (29)i -2-38 (5) -1)-36 (1)8 4-66 (45) 0 11 (38) -12-95 (1) -2 13 (7)9 13-62 (31)§ 11-22 (43)§ -0-96 (7) 0-00 (2)10 2-99 (56) 6-45 (53) -13 42 (1) -16-76 (5)11 8-07 (64)+ 12-92 (48)§ -20-11 (6)' -6-71 (4)12 14-34 (65 § 11 63 (49)§ -17-88 (6) -17 50 (9)13 9-03 (88) 9.17 (76) -11.17 (12) -27-93 (6)t14 10-81 (80)t 13-36 (75)§ 12(07 (5) -35-75 (3)t15 802 (79) 10 25 (68)1 - (0) 10-06 (2)16 15-77 (54) 13 17 (56)1 -60-33 (1) -70 38 (2)17 11-44 (29) 13-57 (41) -26 81 (2) -60 34 (1)18+ 0-00 (17) -4.47 (12) -140-24 (1) - (0)

P=<0-1; 'P=<0*05; $P=<0-01; iP=<0-001.

zero is shown for each age group and sex. Righthanded subjects of both sexes usually recordedhigher right hand readings than left hand ones at allages but this was most noticeable in children aged 9to 17 years. Left handed subjects showed the reverseand again this was most noticeable in children agedover 10 years. Fewer significant differences werefound for left handed than right handed children butthis was due to the difference in numbers rather thangreater differences in right handed children. Indeed,the opposite may be true. There was a suggestionthat the difference between the left hand and theright hand in left handed subjects was greater thanthe corresponding reversed difference in righthanded children.

Discussion

Although there are numerous published reports onhand strength many cover isolated groups, ofinterest only to specialists in a particular field, orsample only small numbers. Studies of a normativenature include: Pierson and O'Connell (in Califor-nia) who tested the grip strength of 299 adult mendrawn from populations representing different ageand physical activity requirements;" Schmidt andToews who presented the results of grip strengthtesting for 1128 men and 80 women employed by anAmerican corporation;'2 Swanson, Matev, and deGroot who established grip and pinch strength for100 adults in an attempt to add to the factual basefor reconstructive surgery of the hand;'3 Beasleywho sampled grip strength in 1524 American adultmen and 1238 women;'4 and Montoye and Lam-

phiear who tested grip and arm strength of 82% ofan entire community in Michigan comprising morethan 6000 subjects.15Human beinigs have long been and continue to be

fascinated by heir own muscular strength; they seekin particular to discover its attainable limits by allmanner of weight lifting, athletic, and endurancefeats. Fair grounds have traditionally catered to thisfascination by some measurement device where thestrong and not so strong may publicly demonstratetheir prowess in raising a strength indicator by theforce of a blow. 17 Among the earliest dynamometerswere those devised by the French to test anthropolo-gical theories of racial differences in strength,'8 anddevelopment of these has continued to thepresent. 17-21For clinical use it would seem that the average

hand grip strength based on four alternate handmeasurements per subject, classified by age, gives asufficiently consistent result for most purposes. Thisshows an approximately linear increase through allage groups in boys. Girls record lower hand gripvalues than boys at all ages and these values alsofollow an approximately linear progression with ageuntil the thirteenth year when they level out. Thediscrepancy in hand grip strength beween the sexeswidens thereafter throughout the teenage years.This is in line with the results of Kellor et a!8 whofound that by age 20 men have about twice the gripstrength of women. Interestingly, they as well asother researchers have noted that this gap narrowsin later years when women retain more of their gripstrength than men.

The authors thank the staff and students of the IndooroopillyPrimary and High Schools, Brisbane for their patience andcooperation in this study.

References

Pearn J, Bullock K. A portable hand-grip dynamometer. AustPaediatr J 1979;15:107-9.

2 Bookwalter KW. Grip strength norms for males. ResearchQuarterly 1950;21:249.

3 Cotton OJ, Johnson A. Use of the T-5 cable tensiometer gripattachment for measuring strength of college men. ResearchQuarterly 1968;41:454-6.

4 Wessel JA, Nelson RC. Relationship between grip strength andachievement in physical education among college women.Research Quarterly 1961 ;32:244-8.

5 Tinkle WF, Montoye HJ. Relationship between grip strengthand achievement in physical education among college men.Research Quarterly 1961;32:238-43.

6 Heyward V, McCleary L. Analysis of the static strength andrelative endurance of women athletes. Research Quarterly1975;48:703-10.

7 Nwuga VC. Grip strength and grip endurance in physicaltherapy students. Arch Phys Med Rehabil 1975;56:296-300.

8 Kellor M, Frost J, Silberberg N, Iversen I, Cummings R. Handstrength and dexterity. Am J Occup Ther 1971;25:77-83.



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Agnew PJ, Maas F. Hand function related to age and sex. ArchPhys Med Rehabil 1982;63:269-71.

'1 Myers DB, Grennan DM, Palmer DG. Hand grip function inpatients with rheumatoid arthritis. Arch Phys Med Rehabil1980;61:369-73.

" Pierson WR, O'Connell EK. Age, height, weight and gripstrength. Research Quarterly 1961;33:439-43.

12 Schmidt RT, Toews RPT. Grip strength as measured by theJamar dynamometer. Arch Phys Med Rehabil 1970;51:321-7.

13 Swanson AB, Matev IB, de Groot MD. The strength of thehand. Bull Prosthet Res 1970;10:145-54.

14 Beasley WC. Efficient estimators of normal adult grip strength.Arch Phys Med Rehabil 1973;54:573.

15 Montoye HJ, Lamphiear DE. Grip and arm strength in malesand females, age 10 to 69. Research Quarterly 1975;48:109-20.

16 Clarke HH. Recent advances in measurement and under-standing of volitional muscular strength. Research Quarterly1956;27:203.

17 Pearn J. Two early dynamometers. Neurol Sci 1978;37:127-34.18 Pearn J. Some early experiments on the measurement of human

strength in Port Jackson and Van Diemen's land. Med J Aust1978;2:167-9.

19 Bechtol CO. The use of a dynamometer with adjustable handspacings. J Bone Joint Surg 1954;34-A:820.

20 Lewey FH, Kuhn WG, Juditski JT. A standardized method forassessing the strength of hand and foot muscles. Surg GynecolObstet 1947,85:785.

21 An KN, Chao EYS, Askew U. Hand strength measurementinstruments. Arch Phys Med Rehabil 1980;61:366-8.

Correspondence to D Newman, Department of Speech andHearing, University of Queensland, St Lucia, Q4067, Brisbane,Australia.

Received 23 January 1984

Twenty five years ago

The fertility of mothers of diplegic children and the fate of their conception

T T S INGRAM (Edinburgh)

'The reproductive performance of 76 mothers of diplegic children was compared with that of mothers ofchildren suffering from other forms of cerebral palsy and of mothers from the general population. Themothers of diplegic children had had fewer pregnancies than those in the other groups though their averageage was slightly greater. There were fewer conceptions in the years immediately preceding and following thebirth of the diplegic child than at earlier or later periods.

Excluding from consideration the pregnancies which resulted in the birth of the patients, only 62% oftheir conceptions had produced healthy siblings who survived at the time of the study. In a high proportionthere had been abnormalities of pregnancy, labour or delivery.There appears to be an aetiological relationship between diplegia and impaired reproductive performance

of the mother.'

(Now termed 'relative infertility'. Murphy wrote about this in 1947 in his book Congenital Malformations,and the Baltimore group (Lilienfield and Parkhurst) termed it 'a continuum of reproductive casualty'. Yetthere are still doctors who ascribe every case of cerebral palsy to birth injury-presumably because the childwas born and birth is dangerous-ignoring all the prenatal factors. RONALD ILLINGWORTH).

Archives of Disease in Childhood 1959;34:357.



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