Authors: Erika Nelson-Wong1,2,Johnathon Crawley2, Kevin Cowell3,Lena Parker2, Emily Higgins2,Stephanie Huang2,Claire Lorbiecki2,Shawn Wood2
1Department of Physical Therapy, Augustana University, Sioux Falls, SD, USA
2School of Physical Therapy, Regis University, Denver, CO USA
3The Climb Clinic, Broomfield, CO USA
Erika Nelson-Wong, PT, DPT, PhD
18770 W. 60th Ave, Golden, CO 80403, USA
Erika Nelson-Wong, PT, DPT, PhD is currently a Professor of Physical Therapy at Augustana University in Sioux Falls, SD. She was a Professor of Physical Therapy at Regis University during the time of this study. Her research interests focus on predictive factors for development of musculoskeletal disorders with an emphasis on biomechanics of movement.
Johnathon Crawley, PT, DPT, Lena Parker, PT, DPT, Emily Higgins, PT, DPT, Stephanie Huang, PT, DPT, Claire Lorbiecki, PT, DPT, and Shawn Wood, PT, DPT were student physical therapists in the School of Physical Therapy at Regis University during the time of this study and were awarded their DPT degrees in May 2022.
Kevin Cowell, PT, DPT, OCS, CSCS, FAAOMPT is the owner of The Climb Clinic and has a specialty physical therapy practice focused on injury rehabilitation and performance improvement of rock climbers of all skill levels.
Effect of Shoulder and Hand Position on Sport-Specific Grip Force in Rock Climbers
Purpose: Rock climbing has become popular as a recreational activity. Overuse injuries of fingers and hands are common due to uniquely high demands placed on these structures. Climbers adapt hand positions to match types of holds on rock climbing routes, with open-hand and half-crimp positions being most used. The primary purpose of this study was to explore differences in climbing-specific grip strength between 2 hand positions and 2 shoulder positions. Methods: Participants’ maximum isometric pull was tested on a 20mm edge climbing hold attached to a force transducer in each of 4 hand/shoulder position combinations bilaterally. 46 participants (20 female) across skill levels were included for analysis. Peak force was extracted and normalized to participants’ body weight. Mixed model ANOVAs were used to explore effects and interactions between shoulder position, hand position and skill level. Paired t-tests were used explore asymmetry between dominant and non-dominant hands. Results: Half-crimp position was stronger than open-hand position and shoulder position did not impact force production. Climbers of higher skill level had higher force production in both hand positions. Greater asymmetry was observed in climbers of higher skill in the half-crimp position only.
Conclusion: Findings support using a single shoulder position for testing finger strength versus multiple positions. Climbers of all levels should emphasize both open-hand and half-crimp training for performance and injury prevention. Applications in Sport: Shoulder position did not impact force in open-hand or half-crimp grip. Higher skill climbers produced greater force. Force was higher in half-crimp versus open-hand positions independent of skill. Climbers use open-hand and half-crimp positions and should train both for performance and injury prevention. Strength testing could include a single shoulder angle for efficiency.
Key Words: Rock Climbing, Performance, Injury Prevention, Training
Rock climbing has gained popularity spurred by its introduction into the Olympics, increasing prevalence of indoor climbing gyms, and media coverage. The American Alpine Club reported climbing contributed $12.45 billion to the United States economy in 2017 and 4.4% (7.7 million) of Americans participated in indoor gym climbing in 2018 (1). In 2020, the climbing market had a global value of $581.2 million, with annual participation worldwide of approximately 9 million people. (2) Participation in the United States for the year 2021 was estimated to be 5.68 million for indoor climbing and 2.3 million for outdoor sport climbing and bouldering, with a 2-year increase of 7.1% and 5.4% respectively for these climbing activities. (3)
While traumatic injuries do occur in climbing, acute injuries related to accidents are rare and the majority of injuries are related to overuse and inadequate training (4). One study reported 93% of climbing injuries were related to overuse, with inflammation of fingers and wrists being the most common (5). Rock climbing places unique demands on tendons and other upper extremity tissues, particularly the fingers. Climbers must adapt their bodies and their finger positions according to terrain features. The two most common grip types are open-hand, used for broad holds, and half-crimp, used for smaller holds (6). High numbers of rock climbers report upper extremity injuries, the majority involving hand and wrist, with 52% involve flexor digitorum profundus (FDP), superficialis (FDS) tendons, and annular (A1-A5) pulley systems (6). A2 and A4 pulley injuries are most common (7-9). The A2 pulley undergoes high loading during climbing, and while it is the strongest annular pulley, it can be injured with high forces in half-crimp positions (6; 7). The A4 pulley is also commonly injured and is susceptible to tears in open-hand positions due to interphalangeal (IP) joint angles (7).
At advanced climbing levels, finger strength becomes a significant determinant of success (10-12).Several studies have sought to quantify grip strength of climbers with handheld dynamometry (13-15). Lack of specificity in arm position and hand/finger orientation makes this a poor tool to evaluate climbing-specific finger strength. To effectively evaluate climbing-specific finger strength, others have developed equipment to simulate climbing demands on finger flexors (10-12; 16).A variety of climbing-specific grip types and arm positions during maximal or submaximal isometric contractions have been tested (10; 12). Findings from these studies have been used to determine characteristics affecting climbing performance (13), training effects (17; 18), and injury risk (19). Maximum isometric strength has also been tested with instrumented climbing holds in fixed shoulder positions (10; 12). This ensures precise positional control, however restricting degrees of freedom reduces ecological validity because climbing specific movement is more unrestricted (20).Finger strength testing protocols allowing greater degrees of freedom may produce data more representative of climbing specific demands (20; 21). It is desirable to consider different hand positions with shoulder position to explore potential relationships that have not been a focus in previous research. There are conflicting findings regarding grip strength asymmetry in climbers (14; 15; 22). Strength asymmetry has been identified as an injury risk factor in athletes, mainly in sports emphasizing lower extremity (23-25). The impact of asymmetrical strength may differ between coordination and strength-based athletic tasks (24). Characterizing strength asymmetry across skill levels in climbers may help inform injury risk.
The primary purpose of this study was to explore interactions between shoulder position and grip type in a maximal isometric pull. It was hypothesized that there would be strength differences between shoulder positions, and half-crimp would elicit greater force production than open-hand position. A secondary purpose was to analyze dominant/non-dominant symmetry in grip force. It was hypothesized that more skilled climbers would have greater symmetry than less skilled climbers.
This cross-sectional, observational study was approved by the IRB at an accredited institution of higher education and written informed consent obtained from participants prior to participation. Athlete participants were not involved in design, conduct, interpretation, or translation of this research. Estimated sample size was 45 participants assuming a medium effect size on ANOVA (f =.30). A total of 49 participants were recruited through advertisements placed in climbing gyms, word of mouth and social media. To be eligible, participants had to be between 19-50 years of age, actively involved in rock climbing (minimum once per week) and have no injuries or medical issues that would impact participation. Participant characteristics are shown in Table 1.
Questionnaires: Prior to arrival, participants completed questionnaires designed by the research team to document climbing experience, skill, and health. Questionnaires were completed by the participants within 3 days prior to arriving for testing through Qualtrics (QualtricsXM, Provo, UT, USA) online survey software. They reported average number of climbing sessions per week, years climbing, proportion of time spent climbing in different disciplines (indoor, bouldering, sport, traditional), hardest climbing grade achieved in previous 6-month period in each discipline, and self-rating of Beginner, Intermediate, Advanced or Expert skill. Categories for self-rating were: Beginner (Top Rope < 5.9, Lead 5.5-5.8, Boulder V0-V3); Intermediate (Top Rope > 5.10, Lead 5.9-5.11, Boulder V4-V6); Advanced (Lead 5.11-5.12, Boulder V7-V9); Expert (Lead > 5.13, Boulder > 5.10), using Yosemite Decimal System (YDS) for climbing and Vermin system for bouldering (26). Self-reported skill in rock climbing has been found to be valid and accurate (27). Participants also reported and described any musculoskeletal injuries requiring time off from climbing or treatment by a health care provider in the previous year, current injuries that would prevent a maximal climbing effort, and history of steroid and antibiotic use during previous 6-months. Medication history was used to screen for tendon injury potential during maximal testing. Participants reporting recent use of these medications were ineligible for participation.
Participants were assigned categories for climbing skill using recommendations from the International Rock Climbing Research Association (IRCA) (26). These categories apply thresholds for male and female climbers and are summarized in Table 1. Given variability in climbing disciplines among participants, particularly between indoor/outdoor climbing experience, bouldering/roped climbing, sport/traditional disciplines, and top-roped/lead climbing, participant’s self-selected skill category was used for those on a threshold between IRCA levels. For participants climbing in multiple disciplines, the highest skill discipline was used for categorization. It should be noted that the Vermin and YDS grading systems are non-linear. Climbing grades are inherently subjective, dependent on the first climber’s opinion and final rating being consensus driven after multiple climbers have ascended the route. Another caveat around climbing grades is routes are highly variable depending on rock type, quality, and steepness with many climbers excelling in particular styles that may not translate well to other styles, for example steep overhanging routes with large holds versus vertical technical routes with small holds. These factors make skill categorization difficult based on climbing grades alone.
Testing Protocol: Upon arrival, participants’ height, weight, age, and dominant hand (self-report) were recorded. They were instructed in the 0-10 Modified Borg Scale for Reported Perceived Exertion (RPE) (28). A standardized whole-body warm-up was conducted with participants instructed to reach RPE of 4-6, recorded after each exercise. The 10-minute warmup included jumping jacks, shoulder pass-throughs, cervical rotation, overhead press, resisted finger roll-ups, resisted deadlift, and resisted bent over row.
Participants were seated under the testing apparatus which was a 20 mm edge climbing hold (Tension, The Block, Denver, CO, USA) attached to a load cell (Exsurgo gStrength, Sterling, VA, USA) with force data sampled at 250 Hz. A fixed steel bar was positioned above participants’ thighs to restrict upward body translation during pulls (Figure 1). Participants were instructed in the two grip positions: four-finger half-crimp and three-finger open-hand. The half-crimp position used the second through fifth digits with 90º bend in proximal interphalangeal (PIP) joints, and open-hand position used the second through fourth digits with distal interphalangeal (DIP) and PIP joints at 30-40º angles (Figure 2). Open-hand position used three-fingers instead of four to accommodate anthropometric differences where not all participants could make contact with four fingers due to a shorter fifth digit. To further warm up the fingers and familiarize participants with the protocol, they performed three isometric pulls with 5 seconds effort and 5 seconds rest in each hand position, alternating sides, with a goal RPE of 6. RPE was recorded following each pull and feedback provided on hand position.
Four hand and shoulder combinations were tested in randomized (random number generator in Excel) order. Test positions were open-hand with 90º shoulder elevation, open-hand with 120º shoulder elevation, half-crimp with 90º shoulder elevation, and half-crimp with 120º shoulder elevation (Figure 3). Left and right sides were alternated; coin toss determined the starting side. Participants were instructed to pull as hard as possible with a goal of RPE 9-10. They were asked to hold maximum effort for 2 seconds and had 2 minutes rest in between each pull. Two trials were performed for each position.
To ensure participants were exerting a true maximal effort, trials with RPE of 7 or lower were not included for analysis. In cases where a participant failed to achieve 7 or greater RPE for both trials in any position, that participant was removed from analysis due to inability to compare between positions. Peak force recorded during each trial was extracted and normalized to participant’s body weight. Paired t-tests were used to compare between trials for each position, with no significant differences detected at the .05 level. Therefore, the two trials were averaged as a data reduction measure. Due to low sample size in the Lower Grade category (2), this category was combined with Intermediate category.
Peak force data for dominant hand were entered into 3x2x2 mixed model ANOVAs with between factor of skill level, and within factors of shoulder position and grip type. LSD post hoc tests were used for multiple comparisons. To explore hand symmetry within each skill category, paired t-tests were used to compare force production between dominant and non-dominant hands for each position. IBM SPSS Statistics software (version 188.8.131.52, IBM Corp., Armonk, NY, USA) was used with significance threshold of p < .05.
Summary characteristics for the 49 participants who completed the protocol are provided in Table 1. Three female participants, two elite and one intermediate, were excluded from analysis due to low RPE’s on both trials for a given position, leaving 46 participants for analysis. Both Elite category participants who did not achieve high enough RPE indicated they felt insufficiently warmed up and were afraid of finger injury if they performed at maximum effort. Across remaining participants, five trials were excluded for low RPE, however each of those individuals achieved required RPE on the other trial for that position.
There were no significant main effects for shoulder position (F1,43 =1.38, p=.247) and no interactions between shoulder position and other variables including grip type (F1,43 =0.023, p=.88) and skill level (F2,43 =0.554, p=.58). There was a significant main effect of grip type (F1,43 =36.4, p < .001), with half-crimp generating higher force production at both 90° (65.4 ± 19.5 %BW) and 120° (66.3 ± 20.2 %BW) shoulder positions compared with open-hand at 90° (55.6 ± 15.8 %BW) and 120° (56.1 ± 16.2 %BW) shoulder positions. There was no interaction between grip-type and skill (F2,43 = 0.513, p=.60).
There was a significant main effect of skill (F2,43 = 13.2, p < .001), with post hoc tests revealing differences between the 3 skill categories. Intermediate climbers had average force of 47.3 ± 3.8 %BW, Advanced climbers had average force of 58.5 ±2.7 %BW and Elite climbers had average force of 74.5 ± 3.6 %BW across all shoulder/grip combinations. There were no significant interactions with skill, shoulder position and/or grip type.
Paired t-tests revealed significant differences between dominant and non-dominant hands for half-crimp only in Advanced and Elite skill groups. These differences were observed for both shoulder positions tested. There were no between side differences detected for Intermediate group in either open-hand or half-crimp positions. Summary data are shown in Table 2.
The primary aim was to explore interactions between shoulder position and climbing-specific grip type on maximum isometric force production. It was expected that force production differences would be observed between shoulder positions (90° and 120° shoulder elevation) and higher force producing capabilities in half-crimp compared to open-hand positions.
The stated hypotheses were partially supported as participants produced significantly higher force in half-crimp compared with open-hand positions. However, the two shoulder positions tested did not impact climbing-specific grip strength. Baláš et al. (10) found shoulder position influenced force production in the fingers with higher force at 130° versus 180° and 90° shoulder elevation. A different study of similar design contradicted these finding with highest force production at 180° shoulder elevation (12). The current study did not test the 180° shoulder position so it is possible force differences would have been found compared with other shoulder positions that were tested. Although force production in both hand positions increased with climbing skill, as expected, there were no interactions between skill and hand position. The lack of interaction between skill and hand position was of interest since anecdotally climbers with higher skill level tend to train open-hand positions more consistently than novices. The half-crimp position is similar to a ‘hook-grip’ and is a functional hand position frequently used in daily activities (29). This finding could mean that this hand position is used more frequently and consistently outside of climbing activities and therefore is stronger in most individuals, regardless of climbing skill. Additionally, while FDP is the main finger flexor in both half-crimp and open-hand, FDS is a primary contributor to grip strength in positions similar to half-crimp (29; 30). In half-crimp position, FDS may provide a greater contribution to force production as its role for PIP joint stabilization is decreased in this position (9). Therefore, combined contributions from FDP and FDS may lead to higher force generation in half-crimp position. In a reliability study investigating open-grip and closed-grip (crimp) hand positions, Baláš et al. (16) found no differences between the positions for female climbers and lower skill male climbers, and observed higher open-grip strength in intermediate and advanced male climbers compared to closed-grip. These authors suggested this finding could be due to preferential training of open grip in more advanced climbers. Although the measured forces expressed as a percentage of body weight were similar to those found in the current study, a major methodological difference was both open- and closed-grip in the Baláš et al. study used 4 fingers, whereas climbers in the current study performed open-hand grip with three fingers due to anthropomorphic differences where not all climbers could place four fingers on the device in open-hand position. Additionally, Baláš et al. used a ‘full-crimp’ test position for closed-grip where the thumb wraps around the other fingers for support (16).
Secondary aims for this study included investigating between-side symmetry and impact of climbing skill level. It was expected that greater symmetry would be observed in climbers with higher skill. This hypothesis was unsupported as results indicated that greater asymmetry was apparent in Advanced and Elite skill groups, however this was only true for half-crimp position. This finding may be related to functionality of half-crimp position and more frequent use of this position with the dominant hand outside of climbing. While asymmetry was statistically significant, these force differences are unlikely to be meaningfully related to climbing performance since they were small (2-3%BW). Another study comparing climbers to non-climbers found asymmetry in whole hand grip strength, tested by handgrip dynamometer, with climbers having higher grip strength in left compared to right hand. Non-climbers had no significant asymmetry. The authors suggested these between sides differences could be due to technical aspects of climbing, for example clipping rope to carabiner, being performed predominantly with the right hand while the left hand was predominantly used to support body weight on the climbing hold (14). There were no asymmetries found in pinch-grip, which can be argued has a closer task profile to gripping a climbing hold (14). Other studies have found advanced climbers demonstrate greater symmetry for grip strength (15), and greater whole-hand grip and pinch strength symmetry has been observed in recreational climbers compared with non-climbers (22). These disparate findings may be attributable to different testing methods where joint positions were fixed (15).
Rock climbing places unique and high-demand stresses on finger flexors and surrounding tissues. Appropriate and specific training protocols can mitigate injury risk while improving performance (18; 31). Attention should be given to both open and crimp positions in training programs since both are widely used as climbers adapt to terrain challenges. Injury risk differs between open and crimp positions with open-hand being safer for A2 pulley and half-crimp being safer for A4 pulley due to joint positions (6; 9). Advantageous tendon adaptations occur with mechanical loading protocols (32). These include increased collagen synthesis, increased tendon size (33), and improved mechanical properties including stiffness (32). Mechanical loading adaptations also improve properties for active muscle components, passive connective tissues, and nervous system (33). Imaging studies have shown rock climbers have hypertrophied flexor tendons, volar plates and other soft tissues of the hand compared with non-climbers, these are assumed to be positive adaptations to climbing and training (34). Specificity of training, including progressive and controlled loading targeting specific hand tissues in multiple positions should be considered for performance and rehabilitation goals in climbers at all levels (17; 31). There were limitations in this study. For example, the testing apparatus allowed rotational movement rather than being fixed in a plane, allowing some self-selection for strongest position. Some participants felt the warm-up was insufficient to feel safe performing maximum effort. Future studies should include more rigorous warm-up. There was a learning component, particularly for lower-skilled climbers with less familiarity in pulling on a 20mm edge and isolating open-hand versus half-crimp positions. This result was mitigated by including the test positions during warm-up and providing feedback. Efforts were made to recruit across skill levels, however there were insufficient Lower Grade climbers making it impossible to analyze this category separately. The questionnaires were designed by the research team to gather information about the climbers’ health history, climbing experience, and skill level. These questionnaires were not evaluated for reliability or validity, and as with all self-report measures, these skill and experience determinations were dependent on participants’ response.
No differences were found in climbing-specific grip strength between shoulder positions. These results suggest clinicians and coaches can perform isometric climbing-specific finger strength testing at a single shoulder position, thus improving efficiency during rehabilitation and training without compromising information quality. Climbers were stronger in half-crimp versus open-hand position, however both positions should be emphasized in training as injury risk profiles differ between them. Further research is needed to explore symmetry.
APPLICATION TO SPORT
Shoulder position did not impact force in open-hand or half-crimp grip. Higher skill climbers produced greater force. Force was higher in half-crimp versus open-hand positions independent of skill. Climbers use open-hand and half-crimp positions and should train both for performance and injury prevention. Strength testing could include a single shoulder angle for efficiency. A limitation was the test protocol allowed out of plane rotation and does not replicate actual climbing. The influence of shoulder position could be different during actual climbing movement. Information gained from this study may help climbers, coaches, and clinicians by providing insights into best practices for climbing-specific strength assessment and areas of focus for training.
The authors would like to thank G1 Climbing and Fitness and The Climb Clinic for the use of facilities and equipment to conduct this study. No financial interests or conflicts of interest declared.
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