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The main purpose of this study was to examine the effect of chalk on the friction coefficient between climber's fingers and two different rock types (sandstone and limestone). The secondary purpose was to investigate the effects of humidity and temperature on the friction coefficient and on the influence of chalk. Eleven experienced climbers took part in this study and 42 test sessions were performed. Participants hung from holds which were fixed on a specially designed hang board. The inclination of the hang board was progressively increased until the climber's hand slipped from the holds. The angle of the hang board was simultaneously recorded by using a gyroscopic sensor and the friction coefficient was calculated at the moment of slip. The results showed that there was a significant positive effect of chalk on the coefficient of friction (+18.7% on limestone and +21.6% on sandstone). Moreover sandstone had a higher coefficient of friction than limestone (+15.6% without chalk, +18.4% with chalk). These results confirmed climbers' belief that chalk enhances friction. However, no correlation with humidity/temperature and friction coefficient was noted which suggested that additional parameters should be considered in order to understand the effects of climate on finger friction in rock climbing.
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Sports Biomechanics
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The effect of chalk on the finger–hold
friction coefficient in rock climbing
Arif Mithat Amca a , Laurent Vigouroux b , Serdar Aritan a & Eric
Berton b
a Biomechanics Research Group, School of Sport Sciences and
Technology, Hacettepe University, Ankara, Turkey
b Institute of Movement Sciences, CNRS UMR 7287, Aix-Marseille
University, Marseille, France
Version of record first published: 03 Oct 2012.
To cite this article: Arif Mithat Amca, Laurent Vigouroux, Serdar Aritan & Eric Berton (): The
effect of chalk on the finger–hold friction coefficient in rock climbing, Sports Biomechanics,
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The effect of chalk on the finger hold friction coefficient
in rock climbing
Biomechanics Research Group, School of Sport Sciences and Technology, Hacettepe University,
Ankara, Turkey, and
Institute of Movement Sciences, CNRS UMR 7287, Aix-Marseille University,
Marseille, France
(Received 30 November 2011;accepted 15 August 2012)
The main purpose of this study was to examine the effect of chalk on the friction coefficient between
climber’s fingers and two different rock types (sandstone and limestone). The secondary purpose was
to investigate the effects of humidity and temperature on the friction coefficient and on the influence of
chalk. Eleven experienced climbers took part in this study and 42 test sessions were performed.
Participants hung from holds which were fixed on a specially designed hang board. The inclination of
the hang board was progressively increased until the climber’s hand slipped from the holds. The angle
of the hang board was simultaneously recorded by using a gyroscopic sensor and the friction coefficient
was calculated at the moment of slip. The results showed that there was a significant positive effect of
chalk on the coefficient of friction (þ18.7% on limestone and þ21.6% on sandstone). Moreover
sandstone had a higher coefficient of friction than limestone (þ15.6% without chalk, þ18.4% with
chalk). These results confirmed climbers’ belief that chalk enhances friction. However, no correlation
with humidity/temperature and friction coefficient was noted which suggested that additional
parameters should be considered in order to understand the effects of climate on finger friction in
rock climbing.
Keywords: Climber, hang board, humidity, temperature, magnesium carbonate
During the last decade, the popularity of rock climbing has grown rapidly and this sport is
now pursued by many as a professional or recreational activity. In rock climbing, climbers
maintain body equilibrium and evolve on vertical supports by applying high-intensity forces
with the hands and fingers. The inability to maintain contact with the handholds is one of the
main reasons for failure in rock climbing (Watts et al., 2000). Consequently, the capacity to
exert high-intensity forces with the fingertips and the capability to resist finger muscle fatigue
are recognized as characteristics of highly skilled climbers (Grant et al., 1996; Quaine et al.,
2003). Moreover, the interaction between fingers and the hold surface is an important
ISSN 1476-3141 print/ISSN 1752-6116 online q2012 Taylor & Francis
Correspondence: Arif Mithat Amca, School of Sport Sciences and Technology, Hacettepe University, 06800 Beytepe, Ankara,
Turkey, E-mail:
Sports Biomechanics
2012, iFirst article, 1–7
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determinant of performance, especially on small holds with limited area available for finger
placement (Bourne et al., 2011) and/or on sloper holds (i.e. holds with a flat inclined surface
relative to the horizontal axis). The rock climbing community has recognized that this
finger hold interaction is highly influenced by transpiration, rock type, ambient
temperature, and humidity. To increase the finger hold friction coefficient, climbers use
‘chalk’ (mainly, magnesium carbonate or MgCO
) to reduce moisture on the hands.
The skin friction coefficient has been investigated by several studies in both dynamic and
static cases (Comaish & Bottoms, 1971; El-Shimi, 1977; Highley et al., 1977; Nacht et al.,
1981; Adams et al., 2007; Derler et al., 2007, 2009a, 2009b; Savescu et al., 2008; Andre
´et al.,
2009). Friction coefficients from different parts of the body were examined parallel to the
effects of various probes (nylon, glass, teflon, steel, etc.) and/or conditions (hydration,
lubricants, moisturizers, etc). Surprisingly, only one study has been conducted to analyse the
effect of chalk on the friction coefficient of finger –rock contact (Li et al., 2001) in which three
types of rock (sandstone, slate, and granite) and four different hand conditions (dry, dry plus
chalk, wet, and wet plus chalk) were studied. Li et al. (2001) used a specially designed table
and followed the ‘beginning slip’ method to measure the friction coefficient between the finger
skin and rock samples. Thus different rock type surfaces were connected to a 3.5-kg load and
subjects were asked to apply vertical fingertip forces on these surfaces to prevent slippage
followed by reduction of normal force till slip. These authors repor ted that using chalk reduces
the static coefficient of friction, which is in total contradiction with the climbers’ belief.
However, the design they used was not specific to rock climbing and the resistant force (3.5 kg
hanging weight and 29 N tangential forces) was very small compared to real situations in
rock climbing where forces could be as large as the body weight. This point is of importance
since the skin and the pulp of human finger tips have viscoelastic material properties (Sivamani
et al., 2003; Derler et al., 2009a). Depending on the applied load, the fingertips change their
form and their characteristics, which directly influence the friction coefficient (Andre
´et al.,
2009; Derler et al., 2009a; Warman & Ennos, 2009). In spite of the importance of these
parameters, no design exists to investigate the finger friction in rock climbing and the precise
effects of magnesium carbonate and ambient climate are still unknown.
The objective of this study was to investigate the effect of chalk on the friction coefficient
between the climber’s fingers and climbing holds. As climbers practice in various climate
conditions and on various rock types, the effect of chalk was tested in a wide range of
temperature humidity conditions and on two different rock characteristics. It was
hypothesized that, in line with most climbers’ perception, chalk would increase the
finger hold friction coefficient.
Eleven (10 males and 1 female) experienced climbers participated in this study:
mass ¼73.9 ^6.3 kg, height ¼178.7 ^4.2 cm, and climbing experience ¼9.6 ^5.0
years. Prior to testing, they were informed about the testing procedure and signed a
voluntary participation form according to the University Guidelines. Tests were performed
on several different days and conducted outside in a wide range of weather conditions
(temperature range: 11.9 28.08C; relative humidity range: 28.5 – 75.9%; Table I) in order to
incorporate the real weather conditions encountered during sport climbing. Temperature
and humidity values were measured at each session by using a digital thermo-hygrometer
(Temperature Station, Conrad Electronics, Barking, UK). A total of 42 sessions were
recorded (one session is defined as tests for all conditions of chalk and rock type for a
A.M. Amca et al.2
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Experimental protocol
A specially designed hang board, consisting of a wooden plate hinged on a fixed frame and a
fastened wooden step bar, was designed and used in this study (Figure 1). Two pairs of
handholds (5.5 cm depth and 10.5 cm width) with flat surfaces were fixed on the wooden
step bar about shoulder width apart. The holds were issue from the Mediterranean coast and
they were representative of sandstone and limestone rock types. The hang board was
articulated on its base in order to gradually change the angle of the holds using a pulley rope
Participants hung from the same pair of holds with straight arms as their natural position.
They hung with only their four fingers (slope grip technique); the thumb was not used to
apply a counter force. The inclination of the hang board was then increased continuously
with a mean speed of 8.0 ^4.0 deg/s until the subjects slipped from the holds. During this
process participants were asked to hang on the holds as they do during rock climbing. They
were required to maintain arm and body positions. This was controlled visually and trials
were repeated if participants changed the test position. When they slipped from the hold, a
short rest was given before they continued with the next tests and conditions. When
participants released the hold voluntarily before the involuntary slip point the data were
ignored and the trial was repeated. Participants were allowed to practice several times until
they were accustomed with the task and the test design. Sandstone and limestone were tested
and three trials were done for each rock type and chalk conditions (with and without chalk).
The sequence of hold types and chalk conditions was randomized for each experimental
session. Chalk was used by subjects as it is a common practice in climbing; by utilizing a
Figure 1. Side and front view of the designed hang board. A wooden bar screwed on the wooden plate and two pairs
of sandstone (S) and limestone (L) handholds with flat surfaces were fixed on this wooden bar about shoulder width
apart. Angle of the hang board was progressively increased until the climbers slipped from the holds.
Table I. Temperature and humidity data (N¼42).
Temperature (8C) % Humidity
Mean 18.7 47.9
Standard deviation 5.1 11.5
Minimum 11.9 28.5
Maximum 28.0 75.9
The effect of chalk in rock climbing 3
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chalk bag. Holds were cleaned with a brush after each session. Furthermore, the subjects
hands were cleaned with water and dried with a towel followed by shaking hands in the air
before each test without chalk. A gyroscopic sensor (Animazoo IGS-190, Brighton, UK) was
fixed on the moving plate to measure the angle of the hang board. The gyroscopic sensor
was calibrated as zero for the starting vertical position, and angular displacement data were
recorded with Animaview software (Animazoo) at a sample rate of 60 Hz.
Data analysis
The slip angle was determined by processing the recorded angle data for each trial (Figure 2).
The coefficient of friction was defined as the ratio between tangential force and normal force
at the moment of slip (i.e. the tangent of slip angle; Sivamani et al., 2003). The results
of each trial were analyzed individually in order to determine the coefficient of friction.
All computation procedures were performed in MATLAB (The Math Works, Inc.,
Natick, MA, USA).
The average value of the three trials of a subject in a condition was considered for
statistical analysis. All results were reported as means and standard deviations. Normality of
the collected data was verified. A two-way repeated measures ANOVA was used to analyse
the effect of hold type and chalk condition on maximal slip angle. A Tukey post hoc test was
used to identify differences when ANOVA showed a significant effect ( p,0.05). A multiple
regression model was used to analyse the relationship between the temperature, humidity,
and the friction coefficient for each condition (hold type and chalk condition). Statistical
analyses were performed using Statistica (StatSoft, Inc., Tulsa, Oklahoma, USA).
In all the measurements, the coefficient of friction ranged from 0.47 to 1.14 (Figure 3).
The mean coefficients of friction value on limestone were 0.64 ^0.10 without chalk and
0.76 ^0.09 with chalk. The sandstone coefficients were 0.74 ^0.10 and 0.90 ^0.10,
respectively. There was a significant effect of chalk on the coefficient of friction (F
p,0.001). The positive effect of chalk was 18.7% and 21.6% for limestone and sandstone,
respectively. The coefficient of friction also differed significantly according to the hold type
¼447.5; p,0.001). The mean coefficient of friction increased by 15.6% without
Figure 2. Typical recording of the angle data for one representative test. Slip angle was determined as the maximum
angle of the trial.
A.M. Amca et al.4
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chalk and 18.4% with chalk between limestone and sandstone. Also a significant interaction
between hold type and chalk condition was found (F
¼20.6; p,0.001).
The multiple regression models showed no significant correlation between humidity,
temperature and friction coefficient ( p.0.05 and r
The aim of this study was to examine the effect of chalk on the friction coefficient between
climber’s fingers and two commonly encountered rock types during rock climbing. In addition,
various temperature and humidity conditions were investigated to observe their combined
effects on the friction coefficient. In this study, a new experimental design was proposed to
measure the friction coefficient of the fingers as encountered during rock climbing. This design
was close to the real rock climbing conditions and it enabled us to measure the friction
coefficient of holdfingers contact under loads resulting from full body weight.
The main result of our study indicated that there was a significant positive effect of chalk
on the friction coefficient for both rock types. This result was in contradiction with the
previous results of Li et al. (2001) which might have been caused by the used load intensity.
Li et al. (2001) used a constant tangential force around 29 N and participants applied normal
forces around 12 N at the moment of slip, while in the present study the contact forces
corresponded to the participants’ body weights (725.3 ^62.2 N). The influence of the
normal force on the friction coefficient of skin has been studied by several authors (Comaish
& Bottoms, 1971; Savescu et al., 2008; Warman & Ennos, 2009). These studies have shown
that the friction coefficient is not constant for fingertips and is modified according to the
applied normal force. This result has also been confirmed for different body parts by several
subsequent studies (El-Shimi, 1977; Derler et al., 2007; Andre
´et al., 2009). Derler et al.
(2009b) concluded that the friction coefficient of bare foot skin systematically decreased
with the normal load applied onto the foot (in the range from 50 to 700 N). This behavior of
skin results from its viscoelastic nature and that the actual contact area changes as a function
of normal load (Derler et al., 2009a; Warman & Ennos, 2009). All these results confirm the
importance of studying the friction coefficient of fingers under force intensities equivalent to
those encountered during rock climbing and explain the differences between conclusions of
the present study and Li et al. (2001). Moreover, the granular layer effect hypothesized by
Figure 3. Mean coefficient of friction values and standard deviations for both rock and chalk conditions.
The effect of chalk in rock climbing 5
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Li et al. (2001) is probably cancelled out by the force intensities encountered during rock
While it was shown that the hold finger contact was improved by chalk, the present study
did not aim to investigate the actual factors which led to these results. Better performance
observed with chalk can be explained by several possible reasons: modifications of the skin
roughness, modification of skin elasticity which enables the fingers to best adapt to the hold
shape and changes in water/sudation elimination behavior. Climbers indeed recognize that
chalk eliminates perspiration and keeps the hands dry. Thus this effect is fundamental to
explaining our results. However, in the literature, it was shown that highly wet or highly dry
skin showed relatively low friction (Highley et al., 1977; Dawson, 1997; Derler et al., 2007;
´et al., 2009). Therefore an optimal use of the chalk is important in order to keep the
hand in the ideal moisture range.
The rock type effect was also shown in the present study. In accordance with the climbers’
testimonies, it was found that sandstone displayed a higher friction coefficient than
limestone. Also, no cross interaction between rock types and chalk usage was observed; chalk
had a positive effect for both rock types. It appeared that the higher friction coefficient on
sandstone was due to the rougher contact surface compared with limestone. This result was
in accordance with Li et al. (2001) who concluded that sandstone produced a higher
coefficient of friction than granite and slate. They found that the normalized performance of
granite and slate was 0.77 and 0.76, respectively, compared with the performance of
sandstone. Granite and slate were not studied in the current study, but the normalized
limestone performance (0.86) indicated that limestone might have a higher coefficient of
friction than slate and granite. Further studies are required to clarify this result and
investigate the coefficient of friction on other rock types.
The positive effect of chalk and the influence of rock type were verified for a wide range of
outdoor climate conditions. While the correlation among air temperature, humidity, and
friction was investigated, no evidence of linear relationships was found. Absence of
significant correlation could be due to the fact that extremely low or high temperature and
humidity values were not assessed. Moreover, these parameters could not be controlled
independently since the tests were conducted outdoors. The effects of these parameters
could be further investigated by controlling them independently in a climate-controlled
room. In addition, the temperature and humidity of rock and/or skin also need to be
controlled in future studies. As mentioned by Tang and Bhushan (2010), temperature and
humidity conditions affect the water in the skin, which leads to changes of the tribological
and mechanical properties of the skin surface. Thus, the effects of temperature and humidity
on the friction properties of finger skin need to be studied in detail to determine optimum
performance conditions.
In summary, this study is the first to demonstrate the positive effect of chalk for rock
climbing, but some limitations need to be considered: the most important of which concerns
the angular speed of the hang board which varied between trials. Since a large number of
trials were tested randomly it was expected that the different velocities were homogenously
distributed across the conditions and this limit did not affect the conclusions of the study.
The angular speed, however, needs to be controlled in further studies. Another limitation
concerns psychological bias: the participants knew when magnesium chalk was used.
Magnesium chalk has a specific color (white) and a specific consistency which makes a blind
test difficult to perform. Another important point concerns the mechanical characteristics
(rough, polished) and elasticity (compliance) of the climbers’ skin which were shown to be
modified with practice and expertise. These characteristics could change over time and vary
from one individual to another, no attempt was made to control them. It is important to
A.M. Amca et al.6
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further investigate the influence of skin characteristics and to determine how the climbers
should prepare their skin to obtain optimal characteristics.
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The effect of chalk in rock climbing 7
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... Bouldern an künstlichen Kletterwänden als eigenständige, wettkampforientierte Disziplinen etablieren konnten [5,6,16,23,25,41,43,46,51,54,60,82,90,91,108,117,124,129,150,152,153,165,166,171]. Infolgedessen lässt sich im Bouldersport eine enorme Zunahme der Wettkämpfe auf regionaler, nationaler und internationaler Ebene beobachten [14,108]. ...
... Weiterhin sollte innerhalb von zwei Stunden vor der Datenerhebung auf Koffeinkonsum verzichtet, sowie eine gleichmäßige Wasserzufuhr während der Datenerhebung gewährleistet werden [16,35,39,58].  Um standardisierte Greifbedingungen zu gewährleisten, durften alle Probanden ausschließlich das Magnesium Carbonat White Gold Loose Chalk vom Hersteller Black Diamond (CH) benutzen, da die Reibung zwischen Haut und Klettergriff in Abhängigkeit des eingesetzten Chalks variieren kann[6,61,103,111,163]. Überdies wurden alle Griffe vor jeder Datenerhebung mit einer Bürste vom Hersteller Lapis (SLO) gesäubert, da gleichzeitig Chalk auf den Griffen und den Händen die Reibung reduzieren kann[61]. ...
... 4.4Apparaturbesprechung). Hierdurch konnten Veränderungen der Raumtemperatur und der Luftfeuchtigkeit diagnostiziert und deren Einfluss als potentielle Störvariablen auf die Testergebnisse bestimmt werden[6,23,110]. ...
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Zielsetzung der Studie war die Untersuchung der Wirkungsweise von Bouldern, Intervall Bouldern, dem Training am Moonboard, am Hangboard und am Vibrationsboard auf die Maximalkraft der Fingermuskulatur, die Kraftfähigkeit der Armbeuger und der Schultergürtelmuskulatur und die lokale Muskelausdauer.
... Magnesium carbonate powder, i.e., "chalk, " is believed to help absorb perspiration and improve grip on the item being held onto while climbing (Li et al., 2001;Fuss et al., 2004;Fuss and Neigl, 2006;Bourne et al., 2011;Amca et al., 2012;Kilgas et al., 2016). Li et al. (2001) investigated the effect of magnesium carbonate powder on the sliding friction coefficient at the fingertip-rock surface interface and found that the coefficient decreased under both dry and wet conditions. ...
... These findings are contradictory to the supposed role of the powder, which is empirically known as a grip-enhancing agent. Conversely, Amca et al. (2012) reported a positive effect of using rosin powder on the friction coefficient between the fingers of climbers and two different rock types (sandstone and limestone), i.e., an increased friction coefficient was observed. Carré et al. (2012) investigated the effects of magnesium carbonate powder and rosin powder on the sliding friction between the fingers and a polished steel surface and showed that the powder decreased the friction coefficient compared with no application of the powder under dry condition; however, the powder increased the friction coefficient when the fingers were wet. ...
Full-text available
Rosin powder, which is composed of magnesium carbonate powder and pine resin, is often used as a grip-enhancing agent in baseball pitching. However, the effect of rosin powder on friction at the baseball–human finger interface remains unclear. This study aimed to investigate the effect of rosin powder on the friction coefficient between a baseball and a finger using sliding friction tests. Ten young adult males participated in this study who were asked to slide the index finger of their dominant hand over the leather skin of a baseball adhered to the force sensor, which was not a real baseball pitching situation. Our findings suggest that rosin powder application stabilizes friction under both dry and wet conditions; that is there was less dependence of the friction coefficient on the normal force and less variation in the friction coefficient among individuals. For most participants, the friction coefficient was not necessarily increased by the presence of rosin powder at the finger pad–leather sheet interface under dry conditions. However, under wet conditions, rosin powder application increased the friction coefficient compared with the non-powdered condition in the large normal force condition, indicating the efficacy of rosin powder as a grip-enhancing agent.
... The maximal CSHT was determined by measuring the hanging time on a 4-centimeter-deep crimp with rounded edges and structuring as is typically found on a hold in a climbing gym of a MOON fingerboard (Moon Climbing Limited, Sheffield, England) without touching the ground. Therefore, participants held a dead hang position with straight arms with the feet lifted at least 20 cm from the ground (depending on body height) on clean holds with loose magnesium on the fingers as commonly practiced in climbing to increase friction [19]. The participants were not allowed to use their thumb while hanging but could use three to four fingers depending on individual preference (see Figure 2). ...
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The objectification of acute fatigue (during isometric muscle contraction) and cumulative fatigue (due to multiple intermittent isometric muscle contractions) plays an important role in sport climbing. The data of 42 participants were used in the study. Climbing performance was operationalized using maximal climbing-specific holding time (CSHT) by performing dead hangs. The test started with an initial measurement of handgrip strength (HGS) followed by three intermittent measurements of CSHT and HGS. During the test, finger flexor muscle oxygen saturation (SmO2) was measured using a near-infrared spectroscopy wearable biosensor. Significant reductions in CSHT and HGS could be found (p < 0.001), which indicates that the consecutive maximal isometric holding introduces cumulative fatigue. The reduction in CSHT did not correlate with a reduction in HGS over multiple consecutive maximal dead hangs (p > 0.35). Furthermore, there were no significant differences in initial SmO2 level, SmO2 level at termination, SmO2 recovery, and mean negative slope of the SmO2 saturation reduction between the different measurements (p > 0.24). Significant differences were found between pre-, termination-, and recovery-(10 s after termination) SmO2 levels (p < 0.001). Therefore, monitoring acute fatigue using athletes' termination SmO2 saturation seems promising. By contrast, the measurement of HGS and muscle oxygen metabolism seems inappropriate for monitoring cumulative fatigue during intermittent isometric climbing-specific muscle contractions.
... The holds were cleaned before each run. Loose magnesium was directly applied to the fingers before carrying out the measurement, as this is performed in sports practice to improve friction [18]. The holding was performed without the use of the thumb, with three or four fingers, as habitually preferred by the subjects. ...
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Handgrip strength (HGS) appears to be an indicator of climbing performance. The trans-ferability of HGS measurements obtained using a hand dynamometer and factors that influence the maximal climbing-specific holding time (CSHT) are largely unclear. Forty-eight healthy subjects (27 female, 21 male; age: 22.46 ± 3.17 years; height: 172.76 ± 8.91 cm; weight: 69.07 ± 12.41 kg; body fat: 20.05% ± 7.95%) underwent a maximal pull-up test prior to the experiment and completed a self-assessment using a Likert scale questionnaire. HGS was measured using a hand dynamometer, whereas CSHT was measured using a fingerboard. Multiple linear regressions showed that weight, maximal number of pull-ups, HGS normalized by subject weight, and length of the middle finger had a significant effect on the maximal CSHT (non-dominant hand: R 2 corr = 0.63; dominant hand: R 2 corr = 0.55). Deeper exploration using a machine learning model including all available data showed a predictive performance with R 2 = 0.51 and identified another relevant parameter for the regression model. These results call into question the use of hand dynamometers and highlight the performance-related importance of body weight in climbing practice. The results provide initial indications that finger length may be used as a sub-factor in talent scouting.
... Hence, they tend to relax the force application to prevent the overexertion of finger muscles. Pinch endurance on the other hand was found to have a slightly lower mean result in measurements using the rubber gloves (increased tactile sensitivity), which differ from findings on the increase in finger endurance when friction is increased (Amca et al., 2012;Fuss & Niegl, 2012). Pinch endurance in this experiment was quantified through the total pinching time of a binder clip. ...
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This study aims to examine tactile sensitivity effects on the pinch force and endurance of elderly people, and propose solutions extending from the statistical outcomes using the theory of inventive problem-solving (TRIZ). Pinch force and endurance time data were collected among 32 subjects aged 55–65 years according to a non-probability sampling method. Each participant received both treatments of increased and decreased tactile sensitivity through an experimental research design. Subjects pinched an experimental apparatus with different tactile sensitivities, and sustained their pinch for as long as possible. The results suggested that a significant difference existed between pinch force from reduced and increased tactile sensitivities, with similar outcomes for endurance. Resolving contradictions from the results led to the partial-action principle, which suggested that elderly people should pinch using less force when they lack the strength to achieve a certain force level, rather than exert a high force in a single attempt. The segmentation and other-way-around principles were also recommended. Su-Field analysis found that harmful effects from pinching can be neutralised using intermediary materials between the fingers and object, such as rubber. The analysis proposed using optical or acoustic fields, where light sensors or buzzers could act as mechanisms to signal users when sufficient force is achieved. These TRIZ-stimulated solutions provide new insights in resolving poor pinch performance caused by degrading tactile sensitivity.
... This position was chosen to decrease the risk of injury to the tendons or ligaments (Vigouroux et al., 2008). All climbers used magnesium on their hands to prevent the fingers from slipping from the holds (Amca, Vigouroux, Aritan, & Berton, 2012). ...
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Sport climbers frequently use campus board (CB) to improve their upper limb strength under similar conditions of high-difficulty sport climbing routes. The objective of this study was to assess the test-retest reliability of peak force and impulse measured using a CB instrumented with two load cells on starting holds. The same evaluator examined 22 climbers on two days with 48 h between the assessments. The participants performed five concentric lunges (CL) and five lunges with stretch-shortening cycle with 1 min intervals between repetitions and 10 min between exercises. All variables were associated with significant intraclass correlation coefficient (ICC) values (p = 0.001), and none variable showed systematic errors (p > 0.05). Peak force ICC was higher than 0.88, and the standard error of measurement (SEM%) was less than 5%. Impulse ICC for the CL was greater than 0.90, and the SEM% was less than 14%. We conclude that the kinetic variables measured using the CB were reliable. The ability of the hands to maintain contact with the holds (peak force) and the abilities of the arms and shoulders vertically move the centre of mass (impulse) should be taken into account by coaches on CB training prescription as well for further research.
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The purpose of this study was to assess the test-retest reliability of a 4-minute all-out critical force test in well-trained rock climbers. Thirteen rock climbers (n=4 females) completed a familiarization session and two all-out critical force tests on different days. During each trial, participants completed 24 repetitions of 7s right-handed, maximal effort hangs from a 20mm edge interspersed with 3 s rest. The end-test force (EF; i.e., critical force), impulse above EF (IEF), and peak force achieved durin g the test were analyzed with paired t-tests to determine differences between trials. Intraclass correlation coefficient (ICC), coefficient of variation (CV), and Bland-Altman analysis were performed to quantify the relative and absolute reliability of the measure, respectively. The level of significance for this study was set at p<0.05. There were no significant differences between trials for any of the reported variables (P≥0.455). For EF, IEF, and peak force, ICC was 0.848, 0.820, and 0.938, respectively; and CV was 21.0%, 13.2%, and 5.6%, respectively. Bland-Altman analyses showed a mean relative bias of -2.3%, -2.8%, and -1.3%, with 95% limits of agreement (LoA) of -62.6% to 58.1%, -40.5% to 30.9%, and -17.2% to 14.6% for EF, IEF, and peak force, respectively, however linear regression revealed a significant proportional bias for EF (p = 0.026, R2 = 0.377). The reliability of this protocol was good to excellent for all parameters; however, there was larger intra-individual variability for EF and IEF. This study suggests that when using the 4-min all-out critical force test in rock climbers, coaches and athletes should be aware that there may be a trade-off between the test’s practicality and the precision of its results.
The purpose of this study was to investigate the friction of finger against polyurethane-coated leather and seam surfaces of new and used softballs. The effects of seam alignment (across and along the seam) and chalk/rosin powder application were also investigated. The coefficient of static friction (COF) was evaluated on 14 college female softball players who rubbed the pad of their index finger on a test surface fixed on a biaxial force plate. The mean COF of the new leather was 1.04, and those of the seam were 1.16 for the across condition, and 1.07 for the along condition. The leather-seam difference in COF was significant. The used ball's leather and seam had lower COF than those of the new ball. The seam alignment difference did not reach the level of significance. For both new and used balls, the application of chalk/rosin powder to the finger reduced COF, and the reduction was greater on the leather than on the seam. It was concluded that the outer cover of softballs, and especially the seam portions, is equipped with reasonably high friction under natural finger condition. The friction is reduced in used balls and with the use of chalk/rosin powder.
The idea of man’s ‘mastery over nature’ is ubiquitous in western philosophy and in western thinking. Technology has been widely used in support of this end. Given the growing interaction design opportunities for personal digital technologies in supporting outdoor and recreational nature activities such as mountaineering, it is timely to unpack the role that technology can play in such activities. In doing so, it is important to consider the intrinsic and extrinsic motivations at play for the individual and the accepted social norms or ‘rules’ that are associated with the activity through its community and passed on through its community of practice. Technologies that may be considered as a form of ‘cheating’ when first introduced (such as handheld GPS) can later become accepted through common practice, although the rules are often nuanced. For example, it is widely regarded that GPS should not replace the skill of map reading and navigation. In this chapter, we consider different forms of mastery over nature that technology can support and reflect on the design sensitivities that these provide.
Magnesium alba—chalk—is regularly applied by indoor and outdoor climbers to their hands to reduce sweat while climbing in order to grip climbing holds. We investigated the potential for suspended chalk dust to lead to unhealthy levels of indoor particulate matter (PM 2.5 and PM 10 ) in two university climbing facilities. Low-cost, Dylos DC 1700 PM monitors sampled air quality during two, 5-day sampling periods. Findings revealed “good” PM values at one university climbing facility and “unhealthy” (PM 2.5 ) or “very unhealthy” (PM 10 ) values at the other institution’s climbing wall. Facility predicted over 60% of the variance in PM readings, and post hoc tests revealed 75% of the variance in PM values at the second institution can be explained by open climbing hours. These findings hold a variety of implications for future research and management of university climbing wall facilities to ensure the health of staff and their patrons.
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It is generally assumed that fingerprints improve the grip of primates, but the efficiency of their ridging will depend on the type of frictional behaviour the skin exhibits. Ridges would be effective at increasing friction for hard materials, but in a rubbery material they would reduce friction because they would reduce contact area. In this study we investigated the frictional performance of human fingertips on dry acrylic glass using a modified universal mechanical testing machine, measuring friction at a range of normal loads while also measuring the contact area. Tests were carried out on different fingers, fingers at different angles and against different widths of acrylic sheet to separate the effects of normal force and contact area. The results showed that fingertips behaved more like rubbers than hard solids; their coefficients of friction fell at higher normal forces and friction was higher when fingers were held flatter against wider sheets and hence when contact area was greater. The shear stress was greater at higher pressures, suggesting the presence of a biofilm between the skin and the surface. Fingerprints reduced contact area by a factor of one-third compared with flat skin, however, which would have reduced the friction; this casts severe doubt on their supposed frictional function.
The in vivo friction of human skin has been measured in the dry, wet and damp states using smooth glass and polypropylene spherically tipped probes. They were selected to be representative of hydrophilic and hydrophobic countersurfaces. The data are interpreted using the adhesion model of friction, which provides an explanation for the influence of the normal load and the surface free energies of the probe materials on the frictional characteristics of the skin. In particular, explanations based on this model are given for the tendency of wet skin to exhibit stick-slip motion and of damp skin to exhibit a peak frictional force against a glass probe.
The friction behaviour of human skin was studied by combining friction measurements using a tri-axial force plate with skin contact area measurements using a pressure sensitive film. Four subjects carried out friction measurement series, in which they rubbed the index finger pad and the edge of the hand against a smooth and a rough glass surface under dry and wet conditions. The normal loads were varied up to values of 50 N, leading to skin contact pressures of up to 120 kPa. The analysis of the pressure dependence of friction coefficients of skin for contrasting sliding conditions allowed to determine the involved friction mechanisms on the basis of theoretical concepts for the friction of elastomers.Adhesion was found to be involved in all investigated cases of friction between skin and glass. If adhesion mechanisms predominated (skin against smooth glass in the dry condition and skin against rough glass in the wet condition), the friction coefficients were generally high (typically >1) and decreased with increasing contact pressure according to power laws with typical exponents between −0.5 and −0.2. Contributions to the friction coefficient due to viscoelastic skin deformations were estimated to be relatively small (<0.2). In those cases where the deformation component of friction played an important role in connection with adhesion (skin against rough glass in the dry condition), the friction coefficients of skin were typically around 0.5 and their pressure dependence showed weak trends characterised by exponents ranging from −0.1 to +0.2. If hydrodynamic lubrication came into play (skin sliding on smooth glass in the wet condition), the friction coefficients were strongly reduced compared to dry friction (<1), and their decrease with increasing contact pressures was characterised by exponents of <−0.7.
This study investigated how the sliding friction coefficients of wet foot skin depend on the microscopic surface properties of contacted hard substrates. Fourteen subjects conducted repeated slip experiments with one foot on each of 28 different wet surfaces. The friction and normal forces transmitted to the substrates were measured using a tri-axial force plate, and coefficients of friction were determined over periods of stationary sliding. The surface structures of the substrates, characterised by an optical 3D profilometer, varied from roughness asperities in the range of micrometers to macroscopic surface elements in the range of millimetres. The analysis of the load dependence of the skin friction behaviour based on a two-term model provided information on the adhesion and deformation components of friction. Both adhesion and deformation were found to increase with the surface roughness of the substrates. Adhesion mechanisms seemed to predominate on smooth surfaces showing low friction coefficients (<0.3), while the contributions due to skin deformations were found to be up to 0.4 on rough surfaces with high friction coefficients (>0.5). Independent of friction measurements, the analysis of the surface microstructure of the substrates indicated that ploughing as a skin deformation mechanism could contribute around 50% to the deformation component of friction.
The friction of untreated human skin (finger) against a reference textile was investigated with 12 subjects using a force plate. In touch experiments, in which the subjects assessed the surface roughness of the textile at normal loads of 1.5 ± 0.7 N, the average friction coefficients ranged from 0.27 to 0.71 and varied among individuals due to different states of skin hydration. In experiments, in which the subjects varied the normal load, the friction coefficients were in the same range and showed practically no load dependence, indicating that both adhesion and hysteresis are contributing to the friction behaviour. The results for human skin were compared with apparative friction measurements using different silicone and polyurethane materials as mechanical skin equivalents. A polyurethane coated polyamide fleece with a surface structure similar to that of skin showed the best correspondence with human skin under dry conditions. The friction coefficients of this material increased with the moisture content of the reference textile. A realistic skin model in combination with an objective friction test method would be very useful for the textile industry and allow the efficient development of new textiles with improved and skin-adapted surface and frictional properties for sport and medical applications.
This study investigates the hypothesis that shallow edge lifting force in high-level rock climbers is more strongly related to fingertip soft tissue anatomy than to absolute strength or strength to body mass ratio. Fifteen experienced climbers performed repeated maximal single hand lifting exercises on rectangular sandstone edges of depth 2.8, 4.3, 5.8, 7.3, and 12.5 mm while standing on a force measurement platform. Fingertip soft tissue dimensions were assessed by ultrasound imaging. Shallow edge (2.8 and 4.3 mm) lifting force, in newtons or body mass normalized, was uncorrelated with deep edge (12.5 mm) lifting force (r < .1). There was a positive correlation (r = .65, p < .05) between lifting force in newtons at 2.8 mm edge depth and tip of bone to tip of finger pulp measurement (r < .37 at other edge depths). The results confirm the common perception that maximum lifting force on a deep edge ("strength") does not predict maximum force production on very shallow edges. It is suggested that increased fingertip pulp dimension or plasticity may enable increased deformation of the fingertip, increasing the skin to rock contact area on very shallow edges, and thus increase the limit of force production. The study also confirmed previous assumptions of left/right force symmetry in climbers.
Skin cream is commonly used to improve skin health and create a smooth, soft, and moist perception by altering the surface roughness, friction, and adhesion of skin surface. In this study, a systematic characterization of the friction and adhesion properties of skin and skin cream was carried out, which is essential to develop better skin care products and advance biological, dermatology, and cosmetic science. Since cream rheology is expected to be a function of its thickness as well as the velocity and normal load during its application, friction and adhesion experiments were performed at a range of cream film thickness, velocity, and normal load in order to study their effect on virgin skin and cream treated skin. Since environmental dependence of skin and skin cream is of importance, the effect of relative humidity and temperature on the coefficient of friction and adhesive force was also studied. Durability of the virgin skin and cream treated skin was studied by repeated cycling tests. These experiments were performed by using an atomic force microscope (AFM) and a macroscale friction test apparatus in order to study the scale effects. Friction and wear mechanisms under various operating conditions are discussed.
When humans manipulate an object, the minimal grip force (GF) required to avoid slipping depends on the frictional properties between the fingers and the object. As a consequence, fingertip skin friction plays a critical role during object manipulation. Here, the effects of the normal force and moisture content on the skin's static coefficient of friction (CF) for human fingertips were studied. Ten subjects were asked to pinch an object with a given normal force. Slippage of the object on the fingertips was generated for different ranges of normal force using a linear translation stage. The exerted forces and moisture of the fingertips were then measured, and the static coefficient of friction was calculated as the ratio between the tangential force and normal force at slippage. These results demonstrate that the effects of the normal force and moisture content on the CF exhibit a complex interaction. For a given moisture condition, the CF varies as a power function of the normal force; in contrast, for a given normal force, the CF is described by a "bell-shaped" function of moisture. A global expression of the CF as a function of the normal force and moisture content is derived, and a method is proposed for a continuous measure of the CF. This new method shall be of particular interest in investigating dexterous manipulation.