ISSN: 0264-0414 (Print) 1466-447X (Online) Journal homepage: www.tandfonline.com/journals/rjsp20 Validity and normative scores of finger flexor strength and endurance tests estimated from a large sample of female and male climbers Patrik Berta, Michail Michailov, Dávid Kaško, Jan Gajdošík, Michal Běhounek & Jiří Baláš To cite this article: Patrik Berta, Michail Michailov, Dávid Kaško, Jan Gajdošík, Michal Běhounek & Jiří Baláš (2025) Validity and normative scores of finger flexor strength and endurance tests estimated from a large sample of female and male climbers, Journal of Sports Sciences, 43:3, 245-255, DOI: 10.1080/02640414.2024.2449316 To link to this article: https://doi.org/10.1080/02640414.2024.2449316 © 2025 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. View supplementary material Published online: 04 Jan 2025. Submit your article to this journal Article views: 1206 View related articles View Crossmark data Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=rjsp20
2025, VOL. 43, NO. 3, 245–255 https://doi.org/10.1080/02640414.2024.2449316 SPORTS PERFORMANCE Validity and normative scores of finger flexor strength and endurance tests estimated from a large sample of female and male climbers Patrik Berta a , Michail Michailov b , Dávid Kaško c , Jan Gajdošík a , Michal Běhounek a and Jiří Baláš a a Faculty of Physical Education and Sport, Charles University, Prague, Czech Republic; bDepartment Theory and Methodology of Sports Training, National Sports Academy “Vassil Levski”, Sofia, Bulgaria; cInstitute of Physical Education and Sport, Pavol Jozef Šafárik University, Košice, Slovakia ABSTRACT KEYWORDS Recent reviews have highlighted conflicting findings regarding the validity of finger flexor strength and endurance tests in sport climbers, often due to small sample sizes and low ecological validity of the tests used. To address these gaps, 185 male and 122 female climbers underwent maximal finger flexor strength, intermittent and continuous finger flexor endurance, and the finger hang tests in a sportspecific setting to determine the predictive and concurrent validity of these tests. The finger hang test showed the strongest relationship to climbing ability for both sexes (R ≈ 0.75). However, despite its widespread use as an endurance test, the finger hang was found to be primarily determined by finger strength, explaining 65% and 80% of the variance in males and females, respectively. Finger strength emerged as the dominant factor, explaining the majority of variance in climbing ability (males 68%; females 64%), followed by intermittent endurance (males 28%; females 34%). These findings emphasize finger strength as the primary predictor of climbing ability and highlight the importance of intermittent endurance testing for assessing climbing-specific endurance of the finger flexors. No significant differ ences were found between male and female climbers in finger flexor strength and endurance when normalized to body mass. Sport climbing; performance; forearm; women; rock climbing Introduction Sport climbing requires a balanced combination of psycholo gical, skill-related, and physiological factors in order to achieve optimal performance (Draper et al., 2021). Among these phy siological characteristics, the strength and endurance of the forearm muscles, particularly the finger flexors, are consistently identified by trainers and researchers as crucial for climbing success (Saul et al., 2019). However, conflicting findings have been reported regarding the predictive validity of finger flexor strength and endurance tests for climbing ability (Faggian et al., 2024; Langer et al., 2023; Stien et al., 2022). Finger flexor strength has been assessed using handheld dynamometers or by applying force on a climbing hold, both of which have demonstrated excellent reliability (Michailov et al., 2018; Torr et al., 2022). It is recommended to use climb ing-specific test setups rather than handheld dynamometers when assessing training effects and comparing different ability levels (Langer et al., 2023; Stien et al., 2022). Testing maximum strength on a rung normalized to body mass provides greater ecological validity and has shown higher predictive validity for climbing ability, with reported correlations ranging from 0.42 to 0.92 (Baláš et al., 2014; Bourne et al., 2011; Michailov et al., 2018; Ozimek et al., 2016; Torr et al., 2022), compared to handheld dynamometers (R = 0.53–0.75) (Baláš et al., 2012; Gajewski & Jarosiewicz, 2008). While the predictive validity is relatively consistent across studies using handheld dynamometers, discrepancies in climbing-specific setups are likely due to var iations in rung size, grip type, arm and body position, statistical analysis methods, and the specific climbing population tested. Often, very small sample sizes that mix males and females have been used, therefore, the relationship between maximal finger flexor strength and climbing ability requires further exploration in larger sample sizes using climbing-specific settings. In this context, normative data for different ability levels and grip configurations would aid in establishing standardized bench marks, which could improve the consistency of strength assess ments and provide more accurate performance predictions across climbers of varying skill levels. Similarly, the testing of finger flexor endurance lacks stan dardization (Stien et al., 2022). Finger flexor endurance has been assessed during actual climbing or through isolated sustained or intermittent contractions (Baláš et al., 2021). While actual climbing provides higher ecological validity by closely replicating muscle behavior during activity, it is chal lenging to standardize and compare results across tests and climbers due to variations in route difficulty, hold size, and configuration. Conversely, isolated tests allow for more pre cise control of contraction intensity and rest duration, improving reliability but potentially sacrificing ecological validity (Baláš et al., 2021; Michailov et al., 2018). These tests typically involve applying 40–100% of maximum voluntary contraction (MVC) on a hold, either continuously (Draper CONTACT Jiří Baláš jiri.balas@ftvs.cuni.cz; balas@ftvs.cuni.cz Faculty of Physical Education and Sport, Charles University, José Martího 31, Prague 16252, Czech Republic Supplemental data for this article can be accessed online https://doi.org/10.1080/02640414.2024.2449316 © 2025 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way. The terms on which this article has been published allow the posting of the Accepted Manuscript in a repository by the author(s) or with their consent.
P. BERTA ET AL. et al., 2021; Fryer et al., 2015; Michailov et al., 2018; Philippe et al., 2012) or intermittently with varying work-rest ratios (Fryer et al., 2017; Giles, Hartley et al., 2021; Vigouroux & Quaine, 2006; Winkler et al., 2023). A specific example of a sustained contraction test is the dead hang or finger hang on a rung, where the climber hangs using their body weight, and the time until exhaustion is measured. Due to the intermittent nature of climbing, intermittent tests have been recommended to better mimic the endurance demands of climbing (Stien et al., 2022). While aerobic meta bolism is more active during intermittent exercise, anaerobic alactic metabolism dominates during continuous exercise, with anaerobic lactic energy systems contributing equally at the peripheral level (Maciejczyk et al., 2022). Surprisingly, continu ous contraction tests have been shown to provide higher pre dictive validity for climbing ability (R = 0.72) than intermittent tests (R = 0.41) (Maciejczyk et al., 2022), although this has been documented primarily in very homogeneous groups of high elite climbers and seldom in female climbers. Among continuous contraction tests, the finger hang test appears to be the most significant predictor of self-reported climbing ability (R = 0.54–0.87) (Baláš et al., 2012; Draper et al., 2021). This test has been utilized in several training intervention studies to assess changes in climbers’ endurance capacity (Hermans et al., 2017, 2022; López-Rivera & González-Badillo, 2019; Medernach et al., 2015). However, the validity of the finger hang test as a measure of finger flexor endurance has been questioned (Baláš et al., 2012; Rokowski et al., 2024). These concerns may arise from the influence of a climber’s body mass and maximal finger strength on the intensity of the exercise, as well as the test’s lack of ecological validity in replicating the intermittent nature of finger flexor contractions during climbing. Consequently, this test may not accurately represent climbing-specific finger flexor endurance, and its relationship to maximal finger flexor strength and other endur ance tests remains unclear. Consequently, the primary aim of this study was to investigate the predictive validity of finger flexor strength and endurance tests to climbing ability across multiple ability groups of male and female climbers and provide normative scores for common tests. Furthermore, this study aimed to determine the concurrent validity of the finger hang test in measuring finger flexor endurance among climbers with varying levels of maximal strength and climbing ability. We hypothesized that finger hang performance would exhi bit a stronger correlation with maximal finger flexor strength compared to endurance measures. Materials and methods Participants A total of 307 sport climbers volunteered to take part in the study (185 males: mean age 27 ± 11.6 years, 122 females: age 23.4 ± 9.7 years). Data was collected over a two-year period, during which participants were recruited using a snowball sampling method through contacts within the national team, climbing clubs, and climbing gyms, following specific inclusion and exclusion criteria. The inclusion cri teria required participants to have at least one year of climbing experience and a self-reported climbing ability ranging from intermediate level (achieving lead climbing level 10) to high elite level (reaching level 30) on the International Rock Climbing Research Association (IRCRA) scale. The exclusion criteria disqualified participants with recent injuries, surgeries, or any conditions affecting grip strength or endurance within the past six months. Participants were divided into four climbing ability groups (intermediate, advanced, elite, and higher elite) according to self-reported red-point performance from the last 3 months (Draper et al., 2016). The group’s specific characteristics are presented in Table 1. Sample size was determined to ensure adequate power for both the multiple regression and ANOVA analyses. For the multiple regression model with three predictors (finger flexor strength, continuous endur ance, intermittent endurance), we targeted a medium effect size (f2 = 0.15), with a significance level of 0.05 and 0.80 power, requiring a total of 77 participants. For ANOVA comparisons between male and female climbers across four ability groups, a medium effect size (f = 0.25), a significance level of 0.05, and a power of 0.80 indicated approximately 44 participants per group (totaling around 180 participants). Medium effect sizes were chosen to bal ance sensitivity to differences with feasible sample size requirements. The research has received approval from the Ethics Committee of the Faculty of Sports and Physical Education, Charles University, Prague. All participants were informed of the potential risks of the experiment and pro vided informed approval before data collection proceeded. Table 1. Number of participants in each climbing ability subgroup along with mean (± standard deviation) values for anthropometric and training characteristics. Performance Group Male Intermediate Advanced Elite Higher Elite Female Intermediate Advanced Elite Higher Elite n Age (years) Height (cm) Body mass (kg) 48 85 45 7 36.3 ± 11.8 23.6 ± 10.2 23.8 ± 8.9 25.4 ± 5.0 27 55 39 1 30.1 ± 11.3 167.3 ± 6.7 58.6 ± 9.0 22.1 ± 8.4 166 ± 7.3 55.1 ± 8.2 20.7 ± 8.6 161.8 ± 7.2 51.5 ± 7.5 18.8 ± NA 170.3 ± NA 61.8 ± NA 177.5 ± 9.1 73.6 ± 12.4 175.4 ± 9.9 66.3 ± 11.4 176.6 ± 7.2 65.2 ± 7.9 171.2 ± 6.8 64 ± 5.5 Climbing experience (years) Climbing training (sessions/ week) Climbing training (hours/week) Non-climbing training (hours/week) 12.0 ± 9.9 9.1 ± 6.8 12.8 ± 5.8 11.4 ± 2.8 2.4 ± 1.5 3.6 ± 1.5 4.5 ± 1.4 5.9 ± 3.0 5.2 ± 3.0 8.4 ± 3.5 10.8 ± 3.8 11.2 ± 5.4 2.5 ± 2.4 3.3 ± 3.1 3.3 ± 2.8 4.3 ± 2.8 9.1 ± 5.3 7.6 ± 4.4 9.8 ± 5.3 12.0 ± NA 2.3 ± 0.9 3.0 ± 1.0 3.7 ± 1.3 4.5 ± NA 4.9 ± 2.1 7.0 ± 3.4 9.4 ± 4.7 14.0 ± NA 3.1 ± 2.7 2.8 ± 2.1 4.2 ± 5.2 4.0 ± NA
Design The procedure to address methodological inconsistencies raised in the introduction involved the following steps in order to apply tests with the highest reported ecological valid ity and reliability: ● Grip-over-shoulder position: Previous research has shown that arm position impacts the forces generated by finger flexors, particularly in climbers (Baláš et al., 2014; Watts et al., 2008). ● Rung size: A rung size of approximately 2.0–3.0 cm optimizes motor unit recruitment across all grip posi tions, with larger sizes being preferable for half-crimp and open grip positions (Amca et al., 2012). Specifically, a 2.3 cm rung has been verified for intraand inter-session reliability and shown to have strong validity for assessing maximum strength and endur ance in relation to climbing ability (Baláš et al., 2014; Michailov et al., 2018). Additionally, a 3 cm rung size for dead-hangs was recently proposed by IRCRA (Draper et al., 2021), facilitating comparisons across studies. ● Intensity for endurance testing: Only continuous and intermittent tests at 60% of MVC were selected to assess finger flexor endurance, as they are the only isolated finger flexor tests with established reliability and known metabolic demands (Baláš et al., 2018; Maciejczyk et al., 2022; Michailov et al., 2018) and are widely used 247 internationally (Feldmann et al., 2022; Kodejška et al., 2018; Rokowski et al., 2024; Winkler et al., 2023). Although all-out tests to determine critical force may provide valuable insights into localized aerobic muscle capacity (Giles, Hartley et al., 2021), their validity in climb ing-specific setups has been questioned (Baláš et al., 2024) and therefore were not included in the current study. ● Contraction-relief ratio: Common training ratios like 7:3 do not reflect typical climbing dynamics, as con traction times vary from 6.2 to 8.5 seconds, with recovery or relaxation phases around 1.5 seconds in lead climbing (Arbulu et al., 2015; Winkler et al., 2022). Therefore, a work-relief ratio of 8:2 seconds at 60% of MVC, validated for metabolic pathways and climbing ability criteria, appears more suitable (Maciejczyk et al., 2022). Before testing, participants underwent anthropometric measurements (body mass, height) and completed ques tionnaires on their climbing experience, preferences, train ing characteristics, and climbing ability. Following this, they engaged in a standardized warm-up routine. The routine included: 5 minutes of aerobic activity, 10 minutes of mobilization exercises and easy climbing, and intermit tent hanging on a fingerboard using 30 mm and 23 mm deep rungs for 5 minutes with progressive increases in load. Testing commenced after a 10-minute passive rest period. Figure 1. (a) Design of the study; (b) finger, arm and body position during maximal finger flexor strength, continuous and intermittent finger flexor endurance tests on a wooden rung 2.3 cm deep. MVC – maximal voluntary contraction.
P. BERTA ET AL. Four tests were completed during a single laboratory visit: (1) maximal voluntary contraction (MVC) for both hands, (2) a continuous or sustained contraction endurance test at 60% of MVC using the weaker hand, (3) an intermittent contraction endurance test at 60% of MVC using the stronger hand, and (4) a finger hang test. The testing schedule with specified rest intervals between tests is shown in Figure 1: 5 minutes between the maximal strength test and the continuous endurance test, 10 minutes between the endurance test and the intermittent endurance test, and 20 minutes between the intermittent endurance test and the finger hang test. Active recovery, consisting of walking, was performed between endurance tests to facilitate recovery from exhaustive contractions (Heyman et al., 2009; Krupková et al., 2024). Tests were conducted using a custom-made dynam ometer (1D-SAC, Spacelab, Sofia, Bulgaria), which has been shown to be reliable and valid for assessing finger flexor strength and endurance (Michailov et al., 2018). The max imal strength, continuous endurance, and intermittent endurance tests were performed using a 23 mm rung with a 10 mm radius, while the finger hang test was conducted using a 30 mm rung with a 10 mm radius to maintain con sistency with previous methodologies (Draper et al., 2021; Michailov et al., 2018). All tests were performed using the grip position preferred by each participant, with the options being a half-crimp grip, a four-finger slope grip (open grip), or a three-finger slope grip (also called a three-finger drag). For the purposes of this study, a four-finger slope grip was defined as any four-finger configuration with a minimum proximal interphalangeal joint angle of 90°. The open grip was emphasized in the methodology as it is considered safer for preventing annular pulley injuries (Lutter et al., 2020). Participants were instructed to maintain their chosen grip consistently across all tests to ensure uniformity and reliability of measurements. However, changes in grip posi tion due to eccentric contractions (e.g. shifting from a fourfinger grip to a three-finger drag) were permitted to reflect common climbing scenarios. These shifts were rare and did not significantly impact the results. The unit kg was used for all finger-strength measurements for easier interpreta tion and comparisons with previous research on finger strength in climbing (Draper et al., 2021; Giles, Hartley et al., 2021). Maximal strength Maximal strength consisted of two MVC attempts of the finger flexor muscles, with each hand contraction followed by a 2-minute passive rest period. The participant in the standing position with the arm in shoulder flexion (180°) and the elbow slightly flexed (Baláš et al., 2014) progressively transferred as much of their weight as possible onto the wooden hold during a 5 s long open grip position. Maximal finger flexor strength was determined based on the highest peak value from the two trials for each hand. The hand with lower and higher values was considered weaker and stronger hand for endurance tests, respectively. When the same force was measured for both hands, the dominant hand was considered as stronger hand. Absolute force values (kg) and force values normalized to body mass (as a percentage of body mass) were used for further analysis. Endurance tests Participants performed continuous and intermittent tests with weaker and stronger hands, respectively. The same body and grip positions used for the MVC test were also used for the endurance tests. During the continuous tests, participants were instructed to sustain that force for as long as possible. Intermittent test was performed at the contraction and rest intervals of 8:2 s and participants were allowed to shake their hands near the body under the heart level. Both endurance tests started with a sound signal, and participants were given visual feedback to ensure the accurate application of target force, as well as to indicate the start and end of each contrac tion/rest period. The target zone has a tolerance of ±10% of the target force. If this force dropped on the target zone for more than 1 second, the test was automatically terminated. Force impulse (kg.s) normalized to body mass (kg) was used for further analysis. Finger hang During the finger hang test, the participants maintained a grip on the rung while keeping their arms fully extended. The test ended when participants failed to maintain a grip on the rung and touched the ground with their feet. To approximate the relative intensity of both hand hanging to individual finger flexor strength, data were calculated as [body mass (kg)/2]/MVC(kg). The relative intensity normalized to MVC is presented in Table 2. Table 2. Intensity estimates of finger hang when normalized to individual finger flexor strength (% MVC). Finger strength corresponding to 100% body mass means that the climber is just able to hold his body mass with a single arm on a rung and the intensity of both arm hang corresponds to 50% of his MVC for each arm. See the text for calculation. Finger strength of one hand normalized to body mass (%) 120 110 100 90 80 70 60 50 MVC – maximal voluntary contraction. Relative intensity of finger hang for both hands (%MVC) 42 45 50 56 63 71 83 100
Statistical analysis Descriptive statistics (mean ± SD) were used to characterize anthropometric data, training background, strength and endur ance performance across different ability groups. Given inher ent morphological differences between male and female climbers – and potential impact on strength and endurance characteristics – male and female climbers were analyzed separately. All data have been found to be normally distributed, homo scedastic, and of equal variance. To explore the relationships between climbing ability, finger hang, and other tests Pearson correlation coefficients were calculated. The predictive validity of finger flexor strength and endurance to climbing ability was determined using linear regression models that included max imal strength, continuous, and intermittent tests for both male and female climbers. Standardized and non-standardized beta coefficients, standard errors, 95% confidence intervals (95% CI), and coefficients of determination (R2) were calculated for all models. To assess the relative importance of each predictor in explaining the variance within the models, squared standar dized beta coefficients were computed. Finger hang perfor mance was excluded from the regression models due to its strong correlation with maximal strength and moderate corre lation with endurance tests, which posed a risk of multicolli nearity and compromised interpretability. Moreover, excluding finger hang reduced multicollinearity (data not shown) and improved the reliability of the regression models. Relationships between finger hang performance, strength, and endurance tests were further explored using a separate linear regression model, where finger hang was the dependent variable and strength, and endurance tests were independent variables. The procedure for selecting the final regression model is illustrated in Supplementary File, Table S1, which identifies the model with the highest coefficient of determina tion and lowest standard error of estimate. To isolate the direct relationships between MVC and both intermittent and continuous tests, partial correlation coeffi cients were computed to assess the relationships between 249 endurance tests and climbing ability. Scatter plots were gener ated to visualize data distribution for male and female climbers. To compare the importance of strength and endurance between male and female climbers in each ability group, we had to modify the initial grouping used by Draper et al. (2016), as the groups with the same names for males and females did not match in terms of performance level. Additionally, each ability group involved a different number of performance grades, making separate correlation analysis problematic. Therefore, we divided both female and male climbers into four ability groups: 1) 10–14 (5+ to 6b+ sport); 2) 15–19 (6c to 7b); 3) 20–24 (7b+ to 8a+); and 4) 25–30 (8b to 9a+). Boxplots were created to display normative data for each ability group of male and female climbers, including median, mean, 25th, and 75th percentiles, with whiskers indicating the 10th and 90th percentiles. Sex differences within ability groups for each performance test were analyzed using one-way ANOVA followed by post-hoc Tukey’s tests. Additionally, nor mative data for each performance test and sex were reported as percentile distributions (10th to 90th percentile) in Supplementary Files (Tables S2–S5) for each decile. Statistical significance was set at p < 0.05. The correlations and squared association indices were interpreted as follows – strong effect: R ≥ 0.8; R2≥0.64; moderate effect: R ≥ 0.5; R2≥0.25, low effect: R ≥ 0.2; R2≥0.04. All calculations were carried out using Microsoft Excel and R (Version 4.4.0 R Core Team, 2024). Results The mean values for strength and endurance tests increased for both sexes from intermediate to higher elite athletes, as shown in Table 3 and Figure 2. Although male climbers generally have high absolute values in MVC compared to females (Table 3), these differences are not significant when the strength is nor malized to body mass (Figure 2). No sex differences were observed for finger hang time, continuous or endurance tests in all ability groups either. Normative data for all tests are shown in the Supplementary file in Tables S2- 5. High elite athletes were omitted due to low numbers of athletes. Table 3. Number of participants in each climbing ability subgroup along with mean (± standard deviation) values for strength and endurance performance tests relative to body mass, as well as absolute values for maximal voluntary contraction. Performance Group Male Intermediate (IRCRA 10–17) Advanced (IRCRA 18–23) Elite (IRCRA 24–27) Higher Elite (IRCRA 28–30) Female Intermediate (IRCRA 10–14) Advanced (IRCRA 15–20) Elite (IRCRA 21–26) Higher Elite (IRCRA 27–28) n MVC (% body mass) MVC (kg) Intermittent test (kg.s.kg−1) Continuous test (kg.s.kg−1) Finger hang (s) 48 73 ± 11 55.4 ± 10.4 32.3 ± 10.3 19.2 ± 5.1 42.0 ± 14.0 85 92 ± 17 62.1 ± 12.5 46.1 ± 14.9 24.1 ± 7.2 68.1 ± 19.9 45 7 107 ± 15 116 ± 9 70.5 ± 11.2 75.4 ± 7.3 59.4 ± 13.1 60.9 ± 9.5 30.3 ± 7.9 33.8 ± 12.1 84.9 ± 13.6 108.3 ± 21.1 27 64 ± 14 38.4 ± 7.5 30.3 ± 13.7 18.2 ± 6.1 39.6 ± 18.1 55 78 ± 14 44.0 ± 10.2 42.6 ± 15.2 21.6 ± 7.1 57.6 ± 15.8 39 1 96 ± 18 115 ± NA 50.3 ± 9.7 79.8 ± NA 54.3 ± 16.2 71.7 ± NA 28.4 ± 8.1 29.9 ± NA 83.0 ± 19.8 120 ± NA IRCRA – International Rock Climbing Research Association, MVC – maximal voluntary contraction.
P. BERTA ET AL. Figure 2. Boxplots depicting the distribution of data across climbing ability subgroups in males and females. The climbing ability subgroups are shown on the X-axis using the sport scale (top) and the IRCRA scale (bottom). Each boxplot displays the median (50th percentile, middle line inside the box), mean (black dot), 25th and 75th percentiles (box edges), and the 10th and 90th percentiles (whiskers) for: (a) finger hang; (b) maximal finger flexor strength; (c) intermittent finger flexor endurance; and (d) continuous finger flexor endurance test. Table 4. Relationships between climbing ability and finger flexor performance tests in males (italicized, lower-left diagonal) and females (upper-right diagonal). Variable Climbing ability MVC Intermittent test Continuous test Finger hang Climbing ability (IRCRA) 1.000 0.700 0.633 0.514 0.748 MVC (% body mass) 0.633 1.000 0.540 0.457 0.786 Intermittent test (kg.s.kg−1) 0.566 0.331 1.000 0.580 0.728 Continuous test (kg.s.kg−1) 0.479 0.381 0.587 1.000 0.546 Finger hang (s) 0.710 0.778 0.559 0.577 1.000 IRCRA – scale International Rock Climbing Research Association; MVC maximal voluntary contraction. The Table 4 shows a moderate association between all tests and climbing ability, with the exception of the con tinuous test for female climbers (R = 0.48). Finger hang has the highest association to climbing ability, regardless of sex (males: r = 0.75; females: r = 0.71). The MVC test has a slightly lower level of association with the climbing ability than the finger hang test (r = 0.70; r = 0.63). Both endurance tests showed low to moderate association with climbing ability with the intermittent test showing a slightly stronger relationship than continuous test (Table 4). The linear regression model, which included finger flexor strength and endurance tests, explained 58% and 54% of the variability in climbing ability for males and females, respectively. Maximal strength emerged as the strongest pre dictor in both males and females, followed by the intermittent and continuous tests (Table 5). To assess the concurrent validity of the finger hang test, a linear model and correlations with finger flexor strength and endurance tests were calculated (Tables 4 and 6, Table S1 and S6, Figure S1). The linear model (adjusted R2 = 0.73–0.75) identified finger strength as the primary predictor of finger hang time for both males and females, accounting for 68% and 80% of the relative importance in the model, respectively (Table 6). Additional linear models and bivariate and partial correlations (Table S1, S6, Figure S1) further supported these findings.
251 Table 5. Regression modeling using finger flexor strength and endurance performance tests in males and females as predictors, and climbing ability as the dependent variable. Dependent variable: climbing ability B Males Model 1: R2 = 0.589; ΔR2 = 0.582; p < 0.001 Finger strength Intermittent test Continuous test Females 2 2 Model 1: R = 0.548; ΔR = 0.537; p < 0.001 Finger strength Intermittent test Continuous test Lower 95% CI Upper 95% CI β β2 P 10.347 0.079 0.060 7.898 0.046 −0.001 12.797 0.111 0.121 0.482 0.305 0.116 0.232 (68%) 0.093 (28%) 0.013 (4%) <0.001 <0.001 0.054 10.063 0.082 0.043 7.274 0.047 −0.035 12.853 0.117 0.120 0.483 0.355 0.086 0.233 (64%) 0.126 (34%) 0.007 (2%) <0.001 <0.001 0.277 CI – Confidence interval. Table 6. Regression models using finger flexor strength and endurance performance tests in males and females as predictors, and finger hang as the dependent variable. Dependent variable: finger hang B Male Model 1: R2 = 0.751; ΔR2 = 0.747; p < 0.001 Finger strength Intermittent test Continuous test Female 2 2 Model 1: R = 0.732; ΔR = 0.726; p < 0.001 Finger strength Intermittent test Continuous test Lower 95% CI Upper 95% CI β β2 P 66.581 0.582 0.205 55.631 0.439 −0.066 77.531 0.726 0.477 0.541 0.395 0.070 0.293 (65%) 0.156 (34%) 0.005 (1%) <0.001 <0.001 0.137 77.981 0.327 0.596 65.091 0.163 0.239 90.871 0.490 0.953 0.624 0.235 0.201 0.389 (80%) 0.055 (11%) 0.040 (8%) <0.001 <0.001 0.001 CI – Confidence interval. Discussion The current study provides normative data for finger hang time, maximal strength, and finger flexor endurance in inter mediate, advanced, and elite male and female climbers. Our findings indicate that finger hang performance on a rung is the strongest predictor of climbing ability across all ability groups. However, this test is not a representative measure of climbing-specific endurance, and its use for assessing the endurance capacity of forearm flexors is not recommended due to its high reliance on maximal strength. Maximal strength, intermittent endurance, and continuous endur ance tests are all significantly associated with climbing abil ity. The linear regression model estimates that maximal strength accounts for approximately two-thirds of the varia bility, while endurance tests account for one-third. These findings emphasize finger strength as the primary predictor of climbing ability and highlight the importance of inter mittent endurance testing for assessing climbing-specific endurance of the finger flexors. Additionally, the results indicate that there are no significant differences between male and female climbers in finger flexor strength and endurance when normalized to body mass. Finger hang as a predictor of climbing ability and endurance performance The finger hang test was identified as the best predictor of selfreported climbing ability, with R2 = 0.56 for males and R2 = 0.50 for females. These findings are consistent with previous studies, which reported associations between the two variables, with R2 = 0.76 for males and 0.66 for females (Baláš et al., 2012), and R2 = 0.31 for males and 0.52 for females (Draper et al., 2021). The higher R2 values in the Baláš et al. study are likely due to the inclusion of lower-grade climbers, which increased the hetero geneity of the sample. In contrast, the sample in the Draper study was more homogeneous in terms of climbing ability. The test’s ease of use and strong correlation with climbing ability make it a valuable tool for coaches and researchers for quickly and easily predicting climbing performance. However, the current study demonstrates that finger hang performance is primarily determined by maximal finger strength rather than endurance capacity, regardless of climbing ability level or sex. The finger flexor strength test showed the strongest correlation with the finger hang test (R = 0.79 for males and R = 0.78 for females). Furthermore, in the regression model that included both intermittent and continuous endur ance tests, finger strength had the highest standardized beta coefficients (β = 0.54 for males and β = 0.62 for females), com pared to β = 0.40 and 0.24 for the intermittent test, and β = 0.07 and 0.20 for the continuous test in males and females, respec tively. Both models explained approximately 75% of the varia bility in finger hang time. Notably, removing the continuous test from the regression model for males did not worsen the model’s performance (Table S1). This suggests that only a small portion of the endurance component, as measured by the intermittent and continuous tests, is reflected in finger hang time. These results align with another test highly dependent on body mass, the bent arm hang test and their modifications, which shows a strong correlation with relative maximal
P. BERTA ET AL. isometric strength and is also a strong indicator of relative maximal dynamic strength (Clemons, 2014) and no relationship with muscular endurance (Clemons et al., 2004). The finger hang on a 3 cm edge, analogous to the bent arm hang, is widely utilized as a climbing-specific endurance test (Hermans et al., 2017, 2022; López-Rivera & González-Badillo, 2019). However, both tests are influenced by maximal strength, making them poor measures of pure endurance. The strong correlation between hang and MVC tests reflects that climbers with higher body weight or lower maximal strength experience greater relative contraction intensity (e.g. intermediate clim bers exerted > 65% MVC, while elite climbers exerted < 44% MVC). Additionally, climbers with high strength but low oxygen utilization capacity can achieve similar results to those with lower strength and better endurance (Kodejška et al., 2016). Thus, finger hang duration is an absolute measure, combining strength and endurance, without distinguishing their relative contributions. For example, climbers with equal body mass but differing strength and endurance levels may achieve the same hang duration, with stronger climbers exhibiting lower relative endurance. Alternative approaches, such as using regression models based on hangs of varying durations and edge sizes (Draga et al., 2024) or tests at the same relative intensity (Rokowski et al., 2024), provide better assessments of relative endurance. Surprisingly, the association between finger hang time and endurance tests is stronger for the intermittent test than for the continuous test, even though the finger hang represents a continuous contraction. The continuous test primarily assesses the alactic and lactic anaerobic system, while the intermittent test reflects the aerobic metabolic system (Maciejczyk et al., 2022). Oxygen delivery to muscles is crucial in determining the extent of aerobic metabolism, and the intensity of exercise significantly influences this oxygen deliv ery (Drouin et al., 2022). Isometric contraction intensity above the critical occlusion threshold prevents muscle blood flow (Bergua et al., 2021; Fryer et al., 2015). Previous studies reported that muscle blood flow decreases at 25–30% of MVC (Hansen et al., 1993; Kahn et al., 1998) and stops above the occlusion threshold at 50–70% of MVC (Barnes, 1980; Heyward, 1975). When approximating the relative intensity of the finger hang from the maximal strength test results (noting the limita tions, such as not accounting for the bilateral deficit and using different rung sizes for the finger hang and intermittent tests), the occlusion threshold at 50%-70% of MVC corresponds to climbers with relative one-arm finger strength ranging from 100% to 71.4% of their body mass (Table 2). This indicates that advanced, elite, and higher elite climbers may exercise below the occlusion threshold and benefit from partial oxygen delivery compared to intermediate climbers who likely exercise over the occlusion threshold. Moreover, as shown in Figure S1, the association between finger hang time and MVC diminishes in climbers with relative strength over 115% of body mass, which may be related to enhanced blood flow and oxygen delivery. Interestingly, Bergua et al. (2021) found no association between the approximated occlusion threshold and climbing ability or finger strength, suggesting that blood flow in the finger flexors varies independently of the climber’s ability level. This variability in hemodynamic responses could potentially explain the weak relationship between the finger hang and endurance tests at fixed intensity of MVC. To sum marize, while the finger hang test is a strong predictor of climbing ability, it serves as a composite measure that incorpo rates both strength and endurance components. Consequently, it provides limited insight into whether strength or endurance is the weaker factor in finger flexor performance. Continuous and intermittent endurance and strength tests as predictors of climbing ability The association between both finger flexor endurance tests, strength tests and climbing ability ranged from R = 0.48 to 0.70, highlighting the importance of high neural stimulation and the contribution of various metabolic pathways in climb ing. However, when all three tests were included in the linear regression model, maximal strength emerged as the strongest predictor (β = 0.48 for males and β = 0.48 for females), followed by the intermittent test (β = 0.31 for males and β = 0.36 for females), and then the continuous test (β = 0.12 for males and β = 0.09 for females). The lower β values for the endurance tests, particularly for the continuous test, might be explained by the fact that the test also involves a strength component, as indicated by the partial correlation in Table S6. Nevertheless, the continuous test is not solely dependent on strength. At the peripheral level, during the continuous test, the energy contribution from the lactic system surpasses that of the alactic system (Maciejczyk et al., 2022). Furthermore, this test and anaerobic capacity were found to have a stronger influence on high-level climbers’ performance compared to the intermittent test (Rokowski et al., 2024). The broad range of participants’ skill levels in the present study likely contribu ted to the higher correlations observed between climbing ability and the intermittent test. The notably high β values for the intermittent test in both male and female climbers are significant. Given that this test involves a 60% contribution from aerobic metabolism (Maciejczyk et al., 2022), these findings emphasize the impor tance of localized adaptations that enhance oxygen delivery and utilization for lead climbing. This supports previous research on the importance of aerobic metabolic pathways and structural adaptations in climbers (Baláš et al., 2021; Ferguson & Brown, 1997; Fryer et al., 2018; Limonta et al., 2018; Philippe et al., 2012; Thompson et al., 2015). However, a high variability in impulse was observed among advanced and elite climbers during both continuous and inter mittent testing (Table 3, Figure 2). Anecdotally, we noted that some very strong climbers had surprisingly short test durations, while others with lower maximal strength performed for longer periods, despite all participants exercising at the same relative intensity (60% MVC). As demonstrated earlier, the level of occlusion threshold and critical force does not depend only on MVC (Baláš et al., 2024; Bergua et al., 2021; Giles, Hartley et al., 2021), meaning that climbers may perform the test at different intensities relative to their critical force, thereby enga ging different metabolic pathways. An important finding of the current study is that it clarifies the relative importance of endurance components compared to strength, using a large sample of both male and female
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