Dr. Biol. A.V. Voronov¹
Dr.Hab., Professor P.V. Kvashuk¹
A.A. Voronova¹
PhD T.V. Krasnoperova^2
1Federal Science Center for Physical Culture and Sport (FRS VNIIIFK)
²St. Petersburg Scientific Research Institute of Physical Culture, St. Petersburg

Keywords: muscle electromyogram, climbing, regression analysis

Background. Isometric strength of the hand/ forearm muscles is known to significantly correlate with the competitive successes in the modern climbing (difficulty and bouldering) disciplines [1, 5-9]. Speed climbing, unlike bouldering, implies competitions on artificial standardized climbing walls with the standard starting positions, routes and holds. Climbers’ performance may be defined as the quadropedic locomotion with upper/ lower limb and trunk muscles being particularly active. Comprehensive tests of the electromyographic activity in the core muscle groups may help rate, analyze and predict competitive performance in this sport discipline.
Objective of the study was to test and analyze the electromyographic activity in the core muscle groups critical for success in the speed climbing sport.
Methods and structure of the study. The electromyographic test data of the speed climbing specific muscle groups were produced by computerized SportLab Test System (made in Russia) with a 8-channel telemetric electromyography and video camera. The right-side surface electromyographic activity was tested in m. gastrocnemius medialis; m. vastus lateralis; m. trapezius; and m. biceps brachii.
Sampled for the experiment were the Class I, CMS and MS qualified climbers (n=10 including 4 males and 6 females) tested by the low-, moderate- and high-speed gender-specific sprint tests, with the male and female group sprint times varying within 6.3-14s and 13.5-18s, respectively. The sprint times were fixed by the video-camera rated at 50 frames/ s from the first move on start and to the final touch. Every subject was given at least 2 successful (fall-free) attempts in every speed band, with 8-10min rest breaks.
The electromyographic amplitude is known to correlate with the strength and functionality of the muscle, fat ratio, test system sensitivity and processing methods [3, 4]. Electromyographic work of every active muscle was rated [2] versus the attempt time, with average EMG (EMGav) calculated. The low-speed EMGav was assumed as an initial value (100%), with the electromyographic amplitude variations analyzed versus the slowest time ( ). In every next attempt, EMGav of every muscle was normalized to EMGav   as follows:

, where  is the change in the average electromyographic amplitude in the i-th attempt (positive or negative), and i is the attempt number. The same procedure was used to calculate the sprint time versus the low-speed attempt time ( ). The higher was the speed, the shorter was the sprint time, and this is why we applied a sprint time variation value ( ):
, where   is the sprint time.

Results and discussion. Times of the best (fastest) attempts were found 35-40% shorter than the initial  level.
The average electromyographic amplitude was found to grow with the growth of the sprint speed, and this trend was typical for every muscle under the study: see Figure 1. Contributions of the muscle traction force (indirectly rated by the electromyographic amplitude) were different [3, 4]). Thus the correlation ratios for m. gastrocnemius medialis and m. biceps brachii were estimated at r = 0.73 and r = 0.78, respectively (see Table 1) that means a high statistical correlation of EMGav  with the result.

Figure 1. Average muscle-specific electromyographic amplitude variations in speed climbing

In case of m. vastus lateralis and m. trapezius, the statistical correlation of EMGav  with the result was less expressed (r=0.66 and r=0.41, respectively).

Table 1. Sprint time to average electromyographic amplitude correlation ratio

For the electromyographic activity analyzing purposes, we analyzed the elite (MS, CMS) versus Class I athletes’ test data. The shorter was the variation range of some index versus the regression line, the higher was its contribution to the result (see the determination ratios R  on Figure 1). It was found that the lower-class climbers should give a special priority in trainings to the foot extensors and forearm flexors strength building components for their competitive progress: see Figure 1. The statistical analysis made it possible to identify the core muscle groups critical for progress of the lower-skilled climbers. As for the elite climbers, their trainings need to be designed on an individual basis as required by the competitive performance analysis. Given on Figure 2 are the EMGav variations for a selected MS.
We assumed the electromyographic values related to the  =9,25 sprint time as the initial levels. The best time (6.32 s) was -31.2% short of the latter, with   of m. gastrocnemius medialis and m. vastus lateralis found to grow by 25% and 15%, respectively (Figure 2) versus EMGav of the lower-limb muscles of the lower-skilled athletes. No meaningful EMGav skills-specific differences were found for m. biceps brachii (see Figures 1 and 2). A significant EMGav growth was found in the MS’ m. trapezius, with the  = 54% (Fig. 2, lower left). The lower-skilled athletes were tested both with the m. trapezius EMGav growth and sags with the growth of the sprint time.
Conclusion
1. We found a statistically significant correlation (r = 0.6) of the lower limb, trunk and upper limb muscles indicative of a harmonized joint extensor-flexor muscle functions.
2. Regardless of the skill level, competitive progress in the modern speed climbing heavily depends on gastrocnemius medialis and m. biceps brachii.
3. Muscular activity controls tend to vary with the competitive progress. The peaks found in the electromyographic amplitudes give grounds to conclude that m. gastrocnemius medialis and m. trapezius are critical for the climbing speed.
4. When reaching the individual best speeds, the lower-skilled athletes are tested with the electromyographic activity growths in the upper limbs (m. biceps brachii) whilst the top-skilled athletes – in the leg muscles (m. gastrocnemius medialis, m. vastus lateralis) and trunk muscles (m. trapezius).
5. Telemetric computerized test systems are recommended for application in the competitive performance studies to fairly rate the individual climbing styles and techniques (using electromyographic tests in the case) and identify the core muscles group critical for competitive progress.

Figure 1. Average electromyographic amplitudes versus the sprint times (Master of Sport): m.  gastrocnemius medialis (upper left), m.  vastus lateralis (upper right), m. trapezius (lower left), m. biceps brachii (lower right)

We appreciate the valuable contributions from A.V. Vavayev and I.V. Bagova to the study

References
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Corresponding author: fizkult@teoriya.ru

Abstract
Objective of the study was to identify muscles that provide the increase of rates in speed climbing. For this purpose, we used the SportLab hardware-software complex (Russia) consisting of an 8-channel telemetric electromyograph and a video camera. The experiment involved 10 climbers (qualified MS – CMS – I Class) including 4 males and 6 females. The athletes ran the distance at slow, average and maximum speed. The distance speed was picked individually. The distance time was registered using the video camera (frame rate - 50 Hz). The beginning of the first movement was taken as a zero point (start), the touch of a control point – as finish. The subjects performed at least 2 successful (without disruption) attempts at each speed rate. The rest breaks between the races were 8-10 min.
Based on the registration and analysis of the electromyographic activity data, we determined the muscles influencing the rates in sport climbing. The data obtained showed that regardless of the athletes’ sports qualification there are two muscle groups affecting the sports results: m. gastrocnemius medialis and m. biceps brahii. The significant increase in the average EMG amplitude of some muscles suggests that these muscles are the "leading" ones when approaching record speeds. In this study, these are m. gastrocnemius medialis and m. trapezius.