Muscle strength refers herein to the maximal voluntary force or torque of short duration that skeletal muscles can bring to bear on the environment. Although the respiratory  and pelvic floor  muscles and the muscles of the trunk  can bring force to bear on the environment, it is the limb muscles whose strength is most often of interest. Of the many limb muscles, those generating grip force are measured most commonly. The frequent measurement of grip strength is likely based on several factors. First, grip strength is the simplest and least complicated of a plethora of instrumented muscle strength measures; this is true even though procedures used to measure it are not fully standardized . Second, there is some, albeit inconsistent, evidence that grip strength tends to reflect overall muscle strength . Beyond these factors, grip strength has clinical and prognostic value. These values are the focus of this review.
CLINICAL VALUE OF GRIP STRENGTH
Herein, grip strength is considered to have clinical value because of its ability to characterize the current strength of an individual. The clinical value of grip strength is also supported by its association with other concurrent clinical measures of importance.
Characterizing current strength
The current strength of an individual can be interpreted in relation to values obtained from ostensibly normal individuals. These values may be norms for comparable individuals or T-scores derived from healthy young adults.
Numerous studies have purported to provide normative values for grip strength, either for specific strata or on the basis of regression equations including relevant independent variables. In 2006 Bohannon et al. used meta-analysis to generate stratified grip strength norms from data obtained from 3317 adults in 12 studies. After the analysis of subsets of the data, Bohannon et al.[7,8] concluded that the consolidation of grip strength data may be justified for adults 20–49 years of age but not for adults greater than 75 years. More recently, numerous studies providing normative grip strength data have been published. Table 1[9,10▪,11–16] summarizes eight studies involving sample sizes in excess of 2000 participants. The studies originated in the UK or Ireland, Japan, South Africa, the Netherlands, the USA, and China. Most of these studies provide norms for older adults, but two include data for children. The Jamar dynamometer, considered by some to be the gold standard among hand-grip dynamometers , was used to measure grip strength in most (but not all) of the studies. Norms provided in the studies are sometimes presented separately for each hand (i.e., left and right or nondominant and dominant) [9,14,15], but at other times norms are based on the maximum force measured without reference to the hand from which they were obtained [10▪,11,13,17]. Reported norms always take sex and age into account. However, other variables associated with grip strength are also used to provide more refined norms. These include height and weight [9,11–14], self-rated health and functional disability , and number of chronic diseases . Recent studies other than those summarized above and in Table 1 have provided additional normative values. They, however, involve smaller samples, and thus provide potentially less dependable estimates of normal grip strength [17–24].
Whereas norms can provide an age-relevant standard for determining an individual's status, T-scores provide a young age standard to which the status of older adults can be compared. Although T-scores are used most often to compare the bone density of older adults with that of younger adults, grip strength T-scores can be used in a similar fashion [10▪,20,25,26▪]. This is an important alternative as it provides an opportunity to see how the strength of an older adult may have declined with age. Having grip strength comparable to younger adults is certainly more desirable for an older adult than having grip strength comparable to other older adults whose strength has also declined with age. Bohannon and Magasi [26▪] used data from the National Institutes of Health Toolbox project to derive T-scores and identify dynapenia in adults 60–85 years of age. Defined as having grip strength that was more than 1.0 standard deviation below the mean for healthy 20–40 year olds, dynapenia was present in the majority of men and women 70–85 years of age.
Association with concurrent clinical measures
Figure 1 shows the association of grip strength with various concurrent clinical measures. Muscle weakness, as measured by hand-grip dynamometry, is often used alone or in conjunction with other measures to describe nutritional status or body composition (e.g., muscle mass). Most notably, hand-grip force stratified by sex and BMI has been used along with unintentional weight loss and three other variables to define frailty . Grip force so stratified has also been used along with muscle mass and physical performance to define sarcopenia . Significant and strong correlations have been reported between the grip strength and muscle mass (determined by bioelectrical impedance) of older community-dwelling women  and older sarcopenic adults residing in assisted living [30▪▪]. A significant correlation between grip strength and muscle mass has also been reported for nonsarcopenic adults residing in assisted living, but the correlation was only of fair magnitude [30▪▪]. Fülster et al. demonstrated that the grip strength of patients with heart failure was significantly lower if they had muscle wasting identified by dual radiograph absorptiometry. Itoh et al. found strong correlations between the grip strength and muscle mass of patients hospitalized with liver related problems. The correlations were somewhat higher when muscle mass was quantified with computerized tomography rather than bioelectrical impedance. Among hospitalized patients grip strength has been shown to correlate with adductor pollicis muscle thickness, midarm circumference , and the Patient-Generated Subjective Global Assessment of nutritional status [32,33]. Flood et al. found changes in grip strength to explain more than 40% of the variance in changes in the Patient-Generated Subjective Global Assessment over a 2-week period. Silva et al. showed that the grip strength of hospitalized pediatric patients ‘was independently associated with undernutrition as defined by BMI z scores’. Martín-Ponce et al. found low but significant correlations between grip strength and the serum albumin and Subjective Nutritional Scores of hospitalized older adults.
Numerous researchers have investigated the concurrent relationship between grip strength and other variables not focused on nutritional status or body composition. Of particular relevance is research addressing physical function. Ramlagan et al. reported functional disability to be significantly lower in older South African adults who had greater grip strength. Beseler et al.[37▪▪] documented a highly significant relationship between grip strength and walking performance as characterized using Functional Ambulation Categories and the Functional Classification of Sagunto Hospital Ambulation in older adults. Alley et al.[38▪▪] found walking speed to be related to grip strength. Using a gait speed criterion of 0.8 m/s, they identified grip strength cutpoints for differentiating older adults who walked above or below this criterion speed. They classified men and women as weak if their grip strengths were less than 26 kg and 16 kg, respectively. Martín-Ponce et al. documented a low but significant correlation between the grip strength and six-minute walk distance of older hospitalized adults. Patients with grip strength below the sample median walked less than half as far as patients with grip strength above the sample median. Research identifying a relationship between grip strength and walking notwithstanding, lower limb (knee extension) strength has been shown to explain walking performance as well or better than grip strength in some populations .
Grip strength is related to diverse health status variables as well. Specifically, grip strength has been shown to be diminished in individuals with a greater number of chronic diseases , lower in patients with depression  or reduced self-rated health , and less in nursing home residents than in rehabilitation inpatients and less in rehabilitation inpatients than in community-dwelling individuals . Grip strength is associated with the severity of Parkinson's disease .
PROGNOSTIC VALUE OF GRIP STRENGTH
Herein, the prognostic value of grip strength refers to its ability to forecast future outcomes. Grip strength is well established historically in this regard. In a 2008 review, Bohannon identified grip strength as an important predictor of future mortality, disability, complications, resource utilization, and discharge disposition . He concluded that ‘grip strength should be considered as a vital sign useful for screening middle-aged and older adults’. Numerous studies published over the past several years have reinforced grip strength as a robust predictor of mortality, hospital length of stay, and physical functioning (Fig. 1).
Recent studies have confirmed consistently that low-grip strength is a risk factor for mortality. Using data from over 139 000 adults residing in 17 countries, Leong et al. determined that grip strength was related to all-cause, cardiovascular, and noncardiovascular mortality over a median 4 years follow-up. They noted that ‘grip strength was a stronger predictor of all-cause and cardiovascular mortality than SBP’. McLean et al.[46▪▪] who pooled data from six cohort studies involving older adults, showed that weak grip was associated with 10-year mortality rates that were 63–74% higher in men and 48% higher in women. Koopman et al. found 20-month mortality to be lower in a sample of rural Africans with high hand-grip strength. Martín-Ponce et al. showed that both in-hospital and postdischarge mortality were higher in patients with low hand-grip strength. According to Matos et al. all-cause mortality over 4 years among Brazilians receiving hemodialysis was higher if they had weaker grip strength. Hand-grip strength was shown to be highly predictive of survival in a study of Canadians with advanced cancer . The mean survival time was 51.9 weeks for patients with grip strength at or above the 50th percentile but only 23.3 weeks for patients at or below the 10th percentile. Mendes et al. noted ‘an, approximate, three-fold decrease in probability of discharge alive’ for patients with low-grip strength. Finally, Kim et al. examined the value of muscle mass, knee extension strength normalized against body weight and grip strength for predicting 5-year mortality; they found grip strength to be a more powerful predictor than either knee extension strength or muscle mass.
Low-grip strength is predictive of longer hospital lengths of stay. This has been demonstrated for patients hospitalized with cancer , older adults hospitalized in Malaysia , Portuguese adults admitted to medical or surgical units [53▪], and older adults admitted to the rehabilitation ward of a community hospital .
Grip strength measured soon after hip fracture is predictive of later physical functioning. Di Monaco et al. reported fair but significant correlations between grip strength measured before rehabilitation and Barthel Index scores and Timed Up and Go test performance after rehabilitation. The correlations remained significant after adjustment for confounders. They also found grip strength measured before rehabilitation to correlate significantly with Barthel Index scores at 6-month follow-up [56▪]. Grip strength measured at the time of admission has been shown by Savino et al. to be associated with ‘both incident and persistent walking recovery’.
Grip strength can provide an indication of an individual's overall strength. Grip strength also informs regarding nutritional status and muscle mass, physical function, and health status. It is predictive of morality, hospital length of stay, and physical function. Grip strength should be considered for routine use as a vital sign.
Financial support and sponsorship
Conflicts of interest
Dr Bohannon is a paid consultant with Hoggan Scientific.
REFERENCES AND RECOMMENDED READING
Papers of particular interest, published within the annual period of review, have been highlighted as:
- ▪ of special interest
- ▪▪ of outstanding interest
1. Rhee MH, Kim LJ. The changes of pulmonary function and strength according to time of day: a preliminary study. J Phys Ther Sci 2015; 27:19–21.
2. Chevalier F, Fernandez-Lao C, Cuesta-Vargas A. Normal reference values of strength in pelvic floor muscle of women: a descriptive and inferential study. BMC Womens Health 2014; 14:143.
3. Guilhem G, Giroux C, Couturier A, Maffiuletti NA. Validity of trunk extensor and flexor torque measurements using isokinetic dynamometry. J Electromyogr Kinesiol 2014; 24:986–993.
4. Roberts HC, Denison HJ, Martin HJ, et al. A review of measurement of grip strength in clinical and epidemiological studies: towards a standardized approach. Age Ageing 2011; 40:423–429.
5. Bohannon RW, Magasi SR, Bubela DJ, et al. Grip and knee extension muscle strength reflect a common construct among adults. Muscle Nerve 2012; 46:555–558.
6. Bohannon RW, Peolsson A, Massy-Westropp N, et al. Reference values for adult grip strength measured with a Jamar dynamometer: a descriptive meta-analysis. Physiotherapy 2006; 92:11–15.
7. Bohannon RW, Peolsson A, Massy-Westropp N. Consolidated reference values for grip strength of adults 20 to 49 years: a descriptive meta-analysis. Isokinet Exer Sci 2006; 14:221–224.
8. Bohannon RW, Bear-Lehman J, Desrosiers J, et al. Average grip strength: A meta-analysis of data obtained with a Jamar dynamometer from individuals 75 years or more of age. J Geriatr Phys Ther 2007; 30:28–30.
9. Spruit MA, Sillen MJ, Groenen MT, et al. New normative values for handgrip strength: results from the UK Biobank. J Am Med Dir Assoc 2013; 14:775e5-e11.
10▪. Dodds RM, Sydall HE, Cooper R, et al. Grip strength across the life course: normative data from twelve British studies. PLOS ONE 2014; 9:e113637.
This study provides normative values for grip strength using a sample of almost 50 000 individuals.
11. Kenny RA, Coen RF, Frewen J, et al. Normative values of cognitive and physical function
in older adults: findings from the Irish longitudinal study on aging. J Am Geriatr Soc 2013; 61:S279–S290.
12. Seino S, Shinkai S, Fujiwara Y, et al. Reference values and age and sex differences in physical performance measures for community-dwelling older Japanese: a pooled analysis of six cohort studies. PLOS ONE 2014; 9:e99487.
13. Ramlagan S, Pelzer K, Phaswana-Mafuya N. Hand grip strength and associated factors in noninstitutionalized men and women 50 years and older in South Africa. BMC Res Notes 2014; 7:8.
14. Ploegmakers JJW, Hepping AM, Geertzen JHB, et al. Grip strength is strongly associated with height, weight, and gender in childhood: a cross sectional study of 2241 children and adolescents providing reference values. J Physiother 2013; 59:255–261.
15. Yorke AM, Curtis AB, Shoemaker M, et al. Grip strength values stratified by age, gender, and chronic disease status in adults aged 50 years and older. J Geriatr Phys Ther 2015; (in press).
16. Auyeung TW, Lee SWJ, Leung J, et al. Age-associated decline in muscle mass, grip strength and gait speed: a 4-year longitudinal study of 3018 community-dwelling Chinese. Geriatr Gerontol Int 2014; 14 (Suppl 1):76–84.
17. Mohammadian M, Choobineh A, Haghdoost A, et al. Normative data of grip and pinch strength in healthy adults of Iranian population. Iranian J Publ Health 2014; 43:1113–1122.
18. Lee JE, Kim KW, Paik N-J, et al. Evaluation of factors influencing grip strength in elderly Koreans. J Bone Metab 2012; 19:103–110.
19. Shim JH, Roh SY, Kim JS, et al. Normative measurements of group and pinch strengths in 21st
century Korean population. Arch Plast Surg 2013; 40:52–56.
20. Montalcini T, Migliaccio V, Yvelise F, et al. Reference values for handgrip strength in young people of both sexes. Endocrine 2013; 43:342–345.
21. Ervin RB, Fryar, Wnag CY, et al. Strength and body weight in US children and adolescents. Pediatrics 2014; 134:e782–e789.
22. Tveter AT, Dagfinrud H, Moseng T, et al. Health-related physical fitness measures: reference values and reference equations for clinical practice. Arch Phys Med Rehabil 2014; 95:1366–1373.
23. de Souza MA, de Jesus Alves de Baptista CR, Baranauskas Benedicto MM, et al. Normative data for hand-grip strength in healthy children measured with a bulb dynamometer: a cross-sectional study. Physiotherapy 2014; 100:313–318.
24. Omar MT, Alghadir A, Al Baker S. Norms for hand grip strength in children aged 6-12 years in Saudi Arabia. Dev Neurorehabil 2015; 18:59–64.
25. Cheung CL, Nguyen US, Au E, et al. Association of handgrip strength with chronic diseases and multimorbidity; a cross-sectional study. Age (Dordr) 2013; 35:929–941.
26▪. Bohannon RW, Magasi S. Identification of dynapenia in older adults through the use of grip strength t-scores. Muscle Nerve 2015; 51:102–105.
This study provides grip strength t-scores ad shows how they can be used to identify dynapenia in older adults.
27. Fried LP, Tangen CM, Walston J, et al. Frailty in older adults: evidence for a phenotype. J Gerontol: Med Sci 2001; 56A:M146–M156.
28. Cruz-Jentoft AJ, Baeyens JP, Bauer JM, et al. Sarcopenia: European consensus on definition and diagnosis. Age Ageing 2010; 39:412–423.
29. Steffl M, Bohannon RW, Houdova V, et al. Association of clinical measures of sarcopenia in a sample of community-dwelling women. Isokinet Exerc Sci 2015; 23:41–44.
30▪▪. Campbell TM, Vallis LA. Predicting fat-free mass index and sarcopenia in assisted-living older adults. Age 2014; 36:9674.
This study reports significant relationships between grip strength and muscle mass among both sarcopenic and nonsarcopenic adults residing in assisted living.
31. Fülster S, Tacke M, Sandek A, et al. Muscle wasting in patients with chronic heart failure: results from the studies investigating comorbidities aggravating heart failure (SICA-HF). Eur Heart J 2013; 34:512–519.
32. Itoh S, Shirabe K, Yoshizumi T, et al. Skeletal muscle mass assessed by computed tomography correlates with muscle strength and physical performance at a liver-related hospital experience. Hepatol Res 2015; (in press).
33. Guerra RS, Fonseca I, Pichel F, et al. Handgrip strength and associated factors in hospitalized patients. JPEN 2015; 39:322–330.
34. Flood A, Chung A, Parker H, et al. The use of hand grip strength as a predictor of nutritional status in hospital patients. Clin Nutr 2014; 33:106–114.
35. Silva C, Amaral TF, Silva D, et al. Handgrip strength and nutritional status in hospitalized pediatric patients. Nutr Clin Pract 2014; 29:380–385.
36. Martín-Ponce E, Hernández-Betancor I, González-Reimers E, et al. Prognostic value of physical function
tests: hand grip strength and six-minute walking test in elderly hospitalized patients. Scientific Reports 2014; 4:7530.
37▪▪. Beseler MR, Rubio C, Duarte E, et al. Clinical effectiveness of grip strength in predicting ambulation of elderly inpatients. Clin Interv Aging 2014; 9:1873–1877.
This study shows grip strength to be associated with walking classified using two different scales.
38▪▪. Alley DE, Shardell MD, Peters KW, et al. Grip strength cutpoints for the identification of clinically relevant weakness. J Gerontol: Med Sci 2014; 69:559–566.
This study reports specific grip strength cutpoints for men and women who walk slowly.
39. Martien S, Delecluse C, Boen F, et al. Is knee extension strength a better predictor of functional performance than handgrip strength among older adults in three different settings. Arch Gerontol Geriatr 2015; 60:252–258.
40. Fukumori N, Yamamoto Y, Takegami M, et al. Association between hand-grip strength and depressive symptoms: Locomotive Syndrome and Health Outcomes in Aizu Cohort Study (LOHAS). Age Ageing 2015; (in press).
41. Hansen AW, Beyer N, Flensborg-Madsen T, et al. Muscle strength and physical activity are associated with self-rated health in a Danish population. Prev Med 2013; 57:792–798.
42. Roberts HC, Syddall HE, Sparkes J, et al. Grip strength and its determinants among older people in different healthcare settings. Age Ageing 2015; 43:241–246.
43. Roberts HC, Syddall HE, Butchart JW, et al. The association of grip strength with severity and duration of Parkinson's: A cross-sectional study. Neurorehabil Neural Repair 2015; (in press).
44. Bohannon RW. Hand-grip dynamometry predicts future outcomes in aging adults. J Geriatr Phys Ther 2008; 31:3–10.
45. Leong DP, Teo KK, Rangarajan S, et al. Prognostic value of grip strength: findings from the Prospective Urban Rural Epidemiology (PURE) study. Lancet 2015; (in press).
46▪▪. McLean RR, Shardell MD, Alley DE, et al. Criteria for clinically relevant weakness and low lean mass and their longitudinal association with incident mobility impairment and mortality. J Gerontol: Med Sci 2014; 69:576–583.
This study shows how 10-year mortality is remarkably higher in men and women with low-grip strength.
47. Koopman JJE, van Bodegom D, van Heemst D, et al. Handgrip strength, aging and mortality in rural Africa. Age Ageing 2015; (in press).
48. Matos CM, Silva LF, Santana LD, et al. Handgrip strength at baseline and mortality risk in a cohort of women and men on hemodialysis: a 4-year study. J Ren Nutr 2014; 24:157–162.
49. Kilgour RD, Vigano A, Trutschnigg B, et al. Handgrip strength predicts survival and is associated with markers of clinical and functional outcomes in advanced cancer patients. Support Care Cancer 2013; 21:3261–3270.
50. Mendes J, Alves P, Amaral TF. Comparison of nutritional status assessment parameters in predicting length of hospital stay in cancer patients. Clin Nutr 2014; 33:466–470.
51. Kim YH, Kim KI, Paik N-J, et al. Muscle strength: A better index of low physical performance than muscle mass in older adults. Geriatr Gerontol Int 2015; (in press).
52. Keevil V, Mazzuin Razali R, Chin AV, et al. Grip strength in a cohort of older medical inpatients in Malaysia: a pilot study to describe the range, determinants, and association with length of hospital stay. Arch Gerontol Geriatr 2013; 56:155–159.
53▪. Mendes J, Azevedo A, Amaral TF. Handgrip strength at admission and time to discharge in medical and surgical inpatients. JPEN J Parenter Enteral Nutr 2014; 38:481–488.
This study demonstrates that hospital length of stay is longer for adults with lower grip strength.
54. Roberts HC, Syddall HE, Cooper C, et al. Is grip strength associated with length of stay in hospitalized older patients admitted for rehabilitation? Findings from the Southampton grip strength study. Age Ageing 2012; 41:641–646.
55. Di Monaco M, Castiglioni C, De Toma E, et al. Handgrip strength but not appendicular lean mass is an independent predictor of functional outcome in hip-fracture women: a short-term prospective study. Arch Phys Med Rehabil 2014; 95:1719–1724.
56▪. Di Monaco M, Castiglioni C, De Toma E, et al. Handgrip strength is an independent predictor of functional outcome in hip-fracture women: a prospective study with 6-month follow-up. Medicine 2015; 94:e542.
This study shows grip strength measured before the beginning of rehabilitation to be predictive of functional independence 6 months later.
57. Savino E, Martini E, Lauretani F, et al. Handgrip strength predicts persistent walking recovery after hip fracture surgery. Am J Med 2013; 126:1068–1075.