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Mean movements and strategy in sport climbing : determinant variables and performance factors
Full text linkIntroduction
Climbing, in all its disciplines, is a emergent sport with a increasing number of athletes involved in competition. The major discipline is the leading, characterized by strength and endurance movements on overhanging artificial structures. Score depends on the height reached by athletes. The ascent needs physical, technical and interpretation ability. Increasing performances and specializations need well specified training programs but, at the moment, this kind of sports lacks in scientific studies about kinematics variables and movement strategy. The aim of this study is to collect preliminary kinematics data to identify mean movements and strategy in sport climbing and to verify if it’s possible to find determinant variables and performance factors.
Methods
Data of kinematics variables were extracted from a video analysis of 8 female athletes who participated at 2007 Lombardia Regional Cup match. The athletes (20±4 years old, 49±5 kg, 162±4 cm) involved in this study are all well experienced climbers with at least 2 years of competition participation. Following variables were collected: total time, number of holds, speed (mean time for hold), number and time of rests, number and time of clipping, number of hands and feet movements, contraction type (concentric or isometric) time per holds, support type (on holds or on structure) time, technical movements (frontal, lateral, etc) used. All these variables were extrapolated by the digital video analysis frame per frame with “final cut pro” software. Data were imported in excel file format
witch ensures simple charts vision and different manipulations to identify differences among athletes on the same route or between different route climbed by one athletes. For each athlete, data were analyzed on the entire height climbed. For interindividual analysis, data were compared normalizing the minimum height reached among all climbers. These information were related with the difficulties of any segments of the routes.
Results
The 2 matches analyzed were characterized by overhanging structures where a lot of endurance movements interrupted by two bouldery sections with strength and technical needing. In both competitions the best results were reached by the fastest athletes with less per cent time spent in concentric phases and clipping. We see that the best athletes are more time in double feet support than the worst ones, and use less movements to reach the same height. Different climbing styles (dominant movements and rhythms) demonstrate to be efficacy at the same way. Comparison between the 2 routes climbed by the same athletes shows that, when it is possible, they choice the climbing style according to their technical and conditioning characteristics.
Discussion
It seems that technical and conditional characteristics are the major variables and their influence is dominant on kinematics data. Total climbing time and technical movements choice are not statistically correlated with results because they depend by individual muscular characteristics, specific technique awareness and routes interpretation. The variables related with results are: clipping time, concentric phase time, mean holding time, movements number and support type time. Finally this analysis method can help to have a better view of athletes profile and to find out weakness points in respect of the racing routes. Interpretation of kinematics data related with physiological aspects is the way to discover determinant results factors and to improve training technique
Passive stretching effects on electromechanical delay and time course of recovery in human skeletal muscle : new insights from an electromyographic and mechanomyographic combined approach
No full textAcute passive stretching has been shown to alter muscle-tendon unit (MTU) stiffness and to reduce peak tetanic force (pF). MTU mechanical properties and electro-mechanical delay (EMD) are closely related. Thus, EMD changes would be expected after stretching. The aim of the study was to assess the stretching-induced changes in both contractile and viscoelastic contributors to EMD. The time course of these changes will be also evaluated. Tetanic stimulations were delivered on the medial gastrocnemius muscle of 16 active males, before and after (every 15 min, for 2 h) passive stretching administration. During contractions, electromyographic (EMG), mechanomyographic (MMG) and force signals were recorded. The delays between EMG and force (Delta t EMG-F, which corresponds to EMD), EMG and MMG (Delta t EMG-MMG) and MMG and force (Delta t MMG-F) signals were calculated, together with pF and EMG conduction velocity (CV). After stretching (i) pF decreased by 31% (P < 0.05) and remained depressed for the entire recovery period, while EMG CV did not change; (ii) Delta t EMG-F, Delta t EMG-MMG and Delta t MMG-F increased significantly from 45.4 +/- A 3.0 ms, 2.2 +/- A 0.3 ms and 42.4 +/- A 3.1 ms to 52.7 +/- A 3.4 ms, 2.4 +/- A 0.3 ms and 50.3 +/- A 3.5 ms, respectively; (iii) Delta t EMG-F and Delta t MMG-F remained lengthened for the entire recovery period, while Delta t EMG-MMG recovered to its pre-stretching condition within 15 min. These findings suggest that after stretching, the reduction in pF was accompanied by an elongation of the overall EMD. However, stretching had effects of short duration at the contractile level, but more persisting effects on MTU viscoelastic characteristics
Cycling efficiency and time to exhaustion are reduced after acute passive stretching administration
No full textThe aim of this study was to assess the effects of acute passive stretching on cycling efficiency during an exercise of heavy intensity. After maximum aerobic power (V̇O(2max) ) assessment, nine active males (24 ± 5 years; stature 1.71 ± 0.09 m; body mass 69 ± 7 kg; mean ± standard deviation) performed tests at 85% of V̇O(2max) (Ẇ(85) ) until exhaustion, with and without pre-exercise stretching. During the tests, we determined the gas exchange, metabolic and cardiorespiratory parameters. With stretching, no differences in V̇O(2max) occurred (3.64 ± 0.14 vs 3.66 ± 0.07 L/min for stretching and control, respectively). During Ẇ(85) , pre-exercise stretching (i) decreased time to exhaustion (t(lim) ) by 26% (P<0.05); (ii) increased average V̇O(2) by 4% (3.24 ± 0.07 and 3.12 ± 0.07 L/min in stretching and control, respectively; P<0.05); and (iii) reduced net mechanical efficiency (e(net) ) by 4% (0.185 ± 0.006 and 0.193 ± 0.006 in stretching and control, respectively; P<0.05). Although acute passive stretching did not have an effect on V̇O(2max) , t(lim) and e(net) during heavy constant load exercise were significantly affected. These results are suggestive of an impairment in cycling efficiency due to changes in muscle neural activation and viscoelastic characteristics induced by stretching
Acute effects of passive stretching and spinal manipulation on muscle activation and fatigability
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Combined effects of fatigue and temperature manipulation on skeletal muscle electrical and mechanical characteristics during isometric contraction
No full textPeripheral fatigue and muscle cooling induce similar effects on sarcolemmal propagation properties. The aim of the study was to assess the combined effects of muscle temperature (Tm) manipulation and fatigue on skeletal muscle electrical and mechanical characteristics during isometric contraction. After maximum voluntary contraction (MVC) assessment, 16 participants performed brief and sustained isometric tasks of different intensities in low (Tm(L)), high (Tm(H)) and neutral (Tm(N)) temperature conditions, before and after a fatiguing exercise (6s on/4s off at 50% MVC, to the point of fatigue). During contraction, the surface electromyogram (EMG) and force were recorded from the biceps brachii muscle. The root mean square (RMS) and conduction velocity (CV) were calculated off-line. After the fatiguing exercise: (i) MVC decreased similarly in all Tm conditions (P<0.05), while EMG RMS did not change; and (ii) CV decreased to a further extent in Tm(L) compared to Tm(N) and Tm(H) in all brief and sustained contractions (P<0.05). The larger CV drop in Tm(L) after fatigue suggests that Tm(L) and fatigue have a combined and additional effect on sarcolemmal propagation properties. Despite these changes, force generating capacity was not affected by Tm manipulation. A compensatory mechanism has been proposed to explain this phenomenon
Effect of respiratory muscle training on maximum aerobic power in normoxia and hypoxia
No full textTo assess the effects of respiratory muscle training (RMT) on maximum oxygen uptake (VO2max) in normoxia and hypoxia, 9 healthy males (age 24 +/- 4 years; stature 1.75 +/- 0.08 m; body mass 72 +/- 9 kg; mean +/- SD) performed on different days maximal incremental tests on a cycle ergometer in normoxia and normobaric hypoxia (FIO2=0.11), before and after 8 weeks of RMT (5 days/week). During each test, gas exchange variables were measured breath-by-breath by a metabolimeter. After RMT, no changes in cardiorespiratory and metabolic variables were detected at maximal exercise in normoxia. On the contrary, in hypoxia expired and alveolar ventilation (V(E(and V(A), respectively) at maximal exercise were significantly higher than pre-training condition (+12 and +13%, respectively; P < 0.05). Accordingly, alveolar O2 partial pressure (PAO2) after RMT significantly increased by approximately 10%. Nevertheless, arterial PO2 and VO2max did not change with respect to pre-training condition. In conclusion, RMT improved respiratory function but did not have any effect on VO2max, neither under normoxic nor hypoxic condition. In hypoxia, the significant increase in V(E) and V(A) at maximum exercise after training lead to higher alveolar but not arterial PO2 values, revealing an increased A-a gradient. This result, according to the theoretical models of VO2max limitation, seems to contradict the lack of VO2max increase in hypoxia, suggesting a possible role of increased ventilation-perfusion mismatch
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Testing protocol affects the velocity at VO 2max in semi-professional soccer players
No full textTo compare three different protocols to assess the velocity associated with the maximal oxygen uptake (V-max) in soccer players. Sixteen semi-professional soccer players performed three maximum incremental tests on treadmill: two continuous protocols [1 km center dot h(-1)center dot min(-1) (CP1); and 1 km center dot h(-1) every 2 min (CP2)], and one discontinuous (DP) protocol to determine V-max, maximum oxygen uptake (VO2max) and oxygen cost of running (i.e., the slope of the VO2 vs velocity relationship at submaximal exercise). V-max was higher in CP1> CP2> DP (19.4 +/- 1.7, 17.4 +/- 1.2, 16.1 +/- 1.1 km center dot h(-1) for CP1, CP2, and DP, respectively; P < 0.05 ES: 0.09 to 3.36). No difference in VO2max was found between CP1, CP2 and DP (P > 0.05). Oxygen cost of running showed between-protocol differences (CP1> CP2> DP; P < 0.05; ES: 0.28 to 3.30). V-max was higher when determined using continuous vs discontinuous protocols due to the greater overestimation in oxygen cost of running. Such differences in V-max should be considered to optimize acute physiological responses during high-intensity running activities
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