Author(s): VIEIRA, T., BRUNO, M., CERONE, G., BACHERO-MENA, B., Institution: POLITECNICO DI TORINO, Country: ITALY, Abstract-ID: 1212

INTRODUCTION:
Climbing is a physically demanding discipline, placing significant loads on the finger flexors. Notwithstanding the documented greater endurance capacity of experienced climbers, the mechanisms explaining these training-induced adaptations remain unknown. We therefore investigate whether two non-competing strategies—muscle adaptation and alternate muscle recruitment—may explain the disparity in endurance capacity in participants with different climbing experience.
METHODS:
A total of 38 climbers volunteered to participate in this study, after providing written informed consent. Participants were split into two groups, Advanced (n=21) and Intermediate (n=17), according to their score in the French system for grading sport climbing routes: at least 7a and from 6a to 6c+, respectively. We analyzed 64 (8×8, 1cm inter-electrode distance) high-density surface electromyograms (EMGs) during suspension exercises using a half-crimp grip with different depths (15mm, 20mm, 30mm). From the spatial distribution of changes in MeDian Frequency (MDF) and Root Mean Square (RMS) values until failure, we assessed how much and how diffusely the myoelectric manifestations of fatigue took place. To account for anatomical, inter-individual differences, intergroup comparisons were conducted after normalizing data based on forearm size.
RESULTS:
Advanced climbers exhibited greater endurance, as evidenced by significantly longer failure time for the three grip depths. With respect to the myoelectric fatigue, MDF values decreased while RMS values increased significantly until the failure time, for both groups and for the three edge depths. These changes in RMS and MDF values were confined to a small skin region (nearly 25% of the grid size) and centered at variable locations across participants, for the three edge depths. In Intermediate climbers, however, MDF decreased significantly more steeply when compared with Advanced climbers, whereas RMS changes did not differ between groups. Correlation analysis indicated the greater time to failure was associated with lower changes in MDF, for the three depths considered. Conversely, RMS slopes were far more variable across groups and edge depths and were not correlated with failure time.
CONCLUSION:
Collectively, our results convey the following practical implications:
• The topography of muscle excitation, as assessed from high-density surface EMGs, revealed relevant differences between Intermediate and Advanced climbers.
• Advanced climbers endured suspension tests for longer durations, regardless of whether holding on 15 mm, 20 mm, or 30 mm thick edges.
• The liability to muscle fatigue was greater in Intermediate than Advanced climbers. The muscle region where fatigue buildup was most evident varied dramatically across subjects and groups, justifying the importance of assessing muscle excitation from multiple skin locations.