Grip Force Safety Margin in Rock Climbers

Abstract

When holding an object, grip force (Gf) is larger than the smallest force needed to prevent slipping (Gmin). The unnecessary grip force is termed safety margin (SM = Gf - Gmin). Because some hand injuries in rock climbing are largely encouraged by excessive grip force, safety margin was examined in a set of expert climbers, and compared to a set of non-climbers. Subjects were asked to hold a heavy or a light object during either a short or a long duration. We focused on the relative safety margin (RSM = 100 × SM/Gmin) adopted at the initiation of each trial. With the heavy object, climbers and non-climbers had similar RSMs (155 versus 148 %). With the light object, higher RSMs were reached, albeit smaller in climbers as compared to non-climbers (232 versus 386 %). Surprisingly, all subjects exhibited larger RSMs at the initiation of a long trial (246 versus 215 %). We conclude that expertise in rock climbing is not accompanied by key changes in RSMs that increase the likelihood of hand injuries. On the other hand, the fact that grip force is so crudely optimized at large load, especially when planning to sustain a hold, does promote the risk of hand injury in climbers.

Key words

grip force - rock climbing - hand injury - endurance - safety margin

References

• 1 Aptel M, Aublet-Cuvelier A, Cnockaert J-C. Work-related musculoskeletal disorders of the upper limb.  Joint Bone Spine. 2002;  69 546-555
• 2 Astrand P, Rodahl K. Textbook of Work Physiology: Physiological Basis of Exercise. New York; McGraw-Hill 1986: 115-122
• 3 Billat V, Palleja P, Charlaix T, Rizzardo P, Janel N. Energy specificity of rock climbing and aerobic capacity in competitive sport rock climbers.  J Sports Med Phys Fitness. 1995;  35 20-24
• 4 Bollen S R. Soft tissue injury in extreme rock climbers.  Br J Sports Med. 1988;  22 145-147
• 5 Cutts A, Bollen S R. Grip strength and endurance in rock climbers.  Proceed Inst Mech Eng. 1993;  207 87-92
• 6 Danion F. How dependent are grip force and arm actions during holding an object?.  Exp Brain Res. 2004;  158 109-119
• 7 Grant S, Hynes V, Whittaker A, Aitchison T. Anthropometric, strength, endurance and flexibility characteristics of elite and recreational climbers.  J Sports Sci. 1996;  14 301-309
• 8 Holtzhausen L M, Noakes T D. Elbow, forearm, wrist, and hand injuries among sports rock climbers.  Clin J Sport Med. 1996;  6 196-203
• 9 Johansson R S. Sensory control of dextrous manipulation in humans. Wing AM, Haggard P, Flanagan JR Hand and Brain: The Neurophysiology and Psychology of Hand Movements. San Diego; Academic Press 1996: 381-414
• 10 Kahn J F, Favriou F, Jouanin J C, Monod H. Influence of posture and training on the endurance time of a low-level isometric contraction.  Ergonomics. 1997;  40 1231-1239
• 11 Logan M J, Makwana N, Mason G, Dias J. Acute hand and wrist injuries in experienced rock climbers.  Br J Sports Med. 2004;  38 545-548
• 12 Mrotek L A, Hart B A, Schot P K, Fennigkoh L. Grip responses to object load perturbations are stimulus and phase sensitive.  Exp Brain Res. 2004;  155 413-420
• 13 Ohki Y, Edin B B, Johansson R S. Predictions specify reactive control of individual digits in manipulation.  J Neurosci. 2002;  22 600-610
• 14 Quaine F, Vigouroux L, Martin L. Finger flexors fatigue in trained rock climbers and untrained sedentary subjects.  Int J Sports Med. 2003;  24 424-427
• 15 Rohrbough J T, Mudge M K, Schilling R C. Overuse injuries in the elite rock climber.  Med Sci Sports Exerc. 2000;  32 1369-1372
• 16 Rooks M D. Rock climbing injuries.  Sports Med. 1997;  20 261-270
• 17 Rougier P. Etude de la posture et du mouvement en escalade: influence du niveau d'expertise et de la nature des prises. Grenoble; Université Joseph Fourier, Thèse de Doctorat 1991
• 18 Stock S R. Workplace ergonomic factors and the development of musculoskeletal disorders of the neck and upper limbs: a meta-analysis.  Am J Ind Med. 1991;  19 87-107
• 19 Vigouroux L, Quaine F. Fingertip force and electromyography of finger flexor muscles during a prolonged intermittent exercise in elite climbers and sedentary individuals.  J Sports Sci. 2006;  24 181-186
• 20 Vigouroux L, Quaine F, Labarre-Vila A, Moutet F. Estimation of finger muscle tendon tensions and pulley forces during specific sport-climbing grip techniques.  J Biomech. 2006;  39 2583-2592
• 21 Visser B, De Looze M, De Graaff M, Van Dieen J. Effects of precision demands and mental pressure on muscle activation and hand forces in computer mouse tasks.  Ergonomics. 2004;  47 202-217
• 22 Watts P B, Martin D T, Durtschi S. Anthropometric profiles of elite male and female competitive sport rock climbers.  J Sports Sci. 1993;  11 113-117
• 23 Watts P B. Physiology of difficult rock climbing.  Eur J Appl Physiol. 2004;  91 361-372
• 24 West W, Hicks A, Clements L, Dowling J. The relationship between voluntary electromyogram, endurance time and intensity of effort in isometric handgrip exercise.  Eur J Appl Physiol. 1995;  71 301-305
• 25 Westling G, Johansson R S. Factors influencing the force control during precision grip.  Exp Brain Res. 1984;  53 277-284

1 As opposed to endurance studies, in which subjects had to maintain a given level of force [[14], [19]], a crucial difference is that here, the level of grip force was not explicitly imposed; as long as Gf was superior to Gmin, subjects were free to adjust their grip force.