Power-time Curves Research Articles

Effects of high-intensity sprint exercise on neuromuscular function in sprinters: the countermovement jump as a fatigue assessment tool.

High-intensity sprint exercises (HIS) are central to sprinter training and require careful monitoring of athlete muscle fatigue to improve performance and prevent injury. While the countermovement jump (CMJ) may be used to monitor neuromuscular fatigue (NMF), little is known about the specific effects from HIS. The purpose of this study is to investigate the effects of HIS on the CMJ to assess its utility for assessing NMF following HIS. Ten male collegiate 400 m sprinters completed a 400 m sprint fatigue protocol and underwent five CMJ-testing sessions (baseline, 3 minutes, 10 minutes, 1 hour and 24 hours) over two days. Three CMJ trials, performed on a force plate, were completed each trial, with rating of perceived exertion (RPE) recorded as a subjective fatigue measure. Changes in RPE, CMJ variables, force-time and power-time curves at baseline and post fatigue were assessed. Significant changes were observed in most variables following the fatigue protocol. In particular, concentric mean power remained significantly lower after 24 hours compared to baseline. In addition, the force-time curves exhibited a significant reduction in all conditions following the fatigue protocol. This decline was most pronounced within 50-75%of the concentric phase relative to baseline measurements. Conclusion. Results indicate that the CMJ may be a useful tool for monitoring fatigue in at least 400 m sprinters. These data also indicate that HIS may disproportionately reduce force output in during concentric movement. These insights may improve training prescriptions and injury prevention strategies for sprint athletes.

Real time microcalorimetric profiling of prebiotic inulin metabolism

The in vitro assessment of prebiotics involves elaborate microbiological techniques or a combination of culture techniques and molecular methods. In this study, the isothermal microcalorimeter, an instrument which can monitor the real time growth of bacteria was applied to investigate the prebiotic effect of inulin in real time. Fresh and standardized frozen faecal slurries were prepared, placed and monitored in the isothermal microcalorimeter. The faecal samples and commercial probiotic strains Lactobacillus acidophilus LA-5®, Bifidobacterium lactis BB-12® were cultured in a mixed medium of cooked meat medium (CMM) and brain heart infusion (BHI) broth with and without supplementation with inulin and monitored in the microcalorimeter. The results showed power-time (p-t) curves that were characteristic for the samples. The p-t curves of the fresh and frozen faecal samples were similar. Augmented microbial activity was observed when the faecal sample was inoculated into CMM-BHI mixed broth with significant enhancement of microbial activity detected in the presence of inulin which was reproducible. Deconvoluted p-t curves showed multiple peaks with time and intensity variance depending on presence or absence of inulin suggesting possible differences in utilization of inulin by the different groups of bacteria in the polymicrobial sample. P-t curves of the pure species did not show any significant change when inulin was supplemented into the medium likely due to the inability of the bacteria to primarily utilize inulin.

Antibacterial activity of reduced graphene oxide prepared by microbe

In previous work, we successfully bioreduced graphene oxide (B-rGO) utilizing organisms, but the antibacterial properties of B-rGO are still unknown. In this study, Escherichia coli (E. coli) was used as a test target and the antibacterial activity of B-rGO was compared to that of commercial reduced graphene oxide (C-rGO), in order to understand its toxicity. Data from levels of extracellular lactate dehydrogenase (LDH), and intracellular reactive oxygen species (ROS) content demonstrate that cell membrane stress and oxidative stress play a role in this antibacterial process. However, when the concentration of co-existing B-rGO was 50.0 mg/L, E. coli damaged easily, the LDH release concentration was 98.75 U/L, the ROS fluorescence signal was 57.75/106 cells, and the phenomenon known as ‘wrapping’ occurred. Indicated here is that B-rGO does indeed demonstrate very good antibacterial activity as evidenced when using Scanning Electron Microscopy (SEM). Meanwhile, numerous oxygen-containing functional groups existed on the surface of B-rGO as confirmed by Fourier transform infrared spectroscopy (FTIR). The power-time curve of microcalorimetry and flow cytometry analysis confirmed that the antibacterial activity of B-rGO was inadequate when compared to that of C-rGO. Despite E. coli mortality being dosage-dependent for both B-rGO and C-rGO, this implies that B-rGO does in fact achieve good biocompatibility. The outcomes reveal that B-rGO has great potential for environmental remediation.

Kinetic time-curves can classify individuals in distinct levels of drop jump performance

ABSTRACT This study examined whether analysing kinetic features of drop jumps (DJ) as one-dimensional biomechanical curves can reveal specific patterns that are consistent and can cluster DJ performance. Hierarchical clustering analysis on DJ from 40 cm data performed by 128 physically active male participants (23.0 ± 4.5 yrs, 1.84 ± 0.07 m, 79.1 ± 10.8 kg) was performed on the derived time-normalised force, power and vertical stiffness curves to unmask the underlying patterns and to explore the dissimilarities identified from the subgroup (cluster) analysis. Results revealed poor, average and top DJ performers. Top performers exhibited larger peak force, power and vertical stiffness compared to the other two groups, and the poor performers had lower values compared to the average performers (p < .05). The time curves of force, power and vertical stiffness exhibited between cluster dissimilarities from ~25% to ~70%, and ~20% to 40% plus ~55% to 70% from the beginning of the ground contact, respectively. The force and power time-curves distinguished DJ ability similarly since they shared 69% of the cases in the top performers’ cluster. The content of cases (membership) for vertical stiffness was different from the membership for the force and power time-curve clusters. In conclusion, stiffness should be considered during plyometric training, but does not distinctly define DJ performance.

Design, synthesis, and biological evaluation of dinuclear bismuth(III) complexes with Isoniazid-derived Schiff bases

Four dinuclear bismuth(III) Schiff-base complexes bearing Schiff-base ligands have been synthesized and structurally characterized by single-crystal X-ray diffraction, elemental analysis, and spectral techniques (FT-IR, NMR and MS). The analytical data reveal the bismuth(III) complexes possess 1:1 metal–ligand ratios. In vitro biological studies have revealed that bismuth(III) complexes displayed much higher antibacterial and antitumor activities than their parent ligands, which involves two gram-negative (S. aureus, B. subtili) and two gram-positive (E. coli, P. aeruginosa) bacteria, and human gastric cancer SNU-16 cells. The power–time curves of S. pombe exposed to tested compounds were detected by bio-microcalorimetry. Some thermokinetic parameters (k, Pmax,tG and Qtotal) were derived based on the metabolic power–time curves, and their quantitative relationships with the concentrations (c) were further discussed.

Altered Joint Powers During Running After Tibial Bone Stress Injury

Background:Tibial bone stress injuries (tib-BSI) are common in adolescent runners. Previous research has examined running mechanics as possible risk factors for tib-BSI’s and implications have been observed for both kinematic and kinetic measures. Combining these measures to examine power absorption and production of the lower extremity can provide context on mechanical differences in individuals with a history of tib-BSI.Hypothesis/Purpose:The purpose of this study was to examine total limb power and percent joint contribution in healthy adolescent runners compared to peers with a history of tib-BSI. It was hypothesized that runners with a history of tib-BSI would have a greater contribution of power production and absorption at the ankle, and less at the hip and knee joints, with no difference in total power.Methods:Twenty-six runners were divided into groups: history of tib-BSI (n=14; male=10, female=4; age=16±2) and healthy controls (n=12; male=5, female=7; age=18±7). Data were collected using 3D motion capture with embedded force plates during overground running at self-selected pace. Total limb power and percent joint contribution were calculated from joint work. Positive and negative joint work was summed from the integrations of the joint power-time curve in each plane. Joint work was divided by step-time to obtain total joint power. Joint powers for the hip, knee, and ankle were summed to determine total limb power and percentage of limb power was calculated for each joint. Variables were grouped by control limb (CON), uninvolved limb (UNI), and involved limb (BSI). Both limbs in the healthy controls were averaged to generate the CON group. A one-way ANOVA was used to compare the variables of limb and joint power.Results:There were no significant differences between BSI and UNI limbs for any variables measured. The CON group exhibited significantly greater hip negative power compared to the BSI group (p=0.047), and significantly less ankle negative power compared to the BSI (p=0.001) and UNI groups (p=0.002). Despite a significant difference in total positive power between groups (p=0.04), there were no differences in joint positive power. Variables are presented in Table 1.Conclusion:This study is preliminary evidence that adolescent runners with a history of tib-BSI can present with adaptations in running mechanics that are not limited to the injured leg. Negative power may be more sensitive to change with the ankle increasing its contribution, comparatively. Clinicians and researchers should be aware of this adaptation after injury as it may influence treatment.

A nine‐coordinated bismuth(III) Schiff‐base complex: Design, synthesis, computational studies, and antimicrobial activity

AbstractA new bismuth(III) Schiff‐base complex [Bi2(HL)2(NO3)4] was synthesized by using equivalent molar of Schiff‐base ligand [H2L = (E)‐N′‐(2‐hydroxy‐3‐methoxybenzylidene)isonicotinohydrazide] and Bi(NO3)3•5H2O with the assistance of Mannitol. The complex was structurally characterized by elemental analysis, spectroscopic methods, and single crystal X‐ray diffraction. The experimental and theoretical vibrational bands (infrared and Raman spectra) have been discussed. The antimicrobial activity of the complex against Schizosaccharomyces pombe was evaluated by bio‐microcalorimetry at 32°C. Some thermokinetic parameters (k, Pmax, tG, and Qtotal) were obtained from the metabolic power–time curves of S. pombe, and their quantitative relationships with the concentration (c) were discussed. The half inhibition concentrations (IC50) of isoniazid, Schiff base, and the complex were calculated. The complex showed the strongest inhibition effect among three compounds.

The study of the biotoxicity effect of alumina nanoparticle on soil microbes

Due to the unique properties, nanoparticles (NPs) have been widely used both in industrial products and individual life. However, with the huge benefits, NPs also possess potential toxicity to human health and ecosystem. Aluminum oxide NPs is so significant in industry that it occupies the second important position in US nanomaterials market. Aluminum oxide NPs belong to metal oxide nanoparticles which may have strong antimicrobial properties. As there is limited prior research on the toxicity of alumina NPs, the main goal of present research is to study the effects of alumina NPs on microorganisms in soils by combination methods of microcalorimetry and urease. Power-time curves and thermo-kinetic parameters (such as total heat evolution QT, growth rate constant k and maximum power output Pmax) were applied to evaluate the microbial community activities of the soil samples. A range of concentration of Aluminum oxide NPs gradient from 0 mg/L to 1000 mg/L was applied. The results showed that the concentration under 500 mg/L has negligible inhibitory effects on soil microorganisms while concentrations at 500mg/L and 1000 mg/L only have mild inhibition on microbes in soil. Urease experiments verified this result, therefore, it suggests that combination of microcalorimetry and urease may provide practical method for microorganism activity evaluating.

Synthesis, crystal structure, density functional theory calculations, and antimicrobial activity of silver(I) complex derived from 2‐aminobenzothiazole ligand

Reaction of silver nitrate with 2‐aminobenzothiazole (abbreviated as Habt) in methanol at 45°C gave mononuclear complex of formula [Ag (Habt)2]NO3•CH3OH. The structure of the complex was characterized by infrared (IR) spectra, single crystal X‐ray diffraction, and elemental analysis. X‐ray diffraction analysis indicated that the title complex was crystallized in the triclinic crystal system with space group P–1, in which silver(I) ion was coordinated to two 2‐aminobenzothiazole ligands through the benzothiazol nitrogen atom. Theoretical study of the complex was carried out by density functional theory (DFT) B3LYP method. The antimicrobial effects of the ligand and its silver(I) complex were evaluated by bio‐microcalorimetry on the growth of Schizosaccharomyces pombe (S. pombe). Some quantitative metabolic parameters, such as growth rate constant (k), maximum heat power (Pmax), inhibition ratio (I), and half inhibition concentration (IC50), were derived from the metabolic power–time curves of S. pombe growth. The half inhibition concentration (IC50) of the ligand was calculated to be 2.58 × 10−3 mol L−1. The complex could strongly influence the lag phase of S. pombe.

New cobalt(II) Schiff base complex: Synthesis, characterization, DFT calculation and antimicrobial activity

A new cobalt(II) Schiff-base complex [Co(L)2] was prepared by using equivalent molar of Schiff-base ligand [HL=(E)-N'-(2-hydroxy-3-methoxybenzylidene)isonicotinohydrazide] and CoCl2·6H2O. The structure of the complex was characterized by single-crystal X-ray diffraction, IR, ESI-MS, elemental analysis and DFT method. X-ray crystal structure analysis showed that the complex crystallized in space group Pbca, with two symmetry-independent molecules. The experimental vibrational bands(IR) have been discussed and assigned based on DFT calculations. The antibacterial activity of Schiff base and its complex against S. pombe were assessed by bio-microcalorimetry at 32 °C. Some thermokinetic parameters (k, Pmax,tG and Qtotal) were derived from the metabolic power–time curves, and their quantitative relationship with the concentration were analyzed. The half inhibition concentration (IC50) of Schiff base and its complex were calculated to be 1.18 × 10−2 mol L−1 and 1.07 × 10−3 mol L−1, respectively. The inhibition effect of the complex showed much stronger than that of Schiff base.

Wind Power Ramps Analysis for High Shares of Variable Renewable Generation in Power Systems

Power system operators should be provided with more information on the characteristics of variable generation power ramps because, although there has been an improvement in the forecasting of wind power, the percentage of error in forecasting is still high to some extent. As a result of the ongoing rise in the participation rate of variable generation, this error will have a significant impact on the balance of power generation and consumption. From the grid operators' viewpoint, in order to balance these ramp events, it is important to get the scale of ramp events in the system as well as the times during which collective events are most likely to arise in order to achieve flexibility and reliability in the power system. Digitization of power systems brings big data which opening opportunities for improving the efficiency of power system operation. This paper analyzes the historical data of power-time curve in two directions: vertical and horizontal, in order to gain details on the behavior of wind power ramps. The method of analysis will be demonstrated by an analysis of actual historical output power of aggregated Belgian wind farms every 15 minutes in 2017 and 2018. Comparing the results of the two years outlined that there are fixed percentages related to wind power ramping behavior and even if the wind capacity is increased, it is possible to determine the extent of these ramps.

The Countermovement Jump Mechanics of Mixed Martial Arts Competitors.

James, LP, Connick, M, Haff, GG, Kelly, VG, and Beckman, EM. The countermovement jump mechanics of mixed martial arts competitors. J Strength Cond Res 34(4): 982-987, 2020-Gross countermovement jump (CMJ) performance measures are greater in higher-level mixed martial arts (MMA) competitors than lower-level (LL) competitors. Differences in CMJ kinetics and kinematics throughout the action may explain those CMJ performance differences, but this remains to be investigated. After warm-up and familiarization, 27 MMA competitors (divided into 2 groups based on competitive standard; higher level [HL]: n = 14 and LL: n = 13) completed 3 maximal effort CMJs. Power, force, velocity, displacement-time waveforms and eccentric phase displacement, eccentric time, eccentric impulse, and the modified reactive strength index (RSImod) were compared between groups using statistical parametric mapping procedures and independent t-tests. Power (between 65 and 71% of the power-time curve) was greater in the HL than that of the LL group (p = 0.01) despite no differences in eccentric displacement (p = 0.50) or movement time (p = 0.17) between groups. The HL group demonstrated a greater RSImod (p = 0.05) alongside a reduced eccentric time (p = 0.02) and eccentric impulse (p = 0.02). These findings suggest that timing and control of lower-body force production contributed to between-group differences in CMJ performance among MMA competitors.

Defect Diagnosis of Disconnector Based on Wireless Communication and Support Vector Machine

Focusing on the shortage of mechanical defect detection and diagnosis technology for disconnectors, a wireless monitoring method for the mechanical state of disconnectors is proposed. The split-core current sensors and improved voltage sensors are used to measure the motor currents and voltages of the disconnector under typical mechanical states at different working voltages. The wireless communication network is used to upload the acquisition data to the cloud server quickly, and the received data are processed by the software system. By comparing and analyzing the curves of current, input power, and output power under different states, it is concluded that the motor output power can adequately reflect the mechanical state of the disconnector. Twenty-three time-domain features of the output power time curve are extracted to form the original feature vector. Kernel principal component analysis (KPCA) method is used to reduce the dimension of the nonlinear features, and the Fisher's criterion function is constructed to determine the width parameter of the kernel function in the feature optimization. Grid search algorithm is used to optimize the kernel parameters of the support vector machine (SVM), and the trained SVM model is used to classify the mechanical state data whose working voltage part is known, and part is unknown, with a classification accuracy of 100%. The results show that the proposed wireless monitoring method can effectively diagnose the mechanical state of the disconnector and has a good generalization ability.

Microcalorimetric evaluation of the effects of three anthraquinone derivatives from Chinese Rhubarb and the synergistic effect of the mixture on Staphylococcus aureus

In this study, a noninvasive and nondestructive microcalorimetric method was used to investigate the antimicrobial activity of three anthraquinone derivatives (emodin, aloe-emodin and physcion) from Chinese Rhubarb. Additionally, we observed a synergistic antibacterial effect of a mixture (emodin + aloe-emodin) on Staphylococcus aureus. Antibacterial effects were further evaluated through principle component analysis and the half-inhibitory concentration (IC50) according to the influence of the anthraquinone derivatives on eight quantitative thermokinetic parameters, which were measured by isothermal microcalorimetry and obtained from metabolic power–time curves of Staphylococcus aureus growth at 37 °C. The inhibitory actions of the anthraquinone derivatives varied at different concentrations. The antibacterial effect of the derivatives on S. aureus was as follows: emodin + aloe-emodin (E + AE) > emodin (E) > aloe-emodin (AE) > physcion. Based on these results, the combined effect of emodin and aloe-emodin was stronger than that of each anthraquinone derivative alone. The combination of emodin and aloe-emodin is a promising antibacterial agent, providing a novel avenue for antibacterial materials.

The Effect of Load Placement on the Power Production Characteristics of Three Lower Extremity Jumping Exercises.

The purpose of this study was to compare the power production characteristics of the jump squat (JS), hexagonal barbell jump (HEXJ), and jump shrug (JShrug) across a spectrum of relative loads. Fifteen resistance-trained men completed three testing sessions where they performed repetitions of either the JS, HEXJ, or JShrug at body mass (BM) or with 20, 40, 60, 80, or 100% of their BM. Relative peak power (PPRel), relative force at PP (FPP), and velocity at PP (VPP) were compared between exercises and loads. In addition, power-time curves at each load were compared between exercises. Load-averaged HEXJ and JShrug PPRel were statistically greater than the JS (both p < 0.01), while no difference existed between the HEXJ and the JShrug (p = 1.000). Load-averaged JShrug FPP was statistically greater than both the JS and the HEXJ (both p < 0.001), while no statistical difference existed between the JS and the HEXJ (p = 0.111). Load-averaged JS and HEXJ VPP were statistically greater than the JShrug (both p < 0.01). In addition, HEXJ VPP was statistically greater than the JS (p = 0.009). PPRel was maximized at 40, 40, and 20% BM for the JS, HEXJ, and JShrug, respectively. The JShrug possessed statistically different power-time characteristics compared to both the JS and the HEXJ during the countermovement and propulsion phases. The HEXJ and the JShrug appear to be superior exercises for PPRel compared to the JS. The HEXJ may be considered a more velocity-dominant exercise, while the JShrug may be a more force-dominant one.

Comparing Biomechanical Time Series Data During the Hang-Power Clean and Jump Shrug.

Kipp, K, Comfort, P, and Suchomel, TJ. Comparing biomechanical time series data during the hang-power clean and jump shrug. J Strength Cond Res 35(9): 2389-2396, 2021-The purpose of this study was to investigate differences in the force-, velocity-, displacement-, and power-time curves during the hang-power clean (HPC) and the jump shrug (JS). To this end, 15 male lacrosse players were recruited from a National Collegiate Athletic Association Division-I team, and performed one set of 3 repetitions of the HPC and JS at 70% of their HPC 1 repetition maximum (1RM HPC). Two in-ground force plates were used to measure the vertical ground reaction force (GRF) and calculate the barbell-lifter system mechanics during each exercise. The time series data were normalized to 100% of the movement phase, which included the initial countermovement and extension phases, and analyzed with curve analysis and statistical parametric mapping (SPM). The SPM procedure highlighted significant differences in the force-time curves of the HPC and JS between 85 and 100% of the movement phase. Likewise, the SPM procedure highlighted significant differences in the velocity- and power-time curve of the HPC and JS between 90 and 100% of the movement phase. For all comparisons, performance of the JS was associated with greater magnitudes of the mechanical outputs. Although results from the curve analysis showed significant differences during other periods of the movement phase, these differences likely reflect statistical issues related to the inappropriate analysis of time series data. Nonetheless, these results collectively indicate that when compared with the HPC, execution of the JS is characterized by greater GRF and barbell-lifter system velocity and power outputs during the final 10% of the movement phase.

Effect of acceleration on the rate of power development and neural activity of the leg extensors across the adult life span.

The rate of power development (RPD) represents the capacity to rapidly generate power during a dynamic muscle contraction. As RPD is highly susceptible to aging, its decline can have important functional consequences. However, the effect of age on RPD in response to rapid changes in movement velocity (cfr. fall incidence) is not yet clear. Therefore, the present study aimed to examine the effect of age on RPD and neural drive in response to different accelerations. Three maximal isokinetic leg extensor tests at 540°/s with different initial acceleration phases at 3200, 5700 and 7200°/s2 were performed. RPD, which is the slope of the power-time curve during the acceleration phase, was calculated for 83 subjects aged between 20 and 69years. Mean electromyography signal amplitude was determined for rectus femoris (RF), vastus lateralis (VL) and biceps femoris muscles. The average annual age-related decline rate of RPD at highest acceleration was - 2.93% and was - 1.52% and - 1.82% higher compared to lower acceleration rates (p < 0.001). This deficit can probably be explained by an age-related impairment in neural drive during the first 75ms of the acceleration phase, as evidenced by a reduced RF and VL neuromuscular activity of - 0.30% and - 0.36% at highest versus lowest acceleration (p < 0.05). These findings highlight the inability of aged individuals to quickly respond to abrupt changes in movement velocity, which requires more focus in training and prevention programs.

Evaluation of Single and Joint Toxicity of Perfluorinated Carboxylic Acids and Copper to Metal-Resistant Arthrobacter Strains.

Perfluorocarboxylic acid compounds (PFCAs) and copper have been regarded as ubiquitous environmental contaminants in aquatic ecosystems worldwide. However, data on their possible joint toxic effects on microorganisms are still lacking. To study the combined effects of four PFCAs with different carbon chain lengths and copper, a series of experiments were conducted to explore the acute toxicity of these PFCAs in the absence and presence of copper on a metal-resistant Arthrobacter strain GQ-9 by microcalorimetry. The thermokinetic parameters, including growth rate constant (k), inhibitory ratio (I), and half inhibitory concentration (IC50), were calculated and compared using the data obtained from the power-time curves. Our work revealed that GQ-9 is more resistant to perfluorooctanoic acid (PFOA) than Escherichia coli. The single and joint toxicity of PFCAs with copper are dose- and carbon chain length-dependent. The longer the carbon chain length of PFCAs, the higher the toxicity. In addition, PFCAs interacted synergistically with copper. This work could provide useful information for the risk assessment of co-exposure to perfluorinated compounds and heavy metals in natural environments.

Anti-Staphylococcus aureus evaluation of gallic acid by isothermal microcalorimetry and principle component analysis

The emergence of antibiotic-resistant Staphylococcus aureus requires new antibacterial drugs. In this study, using a thermal activity monitor air isothermal microcalorimeter, the heat flow power–time curves of S. aureus growth at 37 °C in the presence of different concentrations of gallic acid were determined. By analyzing the metabolic curves and some quantitative thermo-kinetic parameters obtained from these curves with the help of principle component analysis (PCA), the antibacterial effects of gallic acid on S. aureus were rapidly and accurately evaluated. Growth rate constant k2 of the second exponential phase and the maximum heat flow output power P2 for S. aureus growth were selected as the two main parameters for the antibacterial evaluation. Results showed that 10 μg mL−1 of gallic acid began to inhibit the growth of S. aureus, and high concentrations (more than 20 μg mL−1) of this compound exhibited strong anti-S. aureus effects. 63.51 μg mL−1 of gallic acid resulted in a 50% inhibitory ratio on S. aureus. All these illustrated that the anti-S. aureus effects were enhanced with increasing the concentration of this compound. Gallic acid can be used as a new natural and safe antibacterial drug for treating multidrug-resistant S. aureus. This work provided a useful idea of the combination of microcalorimetry and PCA for highly sensitive evaluation of the antibacterial effects of various compounds, providing reliable references for screening out new antibacterial drugs.

Rate of power development of the knee extensors across the adult life span: A cross-sectional study in 1387 Flemish Caucasians.

A growing body of research in elderly populations suggests that the early phase of an explosive muscle contraction (i.e., ≤200 ms) may be more functionally relevant than peak values. However, age-related variation in early phase explosive strength has never been investigated across the full-adult life span. This cross-sectional study investigated the age-related changes in the rate of power development (RPD) and compared it to the changes in peak power (Ppeak), both in terms of magnitude and onset, across the adult life span. Age-related declines in power and determinants of muscle power were compared between sexes. 1387 adults (♂813, ♀574), aged 18-78 years, performed three maximal isoinertial knee extensor tests at 20% of their isometric maximum on a Biodex dynamometer. Ppeak was calculated as the highest value and RPD as the linear slope of the power-time curve. Velocity (v) and torque (T) at Ppeak were registered. In both men and women, the decline in Ppeak and RPD was already apparent from 40 years onwards. Annual percent decline rates were greater for RPD (-1.1% for men and -1.3% for women) than Ppeak (-0.9% for men and -1.0% for women). Velocity at Ppeak showed the lowest annual percent decline rates (-0.3% for men and -0.4% for women). Men performed better than women on all parameters (all p < 0.001). Velocity at Ppeak tended to decline more in women than in men (p = 0.065). To conclude, both knee extensor Ppeak and RPD can be used to screen for age-related neuromuscular weaknesses at an early age. Both sexes seem equally susceptible to age-related declines in knee extensor power. In addition to traditional slow-speed resistance exercise, prevention strategies should include explosive exercises. Explosive exercises may be especially relevant in women, considering that they tend to decline more in the velocity component of muscle power.