A review of strength & endurance research in rock climbing - page 4 Flexibility Body flexibility is another variable which is thought to be relevant in climbing performance as the ability to reach distant holds and maintain positions at extreme joint angles can provide a clear advantage on certain climbing moves (Goddard and Neumann, 1993; Sagar, 2001). Grant et al. (1996, 2001) measured hip flexibility in trained climbers and controls but observed no significant differences. However, issues with the standard of the climbing group discussed above may have affected the validity of the comparison. An intervention study into the effect of flexibility in competitive climbers would yield more useful information. Fatigue factors in climbing To successfully complete a sport route, climbers must maintain the ability to make high force, intermittent isometric contractions of the finger flexors. Indeed, competition routes are designed to have progressively more difficult individual movements (the purpose being to separate out climbers of different abilities). Failure to produce the required finger force, coupled with burning, stiff and painful sensations in the forearm (known as ‘pump’) are recognised as being the dominant symptom of fatigue associated with failure to complete a climb, resulting in a fall (Goddard and Neumann, 1993). Finger endurance has been identified as a key attribute of elite level climbers by several studies (Binney and Cochrane, 1999; Ferguson and Brown, 1997; MacLeod et al., unpublished data; Quaine et al., 2003; Reid et al., unpublished data). Grant et al. (2003) demonstrated that intermediate level climbers do not differ from other athletic groups with respect to finger endurance. The intermittent isometric contractions seen in climbing are unusual in sport generally (Spurway, 1999). The nature of isometric exercise has several important consequences for the development of muscular fatigue with repeated contractions. Asmussen (1981) characterised this type of contraction as causing significant increases in intramuscular pressure. This change causes blood to be squeezed out of intramuscular blood vessels and hinders or even completely stops blood flow through the muscle. Blood flow can only resume when the contraction ends. The magnitude of increases in intramuscular pressure, and hence blood flow occlusion, is dependent on the intensity (that is, the percentage of MVC) of the contraction. It is thought that contractions below 10-25% of MVC receive adequate blood flow and can be maintained without muscle fatigue (Asmussen, 1981). Above 45-75% MVC, blood flow is completely occluded in the forearm and fatigue patterns mimic those where artificial occlusion is present (Barnes, 1980; Heyward, 1980; Serfass et al., 1979). Between these values, blood flow is reduced and fatigue occurs, but at a slower rate. There is considerable variability in the extent of occlusion in a given subject and muscle due to the following factors: the prevalent muscle fibre type, the size and structure of the muscle. MacLeod et al. (unpublished data) measured finger endurance using a climbing specific protocol (a ‘crimp’ grip with 10/3sec contraction/relaxation ratio) in trained climbers and controls. The intensity was 40% MVC and times to failure in the climbers were similar to the total climbing times observed in a world cup climbing event (Schadle-Schardt, 1998). The authors suggested that 40% MVC may be representative of the average MVC percentage required from the finger flexors in climbing. Carlson and McGraw (1971) observed lower isometric endurance in subjects with higher MVC and hypothesised a negative relationship between these variables. Based on these findings, it would be anticipated that the climbers would have shorter endurance times as they exhibit higher MVCs than non-climbers. The literature has demonstrated that this is not the case and it is thought that adaptations present in trained climbers appear to offset any disadvantage due to higher force production (MacLeod et al., unpublished data). Quaine et al. (2003) demonstrated that muscle fatigue, measured by the decline in median frequency of surface electromyogram (EMG) in the active forearm muscles, in a climbing specific finger endurance task was delayed in elite climbers compared to non-climbers. The rate of fatigue in climbers was twice as slow as controls at 80% MVC. The authors concluded that this delay was due to climber’s enhanced ability to recover between contractions, speculating that enhanced vasodilation during rest periods accounted for the climber’s advantage. Reid et al. (unpublished data) also observed EMG fatigue using a similar protocol to MacLeod et al.. Trained climbers and controls had similar times to fatigue and decline in EMG median frequency. However, the climbing group had higher MVC and hence produced significantly higher force for a given test period. Watts et al. (1996) measured maximum hand-grip force before and immediately after a climbing task to exhaustion. Hand-grip MVC decreased 22% after the climbing task and remained depressed for 20 minutes post-exercise. However, later work by Watts et al. (2000, 2003b), which also measured maximum hand-grip and finger strength before and after a fatiguing climbing task showed no drop in ability to exert maximum force. Watts et al. (2003b) showed no change in root mean squared EMG values pre and post climb. However, change in median frequency was not measured. It seems possible that the results of Watts et al. (1996, 2000, 2003b) may be affected by the delay in measuring MVC after the climbing bout ended. It is noted that the measurements were taken within one minute of failure on the climb. However, Quaine et al. (2003) points out that the difference in endurance capacity between climbers and non climbers is due to an ability to recover significantly in the short (5 seconds in this case) rest periods between contractions. Future study employing continuous EMG data during a climbing or climbing specific task is required to fully establish whether loss of finger strength occurs during strenuous climbing.
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