We applied a meta‐analytical approach to derive a robust estimate of the acute effects of pre‐exercise static stretching (SS) on strength, power, and explosive muscular performance. A computerized ...search of articles published between 1966 and December 2010 was performed using PubMed, SCOPUS, and Web of Science databases. A total of 104 studies yielding 61 data points for strength, 12 data points for power, and 57 data points for explosive performance met our inclusion criteria. The pooled estimate of the acute effects of SS on strength, power, and explosive performance, expressed in standardized units as well as in percentages, were −0.10 95% confidence interval (CI): −0.15 to −0.04, −0.04 (95% CI: −0.16 to 0.08), and −0.03 (95% CI: −0.07 to 0.01), or −5.4% (95% CI: −6.6% to −4.2%), −1.9% (95% CI: −4.0% to 0.2%), and −2.0% (95% CI: −2.8% to −1.3%). These effects were not related to subject's age, gender, or fitness level; however, they were more pronounced in isometric vs dynamic tests, and were related to the total duration of stretch, with the smallest negative acute effects being observed with stretch duration of ≤45 s. We conclude that the usage of SS as the sole activity during warm‐up routine should generally be avoided.
Background. Cognitive symptoms and fatigue may persist after intensive care unit (ICU) care. It remains unclear whether post-COVID-19 symptoms are related to ICU care itself or the infection. ...Objective. The primary aim was to investigate the prevalence of residual cognitive impairment and fatigue after ICU care for COVID-19 and to evaluate the importance of demographic factors. A secondary aim was to investigate whether differences in ICU treatment between the first wave (March 2020 to July 2020) and later waves (August 2020 to January 2021) of COVID-19 were associated with differences in cognitive outcomes. Design. Prospective follow-up study. Subjects/Patients. Swedish cohort of COVID-19 patients referred from ICU. Methods. Montreal Cognitive Assessment (MoCA), Multidimensional Fatigue Inventory-20 (MFI-20), Hospital Anxiety and Depression Scale, Insomnia Severity Scale, and RAND-36 were administered approximately three months after admission to ICU. Mann–Whitney tests were used to investigate group differences, and multiple linear regression was used to investigate the relationship between fatigue and covarying factors. Results. 71 patients completed follow-up, and 60 patients underwent a cognitive screening of which 30% had MoCA scores indicative of cognitive impairment (<26 points). Higher age was related to poorer cognitive performance. Patients scored above the normal range on all subscales on the MFI-20. There was a significant difference in length of ICU stay between wave one and following waves, but no statistically significant differences emerged on cognitive screening. Intubated patients’ fatigue ratings were lower compared to those not intubated—despite longer ICU stay. No difference in MoCA scores emerged between patients who were, or were not, intubated. Conclusion. Cognitive impairment and fatigue were evident in patients three months after a severe COVID-19 infection, but global cognitive functioning was not related to ICU length of stay. Less fatigue among patients who had been intubated merits further investigation.
We examined the effects of jump training with negative (-30% of the subject's body weight (BW)) VS. positive loading (+30% BW) on the mechanical behaviour of leg extensor muscles. 32 men were divided ...into control (CG), negative loading (NLG), or positive loading training group (PLG). Both training groups performed maximal effort countermovement jumps (CMJ) over a 7-week training period. The impact of training on the mechanical behaviour of leg extensor muscles was assessed through CMJ performed with external loads ranging from -30% BW to +30% BW. Both training groups showed significant ( P≤0.013) increase in BW CMJ height (NLG: 9%, effect size (ES)=0.85, VS. PLG: 3.4%, ES=0.31), peak jumping velocity ( V(peak); NLG: 4.1%; ES=0.80, P=0.011, VS. PLG: 1.4%, ES=0.24; P=0.017), and depth of the countermovement (Δ H(ecc); NLG: 20%; ES=-1.64, P=0.004, VS. PLG: 11.4%; ES=-0.86, P=0.015). Although the increase in both the V(peak) and Δ H(ecc) were expected to reduce the recorded ground reaction force, the indices of force- and power-production characteristics of CMJ remained unchanged. Finally, NLG (but not PLG) suggested load-specific improvement in the movement kinematic and kinetic patterns. Overall, the observed results revealed a rather novel finding regarding the effectiveness of negative loading in enhancing CMJ performance which could be of potential importance for further development of routine training protocols. Although the involved biomechanical and neuromuscular mechanisms need further exploration, the improved performance could be partly based on an altered jumping pattern that utilizes an enhanced ability of leg extensors to provide kinetic and power output during the concentric jump phase.
Despite the important role of agility in successful performance in many team and racket sports, little is known about their physiological and muscular basis. The aim of this study was to examine the ...relationship between the leg extensor strength and power and agility performance.
Male physical education students (n=76) were assessed by means of 3 typical agility performance tests (lateral stepping, 20-yard shuttle run, and slalom run). Six tests of leg extensor strength (isoinertial squat, isometric squat, and one-leg rising) and power (squat jump power, hopping power, and standing long jump distance) were also obtained.
The correlations between strength and power, and each agility performance were generally low. As a consequence, the multiple correlation coefficients between strength and power predictors and agility, albeit significant (P<0.01), were also rather low (r=0.33, 0.44, and 0.35 for the lateral stepping, 20-yard shuttle run, and slalom run, respectively). The highest relationship with each of the agility tests was revealed by the one-leg rising test (r within -0.3 and -0.44; P<0.02).
The results of the present study suggest that most of the multijoint leg extensor strength and power measures are poor predictors of agility in physically active men. Thus, the effects of interventions aimed towards the improvement of functional movement performance may not require evaluation by means of the common tests of muscular strength and power. A more specific approach including both the functional strength tests and functional movement performance tests could be recommended instead.
The drainage system must ensure a safe disposal of the surface water without endangering the buildings and safety of people. Despite the common use of rainwater infiltration facilities, there is ...still only limited data available evaluating the long-term capacity of such systems especially for underground infiltration facilities. This study presents experimental measurements and evaluation of long-term infiltration efficiency in real conditions and emphasizes the importance of hydrogeological survey. The measurements of infiltration efficiency were applied to an existing percolation drainage system - infiltration shafts. Infiltration shafts were made in year 2007 so that its drainage operation takes more than 8 years. This study was started in 2011 and still continues and presents 5 years measurements of infiltration efficiency for this infiltration facility.
The aim was to generalize the maximum dynamic output (MDO) hypothesis i. e., the muscle power output in vertical jumps (VJ) is maximized when loaded with one's own body mass to variety of VJ. We ...hypothesized that the subjects' own body (a) would be the optimal load for maximizing the power output (i. e., the no-load condition) and also (b) reveal the maximum benefits of stretch-shortening cycle (SSC). 13 participants performed the maximum squat and various counter-movement jumps when loaded by approximately constant external force ranging from -40% to + 40% of their body weight (BW). Regarding the first hypothesis, the differences in both the peak and mean power recorded under different load magnitudes revealed maxima close to no-load condition (i. e., from -3% BW to + 8% BW; R2=0.65-0.96; all P<0.01). Regarding the second hypothesis, the differences in performance between VJ executed with and without SSC also revealed maxima close to no-load conditions (0-2% BW), while the same differences in the power output were observed under relatively low positive loads (14-25% BW; R² = 0.56-0.95; all P<0.01). The findings support the concept that maximal power output occurs close to one's own body mass during VJ with and without SSC, thereby providing additional support to MDO hypothesis.
Wavelength converters placement (WCP) in all-optical WDM networks belongs to the class of hard combinatorial optimization problems. So far, this problem has been solved by various heuristic ...strategies or by application of metaheuristic approaches such as genetic algorithms (GA), particle swarm optimization (PSO), differential evolution (DE), etc. In this paper, we introduce the application of Bee Colony Optimization (BCO) metaheuristic to solve the WCP problem in all-optical WDM networks. Numerous studies prove that BCO is a fast, robust and computationally efficient tool in tackling complex optimization problems. The objective of the proposed BCO-WCP algorithm is to find the best placement of limited number of wavelength converters in given optical network such that the overall network blocking probability is minimized. To evaluate the performances of the BCO-WCP algorithm, numerous simulation experiments have been performed over some realistic optical network examples. The blocking probability performance and computational complexity are compared with optimal solution obtained by exhaustive search (ES) approach as well as with DE and PSO metaheuristics. It will be shown that the BCO-WCP algorithm is not only be able to produce high quality (optimal) solution, but significantly outperforms the computational efficiency of other considered approaches. Index Terms--Artificial intelligence, Computational complexity, Optical fiber networks, Wavelength converters, Wavelength division multiplexing.
Plyometric training (PLY) is a very popular form of physical conditioning of healthy individuals that has been extensively studied over the last 3 decades. In this article, we critically review the ...available literature related to lower-body PLY and its effects on human neural and musculoskeletal systems, athletic performance and injury prevention. We also considered studies that combined lower-body PLY with other popular training modalities, as well as studies that applied PLY on non-rigid surfaces. The available evidence suggests that PLY, either alone or in combination with other typical training modalities, elicits numerous positive changes in the neural and musculoskeletal systems, muscle function and athletic performance of healthy individuals. Specifically, the studies have shown that long-term PLY (i.e. 3-5 sessions a week for 5-12 months) represents an effective training method for enhancing bone mass in prepubertal/early pubertal children, young women and premenopausal women. Furthermore, short-term PLY (i.e. 2-3 sessions a week for 6-15 weeks) can change the stiffness of various elastic components of the muscle-tendon complex of plantar flexors in both athletes and non-athletes. Short-term PLY also improves the lower-extremity strength, power and stretch-shortening cycle (SSC) muscle function in healthy individuals. These adaptive changes in neuromuscular function are likely the result of (i) an increased neural drive to the agonist muscles; (ii) changes in the muscle activation strategies (i.e. improved intermuscular coordination); (iii) changes in the mechanical characteristics of the muscle-tendon complex of plantar flexors; (iv) changes in muscle size and/or architecture; and (v) changes in single-fibre mechanics. Our results also show that PLY, either alone or in combination with other training modalities, has the potential to (i) enhance a wide range of athletic performance (i.e. jumping, sprinting, agility and endurance performance) in children and young adults of both sexes; and (ii) to reduce the risk of lower-extremity injuries in female athletes. Finally, available evidence suggests that short-term PLY on non-rigid surfaces (i.e. aquatic- or sand-based PLY) could elicit similar increases in jumping and sprinting performance as traditional PLY, but with substantially less muscle soreness. Although many issues related to PLY remain to be resolved, the results of this review allow us to recommend the use of PLY as a safe and effective training modality for improving lower-extremity muscle function and functional performance of healthy individuals. For performance enhancement and injury prevention in competitive sports, we recommend an implementation of PLY into a well designed, sport-specific physical conditioning programme.
This study tested the hypothesis that athletes participating in intermittent sports would exhibit a faster heart rate recovery (HRR) during the initial phase (<30 s) following maximal exercise than ...athletes participating in continuous endurance sports. Forty-six male athletes were allocated into continuous (CNT,
n
= 24) or intermittent groups (INT,
n
= 22), matched for age and aerobic fitness. Athletes performed maximal exercise on a treadmill using the ramp protocol. Immediately upon exercise cessation, subjects were placed supine with continuous measurement of HR during the first minute of recovery. Data were analyzed in 10-s intervals and compared between the groups. Repeated measures ANOVA showed a group × time interaction effects (
p
≤ 0.01) for HRR expressed in both beats min
−1
and in percentage of peak post-exercise HR (% HR
peak
). The INT group had lower HR than CNT group at 10 s (189 vs. 192 beats min
−1
,
p
= 0.04; and 96.3 vs. 97.9% HR
peak
,
p
= 0.009) and 20 s (184 vs. 188 beats min
−1
,
p
= 0.049; and 93.6 vs. 95.7% HR
peak
,
p
= 0.021) intervals of recovery. The results suggest that athletes engaged in intermittent sports are likely to have faster HRR during the first 20 s after maximal exercise than their counterparts trained for continuous performance.
Water consumption in residential parts of urban areas is just one part of the water management problems. Contemporary potable water management is not sustainable whereas we use potable water for ...flushing toilets, irrigation or washing vehicles. The appropriate solution is to substitute potable water with rainwater for some purposes and this water source is considered sustainable. Submitted paper presents risk assessment using risk analysis of the rainwater harvesting (RWH) system. This paper does not deal with the system in details but informs about the selected approach of the evaluation methodology verified by analytical hierarchy process.
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