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Boccia G.,University of Turin | Boccia G.,Research Center Sport Mountain and Health | Pizzigalli L.,University of Turin | Formicola D.,University of Turin | And 2 more authors.
Journal of Human Kinetics | Year: 2015

Neuromuscular assessment of rock climbers has been mainly focused on forearm muscles in the literature. We aimed to extend the body of knowledge investigating on two other upper limb muscles during sport-specific activities in nine male rock climbers. We assessed neuromuscular manifestations of fatigue recording surface electromyographic signals from brachioradialis and teres major muscles, using multi-channel electrode arrays. Participants performed two tasks until volitional exhaustion: A sequence of dynamic pull-ups and an isometric contraction sustaining the body at half-way of a pull-up (with the elbows flexed at 90°). The tasks were performed in randomized order with 10 minutes of rest in between. The normalized rate of change of muscle fiber conduction velocity was calculated as the index of fatigue. The time-to-task failure was significantly shorter in the dynamic (31 ±10 s) than isometric contraction (59 ±19 s). The rate of decrease of muscle fiber conduction velocity was found steeper in the dynamic than isometric task both in brachioradialis (isometric:-0.2 ±0.1%/s; dynamic:-1.2 ±0.6%/s) and teres major muscles (isometric:-0.4±0.3%/s; dynamic:-1.8±0.7%/s). The main finding was that a sequence of dynamic pull-ups lead to higher fatigue than sustaining the body weight in an isometric condition at half-way of a pull-up. Furthermore, we confirmed the possibility to properly record physiological CV estimates from two muscles, which had never been studied before in rock climbing, in highly dynamic contractions. © 2015 Gennaro Boccia et al., published by De Gruyter Open. Source


Zoppirolli C.,Research Center Sport Mountain and Health | Zoppirolli C.,University of Verona | Pellegrini B.,Research Center Sport Mountain and Health | Pellegrini B.,University of Verona | And 4 more authors.
Human Movement Science | Year: 2016

The study aim was to evaluate biomechanical and physiological alterations in double poling technique (DP) after a short-term fatiguing exercise. Eight high-level skiers performed a sub-maximal DP trial (20 km h-1, 1°) before (PRE) and after (POST) a DP test to exhaustion while roller skiing on a treadmill. An integrated analysis of DP technique during PRE and POST included measurement of pole, joint, and centre of mass (COM) kinematics, poling forces, cycle timing, and metabolic parameters. Muscle fatigue in three upper-body muscles was assessed by calculating the Dimitrov' fatigue index (FInms5) of specific electromyographic segments. FInms5 tended to increase in the latissimus dorsi and teres major muscles (P = 0.023 and P = 0.030, respectively) across consecutive DP cycles, as did blood lactate concentration (P = 0.001) and rating of perceived exertion (P = 0.005). The changes indicated a state of fatigue during POST and coincided with the reduction in poling force exertion capacity (P = 0.020). Pole, joint and COM kinematics did not differ between PRE and POST (P > 0.050), whereas recovery phase and cycle times were shorter at POST (P < 0.001 and P = 0.001, respectively). Short-term fatigue led to a reduction in poling force exertion capacity and cycle time in high-level skiers, without altering body and pole kinematics. © 2016 Elsevier B.V. Source


Zoppirolli C.,Research Center Sport Mountain and Health | Zoppirolli C.,University of Verona | Holmberg H.-C.,Mid Sweden University | Pellegrini B.,Research Center Sport Mountain and Health | And 7 more authors.
Journal of Electromyography and Kinesiology | Year: 2013

This investigation was designed to evaluate the effectiveness of stretch-shortening cycling (SSCEFF) in upper-limb extensor muscles while cross-country skiing using the double-poling technique (DP). To this end, SSCEFF was analyzed in relation to DP velocity and performance. Eleven elite cross-country skiers performed an incremental test to determine maximal DP velocity (Vmax). Thereafter, cycle characteristics, elbow joint kinematics and poling forces were monitored on a treadmill while skiing at two sub-maximal and racing velocity (85% of Vmax). The average EMG activities of the triceps brachii and latissimus dorsi muscles were determined during the flexion and extension sub-phases of the poling cycle (EMGFLEX, EMGEXT), as well as prior to pole plant (EMGPRE). SSCEFF was defined as the ratio of aEMGFLEX to aEMGEXT. EMGPRE and EMGFLEX increased with velocity for both muscles (P<0.01), as did SSCEFF (from 0.9±0.3 to 1.3±0.5 for the triceps brachii and from 0.9±0.4 to 1.5±0.5 for the latissimus dorsi) and poling force (from 253±33 to 290±36N; P<0.05). Furthermore, SSCEFF was positively correlated to Vmax, to EMGPRE and EMGFLEX (P<0.05). The neuromuscular adaptations made at higher velocities, when more poling force must be applied to the ground, exert a major influence on the DP performance of elite cross-country skiers. © 2013 Elsevier Ltd. Source


Zoppirolli C.,Research Center Sport Mountain and Health | Zoppirolli C.,University of Verona | Pellegrini B.,Research Center Sport Mountain and Health | Pellegrini B.,University of Verona | And 4 more authors.
European Journal of Applied Physiology | Year: 2015

Methods: Eight high-level (HLG) and eight regional-level (RLG) skiers performed a 5-min sub-maximal DP trial, roller skiing on a treadmill at 14 km h−1 and 2°. Energetic cost (ECDP), center of mass (COM) vertical displacement range, body inclination (θ, i.e., the angle between the vertical line and the line passing through COM and a fixed pivot point identified at feet level) and mechanical work associated to COM motion were analyzed. Pole and joint kinematics, poling forces and cycle timing were also considered.Results: HLG showed lower ECDP than RLG, smaller COM vertical displacement range and mechanical work, whereas higher θ during the early part of the poling phase (P < 0.05). In HLG, pole inclination was higher, poling forces greater and cycle duration longer (P < 0.05). Considering all skiers, a forward multiple regression revealed that the maximum value of θ (θmax) and the minimum value of COM vertical displacement resulted the COM-related parameters that better predict ECDP (AdjR2 = 0.734; P < 0.001). Moreover, θmax positively related to poling force integrals and cycle duration (P < 0.05).Conclusions: A pronounced body inclination during the early poling phase and a reduced COM vertical displacement range concur in explaining the differences in ECDP found between the groups and among the skiers. A mechanically advantageous motion of COM during DP improves poling effectiveness, reduces cycle frequency and the mechanical work sustained.Purpose: The aim of this study was to evaluate the energetics and the biomechanics of double poling technique (DP) in two groups of cross-country skiers. © 2014, Springer-Verlag Berlin Heidelberg. Source

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