The physical demands of bouldering were found to be substantially different to research findings on sport climbing (4). In the bouldering competition, there were shorter bouts of activity (30 seconds vs. 2-7 minutes); decreased static periods (25% vs. 38%), and more attempts allowed to ascend a problem (multiple vs. single) than sport climbing (4). The shorter bouts of activity probably reflect the smaller climbing distances in bouldering, but the reasons for the decreased static times are less clear. Steeper routes during difficult sport climbing result in significantly faster climbing speeds and greater blood lactate accumulation than less steep routes (7). Research on climbing surfaces (19,25) also found hold type, patterning, and steepness of the climbing surface can influence energy cost. Perhaps in our study, the steeply overhanging routes (up to 45 degrees beyond vertical) with a limited number of small-sized handholds caused competitors to spend minimum time on each hold and move rapidly in an attempt to conserve energy. Possible evidence for this strategy is the greater amount of time spent in motion during bouldering compared to sport climbing, indicating a more dynamic style of climbing in bouldering. The nature of the problems analyzed, which were short and steeply overhanging, and the necessity for multiple attempts by some elite competitors indicates bouldering requires a high level of skill and physical fitness. This supports the belief among climbers that bouldering represents the physically and technically most intense discipline of the sport with strength being central to bouldering performance.
The overall exercise to recovery ratio during a 6-minute climbing period was ∼1:4, which is similar to intermittent sports such as tennis (6) and rugby (9) and more favorable than the arm paddling-to-rest ratio of 1:1.25 observed in surfing (15). However, comparisons with these sports are not valid as a result of the high level of muscle activity in the forearms, which had an exercise-to-recovery ratio of ∼13:1 during a bouldering problem. It is also unlikely traditional measures of exercise intensity such as heart rate would relate directly to climbing performance because of the small muscle mass utilized and the isometric nature of activity in the upper limbs (4,19,25). Consequently, a more ecologically valid approach is to focus on the periods of high-intensity activity in the forearms observed during bouldering, which concurs with sport climbing research that highlighted the critical role of strength and endurance in fingers/forearms in performance (4,22,27). For example, research on sport climbers found trained rock climbers have significantly greater isometric forearm strength (14,22) and muscular endurance in response to repeated isometric contractions (10,22) than sedentary individuals. The enhanced performance in climbers is proposed to be from specific adaptations such as desensitization of efferent nerves; reduced metabolite accumulation; and a greater vasodilator response during recovery, which improves the performance of intermittent isometric muscle contractions (10,14,22). However, because forearm exercise-to-recovery ratios in the sport climbing studies equated to ∼3:1 seconds, they do not compare well to the 13:1 seconds observed in this study, which would allow minimal reperfusion of muscle tissue, and therefore recovery, between relatively long duration isometric muscular contractions (3,24). As a result of substantial differences in activity patterns between bouldering and sport climbing competition, it is unclear whether similar physiological responses and adaptations occur in bouldering athletes. Consequently, future research could examine training adaptations and physiological responses of bouldering athletes to competition.
There has been no research on the determinants of success in bouldering. Research on sport climbing suggests a high rate of force development in the forearms is critical to performance (27), and our observation of a very high exercise:recovery indicates forearm strength and power are important in bouldering performance. However, more studies are needed to determine the relationships between strength and power measures and climbing performance. This area of research could provide vital information about climbing performance and the physiological requirements of bouldering. For example, climbing literature and websites recommend the use of specifically designed apparatus such as fingerboards or campus boards, which focus on the development of strength, power and endurance in the fingers and upper limbs (11,13). Nevertheless, no study has examined the effectiveness of such devices or training methods, which typically use interval training and plyometric techniques. Strategy also appears to be an important part in successful ascents in bouldering competition. Anecdotal evidence from our study indicates successful competitors typically completed a problem after 1-2 attempts. In contrast, less successful athletes made multiple attempts before selecting a similar movement pattern as successful climbers. Goddard and Neumann (11) suggested successful sport climbers were faster at identifying the optimal route for ascent than less successful athletes. Future research with a larger sample size could investigate time-motion and strategic differences between successful and nonsuccessful attempts by climbers in bouldering competitions.
Analysis of video footage found bouldering consisted of repeated high-intensity efforts in the forearms that were separated by minimal rest periods. Strength and conditioning professionals can use the observed exercise-to-recovery ratio in the design and implementation of sport-specific training programs to replicate activity patterns observed during World Cup-level competitive bouldering. The steep terrain of competitive bouldering requires strength and power in the upper limbs and torso, specifically in the finger flexors. The rate of force development in the fingers also needs to be highly developed to maximize the ability to rapidly grasp holds successfully. Additionally, the results of this study suggest finger-strength endurance is probably important to sustain the high level of forearm muscle activity in bouldering. Climbing training texts commonly recommend 8 to 10 second contractions for specific finger training, which is probably a suitable contraction duration. However, observations from this study suggest this type of contraction needs to be repeated with minimal rest periods a number of times to adequately stimulate specific patterns of muscular activity to develop endurance.
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