An investigation into the histological changes in skeletal muscle fibres and jump performance indicators after 8 weeks of plyometric squat jump training was conducted. Healthy inactive participants ...(n = 13; age: 21.5 ± 1.7 year.; height: 173.6 ± 10.7 cm; weight: 68.5 ± 18.4 kg; BMI 22.4 ± 3.8 kg/m2) were recruited, where eight participants completed plyometric squat jump training and five control participants refrained from performing any jumping activities. Blood samples, vastus lateralis muscle biopsies and functional testing (peak and average power, peak and average velocity, maximal jump height) were collected/recorded 10 days prior to and 3 days after the training/rest period. Participants completed 1644 squat jumps over an 8-week training period of 24 sessions with a progressive increase in the number of squat jumps. The trained group significantly increased their jumping average and peak power (mean increases in average power: 16.7 ± 1.2% and peak power: 8.2% ± 0.1) and velocity (mean increases in average velocity: 13.7 ± 0.1% and peak velocity: 5.2% ± 0.03), resulting in a 25% improvement in vertical jump height. No muscle morphological changes in terms of the cross-sectional area (CSA) or muscle-fibre-type transition were observed after the plyometric training. Improvements in the functional performance indicators following training may more likely be explained by sarcomere ultrastructural adaptation, which did not directly affect myosin heavy chain or CSA.
The active thermal nondestructive testing and evaluation method is a rapidly growing testing procedure for a quick and remote inspection procedure for fibre‐reinforced plastics. Conventional ...modulated lock‐in thermography significantly contributed to this field by allowing usage of low peak power controlled stimulations followed by phase based detail extraction procedures. But demand of repetitive experimentation required for depth scanning of the test object limits its applicability for realistic critical applications and demands multi‐frequency low power stimulations for better resolution and sensitivity for sub‐surface defect detection. Frequency modulated thermal wave imaging and coded excitation thermal wave imaging methods permitting multi‐frequency stimulations cater for these needs and facilitate depth scanning of the test object in a single experimentation cycle. Recently introduced three‐dimensional pulse compression is an alternative to phase based analysis for these stimulations by providing enhanced defect detection even in noisy environmental and experimental conditions. Defect detection capability and sizing by these non‐stationary thermal wave imaging methods are highlighted using the pulse compression approach. The present experimental study has been carried out on a carbon fibre reinforced plastic specimen with flat bottom holes.
We hypothesized short-term endurance exercise (EN) in hypoxia (HY) to exert decreased mitochondrial adaptation, peak oxygen consumption (VO
) and peak power output (PPO) compared to EN in normoxia ...(NOR) and hyperoxia (PER). 11 male subjects performed repeated unipedal cycling EN in HY, PER, and NOR over 4 weeks in a cross-over design. VO
, PPO, rate of perceived exertion (RPE) and blood lactate (Bla) were determined pre- and post-intervention to assess physiological demands and adaptation. Skeletal muscle biopsies were collected to determine molecular mitochondrial signaling and adaptation. Despite reduced exercise intensity (P<0.05), increased Bla and RPE levels in HY revealed higher metabolic load compared to PER (P<0.05) and NOR (n.s.). PPO increased in all groups (P<0.05) while VO
and mitochondrial signaling were unchanged (P>0.05). Electron transport chain complexes tended to increase in all groups with the highest increase in HY (n.s.). EN-induced mitochondrial adaptability and exercise capacity neither decreased significantly in HY nor increased in PER compared to NOR. Despite decreased exercise intensity, short term EN under HY may not necessarily impair mitochondrial adaptation and exercise capacity while PER does not augment adaptation. HY might strengthen adaptive responses under circumstances when absolute training intensity has to be reduced.
The photovoltaic (PV) system’s output power varies owing to solar radiation’s irregularity, which confines their usage for various applications. Implementation of maximum power tracking (MPT) ...algorithms increases the efficiency and power generated from solar cells. When the array is partially obscured by clouds or structures, several local maximum power peaks (LMPPs) appear in the solar cell characteristics. Traditional MPPT algorithms, rather than following the global peak power point (GPPP), are preferable to following the local peak power point. If partial shading causes numerous LPPPs, it is necessary to look into how the MPPT technique can keep track of GPPP. Employing soft computing approaches such as the hybrid neural network/fuzzy method with variable step size perturb and observing MPPT, it is possible to trace the GPPP and also augment solar energy extraction. The present research paper focuses on hybrid fuzzy/neural network MPPT integrated with a high-step-up DC-DC converter to harvest the utmost power from the solar PV array. The voltage transients are reduced by controlling the DC link voltage along with solar radiation and temperature variations. The proposed MPPT technique is shown to be effective under both uniform and partial shade conditions in a series of simulations. From the test results, the efficiency of the overall system has increased from 91 to 98% for partial shading and uniform operating conditions.
Multi-hop relaying is used to extend the reach of wireless communication systems whereas cooperative relaying is used to improve the performance gain by exploiting the spatial diversity. In this ...study, the authors combine these two techniques to improve the range as well as the performance gain of cognitive radio networks (CRNs). Selective decode-and-forward relays are considered and two relay selection schemes are used to study the performance of multi-hop CRNs over Rayleigh fading channels. The exact outage probability and throughput of the considered system are derived for both the schemes by considering the effect of both peak-power and peak-interference constraints. By using the derived outage probability, the diversity gains for both considered schemes are determined. Numerical results show that the outage probability monotonically improves, whereas the throughput has concave behaviour with respect to increasing number of relaying hops.
Energy efficiency is an important issue in computing systems and operating within a safe power budget is a necessary constraint. This paper presents a simple and practical solution both for energy ...minimization and peak power reduction, called Single Voltage Approximation (SVA) scheme, for periodic real-time tasks on multicore systems with a shared supply voltage in a voltage island. SVA is inspired by the Single Frequency Approximation (SFA) scheme, in which all the cores in the island run at a single voltage and frequency such that all tasks can meet their deadlines. In SVA, all the cores in the island are also executed at the same single voltage as in SFA. However, the frequency of each core is individually chosen, such that the tasks in each core can meet their deadlines, but without running at unnecessarily high frequencies. Thus, all the cores are executing tasks all the time and there is no need for any Dynamic Power Management (DPM) technique for reducing the energy consumption for idling. For task partitioning, SVA is combined with the Double Largest Task First (DLTF) partitioning scheme. Most importantly, this paper provides comprehensive analysis for combining DLTF and SVA, deriving its worst-case behavior both for energy minimization and peak power reduction, compared against the optimal solutions. Our analysis shows that, depending on the hardware, the energy consumption by combining DLTF and SVA is at most 1.95 (2.21, 2.42, and 2.59, respectively), compared to the optimal solutions, when the voltage island has up to 4 (8, 16, and 32, respectively) cores, which outperforms the worst-case factors of SFA when the cores fail to sleep efficiently. For peak power reduction, due to running at slower frequencies, combining DLTF and SVA always outperforms SFA, both in average and corner cases. Finally, we extend our analysis considering multicore systems with discrete voltage and frequency pairs and multiple voltage islands.
The Validity of the SmartJump Contact Mat Reeve, Tom C; Tyler, Christopher J
Journal of strength and conditioning research,
2013-June, 2013-Jun, 2013-06-00, 20130601, Letnik:
27, Številka:
6
Journal Article
Recenzirano
Odprti dostop
ABSTRACTReeve, TC and Tyler, CJ. The validity of the smartjump contact mat. J Strength Cond Res 27(6)1597–1601, 2013—The aim of this study was to establish the criterion validity of the SmartJump ...contact mat in assessing vertical jump height (VJH) and peak power (PP). Twenty-three participants (15 men, age = 26 ± 6 years; 8 women, age = 26 ± 9 years) completed a maximal effort vertical jump using 3 different jump types (countermovement jump CMJ, countermovement with arms CMJA, and squat jump SJ). Data were simultaneously collected on both the contact mat and force platform. Vertical jump height was calculated using the time in air (TIA) method with both force platform (TIAplatform) and contact mat (TIAmat) data and the takeoff velocity (TOV) method using the force platform (TOVplatform) data. Peak power was calculated using a validated equation. The results showed that VJH and PP calculated using the TIAmat method were significantly greater than that calculated from the TIAplatform and TOVplatform methods for all jump types (VJHp < 0.001, PPp < 0.001). The results from this study show clear discrepancies between apparatus and calculation methods that may have implications for practitioners and should be considered when assessing VJH and PP in the field.
ABSTRACTMaciejczyk, M, Wiecek, M, Szymura, J, Szygula, Z, and Brown, LE. Influence of increased body mass and body composition on cycling anaerobic power. J Strength Cond Res 29(1)58–65, 2015—Recent ...evidence suggests that not only body fat (BF) but high lean body mass (HLBM) adversely affects aerobic performance and may reduce aerobic endurance performance as well. However, the influence of body composition on anaerobic performance remains controversial. This study aimed to examine the effects of increased body mass (BM) and body composition on cycling anaerobic power. Peak power (PP) and mean power (MP) measurements were conducted in 2 groups of men with similar total BM but different body compositions resulting from (a) high level of BF HBF group or (b) high level of lean body mass HLBM group and in a control group. Peak power and MP were calculated in absolute values, relative to BM and lean body mass (LBM), and using allometric scaling. Absolute PP and MP were significantly higher in the HLBM group compared with the control and HBF groups. However, PP and MP relative to BM and using allometric scaling were similar in the HLBM and control groups, yet significantly higher than in the HBF group. There were no significant differences between groups in PP and MP when presented relative to LBM. Therefore, it seems that it is not BM but rather body composition that affects PP. Increased BM, resulting from increased LBM, does not adversely affect cycling anaerobic power, but a BM increase resulting from an increase in BF may adversely affect PP. Therefore, coaches and athletes should avoid excess BF to maximize cycling anaerobic power.
(1) Background: High-intensity interval training (HIIT) exerts effects indicative of improved health in young and older populations. However, prescribing analogous training programmes is ...inappropriate, as recovery from HIIT is different between young and older individuals. Sprint interval training (SIT) is a derivative of HIIT but with shorter, maximal effort intervals. Prior to prescribing this mode of training, it is imperative to understand the recovery period to prevent residual fatigue affecting subsequent adaptations. (2) Methods: Nine older (6M/3F; mean age of 70 ± 8 years) and nine young (6M/3F; mean age of 24 ± 3 years) participants performed a baseline peak power output (PPO) test. Subsequently, two SIT sessions consisting of three repetitions of 20 s 'all-out' stationary cycling bouts interspersed by 3 minutes of self-paced recovery were performed. SIT sessions were followed by 3 days' rest and 5 days' rest on two separate occasions, in a randomised crossover design. PPO was measured again to determine whether recovery had been achieved after 3 days or after 5 days. (3) Results: Two-way repeated measure (age (older, young) × 3 time (baseline, 3 days, 5 days)) ANOVA revealed a large effect of age (
= 0.002,
= 0.460), with older participants having a lower PPO compared to young participants. A small effect of time (
= 0.702,
= 0.022), and a medium interaction between age and time (
= 0.098,
= 0.135) was observed. (4) Conclusions: This study demonstrates both young and older adults recover PPO following 3 and 5 days' rest. As such, both groups could undertake SIT following three days of rest, without a reduction in PPO.
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