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This study aimed to explore the strength of the force–velocity (F–V) relationship of lower limb muscles and the reliability of its parameters (maximum force [F0], slope [a], maximum velocity [V0], and maximum power [P0]). Twenty-three men were tested in two different jump types (squat and countermovement jump: SJ and CMJ), performed under two different loading conditions (free weight and Smith machine: Free and Smith) with 0, 17, 30, 45, 60, and 75?kg loads. The maximum and averaged values of F and V were obtained for the F–V relationship modelling. All F–V relationships were strong and linear independently whether observed from the averaged across the participants (r?≥?0.98) or individual data (r?=?0.94–0.98), while their parameters were generally highly reliable (F0 [CV: 4.85%, ICC: 0.87], V0 [CV: 6.10%, ICC: 0.82], a [CV: 10.5%, ICC: 0.81], and P0 [CV: 3.5%, ICC: 0.93]). Both the strength of the F–V relationships and the reliability of their parameters were significantly higher for (1) the CMJ over the SJ, (2) the Free over the Smith loading type, and (3) the maximum over the averaged F and V variables. In conclusion, although the F–V relationships obtained from all the jumps tested were linear and generally highly reliable, the less appropriate choice for testing the F–V relationship could be through the averaged F and V data obtained from the SJ performed either in a Free weight or in a Smith machine. Insubstantial differences exist among the other combinations tested.  相似文献   
2.
This study aimed to examine the reliability of different power and velocity variables during the Smith machine bench press (BP) and bench press throw (BPT) exercises. Twenty-two healthy men conducted four testing sessions after a preliminary BP one-repetition maximum (1RM) test. In a counterbalanced order, participants performed two sessions of BP in one week and two sessions of BPT in another week. Mean propulsive power, peak power, mean propulsive velocity, and peak velocity at each tenth percentile (20–70% of 1RM) were recorded by a linear transducer. The within-participants coefficient of variation (CV) was higher for the load–power relationship compared to the load–velocity relationship in both the BP (5.3% vs. 4.1%; CV ratio = 1.29) and BPT (4.7% vs. 3.4%; CV ratio = 1.38). Mean propulsive variables showed lower reliability than peak variables in both the BP (5.4% vs. 4.0%, CV ratio = 1.35) and BPT (4.8% vs. 3.3%, CV ratio = 1.45). All variables were deemed reliable, with the peak velocity demonstrating the lowest within-participants CV. Based upon these findings, the peak velocity should be chosen for the accurate assessment of BP and BPT performance.  相似文献   
3.
This study compared the effects of two velocity loss thresholds during a power-oriented resistance training program on the mechanical capacities of lower-body muscles. Twenty men were counterbalanced in two groups (VL10 and VL20) based on their maximum power capacity. Both groups used the same exercises, relative intensity and repetition volume, only differing in the velocity loss threshold of each set (VL10: 10% vs. VL20: 20%). Pre- and post-training assessments included an incremental loading test and a 15-m linear sprint to assess the force- and load-velocity relationships and athletic performance variables, respectively. No significant between-group differences (P > 0.05) were observed for the force-velocity relationship parameters (ES range = 0.15–0.42), the MPV attained against different external loads (ES range = 0.02–0.18) or the 15-m sprint time (ES = 0.09). A high between-participants variability was reported for the number of repetitions completed in each training set (CV = 30.3% for VL10 and 29.4% for VL20). These results suggest that both velocity loss thresholds induce similar changes on the lower-body function. The high and variable number of repetitions completed may compromise the velocity-based approach for prescribing and monitoring the repetition volume during a power-oriented resistance training program conducted with the countermovement jump exercise.  相似文献   
4.
This study aimed to correlate, compare, and determine the reliability of force, velocity, and power values collected with a force plate (FP) and a linear transducer during loaded jumps. Twenty-three swimmers performed an incremental loading test at 25, 50, 75, and 100% of their own body weight on a FP. A linear velocity transducer (LVT) was attached to the bar to assess the peak and the mean values of force, velocity, and power. Both the peak variables (r = 0.94 – 0.99 for peak force, r = 0.83 – 0.91 for peak velocity, and r = 0.90–0.94 for peak power; p < 0.001) and the mean variables (r = 0.96–0.99 for mean force, r = 0.87–0.89 for mean velocity, and r = 0.93–0.96 for mean power; p < 0.001) were strongly correlated between both measurement tools. Differences in the shape of the force-, velocity-, and power-time curves were observed. The LVT data showed a steeper increase in these variables at the beginning of the movement, while the FP recorded larger values in the latter part. Peak values were more reliable than mean values. These results suggest that the LVT is a valid tool for the assessment of loaded squat jump.  相似文献   
5.
This study aimed to (1) assess the reliability of the force, velocity, and power output variables measured by a force plate and a linear velocity transducer (LVT) for both the unconstrained and constrained loaded countermovement jump (CMJ), and (2) examine the effect of both the CMJ type and the measurement method on the magnitudes of the same variables. Twenty-three men were tested on the free CMJ and the CMJ constrained by a Smith machine. Maximum values of force, velocity, and power were recorded by a force plate and by a LVT attached to a bar loaded by 17, 30, 45, 60, and 75 kg. The reliability of all mechanical variables proved to be high (ICC > 0.70; CV < 10%) and similar for two CMJ types. However, force plate-derived measures displayed greater reliability than the LVT. The LVT also markedly overestimated the magnitudes of the mechanical variables, particularly at lower external loads. Therefore, although both jump types and both methods could be acceptable for routine testing, we recommend the force platform due to a higher reliability and more accurate magnitudes of the obtained variables. The unconstrained loaded CMJ could also be recommended due to the simpler equipment needed.  相似文献   
6.
Eleven male judoka, who compete at national level, were recruited with the aim of investigating changes in peak leg power as a result of successive judo bouts and their relationship with lactate production. The participants executed a force-velocity curve to determine peak power in a 908 squat exercise in concentric work. The group then participated in four 5-min judo bouts each separated by 15 min of passive rest. The power developed as a result of the load associated with the maximum peak power reached in the preliminary test was determined, for the same movement, before and after each bout. Finger capillary blood samples were taken after each bout to determine the maximum lactate concentration achieved and lactate clearance. The results showed no effect of successive bouts on peak leg power (P > 0.05) and no difference when comparing the power measured before and after each bout (P > 0.05). Maximum lactate concentration of the fourth bout was lower than that of the first (12.6 + 3.5 and 14.6+4 mmol · l(-1) respectively; P < 0.05), although there was no difference in their clearance dynamics (P > 0.05). On the basis of the results obtained, we conclude that successive judo bouts, with the structure proposed in this study, produce high acidosis levels, which have no effect on the peak power developed in the legs.  相似文献   
7.
The possibility of giving a continuing value to an abandoned historic mine is not only of academic interest but can be a crucial economic and heritage issue for regions with long mining traditions but which are now severely affected by mine closures. This article suggests a different perspective on the rationale for studying, preserving and developing our mining heritage as an educational facility. To illustrate the case, the ancient iron mine of Llumeres, in the Asturias region, in North Spain, is presented as an example. A key point of our thesis is that a closed mine is not a ‘dead entity’ but simply in transition to another useful state and that after the closure, another organism arises, with very different appearance and vital signs. We suggest that this new organism be recognised for its high patrimonial value and that this heritage value be preserved. Accepting this point of view would mean an increase in efforts to identify and appropriately manage these vital signs. We propose that the particular mining-related aspects (which are usually viewed as negative, such as subsidence or groundwater modification), be considered as part of the heritage of the mining activity, considered in the widest sense. To facilitate understanding, these are discussed in comparison to those for a prehistoric cave, for which there is a broader experience and solid knowledge and recognition of heritage value. We have also analyzed the importance of recognising the geometric and functional relationships between the underground workings and the superficial signatures, in defining an extended patrimonial entity, which has been recently presented to the cultural and political authorities. For the case of the iron mine of Llumeres, we explain the methodology required to analyze and classify the documents in order to investigate and reconstruct the 3D geometric structure of the mine and how this can be integrated into a Geographical Information System (GIS) to improve management and editing of the information. Additionally, the historic mining technological methods employed in the underground workings of Llumeres have been studied and all the information integrated into a 3D visualization package and made available as a free 3D video sample of the subsurface information. In summary, this work represents a major step forward in improving our knowledge of the ancient iron mine of Llumeres and, as a consequence, it has been possible, for the first time, to consider the underground mining heritage in the framework of the better known (but as yet unrecognised) overground heritage. This new patrimonial entity offers enhanced possibilities for acceptance and recognition in a societal context and to aid that acceptance, we propose a radical conceptual change of perspective, pointing out new elements requiring research.  相似文献   
8.
Abstract

Eleven male judoka, who compete at national level, were recruited with the aim of investigating changes in peak leg power as a result of successive judo bouts and their relationship with lactate production. The participants executed a force–velocity curve to determine peak power in a 90° squat exercise in concentric work. The group then participated in four 5-min judo bouts each separated by 15 min of passive rest. The power developed as a result of the load associated with the maximum peak power reached in the preliminary test was determined, for the same movement, before and after each bout. Finger capillary blood samples were taken after each bout to determine the maximum lactate concentration achieved and lactate clearance. The results showed no effect of successive bouts on peak leg power (P > 0.05) and no difference when comparing the power measured before and after each bout (P > 0.05). Maximum lactate concentration of the fourth bout was lower than that of the first (12.6 ± 3.5 and 14.6 ± 4 mmol · l?1 respectively; P < 0.05), although there was no difference in their clearance dynamics (P > 0.05). On the basis of the results obtained, we conclude that successive judo bouts, with the structure proposed in this study, produce high acidosis levels, which have no effect on the peak power developed in the legs.  相似文献   
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