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Grip Strength in Youth Ice Hockey Players

Normative Values and Predictors of Performance

Toong, Tiffany1,2; Wilson, Katherine E.2; Urban, Karolina1,2; Paniccia, Melissa2,3; Hunt, Anne W.1,2,4; Keightley, Michelle1,2,4; Reed, Nick1,2,4

The Journal of Strength & Conditioning Research: December 2018 - Volume 32 - Issue 12 - p 3494–3502
doi: 10.1519/JSC.0000000000002815
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Toong, T, Wilson, KE, Urban, K, Paniccia, M, Hunt, AW, Keightley, M, and Reed, N. Grip strength in youth ice hockey players: Normative values and predictors of performance. J Strength Cond Res 32(12): 3503–3511, 2018—Grip strength is a simple, valid, and reliable tool for estimating overall muscular strength, a key component of health-related fitness and sport performance. To date, there is a paucity of up-to-date and developmentally sensitive grip strength norms specific to youth-athlete populations. The objectives of this study are to (a) establish normative grip strength values in youth ice hockey players, (b) descriptively compare these values with existing Canadian pediatric norms, and (c) explore the relationship between age, sex, body mass, and hockey playing level on grip strength performance. A sample of 690 male and female youth ice hockey players between the ages of 10 and 16 years were included. Participants completed assessments of maximal grip strength using a hand dynamometer on both hands. In addition, age, sex, body mass, and hockey playing level were collected. Maximal absolute grip strength, stratified by age and sex, was higher than previously published Canadian pediatric norms. Grip strength increased with age in both sexes. Males and females performed similarly until 12 years of age, after which point males had greater strength. Individuals with greater body mass had greater strength. For the nondominant hand, competitive players had greater strength than those playing house league or select. This study describes normative grip strength values in youth ice hockey players according to age, sex, body mass, and playing level. These athlete-specific norms may be used to help evaluate and monitor changes in grip strength over time in youth ice hockey players.

1Rehabilitation Sciences Institute, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada;

2Concussion Center, Bloorview Research Institute, Holland Bloorview Kids Rehabilitation Hospital, Toronto, Ontario, Canada;

3Children's Hospital of Eastern Ontario Research Institute, Ottawa, Ontario, Canada; and

4Department of Occupational Science and Occupational Therapy, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada

Address correspondence to Dr. Nick Reed, nreed@hollandbloorview.ca.

This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.

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Introduction

Muscular strength is a key component of physical fitness (8). Grip strength has been shown to correlate with an individual's general muscular strength (31), and is an assessment tool widely used in clinical practice, research, and athletic settings (25). In addition, grip strength measurements have been used to gain important insights into an individual's bone density (25), functional status, and general health (27). Furthermore, as a reliable, inexpensive, and easy-to-use tool (11), grip strength testing is currently included in professional sport combines (20) and national health surveys (32).

To interpret grip strength scores, normative values are needed so that an individual's performance can be directly compared with a reference population. However, to date, there is a paucity of up-to-date and developmentally sensitive grip strength norms for children and adolescents, despite routine use of grip strength within these age groups (23). As a result, there is a strong need for pediatric normative databases.

Furthermore, most of the normative studies conducted use nonathlete samples. However, grip strength is influenced by level of physical activity and training (19). For example, earlier studies have shown that adolescents who played school sports had higher grip strength than their non–sport-playing peers (17), and young competitive rock climbers had higher grip strength than nonclimbers (30). These studies suggest that typical pediatric grip strength norms may be inappropriate for use in youth athletes, particularly those competing in a sport with high grip strength demands.

The sport of ice hockey continues to grow in participation rate worldwide (17). With this increased participation comes a greater interest in research, specifically tools that can assess hockey-specific abilities important for performance success. Grip strength is required in most hockey-specific movements with players continually executing complex skills while gripping a stick. It is therefore likely that youth ice hockey players may have higher grip strength, given these neuromuscular adaptations from training and sport. As a result, typical norms may underestimate their performance. To the best of our knowledge, no studies have been conducted exploring normative grip strength performance in youth ice hockey players.

Previous studies have shown that age, sex, and body composition influence grip strength performance in youth (13,23,28). Grip strength increases with age (13,23,28) and males have been found to have higher grip strength than females (13,18,23). Furthermore, body mass has demonstrated a strong positive correlation with grip strength (13,23). Minor ice hockey, like other sports, is played at various levels ranging from recreational to highly competitive/elite, with the number of hours of training and competition varying accordingly. Thus, it is possible that grip strength could differ by playing level. An understanding of how these factors influence grip strength specifically in youth ice hockey players is important, and may add useful information when comparing performance with normative values.

Thus, the objectives of this study are to (a) establish normative grip strength values in healthy youth ice hockey players, (b) descriptively compare these values with existing Canadian pediatric norms, and (c) explore the relationship between age, sex, body mass, and playing level on grip strength performance. We hypothesize that absolute grip strength in our sample of youth ice hockey players will be higher than previously published pediatric norms. In addition, we expect grip strength to increase with age and males will be stronger than females at all ages. Finally, we hypothesize that grip strength will increase as body mass increases and competitive ice hockey players will have greater strength than house league/select players.

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Methods

Experimental Approach to the Problem

A cross-sectional design was used for this study. Grip strength was collected as part of a larger concussion preinjury/baseline study performed by trained research personnel (24). Participant characteristics including age, sex, height, body mass, and hockey playing level were also collected using a demographic form.

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Subjects

A convenience sample of 690 male and female youth ice hockey players between the ages of 10 and 16 years were included in this study (323 males and 367 females, age: mean ± SD, 13 ± 1.7 years [range 10 to 16 years]). Participants were recruited from youth hockey organizations in the Greater Toronto Area (Ontario, Canada). Individuals were excluded from the study if they had a musculoskeletal condition that would make grip strength measurement unsafe (e.g., sprained wrist), a diagnosis of developmental delay, or could not read or write in English. All participants and their legal guardian provided informed and written consent before participation. Ethics approval was obtained from the Holland Bloorview Research Ethics Board at Holland Bloorview Kids Rehabilitation Hospital.

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Procedures

Grip strength was measured using a Jamar Smedley hand dynamometer (Sammons Preston, Bolingbrook, IL, USA). Participants were told to squeeze the dynamometer maximally for 3 seconds while keeping a neutral upper-extremity position (standing upright, straight arm parallel next to the body, palm facing the body, and wrist neutral), as recommended by the Canadian Physical Activity Fitness and Lifestyle Approach protocol (7). Three consecutive trials were performed on each hand, with 10 seconds of rest given between trials. Verbal encouragement by research personnel was given during the trials to help promote maximal exertion. Maximal grip strength (kg), selected as the highest of the 3 trials, was recorded for both dominant and nondominant hands. To standardize each measurement, the dynamometer was adjusted for each participant based on hand size. Hand dominance was established by the preference of hand for handwriting.

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Statistical Analyses

Descriptive statistics (mean values, SDs, and percentiles) stratified by age and sex were calculated to establish normative dominant and nondominant hand grip strength values in participants. Maximal absolute grip strength values of youth ice hockey players in our sample were descriptively compared with Canadian population norms of Wong (32) at the 50th percentile (median). In addition, multiple regression analyses were performed to explore the effects of age, sex, body mass, and hockey playing level on dominant and nondominant hand grip strength in youth ice hockey players. The independent variables were age, sex (male and female), interaction between age and sex (product term of age × sex), body mass, and hockey playing level (house league/select, competitive). Before creating the product term and consistent with common practice, age was centered at its mean to decrease the multicollinearity produced by multiplicative terms (1). The assumptions of a linear regression (linearity, normality, independence of errors, and homoscedasticity) were all met. All statistical analyses were performed using SPSS Statistics Inc (version 24) with the threshold for statistical significance set to p ≤ 0.05.

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Results

Participants were 690 youth ice hockey players, aged 10–16 years. Demographic characteristics of these participants are reported in Table 1. Grip strength norms for dominant and nondominant hands are provided in Table 2, stratified by age and sex. Figure 1 shows a comparison between normative values found in our study with population-based norms collected from the Canadian Health Measures Survey from 2007–2013 (32). Maximal absolute grip strength values in youth ice hockey players in our study seem to be consistently higher than these published Canadian norms for both males and females aged 10–16 years.

Table 1

Table 1

Table 2

Table 2

Figure 1

Figure 1

Results of the multiple regression analysis showed an overall significant model for both dominant (F[5, 654] = 200.42, p < 0.005) and nondominant hands (F[5,649] = 177.691, p < 0.005).

The 5 predictors accounted for 60.2% (R2 adj = 0.602) of the variance in dominant hand grip strength and 57.5% (R2 adj = 0.575) of the variance in nondominant hand grip strength.

Age and sex demonstrated a significant interaction effect on grip strength in both dominant (β = −0.202, p < 0.005) and nondominant hands (β = −0.213, p < 0.005) (Table 3). The relationship between age and grip strength changed as a function of sex. Independent-sample t-tests confirmed that there were no significant differences in either dominant hand grip (t(123) = 4.22, p < 0.005) or nondominant hand (t(123) = 4.76, p < 0.005) grip strength between males and females until 12 years of age, after which point males were significantly stronger than females (Figures 2 and 3).

Table 3

Table 3

Figure 2

Figure 2

Figure 3

Figure 3

In addition, body mass also showed a significant effect for both dominant (β = 0.444, p < 0.005) and nondominant hand grip strength (β = 0.448, p < 0.005), whereby increased grip strength was found with increasing body mass. Playing level did not demonstrate a significant effect for the dominant hand (β = 0.035, p = 0.172). However, playing level did demonstrate a significant effect on grip strength for the nondominant hand (β = 0.056, p = 0.036), whereby participants playing at competitive levels had higher grip strength (26.1 ± 7.3 kg) than those competing at house league or select levels (23.2 ± 8.3 kg).

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Discussion

To the best of our knowledge, this is the first study to report normative grip strength values in a sample of youth ice hockey players. These norms provide a benchmark that coaches, trainers, researchers, and clinicians can use to evaluate youth ice hockey players. Furthermore, assessment of grip strength may play a role in strength monitoring and injury prevention (12).

On descriptive comparison, our results demonstrated that grip strength performance in youth ice hockey players was higher than previously reported Canadian norms, confirming our hypothesis. This is in line with earlier research that has shown that athletes may have stronger grip strength than nonathletes. For example, data from the American National Health and Nutrition Examination Survey indicate that adolescents who played school sports had stronger grip strength and performed more pull-ups compared with those who did not play school sports (17). Similarly, elite male field hockey players had greater grip strength in both hands than typical adult males (26). With respect to ice hockey, shooting, passing, and stickhandling all place a heavy demand on forearm and surrounding musculature, which may explain the increased grip strength seen in our sample. Furthermore, dryland and off-ice training are often routine practices among players, which may further enhance their grip strength. Taken together, our results offer preliminary support for the need for separate norms for youth ice hockey players because use of typical norms may be inaccurate in this highly trained population.

Previous literature has reported greater grip strength for males at all ages during childhood and adolescence (10,18,23), likely related to sex differences in muscular development (15). However, contrary to our hypothesis, this study showed that males and females have similar dominant and nondominant hand grip strength until the age of 12 years. Only after 12 years of age did males show significantly stronger performance than females. Nikolaidis (21) observed a similar age and sex trend in competitive youth taekwondo athletes (21). Before puberty, increases in muscle strength are mostly due to improved neural adaptations with exercise (15). Thus, it is possible that similar grip strength before puberty seen in our sample and Nikolaidis' sample may be attributed to comparable early sport exposure between males and females, masking any differences between sexes. During puberty, often around the age of 12 in males, changes in sex hormones likely explain the divergence in muscle strength in males compared with females (14,15). Thus, a complex interplay between biological factors and early environmental sport exposure on strength may explain the grip strength trends observed in our sample of youth ice hockey players.

In line with our hypothesis, results from this study demonstrated that individuals with greater body mass had higher grip strength. Previous studies have shown that body mass is a strong predictor of grip strength in youth (6,13,23). However, few studies have evaluated this relationship in youth athletes. One study found that body size was not a significant predictor of grip strength performance in elite youth soccer players (4). However, this study considered body size to be the interaction between height and body mass, which may contribute to the nonsignificant result. Our results support that body mass may be a significant predictor of grip strength performance in youth ice hockey players, after accounting for age. Future studies should also consider other anthropometric variables, such as lean body mass, which have been shown to be correlated with grip strength (29) and explore how differences in muscular strength, coordination, and endurance may contribute to grip strength performance in youth hockey players.

Previous studies have revealed differences in grip strength between elite and subelite athletes (9,22). Our results indicate that playing level only significantly impacted performance on the nondominant hand. Competitive hockey players may train more bilaterally than noncompetitive hockey players. Thus, differences in strength may become only apparent in the nondominant hand because the dominant hand is still continually used for daily activities in both competitive and house league/select players.

The adjusted R2 of the models indicated that the predictors explained between 57.5 and 60.2% of the variance in grip strength performance. We suspect that the additional variance may be attributed to individual differences in muscle mass/composition and neuromuscular recruitment ability as a result of genetics (2,3) and playing different sports (5). Furthermore, age was used as a predictor; however, we recognize that age does not necessarily correspond to achievement of developmental milestones (i.e., when youth reach puberty and associated strength increases). Thus, differences in biological maturity (2) may also help to explain the unaccounted variance in grip strength performance seen in our sample.

This study is not without its limitations. Previous studies have shown relative grip strength (accounting for body size) to be associated with sport participation (30). However, a lack of Canadian normative weight values for youth did not permit for analysis of normalized or relative grip strength. In addition, this study focused specifically on ice hockey players and this may limit the generalizability of the findings to other sports. Finally, the use of convenience sampling and the cross-sectional design may introduce a cohort bias; however, we attempted to reduce this bias by using a large sample size.

In summary, this study presents normative grip strength values specific to youth ice hockey players according to age, sex, body mass, and playing level. These normative values are reported for both dominant and nondominant hands. This study found that absolute grip strength performance in youth ice hockey players was higher than previously reported pediatric norms, giving preliminary support for the importance of athlete-specific norms. Furthermore, grip strength performance is influenced by age, sex, body mass, and playing level (nondominant hand only). Given its practicality and usefulness as a testing instrument, future studies should continue to establish grip strength normative values specific to other sports.

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Practical Applications

These grip strength norms may be valuable for physical educators, trainers, researchers, coaches, and clinicians working with youth ice hockey players to facilitate comparison of performance against a population-specific reference standard. Such comparisons are useful to help evaluate and monitor changes in grip strength in youth ice hockey players for injury management, strength/skill development, or talent identification purposes. In addition, factors found to be related to strength (age, sex, body mass, and playing level) should be considered when interpreting grip strength scores to allow for better contextualization of performance and to aid in the development of individualized strength programs for youth ice hockey players.

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Acknowledgments

This work was funded by the Canadian Institutes of Health Research (#127048), the Ontario Neurotrauma Foundation, and the Ontario Brain Institute. The Ontario Brain Institute is an independent nonprofit corporation, funded partially by the Ontario government. The opinions, results, and conclusions are those of the authors and no endorsement by the Ontario Brain Institute is intended or should be inferred. The authors would also like to acknowledge the efforts of the members of the CIHR “NeuroCare” Team and the members of the Concussion Center (Bloorview Research Institute), specifically Talia Dick, James Murphy, Lee Verweel, and Katherine Mah.

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    Keywords:

    reference values; pediatrics; hand; dynamometer

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